<div class="copy">
   <div class="select">
      <label class="blind" for="sitelink">관련사이트 바로가기</label>
      <select name="" id="sitelink" class="select1">
         <option value="http://www.abc.com">abc</option>
         <option value="http://www.123.com">123</option>
      </select>
      <button class="btn_sel">이동</button>
   </div>
</div>

<script type="text/javascript">
   $(".copy .btn_sel").on("click",function(){
      var link = $(".copy .select1 option:selected").val();
      window.open(link, '_blank');
   })
</script>