You can do this with browser search engines, but as a DuckDuckGo user, I can !bang search_term (`!gh`, `!github` to search in github.) Now, I think DuckDuckGo is very lacking in terms of Zero-click searching, but if I know where to get information I can !bang to it (e.g., `!hn what`) or if you're feeling luck `\hn what` will open the first search result. Much better than spending an afternoon setting up search engines.