选择还原 meaning in English

selective reduction

Restore the database only if its data files or transaction log files no longer exist or are unusable
仅在数据库的数据文件或事务日志文件不再存在或不可用时，才能选择还原数据库。
Using nano lih and nano nah as reducers , in refluxing thf and under normal pressure , cinnamaldehyde were selectively reduced to cinnamyl alcohol with selectivities of 99 % at higher conversions . changing reaction temperature or the molar ratio between reactants and cinnamaldehyde can improve the selectivities and conversions . in addition , the sequence of the reactants is another factor to affect the selectivity and conversion in this reaction
实验还同时考察了温度、 mh的比例、加样顺序等因素对选择还原反应的影响：其中，温度的升高能加快反应的速度并提高反应的转化率和选择性； mh比例的增大也能加快反应速度并提高反应的选择性和转化率；另一方面，改变加样的先后顺序会明显改变反应的选择性和转化率。