<div class="input-group">
<span class="input-group-addon">@</span>
<input type="text" class="form-control">
<div class="input-group-btn">
<button class="btn btn-default"> 提交2 </button>
<button class="btn btn-default dropdown-toggle" data-toggle="dropdown"><span class="caret"></span></button>
<ul class="dropdown-menu">
<li><a href="">首页1</a></li>
<li><a href="">首页2</a></li>
<li><a href="">首页3</a></li>
<li><a href="">首页4</a></li>
</ul>
</div>
</div>

<div class="input-group input-group-lg">
<span class="input-group-addon">@2</span>
<input type="text" class="form-control">
<div class="input-group-btn input-group-lg">
<select name="" id="idsel" class="form-control" style="
width:150px;
padding:3px 10px;
border-top-right-radius: 5px;
border-bottom-right-radius: 5px;
appearance:none;
-moz-appearance:none;
-webkit-appearance:none;
background:url(img/arrow.jpg) no-repeat right center;
background-color: #eee;
background-size:20%;
">
<option value="">@163.com</option>
<option value="">@gmail.com</option>
<option value="">@gsafc.com</option>
<option value="">@qq.com</option>
</select>
</div>
</div>