西藏地处祖国西南边陲的青藏高原,海拔高,空气稀薄,气压低,含氧量少,日光辐射强,日照时间长,昼夜温差大[1],素有“世界屋脊”及“地球第三极”之称。近年来,藏族人民生活水平不断提高,特别是改革开放以来,在党和政府及全国人民的大力支持下,藏族居民物质生活水平有了很大的提高 Tibet is located in the Tibetan Plateau on the southwestern border of the motherland with high altitude, thin air, low pressure, low oxygen content, strong solar radiation, long sunshine duration and large temperature difference between day and night [1], known as “roof of the world” and “the third Very ”. In recent years, the living standards of the Tibetan people have been continuously improved. Since the reform and opening up, in particular, the material living standards of the Tibetan residents have greatly improved with the vigorous support of the party, the government and the people throughout the country