科学家们认为，为了找到一种合适的药品，他们有必要试验数千种的化学药品。
The scientists think that it is necessary for them to try out thousands of chemicals in order to find the right one.
强生公司正在美国完成必要试验，并且希望能在2008年的下半年中能够得到批准进行防止病人腿部栓塞的治疗。（拜耳公司已经在申请欧洲的批准了）
Johnson & Johnson is finishing up a required U. S. trial and hopes to apply for approval for preventing leg clots in the second half of 2008. (Bayer has already filed for European approval. )
一直以来，国会坚持的最关键条件是，将来任何武器修复都要消除进行核试验的必要。
The crucial condition, insisted on by Congress all along, is that any such future weapons tinkering avoid the need for testing.
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