Search (6 results, page 1 of 1)

0.08847439 = product of:
  0.17694879 = sum of:
    0.17694879 = sum of:
      0.142333 = weight(_text_:journals in 2646) [ClassicSimilarity], result of:
        0.142333 = score(doc=2646,freq=8.0), product of:
          0.25656942 = queryWeight, product of:
            5.021064 = idf(docFreq=792, maxDocs=44218)
            0.05109862 = queryNorm
          0.5547544 = fieldWeight in 2646, product of:
            2.828427 = tf(freq=8.0), with freq of:
              8.0 = termFreq=8.0
            5.021064 = idf(docFreq=792, maxDocs=44218)
            0.0390625 = fieldNorm(doc=2646)
      0.03461579 = weight(_text_:22 in 2646) [ClassicSimilarity], result of:
        0.03461579 = score(doc=2646,freq=2.0), product of:
          0.17893866 = queryWeight, product of:
            3.5018296 = idf(docFreq=3622, maxDocs=44218)
            0.05109862 = queryNorm
          0.19345059 = fieldWeight in 2646, product of:
            1.4142135 = tf(freq=2.0), with freq of:
              2.0 = termFreq=2.0
            3.5018296 = idf(docFreq=3622, maxDocs=44218)
            0.0390625 = fieldNorm(doc=2646)
  0.5 = coord(1/2)

Abstract

A statistical analysis of full text downloads of articles in Elsevier's ScienceDirect covering all disciplines reveals large differences in download frequencies, their skewness, and their correlation with Scopus-based citation counts, between disciplines, journals, and document types. Download counts tend to be 2 orders of magnitude higher and less skewedly distributed than citations. A mathematical model based on the sum of two exponentials does not adequately capture monthly download counts. The degree of correlation at the article level within a journal is similar to that at the journal level in the discipline covered by that journal, suggesting that the differences between journals are, to a large extent, discipline specific. Despite the fact that in all studied journals download and citation counts per article positively correlate, little overlap may exist between the set of articles appearing in the top of the citation distribution and that with the most frequently downloaded ones. Usage and citation leaks, bulk downloading, differences between reader and author populations in a subject field, the type of document or its content, differences in obsolescence patterns between downloads and citations, and different functions of reading and citing in the research process all provide possible explanations of differences between download and citation distributions.

Date

22. 1.2016 14:11:17

0.03765778 = product of:
  0.07531556 = sum of:
    0.07531556 = product of:
      0.15063111 = sum of:
        0.15063111 = weight(_text_:journals in 4719) [ClassicSimilarity], result of:
          0.15063111 = score(doc=4719,freq=14.0), product of:
            0.25656942 = queryWeight, product of:
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.05109862 = queryNorm
            0.5870969 = fieldWeight in 4719, product of:
              3.7416575 = tf(freq=14.0), with freq of:
                14.0 = termFreq=14.0
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.03125 = fieldNorm(doc=4719)
      0.5 = coord(1/2)
  0.5 = coord(1/2)

Abstract

During the past decades, journal impact data obtained from the Journal Citation Reports (JCR) have gained relevance in library management, research management and research evaluation. Hence, both information scientists and bibliometricians share the responsibility towards the users of the JCR to analyse the reliability and validity of its measures thoroughly, to indicate pitfalls and to suggest possible improvements. In this article, ageing patterns are examined in 'formal' use or impact of all scientific journals processed for the Science Citation Index (SCI) during 1981-1995. A new classification system of journals in terms of their ageing characteristics is introduced. This system has been applied to as many as 3,098 journals covered by the Science Citation Index. Following an earlier suggestion by Glnzel and Schoepflin, a maturing and a decline phase are distinguished. From an analysis across all subfields it has been concluded that ageing characteristics are primarily specific to the individual journal rather than to the subfield, while the distribution of journals in terms of slowly or rapidly maturing or declining types is specific to the subfield. It is shown that the cited half life (CHL), printed in the JCR, is an inappropriate measure of decline of journal impact. Following earlier work by Line and others, a more adequate parameter of decline is calculated taking into account the size of annual volumes during a range of fifteen years. For 76 per cent of SCI journals the relative difference between this new parameter and the ISI CHL exceeds 5 per cent. The current JCR journal impact factor is proven to be biased towards journals revealing a rapid maturing and decline in impact. Therefore, a longer term impact factor is proposed, as well as a normalised impact statistic, taking into account citation characteristics of the research subfield covered by a journal and the type of documents published in it. When these new measures are combined with the proposed ageing classification system, they provide a significantly improved picture of a journal's impact to that obtained from the JCR.

