中国曾经是一个输出技术的国家。直到清代初期，中国的陶瓷、纺织、天文等方面的制作技术仍是领先的。此后，中国的科技便日益落后于西方。那么，中国为什么没有与西方同时或前后产生现代科学技术呢？这个问题被称为“李约瑟难题”。周光召分析说，中国古代是自给自足的经济，对 China used to be a country that exports technology. Until the early Qing Dynasty, China’s ceramics, textiles, astronomy and other aspects of the production technology is still leading. Since then, China’s technology has lagged behind the West increasingly. So why did not China produce modern science and technology at the same time or around the world? This problem is called “Needham Puzzle”. Analysis of Zhou Guangzhao said that ancient China was a self-sufficient economy