periodic rejuvenation of the oldline

例句：

1. 1. Theperiodic changes in the weather are a sourceof fascination for many people.
   天气的周期性变化是许多人着迷的原因。
2. 2.The periodic table of elements is a fundamentaltool for understanding chemistry.
   元素周期表是理解化学的基础工具。
3. 3. Theperiodic law states that elementswith similar properties tend to grouptogether.
   周期性律表明，具有相似性质的元素倾向于聚集在一起。