.relative{position: relative;overflow: hidden;}
.xiazailist [class*=col-]{position:relative;margin-bottom:30px;}
.xiazailist .tit{position:absolute;top:0px;left:0px;padding-top:52%;width:100%;height:100%;font:24px/1.5 "SYHTregular","黑体";color:#ffffff;text-align:center;background:rgba(0,0,0,0.7);transition:all 0.3s;opacity: 0;}

@media (min-width: 992px) {
.xiazailist a:hover .tit{opacity: 1;}
}