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   34365篇
  免费   693篇
  国内免费   1717篇
安全科学   1281篇
废物处理   1633篇
环保管理   4047篇
综合类   7406篇
基础理论   8669篇
环境理论   18篇
污染及防治   9129篇
评价与监测   2339篇
社会与环境   1947篇
灾害及防治   306篇
  2023年   220篇
  2022年   518篇
  2021年   502篇
  2020年   425篇
  2019年   432篇
  2018年   654篇
  2017年   676篇
  2016年   924篇
  2015年   758篇
  2014年   1176篇
  2013年   2830篇
  2012年   1420篇
  2011年   1797篇
  2010年   1473篇
  2009年   1507篇
  2008年   1728篇
  2007年   1745篇
  2006年   1496篇
  2005年   1280篇
  2004年   1102篇
  2003年   1224篇
  2002年   1059篇
  2001年   1323篇
  2000年   958篇
  1999年   592篇
  1998年   425篇
  1997年   419篇
  1996年   418篇
  1995年   469篇
  1994年   478篇
  1993年   380篇
  1992年   406篇
  1991年   363篇
  1990年   403篇
  1989年   350篇
  1988年   299篇
  1987年   283篇
  1986年   227篇
  1985年   255篇
  1984年   269篇
  1983年   259篇
  1982年   242篇
  1981年   226篇
  1980年   176篇
  1979年   196篇
  1978年   176篇
  1975年   140篇
  1974年   118篇
  1972年   131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.
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   
84.
85.
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   
86.
87.
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   
88.
论土地持续利用   总被引:33,自引:0,他引:33  
在世界上有两种可持续发展思路,一种是西方发达国家的重保护的可持续发展思路;一种是以发展为前提,保护自然资源的可持续发展思路。土地持续利用的思想是在可持续发展的进程中不断发展的。我国要保证土地持续利用,满足未来对食粮和建设的需求,应建立起同土地持续利用相适应的土地持续利用制度和土地持续利用机制  相似文献   
89.
90.
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   
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