1·During periods when commodity prices were high, the rate of westward migration increased spectacularly.
在商品价格较高的时期，西迁的速度大幅增长。
2·Although change in carbon dioxide content closely follows change in temperature during periods of deglaciation, it apparently lags behind temperature during periods of cooling.
虽然在冰川消退期间二氧化碳含量的变化与温度的变化密切相关，但它显然滞后于冷却期间的温度。
3·In the wild, these birds store food for retrieval later during periods of food scarcity.
在野外，这些鸟会储存食物以备日后食物短缺时再取用。
4·Astronomical cycles have an effect on Earth's climate even during periods when there is no glaciation.
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。
5·It must be very difficult for you as a banker to try to satisfy your customers during periods like this .
处于这样的时期，你作为一个银行家，要想尽力去满足你的顾客们的要求肯定是很困难的。
6·Slow, continuous change may be the norm during periods of environmental stability, while rapid evolution of new species occurs during periods of environment stress.
缓慢的、持续的变化可能是环境稳定时期的常态，而新物种的快速进化发生在环境压力时期。
7·In the long run, electricity from large wind farms in remote areas might be used to make hydrogen gas from water during periods when there is less than peak demand for electricity.
从长远来看，在电力需求低于峰值的时期，偏远地区的大型风力发电场的电力可能会被用于电解水，以产生氢气。
8·During periods of low demand, jockey pumps are used to meet these lower water flow requirements.
在需求较低的时期，赛马泵用于满足这些较低的水流量要求。
9·During periods of increased threat increase your disaster supplies to be adequate for up to two weeks.
在危险升级期间，增加你应对灾难的物质贮备，贮备要足够应对至少两个星期。
10·They found that, during periods of high nutrient levels, genetically distinct hybrid species emerged.
他们发现，经过一段时期的高营养水平环境，在遗传学上截然不同的杂交品种产生了。