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   42050篇
  免费   360篇
  国内免费   488篇
安全科学   1024篇
废物处理   2284篇
环保管理   5052篇
综合类   6302篇
基础理论   11379篇
环境理论   20篇
污染及防治   10262篇
评价与监测   3226篇
社会与环境   3153篇
灾害及防治   196篇
  2023年   161篇
  2022年   398篇
  2021年   404篇
  2020年   289篇
  2019年   327篇
  2018年   1918篇
  2017年   1887篇
  2016年   1948篇
  2015年   742篇
  2014年   990篇
  2013年   2568篇
  2012年   1602篇
  2011年   2874篇
  2010年   1981篇
  2009年   1863篇
  2008年   2422篇
  2007年   2765篇
  2006年   1327篇
  2005年   1254篇
  2004年   1163篇
  2003年   1306篇
  2002年   1173篇
  2001年   1300篇
  2000年   898篇
  1999年   549篇
  1998年   379篇
  1997年   372篇
  1996年   373篇
  1995年   434篇
  1994年   460篇
  1993年   362篇
  1992年   383篇
  1991年   362篇
  1990年   391篇
  1989年   345篇
  1988年   300篇
  1987年   285篇
  1986年   230篇
  1985年   259篇
  1984年   287篇
  1983年   272篇
  1982年   246篇
  1981年   228篇
  1980年   175篇
  1979年   199篇
  1978年   178篇
  1975年   142篇
  1974年   119篇
  1972年   131篇
  1971年   132篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
101.
102.
New data on the composition of surface assemblages of plant macroremains from soil and swamp samples have been obtained in the study of geomorphologically different localities in the middle reaches of the Nizhnyaya Tunguska River. The results of paleocarpological analysis of forest soil sections supported by relevant palynological and geochronological data are presented. Natural changes of the forest cover over the past 2400 years and quantitative characteristics of the paleoclimate during each stage are described.Translated from Ekologiya, No. 1, 2005, pp. 3–10.Original Russian Text Copyright © 2005 by Koshkarova, Koshkarov.  相似文献   
103.
104.
105.
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   
106.
107.
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   
108.
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   
109.
110.
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