.back {
    float: left;
    width: 25%;
    margin-top: 68px;
    padding:  0px 20px;
    position: relative;
    transition: 0.5s;
    box-sizing: border-box;
}
.xiaoli {
    margin: 0px -20px;
}

.back:hover img {
    transform: scale(1.2);   
}
.back img {
    transition: 0.5s;
}
.border {
    border: 1px #e7e7e7 solid;
    padding-bottom: 120%;
} 
.border:hover {
    background: #215297;
}
.back .lixiaohui {
    width: 67%;
    overflow: hidden;
    position: absolute;
    left: 17%;
    top: -15%;
}

.back .lixiaohui span{ width:100%; display:block;
    padding-bottom:140%; 
   position:relative; overflow:hidden;
}
.back .lixiaohui span img{width:100%; position:absolute; 
    top:0; left:0; 
   transition:all 0.4s;
   -webkit-transition: all 0.4s ease;
       -moz-transition: all 0.4s ease;
       -ms-transition: all 0.4s ease;
       -o-transition: all 0.4s ease;
       transition: all 0.4s ease;
 }
.back .lixiaohui span img:hover{transform: scale(1.1);}

.back p {
    width: 84%;
    font-size: 16px;
    color: #333333;
    text-align: center;
    position: absolute;
    bottom: 9%;
}
.back:hover p {
    color: #fff;
}
@media only screen and (max-width: 1200px){
.youbu {
    width: 100%;
}
}
@media only screen and (max-width: 850px){
    .back {
        width: 50%;
    }
    .youbu {
        padding: 0px 20px;
        width: 95%;
    }
}

@media only screen and (max-width: 450px){
    .back {
        width: 50%;
    }
    .youbu {
        padding: 0px 0px;
        width: 100%;
    }
    .xiaoli {
        margin: 0px;
    }
    .back p {
        width: 79%;
        font-size: 12px;
        bottom: 3%;
    }
}