A great deal of really good content on www is contained in databases, so what, you say. Well, most search engines are unable to access these databases in their search process. In other words, this is data you'll never locate unless you know it's out there and you know exactly how to access it.
As I said in above paragraph search e-sources for most part are unable to access information contained in these Web-accessible databases. They are however able to access search e-source or interface associated with these databases, if you know how to search for them that is.
Here is an example (a picture is worth a thousand words they say, or should that be changed in this new millennium to "a screen shot is worth a thousand bits of data")
The trick is to search for specific topic you're interested in with Boolean "and" together with word "database" in your query.
Searched web for medicine.
Have a look at results produced using only word medicine for our search. Results 17,900,000 documents found, but no databases.