string(238) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E6%91%98%E8%A6%81%E8%AE%BA%E6%96%87%E6%A0%BC%E5%BC%8F%E8%A6%81%E6%B1%82 => Failed to connect to 14.18.117.71 port 38164: Connection refused"
摘要论文格式要求
