The pistons are graphite-coated to reduce friction.活塞上涂了一层石墨以减小摩擦力。Some pistons have seating rings of metal or leather.有些活塞上有金属或皮革的密封环.A pump uses valves and pistons.泵使用阀和活塞....
A courtesy shuttle bus operates between the hotel and the town.有免费班车往返于酒店和市区。The train operates the 2,400-mile round trip once a week.这趟火车每周一次往返行驶2,400英里。The tourist office operates a useful room-finding service.这家旅游办事处提...
Carboxylic crosslinked polystyrene microsphere was prepared by F - C acylation reaction.通过傅克酰基化反应制备了羧基化交联聚苯乙烯微球.Benzbromarone was synthesized from salicylaldehyde by condensation with chloroacetone, reduction, acylation,...