Search (33 results, page 1 of 2)

  • × author_ss:"Leydesdorff, L."
  1. Leydesdorff, L.: Can networks of journal-journal citations be used as indicators of change in the social sciences? (2003) 0.06
    0.061924826 = product of:
      0.15481207 = sum of:
        0.11293741 = weight(_text_:index in 4460) [ClassicSimilarity], result of:
          0.11293741 = score(doc=4460,freq=6.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.50173557 = fieldWeight in 4460, product of:
              2.4494898 = tf(freq=6.0), with freq of:
                6.0 = termFreq=6.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=4460)
        0.04187466 = weight(_text_:22 in 4460) [ClassicSimilarity], result of:
          0.04187466 = score(doc=4460,freq=2.0), product of:
            0.18038483 = queryWeight, product of:
              3.5018296 = idf(docFreq=3622, maxDocs=44218)
              0.051511593 = queryNorm
            0.23214069 = fieldWeight in 4460, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              3.5018296 = idf(docFreq=3622, maxDocs=44218)
              0.046875 = fieldNorm(doc=4460)
      0.4 = coord(2/5)
    
    Abstract
    Aggregated journal-journal citations can be used for mapping the intellectual organization of the sciences in terms of specialties because the latter can be considered as interreading communities. Can the journal-journal citations also be used as early indicators of change by comparing the files for two subsequent years? Probabilistic entropy measures enable us to analyze changes in large datasets at different levels of aggregation and in considerable detail. Compares Journal Citation Reports of the Social Science Citation Index for 1999 with similar data for 1998 and analyzes the differences using these measures. Compares the various indicators with similar developments in the Science Citation Index. Specialty formation seems a more important mechanism in the development of the social sciences than in the natural and life sciences, but the developments in the social sciences are volatile. The use of aggregate statistics based on the Science Citation Index is ill-advised in the case of the social sciences because of structural differences in the underlying dynamics.
    Date
    6.11.2005 19:02:22
  2. Leydesdorff, L.; Bornmann, L.; Wagner, C.S.: ¬The relative influences of government funding and international collaboration on citation impact (2019) 0.04
    0.04283164 = product of:
      0.1070791 = sum of:
        0.06520444 = weight(_text_:index in 4681) [ClassicSimilarity], result of:
          0.06520444 = score(doc=4681,freq=2.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.28967714 = fieldWeight in 4681, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=4681)
        0.04187466 = weight(_text_:22 in 4681) [ClassicSimilarity], result of:
          0.04187466 = score(doc=4681,freq=2.0), product of:
            0.18038483 = queryWeight, product of:
              3.5018296 = idf(docFreq=3622, maxDocs=44218)
              0.051511593 = queryNorm
            0.23214069 = fieldWeight in 4681, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              3.5018296 = idf(docFreq=3622, maxDocs=44218)
              0.046875 = fieldNorm(doc=4681)
      0.4 = coord(2/5)
    
    Abstract
    A recent publication in Nature reports that public R&D funding is only weakly correlated with the citation impact of a nation's articles as measured by the field-weighted citation index (FWCI; defined by Scopus). On the basis of the supplementary data, we up-scaled the design using Web of Science data for the decade 2003-2013 and OECD funding data for the corresponding decade assuming a 2-year delay (2001-2011). Using negative binomial regression analysis, we found very small coefficients, but the effects of international collaboration are positive and statistically significant, whereas the effects of government funding are negative, an order of magnitude smaller, and statistically nonsignificant (in two of three analyses). In other words, international collaboration improves the impact of research articles, whereas more government funding tends to have a small adverse effect when comparing OECD countries.
    Date
    8. 1.2019 18:22:45
  3. Leydesdorff, L.: On the normalization and visualization of author co-citation data : Salton's Cosine versus the Jaccard index (2008) 0.03
    0.031943526 = product of:
      0.15971762 = sum of:
        0.15971762 = weight(_text_:index in 1341) [ClassicSimilarity], result of:
          0.15971762 = score(doc=1341,freq=12.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.7095612 = fieldWeight in 1341, product of:
              3.4641016 = tf(freq=12.0), with freq of:
                12.0 = termFreq=12.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=1341)
      0.2 = coord(1/5)
    
