These databases have a high concentration of journals and articles about history. Much of their content is scholarly. They are excellent places to begin looking for secondary sources about a topic - articles and commentaries written by scholars and other writers in retrospect years, decades, or event centuries after the events they describe. To find primary sources, try the databases and resources listed on the Primary Sources page.
These databases are more general - that is, each covers multiple subjects - but do include some content relevant to the study of history. Most will help you discover scholarly journal articles on your topic, although Dissertations & Theses contains academic writing created by doctoral and master's candidates as a requirement of completing their degrees, and Academic Search Premier mixes academic content with articles from magazines and trade publications.