The Internet has provided an immense boost to the ability of computers to search databases for information on a myriad of topics. On-line searching enables the perusal of a variety of information sources. The explosive popularity of on-line searching is enhanced by the development of a number of search engines--programs that use a variety of mechanisms to search Internet sites for a requested topic, and then deliver the site to the user's computer.

Databases are often specific to one discipline, such as chemistry, physics, microbiology, or can be more general, including multiple disciplines to address themes such as energy or the environment. If a site has a number of databases and the appropriate tools, simultaneous searches across several databases is possible.

Bibliographic databases provide references to periodical articles and sometimes to other types of literature. Some of these databases provide abstracts, brief summaries, of the articles. Scientific and...