胚胎的质量和受体牛的质量是影响胚胎移植受体牛妊娠率的两个非人为因素。
Recent attempts to improve the recipients' pregnancy rates via the improvement of embryo quality and the proper selection and management of recipients were discussed in this review.
拜尔公司已经不是第一次把导致CCD的原因死死归结于诸如病毒、真菌或杀虫剂等非人为因素了。
This isn't the first time Bayer has mobilized an effort to pin CCD on a non-man made cause, such as a virus, fungus, or parasite.
本文分析了外来生物的入侵途径：人类有意引入、随人类活动无意传入以及非人为因素的自然传入。
The ways of invasion of alien species are examined, mainly: introduction by people intentionally or not intentionally, and introduction by natural factors.
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