r
复数形式
radii
1
半径, 半径
the length of a line segment between the center and circumference of a circle or sphere
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2
罗马字母的第十八个字母, 字母R
the 18th letter of the Roman alphabet
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3
伦琴, 辐射暴露单位
a unit of radiation exposure; the dose of ionizing radiation that will produce 1 electrostatic unit of electricity in 1 cc of dry air
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4
普适气体常数, 气体常数R
(physics) the universal constant in the gas equation: pressure times volume = R times temperature; equal to 8.3143 joules per kelvin per mole