ahmetayan They must be registered to see links. Is there extension fot this?
I suppose you would have to write an extension or hire someone to do it for you.
But what I know for sure: Such tactics regularly keep me from getting involved with a community. I leave it immediately and will never know that some content might persuade me to join.
So my advice is: Don't let your community look less attractive to visitors when you are looking for new users to register.