The drug is derived from the bark of the cinchona tree, native to South America, and by 1856 demand for the drug was surpassing the available supply.

这种药物是从原产于南美洲的金鸡纳树的树皮中提取的。到了1856年，对这种药物的需求已经超过了现有的供应。

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In a tight labour market, demand by employers exceeds the available supply of workers.

在劳动力走俏的市场上，雇主的需求超过工人的供应。

《柯林斯英汉双解大词典》

Countries labeled as moderate to high stress consume 20 percent more water than their available supply.

把一些国家标定为中度到高度“用水紧张”是它们消耗了超过可供应水量的20%以上。

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So the problem is in the low real wages and low level of demand, not a lack of available supply.

BBC: George Osborne must weigh supply against demand

For instance, homes equipped with solar-power panels could feed unused electricity back into the grid, adding to the total available supply.

FORBES: Magazine Article

Another possible contributor to the large drop in 2011, though, is limited available supply from manufacturers rather than decreased demand from dealers.

FORBES: Auto's Lean Inventory & Shifting Market Share