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%E7%9A%84%E6%91%98%E8%A6%81%E6%98%AF%E5%95%A5 => Failed to connect to 101.89.117.144 port 38208: Connection refused"
论文中的摘要是啥
