Searching press release sites: plug in or just copy the URL

I want to create a search set for searching the archives of Websites containing press realeses from universities and reseach organisations like EurekAlert, AlphaGalileo (the european pendant) and idw the (german pendant).

I´m a totally DA-newbie. My question. Do I have to program a plug in for every site, or can I copy a URL in the Search Sets table (but which one)?

My aim: I want to use DA to search phrases in all three sites with one search (not just the recent press releases but the whole archive).

What I have to do?

As long as the sites don’t provide one (or more) comprehensive link pages pointing to (almost) all interesting articles/press releases, you have to do a plugin for all of them.