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   30917篇
  免费   357篇
  国内免费   463篇
安全科学   1010篇
废物处理   1470篇
环保管理   3760篇
综合类   5157篇
基础理论   8072篇
环境理论   18篇
污染及防治   8152篇
评价与监测   2104篇
社会与环境   1809篇
灾害及防治   185篇
  2023年   144篇
  2022年   326篇
  2021年   326篇
  2020年   253篇
  2019年   290篇
  2018年   493篇
  2017年   505篇
  2016年   766篇
  2015年   587篇
  2014年   910篇
  2013年   2456篇
  2012年   1083篇
  2011年   1477篇
  2010年   1190篇
  2009年   1224篇
  2008年   1473篇
  2007年   1531篇
  2006年   1283篇
  2005年   1121篇
  2004年   1006篇
  2003年   1100篇
  2002年   967篇
  2001年   1249篇
  2000年   872篇
  1999年   525篇
  1998年   353篇
  1997年   364篇
  1996年   359篇
  1995年   428篇
  1994年   455篇
  1993年   356篇
  1992年   375篇
  1991年   353篇
  1990年   390篇
  1989年   344篇
  1988年   297篇
  1987年   281篇
  1986年   224篇
  1985年   249篇
  1984年   267篇
  1983年   258篇
  1982年   242篇
  1981年   223篇
  1980年   175篇
  1979年   194篇
  1978年   176篇
  1975年   141篇
  1974年   118篇
  1972年   130篇
  1971年   131篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
83.
84.
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   
85.
86.
Juberg–Hayward syndrome is a rare autosomal recessive syndrome characterised by the association of growth retardation, microcephaly, cleft lip and palate, and thumb and radial ray abnormalities. To date, no prenatal cases have been reported. Here, we report on the first prenatal case of Juberg–Hayward syndrome. The diagnosis was established following fetopathological study. Besides the cardinal features of the syndrome, this prenatal case was remarkable for the severity of the short arm malformation and by the finding of big toe agenesis and cerebral abnormalities including hydrocephalus, agenesis of corpus callosum, and cerebellar hypoplasia. We conclude that the diagnosis of Juberg–Hayward syndrome can be discussed prenatally following ultrasound diagnosis of the association of intrauterine growth restriction, microcephaly, thumb/radial anomalies, and cleft lip/palate. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
87.
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   
88.
89.
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   
90.
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