    Abstract
    The debate about which similarity measure one should use for the normalization in the case of Author Co-citation Analysis (ACA) is further complicated when one distinguishes between the symmetrical co-citation - or, more generally, co-occurrence - matrix and the underlying asymmetrical citation - occurrence - matrix. In the Web environment, the approach of retrieving original citation data is often not feasible. In that case, one should use the Jaccard index, but preferentially after adding the number of total citations (i.e., occurrences) on the main diagonal. Unlike Salton's cosine and the Pearson correlation, the Jaccard index abstracts from the shape of the distributions and focuses only on the intersection and the sum of the two sets. Since the correlations in the co-occurrence matrix may be spurious, this property of the Jaccard index can be considered as an advantage in this case.
    Object
    Salton's Cosine index
    Jaccard index
  4. Leydesdorff, L.; Salah, A.A.A.: Maps on the basis of the Arts & Humanities Citation Index : the journals Leonardo and Art Journal versus "digital humanities" as a topic (2010) 0.03
    0.029160315 = product of:
      0.14580157 = sum of:
        0.14580157 = weight(_text_:index in 3436) [ClassicSimilarity], result of:
          0.14580157 = score(doc=3436,freq=10.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.64773786 = fieldWeight in 3436, product of:
              3.1622777 = tf(freq=10.0), with freq of:
                10.0 = termFreq=10.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=3436)
      0.2 = coord(1/5)
    
    Abstract
    The possibilities of using the Arts & Humanities Citation Index (A&HCI) for journal mapping have not been sufficiently recognized because of the absence of a Journal Citations Report (JCR) for this database. A quasi-JCR for the A&HCI ([2008]) was constructed from the data contained in the Web of Science and is used for the evaluation of two journals as examples: Leonardo and Art Journal. The maps on the basis of the aggregated journal-journal citations within this domain can be compared with maps including references to journals in the Science Citation Index and Social Science Citation Index. Art journals are cited by (social) science journals more than by other art journals, but these journals draw upon one another in terms of their own references. This cultural impact in terms of being cited is not found when documents with a topic such as digital humanities are analyzed. This community of practice functions more as an intellectual organizer than a journal.
    Object
    Arts and Humanities Citation Index
  5. Leydesdorff, L.: ¬The generation of aggregated journal-journal citation maps on the basis of the CD-ROM version of the Science Citation Index (1994) 0.03
    0.026352067 = product of:
      0.13176033 = sum of:
        0.13176033 = weight(_text_:index in 8281) [ClassicSimilarity], result of:
          0.13176033 = score(doc=8281,freq=6.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.5853582 = fieldWeight in 8281, product of:
              2.4494898 = tf(freq=6.0), with freq of:
                6.0 = termFreq=6.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0546875 = fieldNorm(doc=8281)
      0.2 = coord(1/5)
    
    Abstract
    Describes a method for the generation of journal-journal citation maps on the basis of the CD-ROM version of the Science Citation Index. Discusses sources of potential error from this data. Offers strategies to counteract such errors. Analyzes a number of scientometric periodical mappings in relation to mappings from previous studies which have used tape data and/or data from ISI's Journal Citation Reports. Compares the quality of these mappings with the quality of those for previous years in order to demonstrate the use of such mappings as indicators for dynamic developments in the sciences
    Object
    Science Citation Index
  6. Leydesdorff, L.; Park, H.W.; Wagner, C.: International coauthorship relations in the Social Sciences Citation Index : is internationalization leading the Network? (2014) 0.02
    0.024300262 = product of:
      0.12150131 = sum of:
        0.12150131 = weight(_text_:index in 1505) [ClassicSimilarity], result of:
          0.12150131 = score(doc=1505,freq=10.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.5397815 = fieldWeight in 1505, product of:
              3.1622777 = tf(freq=10.0), with freq of:
                10.0 = termFreq=10.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0390625 = fieldNorm(doc=1505)
      0.2 = coord(1/5)
    
