1.运行效果如图所示

wKioL1klOoGA3GhzAAA5lTOxzx0581.png-wh_50


2.实现代码如下

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>导航（垂直分组）</title>
    <!-- 最新版本的 Bootstrap 核心 CSS 文件 -->
    <link rel="stylesheet" 
    href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap.min.css" 
    integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" 
    crossorigin="anonymous">

    <!-- 可选的 Bootstrap 主题文件（一般不用引入） -->
    <link rel="stylesheet" 
    href="https://cdn.bootcss.com/bootstrap/3.3.7/css/bootstrap-theme.min.css" 
    integrity="sha384-rHyoN1iRsVXV4nD0JutlnGaslCJuC7uwjduW9SVrLvRYooPp2bWYgmgJQIXwl/Sp" 
    crossorigin="anonymous">
</head>
<body>
    <div class="btn-group-vertical">
          <button class="btn btn-default" type="button">首页</button>
          <button class="btn btn-default" type="button">产品展示</button>
          <button class="btn btn-default" type="button">案例分析</button>
          <button class="btn btn-default" type="button">联系我们</button>
        <div class="btn-group">
              <button class="btn btn-default dropdown-toggle" data-toggle="dropdown" 
              type="button">关于我们<span class="caret"></span></button>
            <ul class="dropdown-menu">
                <li><a href="##">公司简介</a></li>
                <li><a href="##">企业文化</a></li>
                <li><a href="##">组织结构</a></li>
                <li><a href="##">客服服务</a></li>
            </ul>
        </div>
    </div>


    <script src="https://cdn.bootcss.com/jquery/3.2.1/jquery.min.js"></script>
    <!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
    <script src="https://cdn.bootcss.com/bootstrap/3.3.7/js/bootstrap.min.js" 
    integrity="sha384-Tc5IQib027qvyjSMfHjOMaLkfuWVxZxUPnCJA7l2mCWNIpG9mGCD8wGNIcPD7Txa" 
    crossorigin="anonymous"></script>
</body>
</html>