string(249) "get document error：https://zhidao.baidu.com/search?lm=0&rn=10&pn=0&fr=search&dyTabStr=null&word=%E5%A4%AE%E8%A1%8C%E5%8F%91%E8%A1%8C%E5%80%BA%E5%88%B8%E7%9A%84%E4%BD%9C%E7%94%A8 => Failed to connect to 101.89.117.144 port 38005: Connection refused"
央行发行债券的作用
