限制文本框的内容不允许copy

<script>
 $("#jzmc").focus(function(){
        $("#jzmc").blur();
   });
</script>

<td width="17%" class="TableText_Left">
			<ww:textfield name="tpkYwsl.jzmc" id="jzmc" maxlength="50" 
				cssClass="input_text90 required easyui-validatebox" required="true" validType="certificate" subNum="1"  theme="simple"/>
		</td>