Until recently, bibliographic services were only available on a fee-for-use basis. Overviews of the available services were previously given by Rey-Watson (1988), Watson (1991), and more recently by Davenhall (1993c,d). The commercial or fee-for-use bibliographic databases available via the network include INSPEC, SPIN, PHYS, STN, and Dialog; ideally your local librarian should be the expert in access to and use of these facilities. A number of bibliographic and other information services are available on the net at no charge, however. Some of these are described below.
Updates & comments:
In the above, STN and DIALOG are not commercial databases but rather are commercial services for accessing databases. As an update, PHYS no longer exists, but has been taken over by INSPEC. If you want other examples to round out the sentence you could use SCISEARCH and AEROSPACE. It might be worth mentioning that STN has an academic discount programme that makes such searching relatively inexpensive.
(Marlene Cummins, U of Toronto Astronomy Library, firstname.lastname@example.org 1995-Jan-5.)