Most of our readers who might care already know this, but the National Library in Beijing is a fine place to do research on Republican China. It has it’s own subway stop, which means easy access. The computer system works well (nice search features), getting a card is easy, and the collection is good. Specifically, a lot (all?) of the published journals and reports that used to be in Nanjing are now in Beijing. Many years ago, Nanjing had the Tezangbu (Special Collections Department) which held all the journals and books that used to be in the pre-49 National Library. I spent some time talking to people and looking through the computer, and it seems that the books I read many years ago are still in Nanjing (or somewhere) but pretty much all of the journals and official publications are now in Beijing. This is a big deal, since local and provincial governments loved to publish stuff. If you find a monthly report in a provincial archive there is a good chance that at some point it was published in a monthly report in a nice typeface that does not look like the work of a budding master calligrapher.
They will photocopy stuff for you. Photography is not permitted. I saw some people who were obviously trying to photograph whole books get yelled at. On the other hand, I was in the reading room while some people discretely photographed a few individual articles and nobody noticed or cared.