This is a full-text search. If you're looking for a specific fic, the more words you remember, the likelier you are to find it.

This search may not be much help on subject matter, but it does include all the fics in the Library. The first version of the Library search is available here. That search was abandoned some time ago and has not been updated since, but it's keyword rather than full-text and may help you get what you want.