.big_tab ul{overflow: hidden; width: 100%;}
.big_tab ul li{width: 20%; box-sizing: border-box; float: left; list-style-type: none; border: 1px solid #ccc; text-align: center; line-height: 40px;}
.big_tab ul li.activeClass{font-weight: bold; font-size: 20px;}
.sm_select {display: none;}
.sm_select select {width:100%; height: 40px; }


@media (max-width:768px){
      .sm_select {display: block;}
      .big_tab{display: none;}
 }