0.025161162 = product of:
  0.050322324 = sum of:
    0.050322324 = product of:
      0.10064465 = sum of:
        0.10064465 = weight(_text_:journals in 621) [ClassicSimilarity], result of:
          0.10064465 = score(doc=621,freq=4.0), product of:
            0.25656942 = queryWeight, product of:
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.05109862 = queryNorm
            0.39227062 = fieldWeight in 621, product of:
              2.0 = tf(freq=4.0), with freq of:
                4.0 = termFreq=4.0
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.0390625 = fieldNorm(doc=621)
      0.5 = coord(1/2)
  0.5 = coord(1/2)

Abstract

This article statistically analyzes how the citation impact of articles deposited in the Condensed Matter section of the preprint server ArXiv (hosted by Cornell University), and subsequently published in a scientific journal, compares to that of articles in the same journal that were not deposited in the archive. Its principal aim is to further illustrate and roughly estimate the effect of two factors, early view and quality bias, on differences in citation impact between these two sets of papers, using citation data from Thomson Scientific's Web of Science. It presents estimates for a number of journals in the field of condensed matter physics. To discriminate between an open access effect and an early view effect, longitudinal citation data were analyzed covering a time period as long as 7 years. Quality bias was measured by calculating ArXiv citation impact differentials at the level of individual authors publishing in a journal, taking into account coauthorship. The analysis provided evidence of a strong quality bias and early view effect. Correcting for these effects, there is in a sample of six condensed matter physics journals studied in detail no sign of a general open access advantage of papers deposited in ArXiv. The study does provide evidence that ArXiv accelerates citation due to the fact that ArXiv makes papers available earlier rather than makes them freely available.

0.021349952 = product of:
  0.042699903 = sum of:
    0.042699903 = product of:
      0.08539981 = sum of:
        0.08539981 = weight(_text_:journals in 3376) [ClassicSimilarity], result of:
          0.08539981 = score(doc=3376,freq=2.0), product of:
            0.25656942 = queryWeight, product of:
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.05109862 = queryNorm
            0.33285263 = fieldWeight in 3376, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.046875 = fieldNorm(doc=3376)
      0.5 = coord(1/2)
  0.5 = coord(1/2)

Abstract

Gives an outline of a new bibliometric database based upon all articles published by authors from the Netherlands and processed during 1980-1993 by ISI for the SCI, SSCI and AHCI. Describes various types of information added to the database: data on articles citing the Dutch publications; detailed citation data on ISI journals and subfields; and a classification system of the main publishing organizations. Also gives an overview of the types of bibliometric indicators constructed. and discusses their relationship to indicators developed by other researchers in the field. Gives 2 applications to illustrate the potentials of the database and of the bibliometric indicators derived from it: one that represents a synthesis of 'classical' macro indicator studies on the one hand and bibliometric analyses of research groups on the other; and a second that gives for the first time a detailed analysis of a country's publications per institutional sector

0.020128928 = product of:
  0.040257856 = sum of:
    0.040257856 = product of:
      0.08051571 = sum of:
        0.08051571 = weight(_text_:journals in 1734) [ClassicSimilarity], result of:
          0.08051571 = score(doc=1734,freq=4.0), product of:
            0.25656942 = queryWeight, product of:
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.05109862 = queryNorm
            0.3138165 = fieldWeight in 1734, product of:
              2.0 = tf(freq=4.0), with freq of:
                4.0 = termFreq=4.0
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.03125 = fieldNorm(doc=1734)
      0.5 = coord(1/2)
  0.5 = coord(1/2)

