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   46104篇
  免费   602篇
  国内免费   1647篇
安全科学   1266篇
废物处理   2542篇
环保管理   5325篇
综合类   8276篇
基础理论   12111篇
环境理论   24篇
污染及防治   11686篇
评价与监测   3430篇
社会与环境   3362篇
灾害及防治   331篇
  2023年   248篇
  2022年   606篇
  2021年   637篇
  2020年   442篇
  2019年   433篇
  2018年   2096篇
  2017年   2086篇
  2016年   2162篇
  2015年   982篇
  2014年   1381篇
  2013年   3027篇
  2012年   1976篇
  2011年   3216篇
  2010年   2242篇
  2009年   2108篇
  2008年   2711篇
  2007年   2990篇
  2006年   1594篇
  2005年   1417篇
  2004年   1209篇
  2003年   1359篇
  2002年   1234篇
  2001年   1368篇
  2000年   999篇
  1999年   629篇
  1998年   462篇
  1997年   444篇
  1996年   440篇
  1995年   493篇
  1994年   498篇
  1993年   395篇
  1992年   421篇
  1991年   371篇
  1990年   399篇
  1989年   347篇
  1988年   308篇
  1987年   282篇
  1986年   227篇
  1985年   254篇
  1984年   286篇
  1983年   265篇
  1982年   245篇
  1981年   223篇
  1980年   177篇
  1979年   194篇
  1978年   178篇
  1975年   140篇
  1974年   117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 15 毫秒
111.
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   
112.
113.
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   
114.
INTRODUCTIONIn recent thirty years, due to the decreasing fertility andincreasing life expectancy, China's population is aging ata very rapid pace and the elderly population size is keepingon growing. During the dramatic aging progress, the oldestold group in China is catching our eyes. More and moreold people of China are becoming the oldest old. Theextremely old population (aged 80 and above) is increasingat 5.1% annually, while the old population above 65 isincreasing at 2.9%, and the…  相似文献   
115.
116.
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   
117.
This text describes two different experiences of co-operation between unionists and researchers that resulted in writing of a book. We emphasize their similarities and differences and discuss the importance of these experiences in the dynamics of research and training in Ergonomics.  相似文献   
118.
119.
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   
120.
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