They are only visible when they are bathed in ultra-violet light and subjecting them to such constant bombardment would be not only impractical but harmful.

只有当这些壁画沐浴在紫外灯光下时，这些细节之处才得以可见，但将这些传世珍品一直置于紫外灯的狂轰乱炸之下不仅不现实，对壁画本身也有害。

youdao

Chemical. Poisoning or injury caused by chemical substances, including ex-military chemical warfare agents or legitimate but harmful household or industrial chemicals.

由于化学物质造成的中毒或伤害，这些化学物质包括以前的军用化学战剂或合法但有害的家用或工业化学品。

youdao

It is important to avoid the dead, useless foods that provide nothing but harmful chemicals such as corn syrup. You'll find life is a cruise when eating healthy foods.

避免吃像玉米糖浆这类有害毫无益处的化学制品是重要的，当享受健康食物的时候，你会发现自己好像在一艘平稳行驶的船上，心情愉悦。

youdao

He says calling for reductions in the national diet could have good effects, but it could also have harmful results.

VOA: special.2010.03.03

"Logos He goes on. "But logos," he writes, " "serves to reveal the advantageous and the harmful.

也继续写到，主要是为展露出利害关系。

耶鲁公开课 - 政治哲学导论课程节选

And also, it's useful because harmful stimuli are noticed but when something has shown itself to be part of the environment you don't notice it anymore.

而且它还是非常有用的,因为危险刺激会吸引到你的注意,但当某物被视为环境的一部分时,你便不会再去注意到该物体。

耶鲁公开课 - 心理学导论课程节选

'She likes to loosen light bulbs, to lock doors - but nothing harmful.

BBC: The haunted land of New England

But how harmful is it to bandy the names of such conditions about?

BBC: Magazine

But if harmful levels of stress continue for too long, a person may lose the ability to relax, a condition linked in research to numerous health problems.

WSJ: Stress at Work: Why Women Feel It More Than Men