This database indexes scholarly journals and a few book chapters and conference proceedings across academic disciplines. Its most important feature is the ability to get information based on citation data: who is citing whom, what are the most-cited articles and authors, and where do their authors work. For articles beginning in 2008, you can also search by grant/sponsoring agency.
Date Coverage: Varies by collection
Maximum Users: Unlimited
Another good, cross-disciplinary database, but without as much citation data as Web of Science or Scopus
Contains 4,600 journals, including full text for nearly 3,900 peer-reviewed titles. PDF backfiles are available for well over one hundred journals, and searchable cited references are provided for more than 1,000 titles.
Date Coverage:Varies; primarily 1970s-present with some titles covering earlier dates
A database produced by the U.S. National Agricultural Library that provides access to worldwide periodical literature and USDA publications. Subject coverage includes plant and animal sciences, food and nutrition, agriculture, biotechnology, entomology, forestry, and wildlife.
Large free database of articles across the social sciences
Google Scholar may also be useful for your research. The advantage is that it is extremely broad and interdisciplinary. The disadvantage is that the results can be chaotic and hard to control. Think of Google Scholar not as a replacement for but rather a complement to the libraries databases.