You can download NCBI studies from NIH?

Yes! You can download NCBI studies via FTP! Here's the link. You use software called "client software" or "FTP client software" installed on your PC to access the NCBI FTP site and download files. Be careful how you configure your FTP client. First read the file README.ftp to learn how to optimize your FTP client software.

There seems to be a variety of data here, not just journal articles. Poke around in different directories to see what is there, and in each directory try to read a file called "readme" or "README" or "readme.txt" or "00readme.txt".

Common free FTP clients:

1. FileZilla 64-bit. I like this one the best.
2. Smart FTP.
3. WinSCP. 
4. There are several command line utilities for Linux like "ftp" and "ncftp".  
5. The link above is for browsers so modern browsers can download studies too.