1. It was on such an occasion the other evening, as the conversation moved desultorily here and there, from the most commonplace to thoughts of Jupiter, without any focus and with no need for one, that suddenly the alchemy sth.
有一天晚上的情形正是这样。人们正漫无边际地东扯西拉，从最普通的凡人俗事谈到有关木星的科学趣闻。谈了半天也没有一个中心话题，事实上也不需要有一个中心话题。
911查询·英语单词
2. Focus one's attention on sth.
把注意力集中在某事上
3. Focus on/upon sth.
集中注意力在…。
4. Focus on sth.
把注意力集中于
5. Fix/focus one`s attention on sth.
集中注意力于