    Abstract
    International coauthorship relations have increasingly shaped another dynamic in the natural and life sciences during recent decades. However, much less is known about such internationalization in the social sciences. In this study, we analyze international and domestic coauthorship relations of all citable items in the DVD version of the Social Sciences Citation Index 2011 (SSCI). Network statistics indicate 4 groups of nations: (a) an Asian-Pacific one to which all Anglo-Saxon nations (including the United Kingdom and Ireland) are attributed, (b) a continental European one including also the Latin-American countries, (c) the Scandinavian nations, and (d) a community of African nations. Within the EU-28, 11 of the EU-15 states have dominant positions. In many respects, the network parameters are not so different from the Science Citation Index. In addition to these descriptive statistics, we address the question of the relative weights of the international versus domestic networks. An information-theoretical test is proposed at the level of organizational addresses within each nation; the results are mixed, but the international dimension is more important than the national one in the aggregated sets (as in the Science Citation Index). In some countries (e.g., France), however, the national distribution is leading more than the international one. Decomposition of the United States in terms of states shows a similarly mixed result; more U.S. states are domestically oriented in the SSCI and more internationally in the SCI. The international networks have grown during the last decades in addition to the national ones but not by replacing them.
    Object
    Social Sciences Citation Index
  7. Zhou, P.; Leydesdorff, L.: ¬A comparison between the China Scientific and Technical Papers and Citations Database and the Science Citation Index in terms of journal hierarchies and interjournal citation relations (2007) 0.02
    0.022587484 = product of:
      0.11293741 = sum of:
        0.11293741 = weight(_text_:index in 70) [ClassicSimilarity], result of:
          0.11293741 = score(doc=70,freq=6.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.50173557 = fieldWeight in 70, product of:
              2.4494898 = tf(freq=6.0), with freq of:
                6.0 = termFreq=6.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=70)
      0.2 = coord(1/5)
    
    Abstract
    The journal structure in the China Scientific and Technical Papers and Citations Database (CSTPCD) is analyzed from three perspectives: the database level, the specialty level, and the institutional level (i.e., university journals vs. journals issued by the Chinese Academy of Sciences). The results are compared with those for (Chinese) journals included in the Science Citation Index (SCI). The frequency of journal-journal citation relations in the CSTPCD is an order of magnitude lower than in the SCI. Chinese journals, especially high-quality journals, prefer to cite international journals rather than domestic ones; however, Chinese journals do not get an equivalent reception from their international counterparts. The international visibility of Chinese journals is low, but varies among fields of science. Journals of the Chinese Academy of Sciences have a better reception in the international scientific community than university journals.
    Object
    Science Citation Index
  8. Leydesdorff, L.; Rotolo, D.; Rafols, I.: Bibliometric perspectives on medical innovation using the medical subject headings of PubMed (2012) 0.02
    0.022587484 = product of:
      0.11293741 = sum of:
        0.11293741 = weight(_text_:index in 494) [ClassicSimilarity], result of:
          0.11293741 = score(doc=494,freq=6.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.50173557 = fieldWeight in 494, product of:
              2.4494898 = tf(freq=6.0), with freq of:
                6.0 = termFreq=6.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=494)
      0.2 = coord(1/5)
    
    Abstract
    Multiple perspectives on the nonlinear processes of medical innovations can be distinguished and combined using the Medical Subject Headings (MeSH) of the MEDLINE database. Focusing on three main branches-"diseases," "drugs and chemicals," and "techniques and equipment"-we use base maps and overlay techniques to investigate the translations and interactions and thus to gain a bibliometric perspective on the dynamics of medical innovations. To this end, we first analyze the MEDLINE database, the MeSH index tree, and the various options for a static mapping from different perspectives and at different levels of aggregation. Following a specific innovation (RNA interference) over time, the notion of a trajectory which leaves a signature in the database is elaborated. Can the detailed index terms describing the dynamics of research be used to predict the diffusion dynamics of research results? Possibilities are specified for further integration between the MEDLINE database on one hand, and the Science Citation Index and Scopus (containing citation information) on the other.
  9. Leydesdorff, L.; Hammarfelt, B.: ¬The structure of the Arts & Humanities Citation Index : a mapping on the basis of aggregated citations among 1,157 journals (2011) 0.02
    0.021734815 = product of:
      0.10867407 = sum of:
        0.10867407 = weight(_text_:index in 4941) [ClassicSimilarity], result of:
          0.10867407 = score(doc=4941,freq=8.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.48279524 = fieldWeight in 4941, product of:
              2.828427 = tf(freq=8.0), with freq of:
                8.0 = termFreq=8.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0390625 = fieldNorm(doc=4941)
      0.2 = coord(1/5)
    
