全文获取类型
收费全文 | 24672篇 |
免费 | 158篇 |
国内免费 | 126篇 |
专业分类
安全科学 | 375篇 |
废物处理 | 1396篇 |
环保管理 | 2922篇 |
综合类 | 3414篇 |
基础理论 | 7242篇 |
环境理论 | 4篇 |
污染及防治 | 5671篇 |
评价与监测 | 2014篇 |
社会与环境 | 1826篇 |
灾害及防治 | 92篇 |
出版年
2022年 | 128篇 |
2021年 | 104篇 |
2020年 | 100篇 |
2019年 | 107篇 |
2018年 | 1612篇 |
2017年 | 1541篇 |
2016年 | 1464篇 |
2015年 | 384篇 |
2014年 | 465篇 |
2013年 | 1207篇 |
2012年 | 917篇 |
2011年 | 1954篇 |
2010年 | 1251篇 |
2009年 | 1143篇 |
2008年 | 1495篇 |
2007年 | 1873篇 |
2006年 | 590篇 |
2005年 | 531篇 |
2004年 | 552篇 |
2003年 | 567篇 |
2002年 | 581篇 |
2001年 | 660篇 |
2000年 | 485篇 |
1999年 | 256篇 |
1998年 | 181篇 |
1997年 | 206篇 |
1996年 | 205篇 |
1995年 | 236篇 |
1994年 | 234篇 |
1993年 | 181篇 |
1992年 | 195篇 |
1991年 | 183篇 |
1990年 | 203篇 |
1989年 | 187篇 |
1988年 | 151篇 |
1987年 | 162篇 |
1986年 | 153篇 |
1985年 | 157篇 |
1984年 | 159篇 |
1983年 | 148篇 |
1982年 | 125篇 |
1981年 | 120篇 |
1980年 | 116篇 |
1979年 | 125篇 |
1978年 | 101篇 |
1977年 | 113篇 |
1975年 | 87篇 |
1974年 | 87篇 |
1973年 | 96篇 |
1972年 | 86篇 |
排序方式: 共有10000条查询结果,搜索用时 484 毫秒
241.
While true mosaicism occurs in only 0–25 per cent of genetic amniocenteses, nearly 2–5 per cent of amniotic fluid cell cultures contain a second cell line. In the common practice of prenatal diagnosis, an aberrant cell line confined to a single colony is usually disregarded. We present a case of mosaic trisomy 14 which was not detected on initial chromosome analysis. At birth, multiple malformations were apparent. Newborn cytogenetic studies revealed mosaicism [46,XX/46,XX,-14,+i(14q)] with an isochromosome 14 in 37 per cent of lymphocytes. Additional cells from the initial amniotic fluid culture were analysed post-delivery and the isochromosome 14 identified in only one of 12 total colonies. This case illustrates two important lessons in prenatal diagnosis. First, amniotic fluid cell cultures may not accurately reflect the relative distribution of the normal and abnormal cell lines within a mosaic fetus. Second, while it is generally reasonable to disregard mosaicism confined to a single colony, this policy will, on rare occasion, result in diagnostic error. This should be taken into consideration, particularly when dealing with autosomal trisomies potentially compatible with livebirth. 相似文献
242.
243.
Bosch J 《Die Naturwissenschaften》2002,89(12):575-578
Female midwife toads (genus Alytes) emit highly variable reciprocal calls of unclear function prior to and during courtship. In some species, female-female competition, expressed as physical fighting, has been reported. Males of Majorcan midwife toads (Alytes muletensis) show phonotactic response to female calls, and females of Iberian midwife toads (Alytes cisternasii) respond differently according to the male call characteristics. In this study, I test the hypothesis of female-female acoustic competition as an additional function of female reciprocal calls. Playback tests indicate that female calls are not clearly involved in female acoustic competition in the Iberian midwife toad, therefore female calls could be directed at males rather than towards competitive females. 相似文献
244.
245.
In this paper we deal with the problem of identifying environmental principles for the design and operation of supply chains. The operations that are included in supply chains are briefly described along with the approaches that are applied in order to improve their environmental performance. A background of environmental principles for achieving eco-efficiency and building of environmentally friendly organizational systems is presented and emphasis is put on the application of such principles “from cradle to grave”. Then, environmental principles applicable to particular objects of logistics networks planning are identified and commented upon. In addition, selective case studies from the literature, which show the applicability of the formulated principles and their relevance to practice, are discussed. The paper concludes with some remarks regarding the benefits for companies and societies, in general, that occur as a result of the application of the formulated principles. 相似文献
246.
247.
248.
P. Kramer 《Die Naturwissenschaften》1982,69(3):114-122
The fundamental concepts underlying the application of symmetry to physics are discussed. The exposition employs objects from the geometry of two and three dimensions instead of the algebraic formalism. 相似文献
249.
250.