Ca is a chemical abstract. Ca periodical is the abbreviation of Chemical Abstracts, the largest database of chemical abstracts in the world, and an important retrieval tool for chemistry, chemical engineering and related disciplines, which is widely used in the world. The report covers all areas of interest to chemists, including inorganic chemistry, organic chemistry, analytical chemistry, physical chemistry and polymer chemistry, as well as metallurgy, geochemistry, pharmacy, toxicology, environmental chemistry, biology and physics. It is characterized by a wide range of documents, many types and a large number of documents. There are more than 9,000 periodicals, including patent specifications, reviews, technical reports, monographs, conference records and papers from 47 countries and 3 international patent organizations, covering more than 60 languages in more than 200 countries and regions around the world.