MedNar is a type of search engine that searches selected collections of material such as PubMed, Google Scholar, Mayo Clinic, the Patent Office, and various government health centers. To the left of your results you will find clusters of useful information such as the most frequent subtopics, authors, publications, and publishers. This can be useful in understanding a topic.
Since the underlying collections are often updated, the result count may vary if the search is repeated. MedNar presents initial results quickly, then adjusts the final count as more data arrives from the slower sources.
You can click citations to add to "My Selections" and then view, email, and save them for use in a citation manager such as EndNote.
This company has similar search engines for science and for business, both of which use similar strategies for locating material perhaps hidden in the "deep web" or "grey literature."