我也在寻找这个,发现了这一点
<!-- Place this tag in your head or just before your close body tag -->
<script type="text/javascript" src="https://apis.google.com/js/plusone.js">
{parsetags: 'explicit'}
</script>
<!-- Place this tag where you want the +1 button to render -->
<g:plusone></g:plusone>
<!-- Place this render call where appropriate -->
<script type="text/javascript">gapi.plusone.go();</script>
gapi.plusone.go();放置这个代码,按钮就会出现
