The Study Database Search function found on the left-hand side of the Studies menu, is a search bar that allows you to enter a numerical or text value so that all of the studies containing your query in any of their columns will be displayed. You can even enter several words, in which case studies which do not contain both words will be filtered out. If you put quotation marks around your terms, Studylog will look for only the terms you have specified in their entirety.
To narrow your search further, the [Add Field] function allows you to add a field containing a term that you have specified in the Value column for that field. You can even add multiple fields for maximum specificity.