/*关键设置 tbody出现滚动条*/
table tbody {
    display: block;
    max-height: 700px;
    overflow-y: scroll;
}

table thead,
tbody tr {
    display: table;
    width: 100%;
    table-layout: fixed;
}

tbody thead {
    display: table;
    width: 100%;
    table-layout: fixed;
}

/*关键设置：滚动条默认宽度是16px 将thead的宽度减16px*/
table thead {
/*width: calc(100% - 1em)*/
width: calc(100% - 16px)
}