Journal Citation Reports is an excellent source for determining journal impact factor. It provides impact factors (over the two years citation period) and rankings for approximately 12,000 scholarly and technical journals and conference proceedings in the areas of science, technology, and the social sciences.
The Journal Impact Factor is a ratio devised as a measurement of the average citedness (and, by extension, importance) of a journal. It is calculated by dividing the number of citations of a particular publication in a certain year by the number of citable articles published in the journal in the previous two years. Other related measurements may also be calculated, such as the Five-year impact factor (which looks at the previous 5 years) and the Immediacy index (which is the average number of times an article is cited in the year it is published).
Like author impact measurements, journal impact measures can be only so informative, and researchers in a discipline will have the best sense of the top journals in their field.
What is the Eigenfactor score?
The Eigenfactor score reflects importance or prestige of a scientific journal. Created to help capture the value of publication output vs. journal quality (i.e. the value of a single publication in a major journal vs. many publications in minor journals). It considers not only the number of times in the last five years articles from a journal have been cited during the JCR year, but also the source of those citations. Citations from highly rated (i.e. impactful) journals make a larger contribution to a journal's Eigenfactor score than citations from lesser journals.
Eigenfactor scores are scaled so that the Eigenfactor scores of all journals listed in Thomson's Journal Citation Reports (JCR) sum to 100. Thus if a journal has an Eigenfactor score of 1.0, it has 1% of the total influence of all indexed publications. In 2013, the journal Nature has the highest Eigenfactor score, with a value of 1.603.
NOTE: Eigernfactor scores are also displayed in Journal Citation Reports.
What is the Normalized Eigenfactor score?
The Normalized Eigenfactor score is scaled so that the average journal has a score of 1. Journals can then be compared and influence measured by their score relative to 1; a journal with a Normalized Eigenfactor Score of 3 has three times the total influence of the average journal in the JCR.
What is the Article Influence Score?
Measures the average influence, per article, of the papers in a journal. Article Influence scores are normalized so that the mean article in the entire Thomson Journal Citation Reports (JCR) database has an article influence of 1.00. For example, in 2006, the top journal by Article Influence score is Annual Reviews of Immunology, with an article influence of 27.5 . This means that the average article in that journal has twenty seven times the influence of the mean article in the JCR.
Advantages of Eigenfactor/Article Influence Score:
Disadvantages of Eigenfactor/Article Influence Score: