Databases are subject-focussed collections of searchable references. They bring together the entries of carefully selected academic journals and provide a platform that allows you to search all of those entries simultaneously. Databases themselves rarely contain the full-text of an item, but UCL's comprehensive journal subscriptions mean you will often have the option to read the full text anyway.
Did you know you can download the British National Formulary (BNF) as an app on your phone within the UK? Doing so allows you to access and use this key resource wherever you go.
Simply go to the Apple App Store or Google Play Store (Android users) and search BNF.