string(256) "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%E6%91%98%E8%A6%81%E7%94%A8%E4%BB%80%E4%B9%88%E6%A0%BC%E5%BC%8F%E7%9A%84 => Failed to connect to 14.116.215.7 port 38230: Connection refused"
论文摘要用什么格式的
