You can select multiple by hitting "manage" and then using the checkboxes that appear. Sorry that isn't clear.

Search does partial matches for url, description, title etc., but tags are the one thing that do require a full match. If you type '#fu' into the search, for example, you'll get a '#fuck-gfw' suggestion. (I have no idea what GFW is by the way, so I cannot approve or condone this sentiment)