Reviews and readers expect these databases to be searched in most systematic literature reviews. You'll need a reason not to search them.
Indexes over 18,000 journals in all subjects (coverage back to 1900 for science and social science journals), as well as 80,000 books and more than 180K conference proceedings. Includes the popular "cited reference search" to identify papers which have cited a previously published work or author. Can also sort by "times cited" and find related articles based on commonly cited works.
These databases can be an important complement to your search. They can be essential in their specialized topic areas.
1597-present. From the American Psychological Association. Provides access to scholarly literature in the psychological, social, behavioral, and health sciences. Includes journal articles, books, chapters, and dissertations. Includes approximately 2,500 journals. Updated weekly and includes an index of PsycArticles.
Truly unbiased searches look for unpublished literature in a number of places, included meeting abstracts, white papers, clinical trial registries, and searching by hand.