string(240) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E8%AE%BA%E6%96%87%E4%B8%AD%E6%80%8E%E4%B9%88%E6%A0%87%E5%BC%95%E7%94%A8 => Failed to connect to 101.89.159.206 port 38087: Connection refused"
论文中怎么标引用
