Let's say you had found a citation for an article in the journal Popular Science (July 2002). Popular Science is only full-text in General Reference Center Gold from November, 2002 onward. (You can find this out by searching for your periodical in the Oakland County School's Access Michigan Periodical List).
Let's see if we can find the magazine at your library. In the eLibrary catalog search box, enter popular science. Click on words or phrase and then click on periodical title in the drop down menu. Then click on the Search button.