Chemical composition of tobacco is very complicated, though more than 4,000 of components have been identified.
烟草的化学成分十分复杂，已鉴定出的成分就有4,000多种。
With these spectral methods, the chemical composition and the structure of the polishing paste for plastics were identified.
通过上述光谱法确定了该塑料抛光膏的化学组成和结构。
Chemical Composition More than 180 compounds have been identified in propolis, and many are biologically active.
蜂胶中含有超过180种化学成分，大多数是具有生物活性的成分。
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