The Mote in God's Eye by Larry Niven and Jerry Pournelle.  It has two Navy starships discovering an alien civilization.  From Amazon's review 
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		| In the Mote the humans find an ancient civilization--at least one million years old--that has always been bottled up in their cloistered solar system for lack of a star drive. The Moties are welcoming and kind, yet rather evasive about certain aspects of their society. It seems the Moties have a dark problem, one they've been unable to solve in over a million years. | 
	
   This isn't perhaps quite what you were looking for, but it is very good.