You will need to install a user script manager extension to install this script.
You may also like Fanfiction.net - Customize Default Result Filter.
A little script I hacked together when I got fed up with skipping stuff I was categorically not interested in after sorting broad Fanfiction.net results by faves to make up for the abundance of crud.
You can access the configuration GUI via the "User Script Commands..." section of the Greasemonkey toolbar drop-down.
As a usage example, it defaults to filtering out slash and a few examples of series I have no interest in seeing fanfiction from.
Works well with Fanfiction.net - Customize Default Result Filter to further streamline things.