Search (54 results, page 1 of 3)

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Content

"Zur Kurzmitteilung "Latest enhancements in Scopus: ... h-Index incorporated in Scopus" in den letzten Online-Mitteilungen (Online-Mitteilungen 92, S.31) ist zu korrigieren, dass der h-Index sehr wohl bereits im Web of Science enthalten ist. Allerdings findet man/frau diese Information nicht in der "cited ref search", sondern neben der Trefferliste einer Quick Search, General Search oder einer Suche über den Author Finder in der rechten Navigationsleiste unter dem Titel "Citation Report". Der "Citation Report" bietet für die in der jeweiligen Trefferliste angezeigten Arbeiten: - Die Gesamtzahl der Zitierungen aller Arbeiten in der Trefferliste - Die mittlere Zitationshäufigkeit dieser Arbeiten - Die Anzahl der Zitierungen der einzelnen Arbeiten, aufgeschlüsselt nach Publikationsjahr der zitierenden Arbeiten - Die mittlere Zitationshäufigkeit dieser Arbeiten pro Jahr - Den h-Index (ein h-Index von x sagt aus, dass x Arbeiten der Trefferliste mehr als x-mal zitiert wurden; er ist gegenüber sehr hohen Zitierungen einzelner Arbeiten unempfindlicher als die mittlere Zitationshäufigkeit)."

Date

6. 4.2008 19:04:22

Object

H-Index

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Abstract

This article challenges recent research (Evans, 2008) reporting that the concentration of cited scientific literature increases with the online availability of articles and journals. Using Thomson Reuters' Web of Science, the present article analyses changes in the concentration of citations received (2- and 5-year citation windows) by papers published between 1900 and 2005. Three measures of concentration are used: the percentage of papers that received at least one citation (cited papers); the percentage of papers needed to account for 20%, 50%, and 80% of the citations; and the Herfindahl-Hirschman index (HHI). These measures are used for four broad disciplines: natural sciences and engineering, medical fields, social sciences, and the humanities. All these measures converge and show that, contrary to what was reported by Evans, the dispersion of citations is actually increasing.

Date

22. 3.2009 19:22:35

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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.

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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

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Abstract

In einer früheren Studie wurde bereits der 'informationelle Mehrwert' von bibliographischen Datenbanken durch bibliometrische Nutzung untersucht. Im folgenden soll nun eine visuelle Oberfläche vorgestellt werden, die mit Hilfe einer bibliometrischen 'Sekundärdatenbank' einerseits die Nutzungsmöglichkeiten der zugrundeliegenden bibliographischen Datenbanken vor allem in den Bereichen Wissenschaftsinformation, Forschungsevaluation und Wissenschaftspolitik erweitern soll, andererseits aber auch eine Rückkopplung zu den Aufgaben des traditionellen Retrievals erlaubt. Die visuelle Oberfläche 'Visual Bibliometrics' ist eine Erweiterung des CD-Edition des 'Science Citation Index' und des 'Social Science Citation Index'

Object

Science Citation Index
Social Sciences Citation Index

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Abstract

Investigates the characteristics of Journal Citation Reports (JCR) through the study of the Science Citation Index (SCI). Other criteria for evaluating a journal are also discussed. The compilation process of SCI data, and the characteristics, applications and limitations of SCI are studied. A detailed description of JCR is provided including: journal ranking listing, citing journal listing, cited journal listing, subject category listing, source data, impact factor, immediacy index, cited half-life and citing half-life. The applications and limitations of JCR are also explored. In addition to the criteria listed in JCR, the size, circulation and influence of journals are also considered significant criteria fir evaluation purposes

Object

Science Citation Index

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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

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Abstract

Journal Citation Reports provides a classification of journals most heavily cited by a given journal and which most heavily cite that journal, but size variation is not taken into account. Pudovkin and Garfield suggest a procedure for meeting this difficulty. The relatedness of journal i to journal j is determined by the number of citations from journal i to journal j in a given year normalized by the product of the papers published in the j journal in that year times the number of references cited in the i journal in that year. A multiplier of ten to the sixth is suggested to bring the values into an easily perceptible range. While citations received depend upon the overall cumulative number of papers published by a journal, the current year is utilized since that data is available in JCR. Citations to current year papers would be quite low in most fields and thus not included. To produce the final index, the maximum of the A citing B value, and the B citing A value is chosen and used to indicate the closeness of the journals. The procedure is illustrated for the journal Genetics.

