The following techniques can be used in most search engines to narrow, broaden or eliminate results.
Boolean logic can be used in search engines to narrow or broaden search results, using the words AND, OR and NOT
If you don't know the specific title or author of an item, or if you are searching for literature on a topic, you will probably rely on keyword or subject searches.
Keyword searches use natural language, similar to Google. Using the keyword search will look for you search terms in multiple fields, including title, author name, abstract or summary, and full-text.
Subject searches, use controlled language and only return results in which the term being used appears in the subject field. Databases have different interfaces and use different terms, but most will provide these two options for searching.