    Abstract
    Using the Arts & Humanities Citation Index (A&HCI) 2008, we apply mapping techniques previously developed for mapping journal structures in the Science and Social Sciences Citation Indices. Citation relations among the 110,718 records were aggregated at the level of 1,157 journals specific to the A&HCI, and the journal structures are questioned on whether a cognitive structure can be reconstructed and visualized. Both cosine-normalization (bottom up) and factor analysis (top down) suggest a division into approximately 12 subsets. The relations among these subsets are explored using various visualization techniques. However, we were not able to retrieve this structure using the Institute for Scientific Information Subject Categories, including the 25 categories that are specific to the A&HCI. We discuss options for validation such as against the categories of the Humanities Indicators of the American Academy of Arts and Sciences, the panel structure of the European Reference Index for the Humanities, and compare our results with the curriculum organization of the Humanities Section of the College of Letters and Sciences of the University of California at Los Angeles as an example of institutional organization.
    Object
    Arts and Humanities Citation Index
  10. Ye, F.Y.; Leydesdorff, L.: ¬The "academic trace" of the performance matrix : a mathematical synthesis of the h-index and the integrated impact indicator (I3) (2014) 0.02
    0.021734815 = product of:
      0.10867407 = sum of:
        0.10867407 = weight(_text_:index in 1237) [ClassicSimilarity], result of:
          0.10867407 = score(doc=1237,freq=8.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.48279524 = fieldWeight in 1237, product of:
              2.828427 = tf(freq=8.0), with freq of:
                8.0 = termFreq=8.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0390625 = fieldNorm(doc=1237)
      0.2 = coord(1/5)
    
    Abstract
    The h-index provides us with 9 natural classes which can be written as a matrix of 3 vectors. The 3 vectors are: X = (X1, X2, X3) and indicates publication distribution in the h-core, the h-tail, and the uncited ones, respectively; Y = (Y1, Y2, Y3) denotes the citation distribution of the h-core, the h-tail and the so-called "excess" citations (above the h-threshold), respectively; and Z = (Z1, Z2, Z3) = (Y1-X1, Y2-X2, Y3-X3). The matrix V = (X,Y,Z)T constructs a measure of academic performance, in which the 9 numbers can all be provided with meanings in different dimensions. The "academic trace" tr(V) of this matrix follows naturally, and contributes a unique indicator for total academic achievements by summarizing and weighting the accumulation of publications and citations. This measure can also be used to combine the advantages of the h-index and the integrated impact indicator (I3) into a single number with a meaningful interpretation of the values. We illustrate the use of tr(V) for the cases of 2 journal sets, 2 universities, and ourselves as 2 individual authors.
    Object
    h-index
  11. Leydesdorff, L.: Dynamic and evolutionary updates of classificatory schemes in scientific journal structures (2002) 0.02
    0.02151637 = product of:
      0.10758185 = sum of:
        0.10758185 = weight(_text_:index in 1249) [ClassicSimilarity], result of:
          0.10758185 = score(doc=1249,freq=4.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.4779429 = fieldWeight in 1249, product of:
              2.0 = tf(freq=4.0), with freq of:
                4.0 = termFreq=4.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0546875 = fieldNorm(doc=1249)
      0.2 = coord(1/5)
    
    Abstract
    Can the inclusion of new journals in the Science Citation Index be used for the indication of structural change in the database, and how can this change be compared with reorganizations of reiations among previously included journals? Change in the number of journals (n) is distinguished from change in the number of journal categories (m). Although the number of journals can be considered as a given at each moment in time, the number of journal categories is based an a reconstruction that is time-stamped ex post. The reflexive reconstruction is in need of an update when new information becomes available in a next year. Implications of this shift towards an evolutionary perspective are specified.
    Object
    Science Citation Index
  12. Leydesdorff, L.: Visualization of the citation impact environments of scientific journals : an online mapping exercise (2007) 0.02
    0.018822905 = product of:
      0.09411452 = sum of:
        0.09411452 = weight(_text_:index in 82) [ClassicSimilarity], result of:
          0.09411452 = score(doc=82,freq=6.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.418113 = fieldWeight in 82, product of:
              2.4494898 = tf(freq=6.0), with freq of:
                6.0 = termFreq=6.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0390625 = fieldNorm(doc=82)
      0.2 = coord(1/5)
    
