You can filter your search in the boxes on the left-hand side of the search page, either by study, subject, or sample. For now, filters with free-text entries require an exact word match. The more general you are, the more chance you have to get search results, for example, results will return for "cancer", but not "breast cancer". For more information on filters, hover over the blue question marks.
You can see your results from a filtered search here.