There is a range in quality of evidence available in the literature, with systematic reviews being the very highest quality. As you move up the pyramid, the amount of literature decreases but its clinical relevance increases.
When you search a database for a "Full Text" item, you are only searching through that particular database for the document in full-text, and not our entire collection. An item may exist as a "Full Text" selection within a different database.
If you don't find an item as full-text in the database you're searching, use the "Find It" button to cross-search other databses for that same item. You may discover that we have electronic access to that material after all.
For more on finding the full text, see the Finding Full Text of Articles tab.