Research Metrics

Source-normalized Impact per Paper (SNIP) is a field normalised assessment of journal impact. SNIP scores are the ratio of a source's average citation count and 'citation potential'. Citation potential is measured as the number of citations that a journal would be expected to receive for its subject field. Essentially, the longer the reference list of a citing publication, the lower the value of a citation originating from that publication. SNIP, therefore, allows for direct comparison between fields of research with different publication and citation practices.

The Scopus database is the source of data used to calculate SNIP scores. SNIP is calculated as the number of citations given in the present year to publications in the past three years divided by the total number of publications in the past three years. A journal with a SNIP of 1.0 has the median (not mean) number of citations for journals in that field.

SNIP only considers peer-reviewed articles, conference papers and reviews. 

• Scopus
• CWTS Journal Indicators provides free access to bibliometric indicators in scientific journals. The indicators have been calculated by Leiden University’s Centre for Science and Technology Studies (CWTS) based on the Scopus bibliographic database produced by Elsevier. Indicators are available for over 20,000 journals indexed in the Scopus database.
  SNIP is developed by Leiden University's Centre for Science & Technology Studies (CWTS).

Scimago Journal Rank (SJR) is a measure of the prestige of scholarly journals. SJR scores are computed using network analysis of citations received by journals. The methodology accounts for the number of citations as well as the source of citations, with citations from high-prestige journals being worth more than those from journals with lower prestige. The prestige value depends on the field, quality and reputation of the source journals the citing article is published in.

By incorporating citation behaviour in different disciplines into account, SJR can be used to make comparisons between journals in different disciplines. The effect of SJR is to flatten differences between fields, i.e. citations in high-cite fields (e.g. neuroscience, pharmacology) are worth less than a citation in low-cite fields (mathematics, humanities).

SJR only considers peer-reviewed articles, reviews and conference papers.

Scimago uses the Scopus database and journal classification scheme to rank journals by quartiles across subject areas. The computation of SJR is an iterative process that distributes prestige values among the journals until a steady-state solution is reached, similar to the methodology used for Google PageRank^TM. The average SJR value for all journals in Scopus is 1.000.

• Scopus
• SCIMago Journal and Country Rank is a publicly available portal that includes the journals and country scientific indicators developed from the information contained in the Scopus database. 
  SCImago is a research group from the Consejo Superior de Investigaciones Científicas (CSIC), University of Granada, Extremadura, Carlos III (Madrid) and Alcalá de Henares, dedicated to information analysis, representation and retrieval by means of visualisation techniques.