photochromic gas viewing screen
光色气体观察屏

• work function
• work head
• workholder
• work holding
• working aperture
• working distance
• working distance of microscope
• working drawing
• working ga[u]ge
• working range
• working standard
• working voltage
• workmanship
• workpiece
• work sheet
• workshop ga[u]ge
• workshop instrument
• workshop microscope
• worm
• worm gear
• worm gearing
• worm mesh
• worm thread
• worm wheel
• worn-out