string(267) "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%A0%87%E6%B3%A8%E7%9A%84%E6%A0%87%E5%87%86%E6%A0%BC%E5%BC%8F => Failed to connect to 101.89.117.144 port 38022: Connection refused"
论文引用标注的标准格式
