Journal Impact Factor* and Journal Citescore** are metrics that measure ratios of citations that papers in a given journal have received in one year, to those received in previous years.
A journal's Impact Factor or Citescore is often publicised on its homepage, and there are tools available to benchmark metrics against one another. Free services to lookup Citescore and other journal metrics from the Scopus database are Scopus Journal Metrics and CWTS Journal Indicators. All document types are included in the CiteScore calculation (except in-press items) but it is not field-weighted so it is not appropriate for comparison between different subject areas for which SJR and SNIP values should be used. Journal Impact Factor is not freely available - apart from when advertised on individual homepages - but available via subscription to Journal Citation Reports.
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** Copyright © 2017 Elsevier B.V. All rights reserved