Scholarly journals have articles written by professors for professors. The articles have citations and footnotes.
General databases like Discover@MU and Academic Search Premier have a check box you can select to limit your search to scholarly journals.
Subject databases (databases devoted to one subject or area) usually contain only scholarly articles.
If you want more ways to identify scholarly journals, the video from Vanderbilt University (the link is on the left) is a very good three minute explanation.