<nav class="navbar navbar-default navbar-inverse navbar-fixed-top"> 
//navbar-inverse 设置背景                                                        
//navbar-fixed-top 设置头部固定在顶部,因此需要给body设置顶部padding,一般设置为padding-top:60px
 <div class="Container-fluid"> 
//container-fluid设置导航条内容是否有一定的内间距,如果class="container-fluid"则没有内间距,内容紧贴左侧        
//如果设置class="container",则内容有一定的内间距,内容对称居中
  <!-- Brand and toggle get grouped for better mobile display -->
  <div class="navbar-header">
   <button type="button" class="navbar-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
    <span class="sr-only">Toggle navigation</span>
    <span class="icon-bar"></span>
    <span class="icon-bar"></span>
    <span class="icon-bar"></span>
   </button>   //这里是响应式的写法,在小屏幕上回显示三杆,无需改动
   <a class="navbar-brand" href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >某管理系统</a>
  </div>
  <!-- Collect the nav links, forms, and other content for toggling -->
  <div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
   <ul class="nav navbar-nav">
    <li class="active"><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >首页 <span class="sr-only">(current)</span></a></li>
    <li class="dropdown">
     <a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="false">功能 <span class="caret"></span></a>
     <ul class="dropdown-menu">
      <li class="dropdown-header" >业务功能</li>
      <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >信息建立</a></li>
      <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >信息查询</a></li>
      <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >信息管理</a></li>
      <li role="separator" class="divider"></li>
      <li class="dropdown-header" >系统功能</li>
      <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >设置</a></li>
      <li role="separator" class="divider"></li>
     </ul>
    </li>
    <li><a href="#" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" rel="external nofollow" >帮助</a></li>
   </ul>
   <form class="navbar-form navbar-left pull-right">
    <div class="form-group">
     <input type="text" class="form-control" placeholder="username...">
     <input type="password" class="form-control" placeholder="password...">
    </div>
    <button type="submit" class="btn btn-default">Login</button>
   </form>
  </div><!-- /.navbar-collapse -->
 </div><!-- /.container-fluid -->
</nav>