It gets there when you eat, it comes from you blood and from chemical reactions in your body.

只要你吃东西，就会有屁, 屁在血液中体内化学作用产生。

This is a result of melanin in the dead skin cells reacting with oxygen creating a black color —it's not dirt.

这是死皮细胞中黑色起化学作用生成黑色点点结果——不是脏东西。

Understanding this chemical action forms the basis of drug development and testing today.

理解这种化学作用构成了当今药物研发与测试基础。

I can't. It's like this chemical thing, you know?

我说不出来这像是一种化学作用？

Corrode is a verb that usually describes destroying a metal by oxidation or by some other kind of chemical action.

“腐蚀”是一个动词，通常用来描述金属因化或其他化学作用而遭受破坏过程。

And a big environmental change was also underway in the last half of the Eocene, thanks to the chemistry of mountain-building.

而在始新世后半期，由于造山运动化学作用，也发生了一场环境变化。

So it’s not just the snack you desire, but the smell itself is a perfect example of chemistry at work, stimulating your brain and body.

因此，这不仅仅是您想要零食，而且气味本身就是化学作用完美例子， 可以刺激您脑身体。

Like, how a queen ant's nutrition and pheromones can chemically alter an ant embryo to either produce a soldier or worker ant based on what's needed for the colony.

比如，蚁后营养信息是如何通过化学作用改变蚂蚁胚胎，使其根据蚁群需要产生兵蚁或工蚁。

A yearlong study of more than 400 Alzheimer's patients showed that two drugs that work differently on the brain's chemistry act well together to help slow down the disease.

一项对 400 多名阿尔茨海默病患者进行为期一年研究表明，两种对脑化学作用不同药物可以很好地协同作用，帮助减缓疾病发展。

They also said that findings from animal cases suggest that their addiction-like behaviors happened only when they had intermittent access to sugar, believing those behaviors to come from the intermittent access, not the actual neurochemical effects of sugar.

他们还表示， 动物案例发现表明， 只有当它们间歇性地获取糖时， 才会发生类似成瘾行为，他们相信这些行为来自于间歇性获取，而不是糖实际神经化学作用。