relative index of refraction
相对折射率

• upright projection
• upscattering
• upside
• upside down
• upstage
• upstream
• upstream ionization
• upwash
• upwelling
• uranin
• uraninite
• gas-ballatsing
• gas breakdown
• gas breakdown threshold
• gas chromatograph
• gas chromatography
• gas chromatorgarma
• gas clean up
• gas current
• gas detector
• gas diode
• gas diode phototube
• gas discharge
• gas-discharge
• gas-discharge cell