1. It is the product of radioactive decay (see radioactivity) and is used in helium dating. 氦是由放射性衰变形成的,可用于氦年代测定法。
2. The time required for half the nuclei in a sample of a specific isotopic species to undergo radioactive decay. 半''。'衰'。''期放射性样品的原子核经历一半放射性''。'衰'。''''。'变'。''所需要的时间。
3. It results from cosmic rays reaching the earth from the outer space, and from the radioactive decay of mineral in the soil. 它来自星际空间抵达地球的宇宙射线,来自土壤中矿物质的放射性衰变。
英英解释
n.
1. the spontaneous disintegration of a radioactive substance along with the emission of ionizing radiat