Journal metrics are scores used to rank journals. Each metric calculates its score differently. Some of the journal metrics are described below.
The Journal Impact Factor (JIF), or impact factor (IF) metric is "the number of cites in the current year to any items published in the journal during the previous two years" divided by "the number of substantive articles (source items) published during the same two years." 
The Journal Citation Report (JCR) is an annual report of journals' impact factors. There is also a Five-Year Journal Impact Factor available in JCR from 2007 forward.
Find Journal Impact Factors in BU Libraries' Journal Citation Reports database.
Eigenfactor metrics use the data from Journal Citation Reports (JCR), but take five years instead of two years of data for its metrics. It also incorporates disciplinary differences and other factors into its algorithm.
The SCImago Journal Rank Indicator (SJR) is also a weighted metric. It was developed from the GooglePageRank algorithm. 
Scopus is the data source for SJR. SCImago includes detailed rankings for rehabilitation and behavioral sciences.
Find SJR scores on the SCImago Journal and Country Rank website.
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