I'm going to have to knuckle down to some serious study.

我得开始认认真真地学习了。

He would not knuckle down under their pressure.

他不会在他们的压力下屈服的。

You 'll really have to knuckle down if you want to pass the examination.

如果想通过考试，你确实应专心学习。

He managed to knuckle down to his lessons long enough to pass his examination.

他在离考试还有足够长时间的时候就开始认真学习，从而通过了考试。

As for Ronaldinho's fitness, if he doesn't move I am sure that he will knuckle down and train hard to get back to his previous levels.

鉴于罗纳尔迪尼奥的健康状况，如果他不转会，我确定他能够一扫阴霾并且努力训练找回自己的最佳状态。

You never know what can happen in football but I know I am going to knuckle down, train hard, work hard and perform when I get my chance.

你永远不知道足球会发生些什么，但是我知道我准备开始屈服，努力训练，努力工作，在我得到机会的时候上场表现。

There's a start, a finish, and the faster you run, the further you go: the secret to winning a marathon is to knuckle down and keep going.

有起点，也有终点，你跑得越快，也就跑得越远：马拉松比赛获胜的秘诀是沉下气来，一直往前跑。

She bit down on my knuckle, playfully hard.

她在我的指关节上顽皮地狠狠咬了一口。

I've used three pencils right down to knuckle-stubs, and a whole tablet of paper.

我用掉三枝铅笔，还有一整本簿子。