string(274) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E6%8A%95%E5%85%A5%E4%BA%A7%E5%87%BA%E6%AF%94%E7%8E%87%E5%85%AC%E5%BC%8F%E8%AE%A1%E7%AE%97%E6%96%B9%E6%B3%95 => Failed to connect to 61.171.74.35 port 38027: Connection refused"
投入产出比率公式计算方法
