twitter-bootstrap 媒体查询
示例
Bootstrap中的媒体查询允许您根据视口大小移动，显示和隐藏内容。在LESS文件中，使用以下媒体查询在Bootstrap网格系统中创建关键断点：
/* Small devices (tablets, 768px and up) */
@media (min-width: @screen-sm-min) { ... }
/* Medium devices (desktops, 992px and up) */
@media (min-width: @screen-md-min) { ... }
/* Large devices (large desktops, 1200px and up) */
@media (min-width: @screen-lg-min) { ... }有时这些扩展为包括最大宽度，以将CSS限制为较窄的设备集：
@media (max-width: @screen-xs-max) { ... }
@media (min-width: @screen-sm-min) and (max-width: @screen-sm-max) { ... }
@media (min-width: @screen-md-min) and (max-width: @screen-md-max) { ... }
@media (min-width: @screen-lg-min) { ... }