现象，这个网站我总计能抽取将近500个URL，但实际只抽取了100条

解析：nutch默认从一个页面解析出的链接，只取前 100 个。 

<property>  <name>db.max.outlinks.per.page</name>  <value>100</value>  <description>The maximum number of outlinks that we‘ll process for a page.  If this value is nonnegative (>=0), at most db.max.outlinks.per.page outlinks  will be processed for a page; otherwise, all outlinks will be processed.  </description></property>

将这个值改大一些 1000 .