    Abstract
    Aggregated journal-journal citation networks based on the Journal Citation Reports 2004 of the Science Citation Index (5,968 journals) and the Social Science Citation Index (1,712 journals) are made accessible from the perspective of any of these journals. A vector-space model Is used for normalization, and the results are brought online at http://www.leydesdorff.net/jcr04 as input files for the visualization program Pajek. The user is thus able to analyze the citation environment in terms of links and graphs. Furthermore, the local impact of a journal is defined as its share of the total citations in the specific journal's citation environments; the vertical size of the nodes is varied proportionally to this citation impact. The horizontal size of each node can be used to provide the same information after correction for within-journal (self-)citations. In the "citing" environment, the equivalents of this measure can be considered as a citation activity index which maps how the relevant journal environment is perceived by the collective of authors of a given journal. As a policy application, the mechanism of Interdisciplinary developments among the sciences is elaborated for the case of nanotechnology journals.
  13. Leydesdorff, L.: Betweenness centrality as an indicator of the interdisciplinarity of scientific journals (2007) 0.02
    0.018442601 = product of:
      0.092213005 = sum of:
        0.092213005 = weight(_text_:index in 453) [ClassicSimilarity], result of:
          0.092213005 = score(doc=453,freq=4.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.40966535 = fieldWeight in 453, product of:
              2.0 = tf(freq=4.0), with freq of:
                4.0 = termFreq=4.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=453)
      0.2 = coord(1/5)
    
    Abstract
    In addition to science citation indicators of journals like impact and immediacy, social network analysis provides a set of centrality measures like degree, betweenness, and closeness centrality. These measures are first analyzed for the entire set of 7,379 journals included in the Journal Citation Reports of the Science Citation Index and the Social Sciences Citation Index 2004 (Thomson ISI, Philadelphia, PA), and then also in relation to local citation environments that can be considered as proxies of specialties and disciplines. Betweenness centrality is shown to be an indicator of the interdisciplinarity of journals, but only in local citation environments and after normalization; otherwise, the influence of degree centrality (size) overshadows the betweenness-centrality measure. The indicator is applied to a variety of citation environments, including policy-relevant ones like biotechnology and nanotechnology. The values of the indicator remain sensitive to the delineations of the set because of the indicator's local character. Maps showing interdisciplinarity of journals in terms of betweenness centrality can be drawn using information about journal citation environments, which is available online.
  14. Leydesdorff, L.: How are new citation-based journal indicators adding to the bibliometric toolbox? (2009) 0.02
    0.018442601 = product of:
      0.092213005 = sum of:
        0.092213005 = weight(_text_:index in 2929) [ClassicSimilarity], result of:
          0.092213005 = score(doc=2929,freq=4.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.40966535 = fieldWeight in 2929, product of:
              2.0 = tf(freq=4.0), with freq of:
                4.0 = termFreq=4.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=2929)
      0.2 = coord(1/5)
    
    Abstract
    The launching of Scopus and Google Scholar, and methodological developments in social-network analysis have made many more indicators for evaluating journals available than the traditional impact factor, cited half-life, and immediacy index of the ISI. In this study, these new indicators are compared with one another and with the older ones. Do the various indicators measure new dimensions of the citation networks, or are they highly correlated among themselves? Are they robust and relatively stable over time? Two main dimensions are distinguished - size and impact - which together shape influence. The h-index combines the two dimensions and can also be considered as an indicator of reach (like Indegree). PageRank is mainly an indicator of size, but has important interactions with centrality measures. The Scimago Journal Ranking (SJR) indicator provides an alternative to the journal impact factor, but the computation is less easy.
  15. Leydesdorff, L.; Zhou, P.; Bornmann, L.: How can journal impact factors be normalized across fields of science? : An assessment in terms of percentile ranks and fractional counts (2013) 0.02
    0.015368836 = product of:
      0.07684418 = sum of:
        0.07684418 = weight(_text_:index in 532) [ClassicSimilarity], result of:
          0.07684418 = score(doc=532,freq=4.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.3413878 = fieldWeight in 532, product of:
              2.0 = tf(freq=4.0), with freq of:
                4.0 = termFreq=4.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0390625 = fieldNorm(doc=532)
      0.2 = coord(1/5)
    