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Abstract

Analyses 6 indicators of the Science Citation Index Journals Citation Reports over a 19 year period: number of total citations, number of citations to the previous 2 years, number of source items, impact factor, immediacy index and cited half life. Proposes a box plot method to aggregate the values of each indicator so as to obtain at a glance portrayals of the JCR population from 1974 to 1993. This 'rereading' of the JCR, which presents the JCR product differently, makes it possible to shed new light on the large sub population of journals not at the top of the rankings

Issue

1. Description of the JCR journal population based on the number of citations received, number of source items, impact factor, immediacy index and cited half life

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Object

Science citation index
Social sciences citation index
Arts and humanities citation index

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Abstract

This paper examines the probability structure of the 2005 Science Citation Index (SCI) and Social Sciences Citation Index (SSCI) Journal Citation Reports (JCR) by analyzing the Impact Factor distributions of their journals. The distribution of the SCI journals corresponded with a distribution generally modeled by the negative binomial distribution, whereas the SSCI distribution fit the Poisson distribution modeling random, rare events. Both Impact Factor distributions were positively skewed - the SCI much more so than the SSCI - indicating excess variance. One of the causes of this excess variance was that the journals highest in the Impact Factor in both JCRs tended to class in subject categories well funded by the National Institutes of Health. The main reason for the SCI Impact Factor distribution being more skewed than the SSCI one was that review journals defining disciplinary paradigms play a much more important role in the sciences than in the social sciences.

Object

Science Citation Index
Social Sciences Citation Index

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Abstract

Ein überfordertes Gutachter-System, knapper fließende Forschungsgelder sowie die starke Faszination von Ranglisten bewirken zunehmend den Einsatz bibliometrischer Methoden zur Messung von Forschungsqualität. Grundlage der meisten Bewertungen ist der Science Citation Index, der nun auch in der Version als Online-Datenbank für umfangreiche Analysen genutzt werden kann. Erweiterungen der Retrievalsprache beim Host STN International ermöglichen statistische Analysen, die bisher nur dem SCI-Hersteller und wenigen Spezialisten vorbehalten waren. Voraussetzung für eine sinnvolle Anwendung sind vor allem die Wahl geeigneter Selektionskriterien sowie die sorgfältige Interpretation der Ergebnisse im Rahmen der Grenzen dieser Methoden

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Abstract

The journal impact factors, published by the Institute for Scientific Information (ISI; Philadelphia, PA), are widely known and are used to evaluate overall journal quality and the quality of the papers published therein. However, when making comparisons between subject fields, the work of individual scientists and their research institutions as reflected in their articles' ISI impact factors can become meaningless. This inequality will remain as long as ISI impact factors are employed as an instrument to assess the quality of international research. Here we propose a new mathematical index entitled Impact Factor PointAverage (IFPA) for assessment of the quality of individual research work in different subject fields. The index is established based an a normalization of differences in impact factors, rankings, and number of journal titles in different subject fields. The proposed index is simple and enables the ISI impact factors to be used with equality, especially when evaluating the quality of research work in different subject fields.

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Abstract

We investigated how citations from documents labeled by the Institute for Scientific Information (ISI) as "editorial material" contribute to the impact factor of academic journals in which they were published. Our analysis is based on records corresponding to the documents classified by the ISI as editorial material published in journals covered by the Social Sciences Citation Index between 1999 and 2003 (50,273 records corresponding to editorial material published in 2,374 journals). The results appear to rule out widespread manipulation of the impact factor by academic journals publishing large amounts of editorial material with many citations to the journal itself as a strategy to increase the impact factor.

Object

Social Sciences Citation Index

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Object

Science citation index

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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

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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.

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Abstract

To test feasibility of cybermetric indicators for describing and ranking university activities as shown in their Web sites, a large set of 9,330 institutions worldwide was compiled and analyzed. Using search engines' advanced features, size (number of pages), visibility (number of external inlinks), and number of rich files (pdf, ps, doc, ppt, and As formats) were obtained for each of the institutional domains of the universities. We found a statistically significant correlation between a Web ranking built on a combination of Webometric data and other university rankings based on bibliometric and other indicators. Results show that cybermetric measures could be useful for reflecting the contribution of technologically oriented institutions, increasing the visibility of developing countries, and improving the rankings based on Science Citation Index (SCI) data with known biases.

Object

Science Citation Index

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Abstract

Seeks to describe the social networks, or invisible colleges, that make up a scientific speciality, in terms of mathematically precise sets generated by document citations and accessible through the Social Science Citation Index. The document and author sets that encompass a scientific specialty are the basis for some interdependent citation matrices. The method of construction of these sets and matrices is illustrated through an application to the literature on invisible colleges