After complete diploma eligible for iit / nit jee-2014/15?

I'm chirag from rajkot.i'm in 4th sem mechanical diploma in gtu.& can i join state level clg & university in 2nd year.but my question is am i eligible to be in iit / nit ? if yes whats the procedure ? if yes study in iit which ,when where r the entrance exams. releted to entrance test.