string(239) "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%E5%BC%95%E7%94%A8%E6%80%8E%E4%B9%88%E6%A0%87%E6%B3%A8%E7%AC%A6%E5%8F%B7 => Received HTTP code 403 from proxy after CONNECT"
论文引用怎么标注符号
