Most bibliometric studies are based on data covering only international scientific journals indexed in the most widely used commercial citation index databases:
- Web of Science (Clarivate Analytics)
- Scopus (Elsevier).
The databases, however, might give a limited picture on publishing activities in academic disciplines since they largely exclude books, national publications and non-scholarly publications, which are important especially in social sciences and humanities.
Besides the multidisciplinary WoS and Scopus, several specialist databases, such as PubMed (medicine and the biomedical sciences), Chemical Abstracts, Mathematical Reviews, the ACM Digital Library (computer sciences) and CiteSeer (computer and information sciences), are available online, and most of them provide free access to bibliometric data in their particular field.
The most common databases, also other than Web of Science and Scopus, used for bibliometrics are presented in the following sections.