Abstract

The purpose of this paper is to examine the effects of the use of the citation-based journal impact factor for evaluative purposes upon the behaviour of authors and editors. It seeks to give a critical examination of a number of claims as regards the manipulability of this indicator on the basis of an empirical analysis of publication and referencing practices of authors and journal editors Design/methodology/approach - The paper describes mechanisms that may affect the numerical values of journal impact factors. It also analyses general, "macro" patterns in large samples of journals in order to obtain indications of the extent to which such mechanisms are actually applied on a large scale. Finally it presents case studies of particular science journals in order to illustrate what their effects may be in individual cases. Findings - The paper shows that the commonly used journal impact factor can to some extent be relatively easily manipulated. It discusses several types of strategic editorial behaviour, and presents cases in which journal impact factors were - intentionally or otherwise - affected by particular editorial strategies. These findings lead to the conclusion that one must be most careful in interpreting and using journal impact factors, and that authors, editors and policy makers must be aware of their potential manipulability. They also show that some mechanisms occur as of yet rather infrequently, while for others it is most difficult if not impossible to assess empirically how often they are actually applied. If their frequency of occurrence increases, one should come to the conclusion that the impact of impact factors is decreasing. Originality/value - The paper systematically describes a number of claims about the manipulability of journal impact factors that are often based on "informal" or even anecdotal evidences and illustrates how these claims can be further examined in thorough empirical research of large data samples.

0.014233301 = product of:
  0.028466603 = sum of:
    0.028466603 = product of:
      0.056933206 = sum of:
        0.056933206 = weight(_text_:journals in 3882) [ClassicSimilarity], result of:
          0.056933206 = score(doc=3882,freq=2.0), product of:
            0.25656942 = queryWeight, product of:
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.05109862 = queryNorm
            0.22190176 = fieldWeight in 3882, product of:
              1.4142135 = tf(freq=2.0), with freq of:
                2.0 = termFreq=2.0
              5.021064 = idf(docFreq=792, maxDocs=44218)
              0.03125 = fieldNorm(doc=3882)
      0.5 = coord(1/2)
  0.5 = coord(1/2)

Abstract

Statistical relationships between downloads from ScienceDirect of documents in Elsevier's electronic journal Tetrahedron Letters and citations to these documents recorded in journals processed by the Institute for Scientific Information/Thomson Scientific for the Science Citation Index (SCI) are examined. A synchronous approach revealed that downloads and citations show different patterns of obsolescence of the used materials. The former can be adequately described by a model consisting of the sum of two negative exponential functions, representing an ephemeral and a residual factor, whereas the decline phase of the latter conforms to a simple exponential function with a decay constant statistically similar to that of the downloads residual factor. A diachronous approach showed that, as a cohort of documents grows older, its download distribution becomes more and more skewed, and more statistically similar to its citation distribution. A method is proposed to estimate the effect of citations upon downloads using obsolescence patterns. It was found that during the first 3 months after an article is cited, its number of downloads increased 25% compared to what one would expect this number to be if the article had not been cited. Moreover, more downloads of citing documents led to more downloads of the cited article through the citation. An analysis of 1,190 papers in the journal during a time interval of 2 years after publication date revealed that there is about one citation for every 100 downloads. A Spearman rank correlation coefficient of 0.22 was found between the number of times an article was downloaded and its citation rate recorded in the SCI. When initial downloads-defined as downloads made during the first 3 months after publication-were discarded, the correlation raised to 0.35. However, both outcomes measure the joint effect of downloads upon citation and that of citation upon downloads. Correlating initial downloads to later citation counts, the correlation coefficient drops to 0.11. Findings suggest that initial downloads and citations relate to distinct phases in the process of collecting and processing relevant scientific information that eventually leads to the publication of a journal article.