What is the best free scientific search engine (besides GoogleScholar) alternative for Scirus?

Doesn’t seem like there are a lot of choices….this article gives you the low-down on the most popular and this article lists search engines by science search engines, portals, and directories by specialty.

There are no good “free” search engines for science, because it is presumed that if you need one, you have access to it through your institution’s library. Are you affiliated with an institution? If not, your best bet is to go to a university library when you have some time to spend there. Usually, they’ll let you download papers for free on guest terminals.

If you are affiliated with an institution, there’s no reason for you to ask this question here. Contact your subject librarian and they’ll be happy to run you through the options.

Sirus has proved some: http://www.sciencedirect.com/scirus/