string(251) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E9%AB%98%E6%95%B0%E4%B8%ADdy%E8%A1%A8%E7%A4%BA%E4%BB%80%E4%B9%88%E6%84%8F%E6%80%9D => Failed to connect to 101.89.143.195 port 38205: Connection refused"
高数中dy表示什么意思
