Subscriptions is a new service from Yahoo. Currently at a beta stage is allows users to search fee-based content. Since you would normally subscribe to such content regular search engine robots cannot get access to it. Subscriptions allows you to search through documents as if they were regular pages open to all. The idea is you would find a document covering material you would be interesting in researching and willing to pay a fee for.

"Yahoo! Search Subscriptions beta is a new way to search the subscription content that's important to you. By partnering with publishers, Yahoo! is providing the convenience of a single place to access and find all relevant content, whether it's generally available web content or content from your personal subscriptions."

Currently Yahoo Subscription gets it sources from;

• Consumer Reports
• FT.com
• Forrester Research
• IEEE publications
• New England Journal of Medicine
• TheStreet.com
• Wall Street Journal

I imagine there will be many more sources to add to this list shortly.