string(255) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E5%87%80%E5%88%A9%E6%B6%A6%E7%9A%84%E4%B8%A4%E7%A7%8D%E8%AE%A1%E7%AE%97%E5%85%AC%E5%BC%8F => Failed to connect to 14.18.46.51 port 38206: Connection refused"
净利润的两种计算公式
