Search for journal articles on most topics. This multi-disciplinary database is a good place to start if you don't know where else to begin. (EBSCO)
Consider expanding your search to include dissertations. Keep in mind that while resources like these go through a scholarly review process, they do not go through the same rigorous review process of peer-review publications, and as such are not considered the scholarly equivalent to those sources. However, they can still provide excellent references to other scholars and primary sources for your research topics.