There aren't many and some are frightfully expensive, but here are three good ones. There's a difference between the two that's important for you to know. If your question lends itself to this kind of searching, start with one of these. You should also start with one of these if you just like searching by category, rather than by keyword. So, if your search is most easily done by keywords, this is a good place to start.
Search engines are eccentric about how they index and rank Web pages.
You'll get the best results if you pay attention to the following. Each engine has it's own rules for searching. Follow them and your searches will be more effective. There is not best search engine, there are only the ones that you like to use and the ones you don't. Generally speaking, using more keywords will narrow your search and using fewer will broaden it.