Celluloid had been commercially available for decades as a substitute for tortoise-shell, horn, bone and other materials.

几十年来，赛璐璐一直在商业上充当龟甲、角、骨和其他材料的代用品。

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"Infant formula" means a milk-based or soy-based powder, concentrated liquid or ready -to-feed substitute for human breast milk that is intended for infant consumption and is commercially available.

“婴幼儿配方乳”指在商铺中可购买的供婴幼儿食用的奶粉、大豆粉或浓缩液体，或即饮的母乳替代品。

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U.S. company Steelcase now manufactures its own commercially available "Walkstation, " and while it's no substitute for a session in the gym, you may soon be able to burn extra calories while you reply to emails from the boss.

CNN: Boosting employee wellbeing