Journal Impact Factors are released annually by Thomson Reuters' Journal Citation Reports (KUMC subscription).
A journal's Impact Factor for a particular year = the total number of times its articles were cited during the two previous years divided by the total number of citeable articles in the journal during those two years.
Within a given research field, journals with higher impact factors are thought to be more influential than journals with lower impact factors. The magnitude of impact factors varies substantially across different research fields.,
One journal's impact factor on its own doesn't mean much. Instead, it's important to look at impact factors of multiple journals in the same subject area. This way one can determine if the impact factor of the journal of interest is high or low compared to other journals in the subject area.
How to Find A Journal Impact Factor: Journal Citation Reports Tutorial
A journal's Eigenfactor is a measure of the journal's overall importance to the research community. It considers not just direct citations to a journal's articles but rather the entire network of citations that are linked to that journal's articles.
Like the Impact Factor, the Eigenfactor Score is essentially a ratio of number of citations to total number of articles, but takes into account the source of those citations. Unlike the Impact Factor, the Eigenfactor Score:
The Eigenfactor uses Thomson Reuters (ISI Web of Science) citation data.
The SJR indicator is inspired by Google's PageRank algorithm. A journal's SJR indicator is a measure of the number of citations received by its articles considering the importance of the journals where those citations came from. It is intended to measure journal prestige as opposed to journal popularity. It ranks journals by their average prestige per article.
Calculation of the SJR measure was recently modified; the average SJR is now equal to 1, which means that journals with SJRs higher than 1 are more prestigious than average.
The Source Normalized Impact per Paper (SNIP) indicator, created by Henk Moed, corrects for differences in citation patterns among disciplines. A journal's SNIP = (citation count per paper) / (citation potential within its field).
Calculation of the SNIP measure was recently modified; the average SNIP is now equal to 1, which means that journals with SNIPs higher than 1 are better than average for their discipline.
A journal's Article Influence is a measure of the average influence of its articles over the first five years after publication. The AI measures the relative importance of the journal on a per-article basis. It is the journal's Eigenfactor Score divided by the number of articles published by the journal. The mean Article Influence Score is 1.00.
The Article Influence uses Thomson Reuters (ISI Web of Science) citation data.