Scopus - Journal Metrics"citation impact ... based on ... Scopus as the data source ... free of charge."
....Source Normalized Impact per Paper (SNIP)
........weighting citations based on the total number of citations in a subject field.
.....Impact per Publication (IPP)
..........Similar to JCR but with a 3 year window and only scholarly papers.
.....SCImago Journal Rank (SJR)
..........the subject field, quality and reputation ... [determine] the value of a citation.