display: flex 子项指定宽度
<style>
.father{
width:100%;
background-color:red;
height:400px;
display:flex;
}
.son{
background-color:green;
width:100%;
flex-shrink:0;
height:300px;
}
</style>
<body>
<div class="father">
<div class="son">1</div>
<div class="son">2</div>
<div class="son">3</div>
</div>
</body>
关键代码：flex-shrink:0;