Research on economy and environment problems of Northern Area in the Ming and Qing Dynasties 并列题名：Research on economy and environment problems of Northern Area in the Ming and Qing Dynasties Research on development and environmental problems of polders in the lower reaches of Yangtze River in Tang and Song Dynasties Research on mining industry in Central China during Ming and Qing dynasties Research on export porcelain in Ming and Qing dynasties Research on scholars' making a living in south of the Yangtze River in Ming and Qing dynasties Study of ecological environment during the Qin and Han dynasties