string(373) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E7%94%9F%E4%BA%A7%E8%83%BD%E5%8A%9B%E6%8C%87%E6%95%B0%E4%BC%B0%E7%AE%97%E6%B3%95%E8%A6%81%E6%B1%82%E5%85%B7%E5%A4%87%E7%9A%84%E8%B5%84%E6%96%99%E5%B0%91%E8%80%8C%E4%B8%94%E7%B2%BE%E5%BA%A6%E5%BE%88%E9%AB%98 => Failed to connect to 61.171.74.35 port 38041: Connection refused"
生产能力指数估算法要求具备的资料少而且精度很高
