How would it be possible to redirect you power needs in case of an emergency.?

I understand all the wiring goes directly to the power box which in turn goes to the power lines. If you were to be self sufficient in case of an emergency, would it be possible to divert and directly use you own power source ie a generator; similar to hospitals.

Sometimes when you use generators you have to bring either the appliance to the generator or vice versa. Instead of getting all the rooms and electrical wiring connected together to then automatically plug into a generator. So you the home and the people living in it can still go about there business without be affected to greatly.

The question is, is this possible.