Hi, 

For being eligible for aiims exam you need to qualify your cbse 12th boards i.e you should have an aggregate of 60% in physics, chemistry, biology and english.(along with practicals)

But AIIMS as such is an Online based test where the questions are of mcq pattern and dres no practical exam involved. 

So only practical which ll play a role are your class 12th practical marks in boards inorder to make u eligible to sit for the aiims exam.

All the best.