CSS changes don't update

Hi
I added

<style type="text/css" media="screen">
@import url( <?php bloginfo('stylesheet_url'); ?>?<?php echo time(); ?> );
</style>

in the header but it didn’t work.
I tried this one too but it didn’t work
<link rel="stylesheet" href="<?php bloginfo('stylesheet_url'); echo '?' . filemtime( get_stylesheet_directory() . '/style.css'); ?>" type="text/css" media="screen, projection" />.

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