He spoke with a seriousness that was unusual in him.

他说话时神情少有地认真。

《牛津词典》

When he came over I saw a seriousness in him that I had never seen before.

他来时，我从他身上看出了一丝从未有过的严肃。

youdao

She gazed at the sheets of music for a long moment, then started to pound on the keys with a seriousness that took Hanfeng by surprise.

她凝神注视乐谱好久，然后开始一本正经地敲击琴键，让瀚峰感到有点惊奇。

youdao

He never smiled,he never frowned, But all through the endless story there was a feeling of great seriousness and honesty.

VOA: special.2009.08.29

So there, Machiavelli gives us a sense of the seriousness with which he approached his subject, and what it was he came to write.

从这些观点看来马奇亚维利,传达了,他对学习科目的严谨态度，他写作的来由。

耶鲁公开课 - 政治哲学导论课程节选

This is quite a remarkable change reflecting the seriousness of the crisis.

这确实是一个非凡的改变,预示着危机的严重性。

耶鲁公开课 - 金融市场课程节选

Establishing a formal presence also demonstrates to potential customers a seriousness of purpose with respect to China.

FORBES: Staking Out Your Market Position In China: Part II

Let's work together, with a seriousness of purpose, to do what must be done to keep our country safe.

WHITEHOUSE: Weekly Address: The Fight Against Al Qaeda

And they're looking for folks in Washington to have a seriousness of purpose that matches the reality of their struggle.

WHITEHOUSE: Job Creation and Economic Growth