正则表达式提取汉字

如题：
(1) <div class="post_body">
                <div class="modified_message">修改</div>
           需要提取的内容<br />
<a href="http://ibm/index.html" target="_blank"> 软件技术峰会</a>
              <div class='topic-extra-info'>
                <div class="tag">
                </div>
                <div class='social-share' >
                  <span class='prompt'>分享到：</span>
                  <span class='social-share-buttons' data-title='x' data-pics=''></span>
                </div>
              </div>
        </div>
 (2)<div class="post_body">需要提取的内容</div>正则表达式技术tag