The Chinese bought bits and bobs of aircraft from all over the world, often enough civilian transports that the manufacturer promised could be used as bombers. I remember reading in the Foreign Relations of the United States about the State Department's efforts to block the shipment of twenty-odd Bellancas in 1938 or 1939--probably did a favor to the Chinese!
There were a few Heinkels in CAF service at the outbreak of war in August 1937, but the most successful imports were those assembled locally, including Italian planes (not many left by August 1937) and American, notably Curtiss Hawk II and III biplanes.
Blue skies! -- Dan Ford
Coming August 21:
Flying Tigers: Claire Chennault and His American Volunteers, 1941-1942