A search engine that specializes in a particular field is called a "vertical" engine.
Only time will tell if the future belongs to "vertical" or "broad" search. Broad search is exemplified by Google where millions of websites fight for the coveted 10 spots on the first page of results.
If you tired of assembling queries like "pneumonia + eMedicine", go to one of the medical search engines where professional websites are included by default.
The list below shows some vertical search engines focused on medicine:
- OmniMedicalSearch covers even Web 2.0 (whatever that means related to search results)
Notes from Dr. RW recently pointed out to Dermap: a Google Images enhancement for dermatology. Clicking on a body map generates a list differential diagnoses which can be entered into Google image search.
Healthline, Kosmix & MammaHealth - Medical Search in the News. UBC Google Scholar Blog.
Image source: OpenClipart.org.