You have many choices for ontology or annotation browsers, including AmiGO, QuickGO, OLS Ontology Search, etc.
When using the GO’s powerful browser AmiGO, boolean operators, wildcards and fuzzy searches are supported. However, the easiest way to narrow your results is just to adding a space after your search! Here’s a search for adenosine
And a similar search, this time for adenosine 
see that extra space?
You can also do more advanced searches, like add and subtract different ontology closures from each other, etc. Here’s a relatively simple search for food and behavior
Now food and behavior see that space
Compare to food and -behavior
Try it on your next AmiGO search and see how what a difference a space (or other search modification) makes!