The JCR provides quantitative tools for ranking, evaluating, categorizing, and comparing journals. The impact factor is one of these; it is a measure of the frequency with which the "average article" in a journal has been cited in a particular year or period. [Garfield, 2005] Journal impact factor applies only to a journal or groups of journals, but not to individual articles or individual researchers.
The impact factor of a journal in a particular year is the number of citations received in the current year to articles published in the two preceding years divided by the number of articles published in the same two years. For example, Pediatrics has a 2006 impact factor of 5.012, which means that on average each of its 2004 and 2005 articles was cited 5.012 times in 2006.
Note that Eigenfactor Metrics (Eigenfactor score and Article Influence score) are available in JCR for the years 2007 and later.
How to find the Journal Impact Factor by individual journal title or by subject groupings:
Individual Journal Title:
In results table click individual journal title for complete information (e.g., explanations of impact factor, immediacy index, citing and cited half-life)
For more details see:
Eigenfactor ranks and maps scientific knowledge:
How to find the Eigenfactor:
Note: advanced search (searches by Thomson JCR subject categories, publisher, and other fields) is also available.
SCImago Journal & Country Rank (SJR) is free source that includes the journals and country scientific indicators developed from Elsevier's Scopus database. It ranks journals and compares journal citation among countries. Journals are assigned to major thematic categories as well as to specific subject categories according to Scopus Classification.
How to find journal rankings in SJR: