The basic indicators for bibliometric analyses are the number of publications as well as the number of citations, from which the citation rate can be determined. The citation rate gives the average number of citations of the article. However, practices regarding publications and citations differ in the various fields, and a direct comparison of the numerical values within a certain special field is not always possible, as it depends on the database used. More extensive analyses would require standardization based on clearly defined criteria.
Depending on the enquiry, journal or author-based measures can be identified.
The Journal Impact Factor is a measure reflecting the average number of citations for a particular article. It is calculated from the number of citations of articles in a magazine in a certain year relative to the number of citations in the two previous years. The value is influenced by many variables. These include differing citation practices in the various fields on the one hand, and journal-related factors such as type of article, journal format, title changes, “cited only journals” or restrictions of citations by the editor of the journal on the other. Since 1999, an additional 5-year-factor can be determined.
The h-Index, also called Hirsch-factor, is named after the developer Jorge E. Hirsch. The h corresponds to a number of publications of an author with h or more citations. This is based on a list of publications of an author, sorted by the number of citations in descending order. Advantages are the fact that the high number of citations of individual publications is not taken into account, and the reduced effect of the so-called Matthew effect. However, the h-index depends upon the number of publications of the author, meaning that this method has advantages for experienced scientists.
Originally developed as a factor for comparing authors and as an alternative to journal-based impact factor, an h-index can also be determined for other categories, such as journals or specific topics.
If you would like to use these and other measures, such as the Immediacy Index, Cited and Citing Half-Life, the Eigenfactor score, Article Influence score or SCImago Journal Rank (SJR) for your research, we’d be happy to assist you.