When you can't do any more full reps, you're going to do partial reps in ONLY the top, stronger half of the range of motion. (hardgainermusclebuilding.com)
Check out this video where a traditional drop set is combined with partial reps on the last drop. (fitnessandpower.com)
One of the techniques I like to use in to order get most out of strength training exercises is to combine 1.5 reps with partial reps in the strategic way I discuss below. (nicktumminello.com)