The National Library does not charge for downloading papers. This is the National Digital Library of China, which supports free online electronic media reading and provides various materials and documents. It is the leader of China Library, where you can find some special documents and periodicals. Here is dedicated to the open sharing, introduction and recommendation of precious rare books of ancient books. It provides an online platform for the publication of scientific research papers and the rapid exchange of innovative ideas. Collect all kinds of scientific papers, and check and download them if necessary.