Selecting search engines

Web-based searching for research evidence

When we discuss finding the evidence or systematic searching we generally mean the use of bibliographic databases such as Medline. However, increasingly the Web is being used to assist these processes. It is therefore important to understand how the Web is constructed and how different search engines work.

Web searches use indexes of pages created automatically by crawler spiders or directories of websites that have been submitted and reviewed by editors. Search engine software compares the query with the information retained in the indexes or directories and ranks them in the order it calculates to be most relevant. These results are what the user sees in response to entering a search request.

Choosing a search engine

There are many different search engines available. They differ in terms of their features, the parts of the Web included in their index or directories and the way in which they present their results.

The following sources list different search engines and provide useful information on their features and how to get the best out of them:

• University of Berkeley: Recommended Search Engines Table of Features

Subject gateways

Subject gateways are lists of websites and online resources identified by specialists in a field on the basis of their quality and relevance. Online resources relevant to palliative care have been included in the CareSearch page Databases and Resources.

An example of a subject gateway:

• The WWW Virtual Library