Citation Databases

ISI Web of Science

• ca 12000 journals 
• 150 000 proceedings
• 1975- (counts citations from 1945-)
• Updated weekly
• Very good coverage of science and medicine. Good coverage of engineering science, mathematics and business. Poor coverage of other social sciences and arts and humanities. 

Scopus

• ca 19400 journals (including 1900 Open Access-journals)
• 360 book series
• 5.3 million conference proceedings 
  What journals/series are included?
• 1966-
• Counts citations from 1996-
• Updated daily
• Very good coverage of science and medicine. Better coverage than ISI Web of Science for social sciences, business and computer science.

Google Scholar

• Started 2004
• Coverage?
• All subjects
• Updates?
• Many document types:
  Journals, conference proceedings, books, theses, reports, preprints
  Also some non science material
• Better coverage of non-english language material than Web of Science and Scopus
• Most useful for business, engineering science, computer science, mathematics, social sciences and arts and humanities.
• Analytical tool: Publish or Perish

Further reading

Harzing, A-W, van der Wal, R (2007) Google Scholar: The democratization of citation analysis. Accepted for: Ethics in Science and Environmental Politics.

Meho, LI, Yang, Kiduk (2007) Impact of data sources on citation counts and rankings of LIS faculty: Web of Science versus Scopus and Google Scholar. Journal of the American Society for Information Science and Technology. 58(13):2105-2125.