The Brookings Institution has assembled a collection of essays from foreign affairs experts.布鲁金斯研究所将一批外交专家撰写的文章结集出版。Pollack, is a specialist on Iran with the Washington - based Brookings Institution.肯尼思?波拉克是华盛顿布鲁金机构的专家致力...
A hydrocarbon was known to be either an alkene or alkane.某碳氢化合物已知可能是烯烃或是烷烃.The hydrocarbon must be an alkene.这个碳氢化合物必定是烯烃.The betaine will collapse to the alkene only when these two functions are eclipsed.只有当这两个基团移至重迭位置时...