Not all external search engines allow Boolean searches. A more recent innovation is the metasearch engine . This allows the user to construct a query and submit it to many different search engines at the same time. Often the metasearch engine will reomve duplicate results received from the different search engine sites and will present a coordinated list. This web site is indexed and can be searched by an engine on the server.
Boolean searches are possible and usually produce better results than simple keyword searches.
Also, you can restrict your next search to the resulting list from a previous search. Usually a result of wrong, incorrect, outdated or simply mispelled words in the search. Try using as many synonyms as you can. Try more general words and then look at the resutls with a more restrictive search. Try searching for phrases when the search engines have that feature.