光度计用来测量光的性质、尤其是光的强度和通量的仪器 An instrument for measuring a property of light, especially luminous intensity or flux.
单位面积上的发光强度。 The luminous intensity on unit area.
把铝和其他金属混合，科学家们能够制造出各种合金，其中一些具有钢一样的强度，但其重量只是钢的三分之一。 By mixing aluminium with other metals, scientists have been able to produce a variety of alloys, some of which have the strength of steel but weigh only one third as much.
金属有许多有用的性能，其强度是首要的。 Metal has many useful properties, of which strength is the most important.
