Scientists know planets form out of the discs of material around young stars, but theory says the transition from dust disc to planetary system is rapid and few objects are caught during this phase.

科学家们知道行星是从年轻的恒星周围的物质盘中形成的，但是理论认为从尘埃盘到行星系统的转变非常快，人们很少见到在这一阶段的物体。

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The course teaches you the theory but there's no substitute for practical experience.

这门课教的是理论，但没有任何东西能代替实践经验。

《牛津词典》

It's only a theory, admittedly, but the pieces fit together.

得承认这只是一种理论，但其各部分自成一体。

《柯林斯英汉双解大词典》

The researchers had a theory. They thought that people who were bitten by infected mosquitoes,but recovered, were protected in the future.

VOA: special.2011.05.31

Now in addition to defining literature, literary theory also asks questions obviously not unrelated but which open up the field somewhat.

除了定义文学以外，文学理论还提出一些,显然不是不相关，却开辟了新领域的问题。

耶鲁公开课 - 文学理论导论课程节选

But before we do that, I wanted to just make a few concluding remarks about source theory and the Pentateuch.

但在我们开始之前，我想做一个总结,并且来源理论和摩西五经。

耶鲁公开课 - 旧约导论课程节选

In theory, that means the beans can aid metabolic regulation but theory is not data.

NEWYORKER: The Operator

Research on coaching has grown tremendously in the last decade but theory itself is mostly adapted from other closely allied disciplines.

FORBES: What kind of coach are you?

But economic theory struggles to explain the bizarre world of fund management, where the market is fragmented but fees stay stubbornly high.

ECONOMIST: Fund management