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Data only available through Journal Citation Reports (JCR) in Web of Science (subscription required). Journal Impact Factors should only be used to compare journals in the same discipline.
Below is the how the 2018 Journal Impact Factor of the New England Journal of Medicine (NEJM) was calculated. An Impact Factor of 71 means that in 2018 on average an article published in 2016 or 2017 in NEJM was cited 71 times.
The Eigenfactor Score of a journal is calculated using Web of Science citation data. It measures how many times on average an article published in a specific journal have been cited in the past five years. It eliminates journal self citations and gives citations from highly ranked journals more weight. The sum of Eigenfactor scores of all journals listed in Journal Citation Report is 100. Eigenfactor Scores are adjusted for differences across disciplines.
A journal's Eigenfactor score can be found in Journal Citation Report (in Web of Science, Subscription required) or at Eigenfactor's website (free).
SJR is calculated with Elsevier's Scopus citation Data. It accounts for the prestige of journals where the citations come from when counting the number of citations received by a journal. It measures weighed average number of citations that an article in a journal received from previous three years. It is adjusted for differences across disciplines.
The h-index was proposed in 2005 by Dr. Jorge E. Hirsch to quantify a researcher's scholarly output. The h-index is defined as: “A scientist has index h if h of his or her Np papers have at least h citations each and the other (Np – h) papers have ≤h citations each.” The graph below marks where the number of citations meets the number of publications.
Enter a researcher's last name and first name initial in Author Index and add corresponding author name(s) in Author search box.
Click on "Create Citation Report" on the up right corner of the search results page and the author's h-index will be calculated automatically.
A researcher's Google Scholar profile needs to be set up.
Many bibliographic databases, such as Web of Science and SciFinder-n, provide citation counts for articles indexed in them. Google Scholar provides citation counts for items in it, and links to citation counts in Web of Science (with a subscription).
Altmetrics are metrics complementary to citation-based metrics. They can include "citations in public policy documents, discussions on research blogs, mainstream media coverage, bookmarks on reference managers like Mendeley, and mentions on social networks."
Databases from EBSCOhost, such as Academic Search Complete, provide PlumX metrics. Many journals and publishers, such as Science and PLOS One, provide article-level altmerics.