.bg_main {
background:url(../images/bg_main.jpg) no-repeat;
height:37px;
display:block;
overflow:hidden;
margin-bottom:25px;
zoom:1;
}
.bg_main span {
display:none;
}

.bg_main_lecture {
margin-bottom:15px;
overflow:hidden;
zoom:1;
}

.bg_sub {
margin-bottom:15px;
overflow:hidden;
zoom:1;
}



.index_btn_lecture a,
.index_btn_research,
.index_btn_data {
display:block;
overflow:hidden;
zoom:1;
height:205px;
}
.index_btn_lecture a span,
.index_btn_research span,
.index_btn_data  span {
display:none;
}

.index_btn_lecture a {
background:url(../images/index_lecture.jpg) no-repeat center top;
}
.index_btn_lecture a:hover {
background:url(../images/index_lecture_on.jpg) no-repeat center top;
}

.index_btn_lecture2 a {
background:url(../images/index_lecture2.jpg) no-repeat center top;
}
.index_btn_lecture2 a:hover {
background:url(../images/index_lecture2_on.jpg) no-repeat center top;
}

.index_btn_heat_stroke a {
background:url(../images/index_heat_stroke.jpg) no-repeat center top;
}
.index_btn_lecture a:hover {
background:url(../images/index_heat_stroke_on.jpg) no-repeat center top;
}

.index_btn_lecture4 a {
background:url(../images/index_lecture4.jpg) no-repeat center top;
}
.index_btn_lecture4 a:hover {
background:url(../images/index_lecture4_on.jpg) no-repeat center top;
}

.index_btn_lecture5 a {
background:url(../images/index_lecture5.jpg) no-repeat center top;
}
.index_btn_lecture5 a:hover {
background:url(../images/index_lecture5_on.jpg) no-repeat center top;
}

.index_btn_research a {
background:url(../images/index_research.jpg) no-repeat center top;
}
.index_btn_research a:hover {
background:url(../images/index_research_on.jpg) no-repeat center top;
}

.index_btn_data {
background:url(../images/index_data.jpg) no-repeat center top;
}