Now you can search in Google Scholar and get direct access to some online resources in National Library of China. Here is how to do:

  1. Go to Google Scholar, select search preference
  2. In the section for add library, you search for China
  3. And there is only one result, which is National Library of China.

You are done. I did some try, but cannot trigger result from NL of China. Maybe the resources they provide is not within my field.