Where am I not (only) looking? - General search engines

Are Google, Yahoo, DuckDuckGo and Co. suitable for efficient scientific research?

Clearly: No.

You may have already been annoyed by the fact that a query to Google delivers huge numbers of hits that you can't keep track of.

And you're not always sure how relevant, reliable or serious these results are. Web search engines are quite practical when searching for certain facts or trivia and for brainstorming but their use is too inefficient for comprehensive, information-oriented research.

One reason for the insecure search with general search engines is that they do not (or cannot) capture all content on the web. Thus, these search engines do not search the contents of specialized databases that are "hidden" behind search forms or passwords. Or they cannot search all file formats (e.g. Flash).

You have probably heard the term Deep Web for this "hidden content" of the web before. General search engines search only the Visible or Surface Web .