The problem of hunger worldwide is a hard nut to crack. I'm afraid that scientists need to put in more efforts.

全球性的饥饿问题是个棘手的问题，恐怕科学家们需要付出更多的努力。

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Given curiosity's complexity, scientists have found it hard to define.

考虑到好奇的复杂性，科学家们发现很难定义它。

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But that their minds are not different from our own is demonstrated by the fact that the hard-won discoveries of scientists like Kepler or Einstein become the commonplace knowledge of schoolchildren.

但是，他们的头脑与我们的头脑并没有什么不同，这一点已被一个事实所证明，即像开普勒或爱因斯坦这样的科学家们的来之不易的发现，已成为小学生们的常识。

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He led the team of scientists. They developed a new method of making maps of hard-to-reach areas.

VOA: special.2009.11.17

The Green Revolution was the result of hard work by agricultural scientists who had green thumbs.

VOA: special.2010.05.23

When I was asked in 1988 by Science to write about economics fiscal relativity problem I was struck that the hard scientists could get this point so quickly and that so many economists could not.

FORBES: Krugman's Four Dangerous Fiscal Fables

Turner says it's hard enough for scientists to understand how the supposedly empty vacuum of space can be suffused with some form of cosmic energy.

NPR: New Clue to Universe's Darkest Mystery

Radarsat will supply scientists with hard data on how much ice is lost or gained each year.

CNN: Nature - Satellite sees through Arctic ice for signs of climate change