The citation data will relate only to articles indexed within the database. Using citation information from multiple databases and comparing the results can offer a better perspective of impact within a field.The three best known citation analysis databases are Web of Science (WoS), Scopus and Google Scholar (GS).

Web of Science by Clarivate Analytics
A citation database of select high profile journals and other scientific publications.
Content overview
Web of Science instructions: how to create citation report with h-index
Web of Science Training videos

Scopus by Elsevier
A citation database of peer-reviewed literature: scientific journals, books and conference proceedings.
Content overview
Scopus Tutorials

Google Scholar by Google
Consists of scholarly articles including journal papers, conference papers, technical reports, theses, pre-prints, post-prints and other publications on the Web.
Google Scholar Content Coverage
Google Scholar Quick Guide / Oulu University Library
  
Tools that draw data from Google Scholar to analyse citations:
Scholarometer is a social tool to facilitate citation analysis and help evaluate the impact of an author's publications. It works as a browser extension for Google Chrome or Mozilla Firefox.
Publish or Perish is a software program that must be installed on your computer. It offers a wide range of statistics, with several types of indexes provided.

Dimensions by Digital Science
Launched in 2018, Dimensions offers an open tool to researchers to check their citations. The database is still being developed.

University of Helsinki

• University of Helsinki Research Portal public research portal
• Research  information system Tuhat for Helsinki university personnel. Read more from the guide.

Finnish Universities

• Vipunen-portal
  The publication reports provide information on the papers published each year by Finnish universities.