    Abstract
    Using the CD-ROM version of the Science Citation Index 2010 (N = 3,705 journals), we study the (combined) effects of (a) fractional counting on the impact factor (IF) and (b) transformation of the skewed citation distributions into a distribution of 100 percentiles and six percentile rank classes (top-1%, top-5%, etc.). Do these approaches lead to field-normalized impact measures for journals? In addition to the 2-year IF (IF2), we consider the 5-year IF (IF5), the respective numerators of these IFs, and the number of Total Cites, counted both as integers and fractionally. These various indicators are tested against the hypothesis that the classification of journals into 11 broad fields by PatentBoard/NSF (National Science Foundation) provides statistically significant between-field effects. Using fractional counting the between-field variance is reduced by 91.7% in the case of IF5, and by 79.2% in the case of IF2. However, the differences in citation counts are not significantly affected by fractional counting. These results accord with previous studies, but the longer citation window of a fractionally counted IF5 can lead to significant improvement in the normalization across fields.
    Aid
    Science Citation Index
  16. Leydesdorff, L.; Moya-Anegón, F. de; Nooy, W. de: Aggregated journal-journal citation relations in scopus and web of science matched and compared in terms of networks, maps, and interactive overlays (2016) 0.02
    0.015368836 = product of:
      0.07684418 = sum of:
        0.07684418 = weight(_text_:index in 3090) [ClassicSimilarity], result of:
          0.07684418 = score(doc=3090,freq=4.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.3413878 = fieldWeight in 3090, product of:
              2.0 = tf(freq=4.0), with freq of:
                4.0 = termFreq=4.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.0390625 = fieldNorm(doc=3090)
      0.2 = coord(1/5)
    
    Abstract
    We compare the network of aggregated journal-journal citation relations provided by the Journal Citation Reports (JCR) 2012 of the Science Citation Index (SCI) and Social Sciences Citation Index (SSCI) with similar data based on Scopus 2012. First, global and overlay maps were developed for the 2 sets separately. Using fuzzy-string matching and ISSN numbers, we were able to match 10,524 journal names between the 2 sets: 96.4% of the 10,936 journals contained in JCR, or 51.2% of the 20,554 journals covered by Scopus. Network analysis was pursued on the set of journals shared between the 2 databases and the 2 sets of unique journals. Citations among the shared journals are more comprehensively covered in JCR than in Scopus, so the network in JCR is denser and more connected than in Scopus. The ranking of shared journals in terms of indegree (i.e., numbers of citing journals) or total citations is similar in both databases overall (Spearman rank correlation ??>?0.97), but some individual journals rank very differently. Journals that are unique to Scopus seem to be less important-they are citing shared journals rather than being cited by them-but the humanities are covered better in Scopus than in JCR.
  17. Leydesdorff, L.; Bihui, J.: Mapping the Chinese Science Citation Database in terms of aggregated journal-journal citation relations (2005) 0.01
    0.013040888 = product of:
      0.06520444 = sum of:
        0.06520444 = weight(_text_:index in 4813) [ClassicSimilarity], result of:
          0.06520444 = score(doc=4813,freq=2.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.28967714 = fieldWeight in 4813, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=4813)
      0.2 = coord(1/5)
    
