string(283) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E4%BB%80%E4%B9%88%E5%8F%AB%E5%81%9A%E8%87%AA%E7%84%B6%E6%95%B0%E8%87%AA%E7%84%B6%E6%95%B0%E6%9C%89%E5%93%AA%E4%BA%9B => Failed to connect to 61.171.74.35 port 38027: Connection refused"
什么叫做自然数自然数有哪些
