It can't be downloaded from any website for free, You can purchase it from any book store or online. If you are preparing for NEET Entrance Exam then firstly I would suggest you to complete NCERT books as it will help you to clear your basics then you can prefer other books. The other books you can prefer below given:

Physics

    Concepts of Physics by H. C. Verma

    Objective Physics by DC Pandey

    Fundamentals of Physics by Halliday, Resnick and Walker

    Fundamental Physics by Pradeep

    Problems in General Physics by IE Irodov

    Physical Chemistry by OP Tandon

Chemistry

    ABC of Chemistry for Classes 11 and 12 by Modern

    Concise Inorganic Chemistry by JD Lee

    Dinesh Chemistry Guide

Biology

    Biology Vol 1 and Vol 2 by Trueman

    Objective Biology by Dinesh

    Objective Botany by Ansari

    Pradeep Guide on Biology

 
Good Luck!