妇女的平均月经周期是28天。
并非所有的医生都完全地了解生育周期。
进行周期性检查以确保高标准得以维持。
Periodic checks are taken to ensure that high standards are maintained.
这个周期一直循环往复。
我们必须避免类似20世纪80年代那样破坏性的繁荣-萧条周期。
We must avoid the damaging boom-bust cycles which characterized the 1980s.
更新周期的循环永远不会结束。
早期的元素周期表有空缺，缺少一些元素。
Early versions of the periodic table had gaps, missing elements.
这使人们确信天文周期已经存在了数十亿年。
It assures that the astronomical cycles have been in existence for billions of years.
这能解释为什么它在元素周期表中缺失了吗？
正确的选择将消除沟通周期中可能出现的故障。
Proper selection will eliminate one source of likely breakdown in the communication cycle.
正确的选择将消除沟通周期中可能出现的故障。
Proper selection will eliminate one source of likely breakdown in the communication cycle.
鼻翼两边的阻力呈现一种有规律的周期性变化。
There is a regular cycle of change in resistance between the two sides of the nose.
哈里森教授，你是在说周期表是可以预测的吗？
Professor Harrison, were you saying that the periodic table is predictive?
地磁活动是地球磁场的自然变化，其波动周期为11年。
Geomagnetic activity, the natural variations in Earth's magnetic field, it fluctuates in 11-year cycles.
科学家们得出结论，太阳风的活动必须遵循相同的周期。
The scientists concluded that the solar wind activity must follow the same cycle.
这些相同的变化周期对该区域稀少的人口产生了重大影响。
These same cycles of change had momentous impacts on the sparse human populations of the region.
这是我们的身体在一天24小时内要自然经历的完整周期。
This is the complete cycle our bodies are naturally geared to undergo within the passage of a twenty-four-hour day.
打哈欠可能通过周期性地降低肺部的压力来帮助清理肺部。
It might be that yawning helps to clear out the lungs by periodically lowering the pressure in them.
地轴的倾角也会周期性地变化，在22度到5度之间移动。
The inclination, or tilt, of Earth's axis also varies periodically, moving between 22 degrees and 5 degrees.
沿着周期表的对角线的中间有大约包含六个元素的元素组。
There is this group of about half a dozen right down the diagonal middle of the periodic chart.
如果雄蛙能够设法不经历这样的冻结周期就更可能交配成功。
If the male frog could manage not to go through this freezing cycle, he'd probably have more success in mating.
这是我们的身体在一天24小时内自然调整经历的完整周期。
This is the complete cycle that our bodies are naturally geared to undergo within the passage of a twenty-four hour day.
即使在没有冰川的时期，天文周期也会对地球的气候产生影响。
Astronomical cycles have an effect on Earth's climate even during periods when there is no glaciation.
地球轨道偏心率的变化大约在96000年的一个周期内发生。
Changes in the eccentricity of Earth's orbit occur in a cycle of about 96,000 years.
现在我们继续讨论，谈谈轨道，特别是那些所谓的周期轨道彗星。
Let's continue our discussion now by talking about orbits, especially those of the so-called periodic-orbit comets.
在低纬度地区制定的历法受月球周期的影响比受太阳年的影响更大。
The calendars that were developed at the lower latitudes were influenced more by the lunar cycle than by the solar year.
这些数据已经建立了地球轨道变化和冰期周期之间的强有力的联系。
These data have established a strong connection between variations in the Earth's orbit and the periodicity of the ice ages.
通过观察速溶咖啡的推行，我们可以看到产品生命周期是如何运作的。
We can see how the product life cycle works by looking at the introduction of instant coffee.
生态学家在研究野兔种群时发现，北美雪兔的生长周期大约为10年。
Ecologists studying hare populations have found that the North American snowshoe hare follows a roughly ten-year cycle.
每个潮汐周期都会将植物带到近海海水中，从而被潮水下的生物所利用。
Each tidal cycle carries plant material into the offshore water to be used by the subtidal organisms.
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