<select id="" onchange="window.location=this.value">
<option>请选择</option>
<option value="https://www.baidu.com">选项1</option>
<option value="https://www.baidu.com">选项2</option>
<option >选项3</option>
</select>
<select id="" onchange="window.location=this.value">
<option>请选择</option>
<option value="https://www.baidu.com">选项1</option>
<option value="https://www.baidu.com">选项2</option>
<option >选项3</option>
</select>