A B737 STAB trim would only trim nose down after takeoff. The STAB Trim Inoperative checklist did not appear to apply. The crew flew with manual trim; declared an emergency and returned to land. Full trim became available on final when configured for landing.

Narrative

After departure (gear/flaps up); I noticed that the airplane would not trim nose-up with electric trim. Captain's trim wheel gave the same result. Nose down trim worked fine. We made the decision to level at 9;000 FT and return. Captain consulted the Quick Reference Handbook; and decided to reference the STAB Trim Inoperative checklist; although it did not exactly match our condition. (During my initial transition training on the B737; I was taught that 'STAB Trim Inoperative' was the equivalent of 'Jammed STAB.') We elected not to use the STAB trim cutout switches; since part of the system was working; and would be useful in the event of a go around. We declared an emergency and were vectored for an ILS. The Captain decided he wanted to fly the approach; so I transferred control to him; set up for the approach and did the approach brief. We originally set up for a flaps 15 degree landing. Descending through about 3;300 FT; the Captain noticed that he once again had full use of electric trim. He elected at that point to perform a normal flaps 30 degree landing; so we re-bugged; and landed at flaps 30 degrees without further problems. As mentioned before; I was trained to use the STAB Trim Inoperative checklist for a jammed STAB. The condition statement 'The STAB fails to respond to electric trim inputs' is somewhat ambiguous. Does that mean 'will not respond to any input;' or 'will not respond to some inputs'? Perhaps the condition statement could be changed to include or differentiate between partial or complete failures.