visual observation
(1)目察法，直观研究法
(2)目视，观测

• six colo(u)r infrared photometer
• six-sided out
• six-spindle polishing machine
• sixteen-millimeter projector
• size
• sizing
• skeleton
• sketch
• sketchmaster
• skew-axes gear
• skew bevel gear
• skew gear
• skewness
• skew ray
• skew wheel
• skiameter
• skiascope
• Skiascopic rack
• skiatron
• skim
• skin
• skin depth
• skin-effect
• skin emissivity
• skin layer