李贽的“童心”说
噪声的来源主有哪些?人耳开始感到疼痛的声音叫做痛阈,其声级为多少分贝(dB)左右?
国家标准《机械制图》规定了各种图线的宽度,如果粗实线宽度为b(0.25~2mm间选择),则细实线、细点画线、细虚线的宽度为() ["A.b","B.b/3","C.b/2","D.b/4"]
“隐秀”
平直度检查仪测微鼓轮的刻度值是()。 ["A、0.01mm/200mm","B、0.001mm/200mm","C、0.02mm/200mm","D、0.002mm/200"]
城市5类环境噪声(昼、夜)的标准是多少?