J1 2-year home state service

From Dec.1, 2011 to Dec.26, 2012, as postdoctoral fellow (holding J1 visa, research scholar), I was offered by a professor from Y University in the US, to work at his laboratory for one year. After completing the project, I had returned my home countries, China, on Jan. 1, 2013; I wish to know whether I may still qualify for applying for a J1 visa (research scholar) to work, as postdoctoral fellow, at any other university in USA in the next 24 months, or I have to remain in China for two years?
Note:
1, my research is in the field of biology

我是2009年9月到2010年8月，国家公派，拿的是J1（research scholar）~
2011年6月博士毕业，之后想再去美国读postdoc~

再申请J1类签证的话单独一个最长只有1年多的~

想问问，可否申请某个J1类签证后，待到其到期后再申请另一个J1类签证？
最长可以在国外呆多久？

非常感谢！！！

ps，我本人在读完postdoc后准备回国的~

去年持J1签证在美国呆过四个月（short-term scholar)，是学校的一个交换项目。

今年毕业打算去美国做Postdoc。与申请的学校（不是同一学校、同一个项目）联系过，并告知我的签证情况，对方HR核实后联系我说可以继续申请J1签证。