Not really ANSI SQL compliant.
Try

select count(*) from 
(SELECT distinct `idResource`,`workDate` FROM `work` WHERE `week`=201247) as ww

this is my code

$Ressource=SqlList::getList('Resource');
foreach($Ressource as $keyresource => $valresource)
{
$crit=array('week'=>$y.''.$week);
$obj=new Work();
$Jours=$obj->countSqlElementsFromCriteria($crit);
}

So i should modify the file sqlElement.php.
But i try this way w and i can't create a new function to generate a request to reply this need.

Sure this code

$Ressource=SqlList::getList('Resource');
foreach($Ressource as $keyresource => $valresource) 
{ 
$crit=array('week'=>$y.''.$week);
$obj=new Work();
$Jours=$obj->countSqlElementsFromCriteria($crit);
}

will not generate

SELECT count(distinct `idResource`,`workDate`)FROM `work` WHERE `week`=201248

unless you changed SqlElement code (I stongly recommand against this !).
It will more likely generate

select count(*) as cpt from work where week='201248'

Maybe if you describe what you try to get (and not how you try to get it), answers may be more helpfull. 😉