Can a physically disabled person serve in the Navy, Marines, or Army?

If they were already serving when they became disabled and can use prosthetics assistance to perform their duties they can stay in the military.

No. it doesn't fit the physical requirements.

If they get disabled in the course of the job, then it depends upon the degree of disability and the job they are doing.Being a soldier without legs they are not gonna send you back to battle filed.
I've an engineer friend who does all the technical stuff.He was badly hurt in an unfortunate accident while he was based at Afghanistan.As his job includes the technical part and not much of field work, he's doing it okay in army.

Well in the case of the Marine I don't think so because every Marine must go threw basic to get the EGA. I don't know for sure and I just realized this is from 2006.

There may be specific tasks you can do - they all have office work as well as more physically demanding tasks. Whether you'll be accepted is a different matter.

if they were diasbled before enlisting, the only jobs that MAY be open would be through civilian contracters.

if diasbled after enlisting maybe but there is lot of paper work and review boards to stay in. If the disabled salior , airmen, make it thorugh all that it may lead up to a desk job or a non combat duty.. it all depends on the indivdual cases since each one is differ.