织梦默认的搜索可以搜索全部栏目或者指定的搜索某一个栏目，不能搜索指定的多个栏目，需要加装修改才能实现。
1、在搜索框表单里加个typeid提交过去
例如
<form name="formsearch" action="/plus/search.php">
<input type="hidden" name="typeid" value="1,2,3">
</form>
2、打开/plus/search.php找到
$typeid = (isset($typeid) && is_numeric($typeid)) ? $typeid : 0;
删除这一行后，继续找到
$typeid = intval($typeid);
再删除这一行
3、打开 /include/arc.searchview.class.php 找到
$ksqls[] = " typeid IN (".GetSonIds($this->TypeID).") ";
改成
//指定了多个栏目时
if( preg_match('#,#', $this->TypeID) )
{
    $typeids = explode(',', $this->TypeID);
    foreach($typeids as $ttid) {
        $typeidss[] = GetSonIds($ttid);
    }
    $typeidStr = join(',', $typeidss);
    $typeidss = explode(',', $typeidStr);
    $typeidssok = array_unique($typeidss);
    $typeid = join(',', $typeidssok);
    $ksqls[] = " arc.typeid IN ($typeid) ";
}
else
{
    $ksqls[] = " arc.typeid IN (".GetSonIds($this->TypeID).") ";
}