I've noticed that lots of students come in asking for help with MLA citation and that they usually need help citing articles found in a database. It's important to note that there is a difference between the way you format a citation for an article in a periodical in print or on the web. Here are two helpful resources you can use to figure out what information to include and how to arrange that information in the entry:
1. The Everyday Writer online supplement has copies of the source maps available in the book on pages 394-395. In my opinion, the 4 source maps available in the MLA section are some of the best and most helpful material in the whole book. Here is the link to the source map for citing an article found in a database.
2. The Purdue Online Writing Lab has a page explaining how to cite electronic sources. You'll want to read the top of the page down through the end of the section on "Basic Style for Citations of Electronic Sources (including Online Databases)" and then check out the entry below called "An Article from an Online Database (or Other Electronic Subscription Service)" at this link.