How to search categorywise in the web? are there any categorysearch search engines

Question

Example: I want to search results only from the research papers or I want to search results only from opensource tools/packages/codes Kindly help me

Answer 1

Google provides these as separate search features:

• http://www.google.com/codesearch
• http://scholar.google.com

An alternative Code search engine is Koders.

Other sources are book search and personal search engines.

Answer 2

For research, in some cases other than code, Wolfram Alpha is also very useful:

• http://www.wolframalpha.com/