Apple took a step away from Google when it launched iOS 7, choosing instead to have Siri search results come from Bing, the Microsoft search service.
When you ask Siri to search for a topic, she’ll just use Bing, and place the results on the Siri screen. This is fine, if you like Bing.
If you want to search, say, Google or Wikipedia, you’ll need to specify.
Engage Siri with a click and hold on the Home button, and then speak your search term. This time, however, say “Search Google for (search term)” or “Search Wikipedia for (search term).”
If you choose Wikipedia, the results will show up in a nice Siri screen. If, however, you search using Siri and Google, you’ll go to Safari. If you engage Siri from the Lock Screen, that means you’ll have to unlock your iPhone or iPad to do so.
Of course, you can also search Twitter with Siri as well..