You will need some line of script, there isnt an option built in for that. You can open the script editor and put the following into a mel tab, select the objects you want to filter, then execute the script. It selects objects smaller than the given max size value.
{
float $maxSize = 1; // max length of objects bounding box diagonal in grid units
string $selection[] = `ls -sl`;
string $filteredObj[] = {};
for($node in $selection){
float $bb[] = exactWorldBoundingBox($node);
if( $maxSize > mag(<<($bb[3] - $bb[0]),($bb[4] - $bb[1]),($bb[5] - $bb[2])>>) )
$filteredObj[`size $filteredObj`] = $node;
};
select $filteredObj;
};