web keyword search within several domains?

Can anyone advise how I can use Google "site" operator for searching within more than one url? e.g. in several different domains?
Say I have a list of websites in which i’de like to find in all of them specific keyword/s.
Example: find in sites oracle.com, microsoft.com the phrase: "CRM specialist".
If to expand this requirement maybe some file that I can enter list of domains and mark the relevant domains that will participate in the relevant keyword search.
Any idea will be highly appreciated