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Leydesdorff, L.: ¬The construction and globalization of the knowledge base in inter-human communication systems (2003)
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- Date
- 22. 5.2003 19:48:04
-
Leydesdorff, L.: Can networks of journal-journal citations be used as indicators of change in the social sciences? (2003)
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- Date
- 6.11.2005 19:02:22
-
Leydesdorff, L.; Sun, Y.: National and international dimensions of the Triple Helix in Japan : university-industry-government versus international coauthorship relations (2009)
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- Date
- 22. 3.2009 19:07:20
-
Leydesdorff, L.; Bornmann, L.; Wagner, C.S.: ¬The relative influences of government funding and international collaboration on citation impact (2019)
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- Date
- 8. 1.2019 18:22:45
-
Leydesdorff, L.; Bornmann, L.: How fractional counting of citations affects the impact factor : normalization in terms of differences in citation potentials among fields of science (2011)
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- Date
- 22. 1.2011 12:51:07
-
Hellsten, I.; Leydesdorff, L.: ¬The construction of interdisciplinarity : the development of the knowledge base and programmatic focus of the journal Climatic Change, 1977-2013 (2016)
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- Date
- 24. 8.2016 17:53:22
-
Leydesdorff, L.; Johnson, M.W.; Ivanova, I.: Toward a calculus of redundancy : signification, codification, and anticipation in cultural evolution (2018)
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- Date
- 29. 9.2018 11:22:09
-
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)
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- 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.
-
Leydesdorff, L.: Theories of citation? (1999)
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- Source
- Scientometrics. 43(1998) no.1, S.5-25
-
Leydesdorff, L.: Why words and co-word cannot map the development of the science (1997)
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- Source
- Journal of the American Society for Information Science. 48(1997) no.5, S.418-427
-
Leydesdorff, L.: Can scientific journals be classified in terms of aggregated journal-journal citation relations using the Journal Citation Reports? (2006)
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- Source
- Journal of the American Society for Information Science and Technology. 57(2006) no.5, S.601-613
-
Egghe, L.; Leydesdorff, L.: ¬The relation between Pearson's correlation coefficient r and Salton's cosine measure (2009)
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- Source
- Journal of the American Society for Information Science and Technology. 60(2009) no.5, S.1027-1036
-
Leydesdorff, L.; Rafols, I.: Local emergence and global diffusion of research technologies : an exploration of patterns of network formation (2011)
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- Source
- Journal of the American Society for Information Science and Technology. 62(2011) no.5, S.846-860
-
Leydesdorff, L.; Opthof, T.: Citation analysis with medical subject Headings (MeSH) using the Web of Knowledge : a new routine (2013)
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- Source
- Journal of the American Society for Information Science and Technology. 64(2013) no.5, S.1076-1080
-
Rotolo, D.; Leydesdorff, L.: Matching Medline/PubMed data with Web of Science: A routine in R language (2015)
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- Abstract
- We present a novel routine, namely medlineR, based on the R language, that allows the user to match data from Medline/PubMed with records indexed in the ISI Web of Science (WoS) database. The matching allows exploiting the rich and controlled vocabulary of medical subject headings (MeSH) of Medline/PubMed with additional fields of WoS. The integration provides data (e.g., citation data, list of cited reference, list of the addresses of authors' host organizations, WoS subject categories) to perform a variety of scientometric analyses. This brief communication describes medlineR, the method on which it relies, and the steps the user should follow to perform the matching across the two databases. To demonstrate the differences from Leydesdorff and Opthof (Journal of the American Society for Information Science and Technology, 64(5), 1076-1080), we conclude this artcle by testing the routine on the MeSH category "Burgada syndrome."
-
Zhou, Q.; Leydesdorff, L.: ¬The normalization of occurrence and co-occurrence matrices in bibliometrics using Cosine similarities and Ochiai coefficients (2016)
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- Abstract
- We prove that Ochiai similarity of the co-occurrence matrix is equal to cosine similarity in the underlying occurrence matrix. Neither the cosine nor the Pearson correlation should be used for the normalization of co-occurrence matrices because the similarity is then normalized twice, and therefore overestimated; the Ochiai coefficient can be used instead. Results are shown using a small matrix (5 cases, 4 variables) for didactic reasons, and also Ahlgren et?al.'s (2003) co-occurrence matrix of 24 authors in library and information sciences. The overestimation is shown numerically and will be illustrated using multidimensional scaling and cluster dendograms. If the occurrence matrix is not available (such as in internet research or author cocitation analysis) using Ochiai for the normalization is preferable to using the cosine.
-
Comins, J.A.; Leydesdorff, L.: Identification of long-term concept-symbols among citations : do common intellectual histories structure citation behavior? (2017)
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- Source
- Journal of the Association for Information Science and Technology. 68(2017) no.5, S.1224-1233
-
Leydesdorff, L.; Moya-Anegón, F. de; Guerrero-Bote, V.P.: Journal maps, interactive overlays, and the measurement of interdisciplinarity on the basis of Scopus data (1996-2012) (2015)
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- Journal of the Association for Information Science and Technology. 66(2015) no.5, S.1001-1016
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Leydesdorff, L.; Bornmann, L.; Mingers, J.: Statistical significance and effect sizes of differences among research universities at the level of nations and worldwide based on the Leiden rankings (2019)
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- Journal of the Association for Information Science and Technology. 70(2019) no.5, S.509-525
-
Leydesdorff, L.; Wagner, C.S.; Porto-Gomez, I.; Comins, J.A.; Phillips, F.: Synergy in the knowledge base of U.S. innovation systems at national, state, and regional levels : the contributions of high-tech manufacturing and knowledge-intensive services (2019)
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- Date
- 5. 9.2019 19:07:48
