“unit”的概念、定义、翻译、参考文献-科学参考

unit

Physics

A specified measure of a physical quantity, such as length, mass, time, etc., specified multiples of which are used to express magnitudes of that physical quantity. For many scientific purposes previous systems of units have now been replaced by SI units.

Mathematics

See SI units.
An element u, in a ring R with a 1, such that there exists v in R with uv = 1 = vu. The units of R form a group under multiplication, denoted R*. For R, the ring of n × n real matrices, R* = GL(n,ℝ), while for a field F, then F* = F\\{0}.

Chemistry

A specified measure of a physical quantity, such as length, mass, time, etc., specified multiples of which are used to express magnitudes of that physical quantity. For scientific purposes previous systems of units have now been replaced by SI units.

Chemical Engineering

1. The fundamental measure of a physical quantity such as length, mass, and time. Derived units include area, velocity, density, etc. SI units have replaced previous systems for scientific and engineering purposes.

2. An item of process equipment or plant designed to carry out a specific task.

Electronics and Electrical Engineering

A precisely specified quantity, such as the ampere or second, in terms of which the magnitude of other physical quantities of the same kind can be stated:
physical quantity = numerical value × unit
current = n amperes
charge = n amperes per second = n coulombs
In a purely mechanical system the units can be defined in terms of three base units of mass, length, and time: other units are derived by multiplying and/or dividing these base units. In any system concerned with electric and magnetic properties a fourth base unit is necessary to make the system totally self-consistent. In the past, various choices of this quantity and its value led to several different systems of units, including the CGS and MKS systems.
The system of SI units was formulated, by international agreement, in order to produce a coherent set of units that can be used in every field of science and technology in a consistent manner. There are seven base SI units from which almost every other unit can be derived. See also Tables 4–9, in the back matter.

Biology

A specified measure of a physical quantity, such as length, mass, time, etc., specified multiples of which are used to express magnitudes of that physical quantity. For scientific purposes previous systems of units have now been replaced by SI units.

单词	unit
释义	unit Physics A specified measure of a physical quantity, such as length, mass, time, etc., specified multiples of which are used to express magnitudes of that physical quantity. For many scientific purposes previous systems of units have now been replaced by SI units. Mathematics See SI units. An element u, in a ring R with a 1, such that there exists v in R with uv = 1 = vu. The units of R form a group under multiplication, denoted R. For R, the ring of n × n real matrices, R = GL(n,ℝ), while for a field F, then F* = F\\{0}. Chemistry A specified measure of a physical quantity, such as length, mass, time, etc., specified multiples of which are used to express magnitudes of that physical quantity. For scientific purposes previous systems of units have now been replaced by SI units. Chemical Engineering 1. The fundamental measure of a physical quantity such as length, mass, and time. Derived units include area, velocity, density, etc. SI units have replaced previous systems for scientific and engineering purposes. 2. An item of process equipment or plant designed to carry out a specific task. Electronics and Electrical Engineering A precisely specified quantity, such as the ampere or second, in terms of which the magnitude of other physical quantities of the same kind can be stated: physical quantity = numerical value × unit current = n amperes charge = n amperes per second = n coulombs In a purely mechanical system the units can be defined in terms of three base units of mass, length, and time: other units are derived by multiplying and/or dividing these base units. In any system concerned with electric and magnetic properties a fourth base unit is necessary to make the system totally self-consistent. In the past, various choices of this quantity and its value led to several different systems of units, including the CGS and MKS systems. The system of SI units was formulated, by international agreement, in order to produce a coherent set of units that can be used in every field of science and technology in a consistent manner. There are seven base SI units from which almost every other unit can be derived. See also Tables 4–9, in the back matter. Biology A specified measure of a physical quantity, such as length, mass, time, etc., specified multiples of which are used to express magnitudes of that physical quantity. For scientific purposes previous systems of units have now been replaced by SI units.
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