要在输入组中细分按钮下拉菜单，请使用与下拉按钮相同的常规样式，但要在下拉菜单中添加主要操作，如以下示例所示：
<!DOCTYPE html> <html> <head> <title>Bootstrap Example</title> <link href = "/bootstrap/css/bootstrap.min.css" rel = "stylesheet"> <script src = "/scripts/jquery.min.js"></script> <script src = "/bootstrap/js/bootstrap.min.js"></script> </head> <body> <div style = "padding: 100px 100px 10px; background: red;"> <form class = "bs-example bs-example-form" role = "form"> <div class = "row"> <div class = "col-lg-6"> <div class = "input-group"> <div class = "input-group-btn"> <button type = "button" class = "btn btn-default" tabindex = "-1">Subject</button> <button type = "button" class = "btn btn-default dropdown-toggle" data-toggle = "dropdown" tabindex = "-1"> <span class = "caret"></span> <span class = "sr-only">Toggle Dropdown</span> </button> <ul class = "dropdown-menu"> <li><a href = "#">Maths</a></li> <li><a href ="#">Science</a></li> </ul> </div><!-- /btn-group --> <input type = "text" class = "form-control"> </div><!-- /input-group --> </div><!-- /.col-lg-6 --> <br> <div class = "col-lg-6"> <div class = "input-group"> <input type = "text" class = "form-control"> <div class = "input-group-btn"> <button type = "button" class = "btn btn-default" tabindex = "-1"> Course </button> <button type = "button" class = "btn btn-default dropdown-toggle" data-toggle = "dropdown" tabindex = "-1"> <span class = "caret"></span> <span class = "sr-only">Toggle Dropdown</span> </button> <ul class = "dropdown-menu pull-right"> <li><a href = "#">BCA</a></li> <li><a href = "#">MCA</a></li> </ul> </div><!-- /btn-group --> </div><!-- /input-group --> </div><!-- /.col-lg-6 --> </div><!-- /.row --> </form> </div> </body> </html>