Update header.html

Author: Gangzi-Jia

_includes/header.html

@@ -57,7 +57,17 @@
           </div>
         </li>
         <li><a class="waves-effect" href="{{site.baseurl}}/"><i class="material-icons">home</i>首页</a></li>
-        <li><a class="waves-effect" href="{{site.baseurl}}/internship-achievements"><i class="material-icons">description</i>本科生实习成效</a></li>
+        <li>
+          <a class="waves-effect collapsible-header" href="javascript:void(0);">
+            <i class="material-icons">description</i>本科生实习成效
+            <i class="material-icons right">arrow_drop_down</i>
+          </a>
+          <ul class="collapsible-body">
+            <li><a class="waves-effect" href="{{site.baseurl}}/internship-achievements"><i class="material-icons">assignment</i>总体介绍</a></li>
+            <li><a class="waves-effect" href="{{site.baseurl}}/internship-projects"><i class="material-icons">science</i>科研实习项目</a></li>
+            <li><a class="waves-effect" href="{{site.baseurl}}/internship-outcomes"><i class="material-icons">psychology</i>培养成果和成效</a></li>
+          </ul>
+        </li>
         <li><a class="waves-effect" href="{{site.baseurl}}/competition-achievements"><i class="material-icons">emoji_events</i>本科生竞赛成果</a></li>
         <li><a class="waves-effect" href="{{site.baseurl}}/recruitment-info"><i class="material-icons">people</i>持续招生信息</a></li>
         <li><div class="divider"></div></li>