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Metrics definitions


Metric Definition
Impact factor The average number of citations in a given year per paper published in the journal over the previous 2 years. Different subject areas exhibit different ranges of IF. Journals are best viewed in the context of their specific field.
5-year impact factor Offers a smoother variation and may be more appropriate in a field where the number of citations is small or where it takes longer than 2 years to disseminate and respond to published works.
Eigenfactor score A measure of the journal’s influence within the network of academic citations with a 5- year target window based on Thomson ISI data. Considers the origins of the incoming journal citations to articles in that journal. Citations from highly ranked journals are weighted to make a larger contribution to the Eigenfactor score
Article influence score As for the Eigenfactor score, measures influence but on an average per-article basis. The mean Article Influence score is 1.00. A score greater than 1.00 indicates that the articles in a journal have an above average influence.
h-index Intended to measure both the quality and quantity of scientific output. The measure discounts the disproportionate weight of highly cited papers or papers that have not yet been cited. The h-index only ever increases, never decreases and older articles do better than younger articles.
SJR indicator As for the Eigenfactor score, ranks journals by their 'average prestige per article'. Based on the SCOPUS database.
Cited half-life A measure of how long content is referred to after publication. The number of years, going back from the current year, that account for half the total citations received by the journal in the current year.
Immediacy index The average number of times that an article is cited in the same year it is published.
2-year median The median number of citations received in a given year per paper published in the journal over the previous 2 years. Data from Web of Science was used for this calculation.


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