Yes, it is possible to pursue M.Tech. after BSc. You have to write GATE (acronym for Gradute Aptitude Test in Engineering). Based on your bachelors subject you can opt for the subject you want to write the GATE exam and pursue MTech. You have to be very clear about the basic concepts and the tricks of that subject. Better if you take some coaching, in that way you will be familiar with the depth of content you have to cover as Bsc is very rigorous in its approach.