Academic Search Premier is a general coverage database providing full-text access to thousands of scholarly journals across a wide range of disciplines, including history, social science, library science, computer science, language and literature, art, education, and life sciences.
JSTOR is a multi-disciplinary database providing archival access to scholarly journals in the arts, language and literature, history, sciences, and social sciences. Typically, the most recent three to five years of a journal are not available through JSTOR.
DOAJ covers free, full text, quality controlled scientific and scholarly journals. DOAJ contains thousands of open access journals covering all areas of science, technology, medicine, social science and humanities.
Google Scholar searches academic publishers, professional societies, online repositories, universities and other web sites. Be aware that many of the results that Google Scholar returns are not peer-reviewed journal articles. Still, it can be a helpful tool for searching a broad range of sources that go beyond those available in library databases.