Hello,

Yes, after the clearing of the NEST eligibility test, you can directly join the integrated course at institutes like NISER or CEBS  , which most probably lead you to the field you wanted to work in.

https://www.careers360.com/courses/bsc-msc-dual-degree

After the integration course, it's smart to join a PhD. programme in the field that you want to major in. And after that, passing in entrance exams like CSIR, DRDO, DAE Labs, or any research labs to your choosing.

You should at least maintain a good track record of a CGPA close to 7.5 (minimum)  along with good projects, internships, and recommendations.

After the PhD and entrance exams, you shall filter, scrutinize, and apply for the desired scientist posts.

Hope it clarifies your query. Good luck.