Also, you can easily add custom keyword searches under Preferences. For example:

Name: Youtube Keyword: y URL: http://www.youtube.com/results?search_query=%s

Then just type "y civilization v" and shazam, you're on Youtube, looking at a list of trailers and previews for Civilization V.

Firefox has the same feature; I believe it's called "Keyword Search" and can be accessed through Bookmark Manager. I always found Firefox's separate search box redundant for this reason.

ctrl+L gets you to the address bar. "?" + your query forces a default search (so you can do ?http://www.cnn.com and it will actually search for cnn.com, not take you to the site). If you add keywords, then you just ctrl+l then type, say "php in_array" and your query gets submitted directly to php.net's search engine (if you've pre-programmed it). This is actually very much like Firefox's implementation.

I really hate to not search directly on the service that I need, such as gamefaqs, jstor or arxiv

You don't need a search bar in chrome, just type the address of the site you want to search with and hit TAB. Example:

youtu+TAB and then enter your keyword. Works with every site that support opensearch. en.wiki+TAB will search wikipedia etc.