Research Guides

Research Metrics

Terms and definitions

Citation Index is a bibliographic tool in print or electronic format that lists all referenced or cited source items published over a given time. The tool that tracks the historical development of an idea covered by a selection of journal titles. Citation indexes include all the references (footnotes or bibliographies) published with each article indexed. Also see the essay: The Concept of Citation Indexing: A Unique and Innovative Tool for Navigating the Research Literature.

Eigenfactor Score measures the frequency articles from the journal published in the past five years have been cited in the JCR year. Like the Impact Factor, the Eigenfactor Score is essentially a ratio of number of citations to total number of articles. However, unlike the Impact Factor, the Eigenfactor Score

  • Counts citations to journals in both the sciences and social sciences
  • Eliminates self-citations. Every reference from one article in a journal to another article from the same journal is discounted
  • Weights each reference according to a stochastic measure of the amount of time researchers spend reading the journal

Immediacy Indexes refer to the average frequency articles are cited in the year of publication. It is calculated by dividing the number of citations to articles published in a given year by the number of articles published in that year.

  • The Journal Immediacy Index indicates how quickly articles in a journal are cited.
  • The Aggregate Immediacy Index indicates how quickly articles in a subject category are cited.

Journal Cited Half-Life refers to the median age of the articles that were cited in the JCR year. Half of a journal's cited articles were published more recently than the cited half-life. For example, in JCR 2001 the journal Crystal Research and Technology has a cited half-life of 7.0 meaning the articles published in the 7 years between 1995-2001 (inclusive) account for 50% of all citations to articles from that journal in 2001.

Journal Impact Factor measures the importance of a journal with the frequency with which the 'average article' in a journal has been cited in a particular year or period.

Journal Self-Citation is a reference to an article from the same journal.

Definitions from the Glossary of Thomson Scientific Terminology

The "indexes"

h-index: Developed by J.E. Hirsch in his paper An Index to Quantify an Individual's Scientific Research Output, Proceedings of the National Academy of Sciences of the United States of America 102, Vol. 46 (2005), pp.16569-16572, the h-index measures the research impact of an individual scholar.

g-index: Proposed by Leo Egghe in his paper Theory and Practice of the g-index, Scientometrics, Vol. 69, No 1 (2006), pp. 131-152, the g-index weighs highly-cited articles more than the h-index does.