Sci retrieval certificate needs to be issued by domestic authorities. Sci papers can be issued in two places. If it is a medical major, the medical information office and the science and technology information office, the hospital staff need to go to the medical information office to issue it. If it is a school, you need to go to the science and technology information office or the library. SCI (Extended Information Citation Index) is a world-famous periodical literature retrieval tool published in institute for scientific information, USA. Its publishing forms include printed periodicals, CDs and online databases, and now a network-based database has been published on the Internet. SCI contains about 3,500 core journals published all over the world in the fields of mathematics, science, chemistry, agriculture, forestry, medicine, life sciences, astronomy, geography, environment, materials and engineering technology.