the_post_thumbnail(); //采用默認參數(shù)，請參考wp-includes/post-image-template.php文件
the_post_thumbnail('thumbnail'); //小尺寸縮略圖
the_post_thumbnail('medium'); //中等縮略圖
the_post_thumbnail('large'); //大縮略圖
the_post_thumbnail('medium', array('class' => 'alignleft', 'alt' => 'alttext'));

//采用中等縮略圖
//設定圖片分辨率為100x100像素，并加上class="alignleft"和描述
the_post_thumbnail(array(100,100), array('class' => 'alignleft', 'alt' => 'alttext'));