- Industry: Government
- Number of terms: 33950
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United States Department of Health and Human Services, Radiation Emergency Medical Management
一定数量的一种放射性同位素衰变一半所需的时间。例如，因为碘-131 (i-131) 的半衰期为 8 天，1 月 1 日有活动的 10 mci 的 i-131 的样本会有 5 mci 的活动 8 天后，1 月 9 日。也请参阅生物半衰期，衰变常数、 有效半衰期。(插图)
Industry:Medical devices
分钟，慢慢地从大气中降落在核爆后放射性碎片颗粒。更多的信息，请参阅疾病预防控制中心的辐射报告 (pdf-32.24 mb) 的第 2 章。
Industry:Medical devices
结果从不断变化的电场和磁场的旅行波动。类型的电磁波辐射范围从那些波长短，像 x 射线和伽玛射线，通过紫外线、 可见光和红外的地区，对雷达和较长波长的无线电波。
Industry:Medical devices
The new international system (si) unit of radiation dose, expressed as absorbed energy per unit mass of tissue. The si unit "gray" has replaced the older "rad" designation. (1 gy = 1 joule/kilogram = 100 rad). Gray can be used for any type of radiation (e.g., alpha, beta, neutron, gamma), but it does not describe the biological effects of different radiations. Biological effects of radiation are measured in units of "sievert" (or the older designation "rem"). Sievert is calculated as follows: gray multiplied by the "radiation weighting factor" (also known as the "quality factor") associated with a specific type of radiation.
Industry:Medical devices
