Adding Script To PHP File - CSS Style

I have this javascript that checks screen resolution and opens a custom css file depending on the results and its working fine if I run it from an html version of my site. What I want to try and do is add this script to my header.php file. header.php currently uses this code to define the css style:
Code:
<style type="text/css" media="screen">@import "<?php echo $this->getStyleSheet('style.css')?>";</style>

The javascript I want to use is in a file called detect.js that looks like this:
Code:
$(document).ready(function() {
if ((screen.width>=1400) && (screen.height>=1050)) {
alert('Screen size: 1400x1050 or larger');
$("link[rel=stylesheet]:not(:first)").attr({href : "style.css"});
}
else {
alert('Screen size: less than 1024x768, 800x600 maybe?');
$("link[rel=stylesheet]:not(:first)").attr({href : "style1.css"});
}
});

So heres what I tried but it didn't work instead it just loaded the page without a template.
Code:
<?php echo '<script type="text/javascript" src="jquery.js"> </script>';
?>
<?php echo '<script type="text/javascript" src="detect.js"></script>';
?>