MOTM

Ok, off topic question about schematics and Op Amps.  

I have seen a lot of schematics that involve Op Amps, yes they seem to 
make the world go 'round.  I am no expert on schematics. but one thing 
is troubling me.

I see these lovely OpAmps connected with the + input, - input and the 
output.  Many times I don't see any other connections.  Now I am 
pretty sure that these things take V+ and V- (to the chip) to make 
them run, but they don't show on the schematics.  

Are these connections just assumed?  Or are there real ways to use 
OpAmps with just the 2 inputs and the output with no power applied? 

Thanks in advance for the answers.

Bruce