    Abstract
    Methods developed for mapping the journal structure contained in aggregated journal-journal citations in the Science Citation Index (SCI; Thomson ISI, 2002) are applied to the Chinese Science Citation Database of the Chinese Academy of Sciences. This database covered 991 journals in 2001, of which only 37 originally had English titles; only 31 of which were covered by the SCI. Using factor-analytical and graph-analytical techniques, the authors show that the journal relations are dually structured. The main structure is the intellectual organization of the journals in journal groups (as in the international SCI), but the university-based journals provide an institutional layer that orients this structure towards practical ends (e.g., agriculture). This mechanism of integration is further distinguished from the role of general science journals. The Chinese Science Citation Database thus exhibits the characteristics of "Mode 2" or transdisciplinary science in the production of scientific knowledge more than its Western counterpart does. The contexts of application lead to correlation among the components.
  18. Leydesdorff, L.: Can scientific journals be classified in terms of aggregated journal-journal citation relations using the Journal Citation Reports? (2006) 0.01
    0.013040888 = product of:
      0.06520444 = sum of:
        0.06520444 = weight(_text_:index in 5046) [ClassicSimilarity], result of:
          0.06520444 = score(doc=5046,freq=2.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.28967714 = fieldWeight in 5046, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=5046)
      0.2 = coord(1/5)
    
    Abstract
    The aggregated citation relations among journals included in the Science Citation Index provide us with a huge matrix, which can be analyzed in various ways. By using principal component analysis or factor analysis, the factor scores can be employed as indicators of the position of the cited journals in the citing dimensions of the database. Unrotated factor scores are exact, and the extraction of principal components can be made stepwise because the principal components are independent. Rotation may be needed for the designation, but in the rotated solution a model is assumed. This assumption can be legitimated on pragmatic or theoretical grounds. Because the resulting outcomes remain sensitive to the assumptions in the model, an unambiguous classification is no longer possible in this case. However, the factor-analytic solutions allow us to test classifications against the structures contained in the database; in this article the process will be demonstrated for the delineation of a set of biochemistry journals.
  19. Leydesdorff, L.: Caveats for the use of citation indicators in research and journal evaluations (2008) 0.01
    0.013040888 = product of:
      0.06520444 = sum of:
        0.06520444 = weight(_text_:index in 1361) [ClassicSimilarity], result of:
          0.06520444 = score(doc=1361,freq=2.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.28967714 = fieldWeight in 1361, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=1361)
      0.2 = coord(1/5)
    
    Abstract
    Aging of publications, percentage of self-citations, and impact vary from journal to journal within fields of science. The assumption that citation and publication practices are homogenous within specialties and fields of science is invalid. Furthermore, the delineation of fields and among specialties is fuzzy. Institutional units of analysis and persons may move between fields or span different specialties. The match between the citation index and institutional profiles varies among institutional units and nations. The respective matches may heavily affect the representation of the units. Non-Institute of Scientific Information (ISI) journals are increasingly cornered into transdisciplinary Mode-2 functions with the exception of specialist journals publishing in languages other than English. An externally cited impact factor can be calculated for these journals. The citation impact of non-ISI journals will be demonstrated using Science and Public Policy as the example.
  20. Bensman, S.J.; Leydesdorff, L.: Definition and identification of journals as bibliographic and subject entities : librarianship versus ISI Journal Citation Reports methods and their effect on citation measures (2009) 0.01
    0.013040888 = product of:
      0.06520444 = sum of:
        0.06520444 = weight(_text_:index in 2840) [ClassicSimilarity], result of:
          0.06520444 = score(doc=2840,freq=2.0), product of:
            0.2250935 = queryWeight, product of:
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.051511593 = queryNorm
            0.28967714 = fieldWeight in 2840, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              4.369764 = idf(docFreq=1520, maxDocs=44218)
              0.046875 = fieldNorm(doc=2840)
      0.2 = coord(1/5)
    
    Abstract
    This paper explores the ISI Journal Citation Reports (JCR) bibliographic and subject structures through Library of Congress (LC) and American research libraries cataloging and classification methodology. The 2006 Science Citation Index JCR Behavioral Sciences subject category journals are used as an example. From the library perspective, the main fault of the JCR bibliographic structure is that the JCR mistakenly identifies journal title segments as journal bibliographic entities, seriously affecting journal rankings by total cites and the impact factor. In respect to JCR subject structure, the title segment, which constitutes the JCR bibliographic basis, is posited as the best bibliographic entity for the citation measurement of journal subject relationships. Through factor analysis and other methods, the JCR subject categorization of journals is tested against their LC subject headings and classification. The finding is that JCR and library journal subject analyses corroborate, clarify, and correct each other.