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   39832篇
  免费   375篇
  国内免费   481篇
安全科学   998篇
废物处理   2180篇
环保管理   4986篇
综合类   5976篇
基础理论   10902篇
环境理论   25篇
污染及防治   9766篇
评价与监测   3047篇
社会与环境   2622篇
灾害及防治   186篇
  2023年   147篇
  2022年   333篇
  2021年   327篇
  2020年   259篇
  2019年   298篇
  2018年   1825篇
  2017年   1780篇
  2016年   1872篇
  2015年   719篇
  2014年   928篇
  2013年   2493篇
  2012年   1525篇
  2011年   2694篇
  2010年   1829篇
  2009年   1737篇
  2008年   2256篇
  2007年   2604篇
  2006年   1299篇
  2005年   1137篇
  2004年   1046篇
  2003年   1158篇
  2002年   1052篇
  2001年   1259篇
  2000年   887篇
  1999年   535篇
  1998年   373篇
  1997年   376篇
  1996年   369篇
  1995年   431篇
  1994年   448篇
  1993年   362篇
  1992年   382篇
  1991年   360篇
  1990年   388篇
  1989年   345篇
  1988年   301篇
  1987年   288篇
  1986年   229篇
  1985年   252篇
  1984年   278篇
  1983年   267篇
  1982年   244篇
  1981年   224篇
  1980年   180篇
  1979年   194篇
  1978年   178篇
  1977年   118篇
  1975年   140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 15 毫秒
91.
92.
93.
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   
94.
95.
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   
96.
97.
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   
98.
99.
Haque CE  Zaman MQ 《Disasters》1989,13(4):300-314
As a deltaic plain, Bangladesh annually experiences riverbank erosion hazard due to sudden and rapid channel shifting, particularly in the major floodplain areas of the country. Consequently, valuable cultivable land is lost; also village settlements, markets and towns are destroyed, displacing tens of thousands of people. This paper examines the magnitude of river channel migration and encroachment on land, and the nature of human adjustment systems in the Brahmaputra–Jamuna floodplain, by investigating aspects of the social and cultural dynamics of resettlement of the displaced people. Some policy measures are recommended to improve the ability of the people in the floodplain to cope with these hazards.  相似文献   
100.
Earthquake hazard assessment after Mexico (1985)   总被引:1,自引:0,他引:1  
Degg MR 《Disasters》1989,13(3):237-246
The 1985 Mexican earthquake ranks foremost amongst the major earthquake disasters of the twentieth century. One of the few positive aspects of the disaster is that it provided massive quantities of data that would otherwise have been unobtainable. Every opportunity should be taken to incorporate the findings from these data in earthquake hazard assessments. The purpose of this paper is to provide a succinct summary of some of the more important lessons from Mexico. It stems from detailed field investigations, and subsequent analyses, conducted by the author on the behalf of reinsurance companies.  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