string(260) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E6%95%B0%E5%AD%A6%E5%88%86%E6%9E%90%E4%B8%ADdy%E6%98%AF%E4%BB%80%E4%B9%88%E6%84%8F%E6%80%9D => Failed to connect to 101.89.159.206 port 38075: Connection refused"
数学分析中dy是什么意思
