首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   34919篇
  免费   558篇
  国内免费   1620篇
安全科学   1232篇
废物处理   1684篇
环保管理   4101篇
综合类   6891篇
基础理论   8938篇
环境理论   20篇
污染及防治   9562篇
评价与监测   2375篇
社会与环境   1988篇
灾害及防治   306篇
  2023年   221篇
  2022年   492篇
  2021年   468篇
  2020年   387篇
  2019年   404篇
  2018年   653篇
  2017年   637篇
  2016年   912篇
  2015年   801篇
  2014年   1115篇
  2013年   2833篇
  2012年   1318篇
  2011年   1768篇
  2010年   1461篇
  2009年   1466篇
  2008年   1729篇
  2007年   1756篇
  2006年   1502篇
  2005年   1269篇
  2004年   1159篇
  2003年   1229篇
  2002年   1101篇
  2001年   1464篇
  2000年   1039篇
  1999年   621篇
  1998年   435篇
  1997年   429篇
  1996年   417篇
  1995年   491篇
  1994年   504篇
  1993年   403篇
  1992年   413篇
  1991年   387篇
  1990年   410篇
  1989年   370篇
  1988年   319篇
  1987年   294篇
  1986年   237篇
  1985年   259篇
  1984年   280篇
  1983年   267篇
  1982年   260篇
  1981年   233篇
  1980年   183篇
  1979年   200篇
  1978年   187篇
  1975年   150篇
  1974年   123篇
  1972年   137篇
  1971年   135篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
Indices of abundance and reproduction rate are considered in some groups of aquatic and terrestrial vertebrates from the zones of technogenic disasters. Upon a critical population decline caused by external destructive factors, such as emissions of acute ecotoxicants, the ecophysiological and behavioral compensatory mechanisms are activated, which provide for restoration of the total population size to the optimum within a short period of time. Environmental pollution with substances disturbing the reproductive function has the gravest consequences for animals. In this case, population size may remain fairly high, and, therefore, the effect of enhanced reproduction as a response to population decline does not take place, which eventually leads to a gradual but irreversible destruction of the population. Pathologies of reproduction should be used as a criterion for assessing the state of animals in the zones of technogenic disasters.Translated from Ekologiya, No. 1, 2005, pp. 32–38.Original Russian Text Copyright © 2005 by Shilova, Shatunovskii.  相似文献   
82.
83.
5p deletion syndrome commonly known as cri du chat is well described in affected neonates with catlike cry and hypotonia. Karyotyping will usually show a deletion of the short arm of one chromosome 5 with variable breakpoints. Only a few cases have been reported prenatally, and the fetal form of the syndrome has not been clearly individualised. We report a new case of 5p deletion syndrome diagnosed prenatally in association with Dandy–Walker syndrome and agenesis of the corpus callosum. Other brain anomalies have been reported previously, but this unusual association suggests the use of a specific probe in the investigation of these malformations. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
84.
85.
86.
The towed undulating vehicle (TUV), named SARAGO, was used for two fine-scale surveys between the Italian and the Sardinian coasts during the Astraea 2 cruise (6-7 and 26-27 September 1995), studying the deep chlorophyll maximum distribution. SARAGO sections identify a sub-surface doming with higher chlorophyll a and primary production concentrations in the upwelling area of a cyclonic gyre region, detected by sea-surface temperature images. In the first section, the cyclone presents a double doming, in density and salinity, with shallower and concentrated patches of chlorophyll a for about 2 miles. Twenty days later, the second section shows that the gyre changes shape and extension, showing a single doming with higher primary production and chlorophyll a concentrations, distributed over a large area of about 40 nautical miles. SARAGO allows analysis of this high-variability phenomenon (cyclonic gyre) and allows concentrated patches (2 nm) to be identified, thus proving the importance of TUVs in the study of mesoscale processes.  相似文献   
87.
88.
Spilt notochord syndrome is an extremely rare form of spinal dysraphism characterized by a complete cleft of the spine and a persistent communication between endoderm and ectoderm. A variant of split notochord syndrome was diagnosed in a 25-week-old fetus showing a prolapsed congenital colostomy and a spinal cystic lesion. The final diagnosis included protruding colon segment, imperforate anus with a rectourethral fistula and lipomyelomeningocele. The ultrasound features of the condition and the post-natal management are discussed. The neonate was successfully treated with a posterior sagittal anorectoplasty, while the lipomyelomeningocele was resected at a later stage. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
89.
90.
One of the most difficult tasks in conservation biology is identifying populations subject to stress before such stress has a detrimental impact on the population, thus allowing conservation and remedial action to be undertaken. Measuring fitness (fecundity, survival, etc.) changes directly is often difficult, expensive, or impractical. The ability of an organism to buffer its development against disturbances (developmental stability) is often considered an integral component of an individual's fitness. Data are presented from a number of studies that establish a clear relationship between developmental stability and fitness in response to both genetic and environmental stress. Consequently, I suggest that developmental stability may be used as a surrogate for more direct fitness estimation for use in conservation biology and biomonitoring programs and that is has widespread application as an early warning system for monitoring the effect of genetic and environmental stresses on natural populations.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号