The tilt of Earth's axis, toward the Sun at some times of the year and away from the Sun at other times, is responsible for the annual cycle of seasons.
地轴的倾斜在一年中的某些时候朝向太阳，而在其它时间远离太阳，造成了每年的季节循环。
The Moon's brightness varies throughout its annual cycle, during the mid-winter in the northern hemisphere it can appear brighter simply because it is higher in the sky.
月球的亮度随着轨道位置的变化而变化，在北半球的深冬，月亮会更亮，因为它在天空中更高。
The annual cycle of gonad development and the fertilization of the nemertean, Procephalothrix simulus, were studied by histological method.
用组织切片法对扁额原细首纽虫周年性腺发育及受精过程进行了初步的研究。
The annual cycle of gonad development and the fertilization of the nemertean, Procephalothrix simulus, were studied by histological method.
用组织切片法对扁额原细首纽虫周年性腺发育及受精过程进行了初步的研究。
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