Most browsers allow search to default search engine in address bar, but what if you want a different engine? You can switch on the right box, choose one and then start the search.

That’s suck!

So you can try this:

• click the little arrow in the search engine box to open the drop down menu.
  
• select Manage Search Engines…
  
• select an engine and then click on Edit Keyword…
• add the keyword you prefer and then click OK

From now on, if you want make a search with the engine in the URL bar, construct your research like:
keyword query
Examples:
wiki power law distribution
answer AAPL growth
twitter Barack Obama

NOTE: if your keyword doesn’t work and your query is answered by the default search engine, try to change it! I have noticed that if you use the name of the service (e.g., Wikipedia, Yhaoo) most of the time the keyword doesn’t work. 😦