His voice took on a more serious tone.

他说话的语气变得严肃起来。

《牛津词典》

Stress has an immeasurably more serious effect on our lives than we realize.

压力对我们的生活造成的影响比我们意识到的要严重得多。

《牛津词典》

More serious leaks, possibly involving national security, are likely to be investigated by the police.

可能涉及国家安全的更严重泄密会受到警方的调查。

《柯林斯英汉双解大词典》

They were not charged with the more serious crime of espionage, so the extent of their success as spies is not clear.

VOA: special.2010.07.10

It's much more serious and strange. Okay. So that's enough on Eliot.

那个更严肃更奇怪，好吧，关于艾略特的讨论就到这。

耶鲁公开课 - 1945年后的美国小说课程节选

Here's another example. A more serious example.

还有一个稍显严肃的例子。

How long课堂 - SpeakingMax英语口语达人

In the US, criminals are punished in prisons for more serious crimes and in jails for lesser offences.

BBC: Orlando Bloom burglary: Reality star admits charge

More serious penalties could follow for some of the 54 officials criticised in the report.

BBC: China bullet train crash 'caused by design flaws'

An ultrasound, however, turned up a more serious condition: an abdominal aortic aneurysm (AAA).

FORBES: By the Numbers