Yes.
Ctrl⇧+F on Windows/Linux or ⌘⇧+F on a Mac.
or just go to the menu "Find" and use the option almost at the bottom called "Find in Files".
To search in all open files, add this to the Where textbox:
<open files>
If you want to search in folders and such, please just look at the right of the textbox and see there's a button ...
. Click on it and it will show you options.