professional search engine 基本例句 专业搜索引擎 Focused crawler can fetch large quantities of domain resources from the Web in a short time.It is very helpful in both foused search engines and data mining companies.定题爬虫能迅速获取网络上特定主题的大量信息，对专业搜索引擎及数据挖掘应用都具有重大价值。