web crawler，python ，针对puchem，收取化学物质信息，以csv格式记录。采用beautifulsoup 开发，采用lxml解析器，爬取速度较慢，请多等待。可以修改指定爬取范围，也可以根据cid来爬取(Web crawler, python, for puchem, collection of chemical information, recorded in CSV format. Use beautifulsoup development, use lxml parser, crawl speed is slower, please wait more. The specified climb range can be modified, and it can be crawled according to CID)