** apologies for cross-postings
Local Citation Impact Environments of 9,162 Scientific Journals in 2009 <http://www.leydesdorff.net/jcr09/index.htm> One can click on any of the journal names below and obtain the Pajek file corresponding to the citation impact environment ("cited") or the citation activity environment ("citing") of the respective journal. See for further explanation: <http://www.leydesdorff.net/jcr04/index.htm> "Visualization of the Citation Impact Environment of Scientific Journals: An online mapping exercise," Journal of the Amererican Society for Information Science and Technology 58(1), 25-38, 2007. <http://www.leydesdorff.net/jcr04/jcr2pajek.pdf> <pdf version> Please, provide this reference if you use the information. 2009 SCI <http://www.leydesdorff.net/jcr09/cited> and Social SCI combined, cited SCI <http://www.leydesdorff.net/jcr09/citing> and Social SCI combined, citing 9162 journals The (local) matrices are since 2006 based on taking the one-percent threshold of "total citations" after correction for within-journal citations. This main-diagonal value is sometimes so large that it overshadows the environment and therefore it is no longer included in setting the threshold for the delineation of the set. (with Lutz Bornmann), How fractional counting of citations affects the Impact Factor: <http://www.leydesdorff.net/weighted_if/weighted_if.pdf> Normalization in terms of differences in citation potentials among fields of science <http://www.leydesdorff.net/weighted_if/weighted_if.pdf> Journal of the American Society for Information Science and Technology (JASIST; in press) The ISI-Impact Factors suffer from a number of drawbacks, among them the statistics-why should one use the mean and not the median?-and the incomparability among fields of science because of systematic differences in citation behavior among fields. Can these drawbacks be counteracted by counting citation weights fractionally instead of using whole numbers in the numerators? (i) Fractional citation counts are normalized in terms of the citing sources and thus would take into account differences in citation behavior among fields of science. (ii) Differences in the resulting distributions can be tested statistically for their significance at different levels of aggregation. (iii) Fractional counting can be generalized to any document set including journals or groups of journals, and thus the significance of differences among both small and large sets can be tested. A list of fractionally counted Impact Factors for 2008 is available online at http://www.leydesdorff.net/weighted_if/weighted_if.xls. The in-between group variance among the thirteen fields of science identified in the U.S. Science and Engineering Indicators is not statistically significant after this normalization. Although citation behavior differs largely between disciplines, the reflection of these differences in fractionally counted citation distributions could not be used as a reliable instrument for the classification. (with Ismael Rafols), Indicators of the Interdisciplinarity of Journals: <http://www.leydesdorff.net/interdisc/interdisc.pdf> Diversity, Centrality, and Citations <http://www.leydesdorff.net/interdisc/interdisc.pdf> Journal of Informetrics (2011, forthcoming) A citation-based indicator for interdisciplinarity has been missing hitherto among the set of available journal indicators. In this study, we investigate network indicators (betweenness centrality), journal indicators (Shannon entropy, the Gini coefficient), and more recently proposed Rao-Stirling measures for "interdisciplinarity." The latter index combines the statistics of both citation distributions of journals (vector-based) and distances in citation networks among journals (matrix-based). The effects of various normalizations are specified and measured using the matrix of 8,207 journals contained in the Journal Citation Reports of the (Social) Science Citation Index 2008. Betweenness centrality in symmetrical (1-mode) cosine-normalized networks provides an indicator outperforming betweenness in the asymmetrical (2-mode) citation network. Among the vector-based indicators, Shannon entropy performs better than the Gini coefficient, but is sensitive to size. Science and Nature, for example, are indicated at the top of the list. The new diversity measure provides reasonable results when (1 - cosine) is assumed as a measure for the distance, but results using Euclidean distances were difficult to interpret. _____ Loet Leydesdorff Amsterdam School of Communications Research (ASCoR) Kloveniersburgwal 48, 1012 CX Amsterdam. Tel. +31-20-525 6598; fax: +31-842239111 <mailto:l...@leydesdorff.net> l...@leydesdorff.net ; <http://www.leydesdorff.net/> http://www.leydesdorff.net/ Visiting Professor 2007-2010, <http://www.istic.ac.cn/Eng/brief_en.html> ISTIC, Beijing; Honorary Fellow 2007-2010, <http://www.sussex.ac.uk/spru/> SPRU, University of Sussex Now available: <http://www.universal-publishers.com/book.php?method=ISBN&book=1581129378> The Knowledge-Based Economy: Modeled, Measured, Simulated, 385 pp.; US$ 18.95; <http://www.universal-publishers.com/book.php?method=ISBN&book=1581126956> The Self-Organization of the Knowledge-Based Society ; <http://www.universal-publishers.com/book.php?method=ISBN&book=1581126816> The Challenge of Scientometrics
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