<style type="text/css">        
        .toc {
             position: fixed;
             width:220px;
             padding-right: calc(( 100% - 700px ) / 2 - 233px );
            }
        @media only screen and (max-width: 1000px) {
             /*主内容700px宽度*/
            .toc {
                max-width: 100%;
                position: static;
                padding: 0.5em 1em;
                border: 0.1em dashed silver;
            }
        }
  </style>