Few records related to toothpaste or powder then exist, until around 1000 AD when the Persians wrote to advise their people to be wary of the dangers1 of using hard abrasives as toothpowders.
现存的有关牙膏或牙粉的古时记录很少，直到约公元1000年才有波斯人的书面记载，提醒他们的人民提防用硬磨料做牙粉的危险。
Your goal should be to work very hard at one, then work at the other on an AD hoc, as-needed basis.
您的目标应当是在某一方面非常努力，然后另一方再根据需要改进。
"It's hard to sell ads when you don't have an audience," he said, and it's hard to build an audience without AD money flowing in.
他说：“当你没有受众时，很难卖得出广告，”而没有广告资金流入，又很难获得受众。
In the absence of hard data on how many people actually saw an ad in predigital times, advertisers were willing to give print media the benefit of the doubt.
在过去，在我们进入数字时代之前，一个广告究竟被多少人真正看过，这个数据无从统计，结果就是，报社说什么，广告客户就信什么。
That deal will only concern AD sales, the company says, but it's hard to believe the money connection won't have at least subtle consequences in other parts of the business.
此次交易只涉及广告业务，但是既然有金钱挂钩，难免会发生其它关系。
It will never return to its glory days of 1999, it will be hard enough to keep Google and Facebook from stealing AD dollars from big advertisers.
它再也无法重现1999年的光辉岁月，要阻止谷歌和Facebook从大型广告客户手中抢走大量生意，难如登天。
There, of course, Microsoft had a relatively easy target (Apple) - but it would really be hard to construct an AD that attacks Google's search prowess.
当然，微软的宣传目标比较容易达到(相对苹果来说)，但要想弄出个能和Google分庭抗礼的广告，恐怕还是有难度。
Are you the carrot that seems hard, but with pain AD adversity you wilt and become soft and lose your strength?
你是看似强硬，但遭遇痛苦和逆境后畏缩、软弱、失去力量的胡萝卜吗？
So we work hard to build great AD products that people find useful-and that give revenue back to creators and publishers.
为此，我们致力于打造有效的优质广告产品，为创作者和发布者创造收益。
And recently, Yahoo announced a deal with 176 newspapers that did not include offline AD sales, although newspaper executives say it is hard to know.
最近，雅虎宣布了一份与176家报纸只有在线广告销售的合同，尽管报社负责人表示这是很难去了解的。
And recently, Yahoo announced a deal with 176 newspapers that did not include offline AD sales, although newspaper executives say it is hard to know.
最近，雅虎宣布了一份与176家报纸只有在线广告销售的合同，尽管报社负责人表示这是很难去了解的。
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