Martinez finished with 307 passing yards. Bell hauled down nine passes overall for 135 yards.
Ameer Abdullah compiled 80 yards on 18 carries for the Cornhuskers (9-3, 6-1 Big Ten), who are in the driver's seat for the Big Ten's Legends Division crown.
Nebraska can claim the division title with a victory in next week's season finale against Iowa or a loss by Michigan to undefeated Ohio State.
The Golden Gophers (6-4, 2-5) stumbled as Philip Nelson was held to just eight completion on 23 pass attempts for 60 yards and two interceptions.