string(234) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E7%94%A8rank%E5%87%BD%E6%95%B0%E8%AE%A1%E7%AE%97%E6%8E%92%E5%90%8D%E9%99%8D%E5%BA%8F => Received HTTP code 403 from proxy after CONNECT"
用rank函数计算排名降序
