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   38664篇
  免费   826篇
  国内免费   3069篇
安全科学   1508篇
废物处理   1640篇
环保管理   4506篇
综合类   11752篇
基础理论   8723篇
环境理论   8篇
污染及防治   10115篇
评价与监测   2134篇
社会与环境   1675篇
灾害及防治   498篇
  2023年   269篇
  2022年   656篇
  2021年   630篇
  2020年   553篇
  2019年   547篇
  2018年   748篇
  2017年   825篇
  2016年   995篇
  2015年   881篇
  2014年   1254篇
  2013年   3045篇
  2012年   1469篇
  2011年   1763篇
  2010年   1476篇
  2009年   1489篇
  2008年   1673篇
  2007年   1687篇
  2006年   1479篇
  2005年   1156篇
  2004年   1198篇
  2003年   1146篇
  2002年   1050篇
  2001年   1365篇
  2000年   980篇
  1999年   709篇
  1998年   573篇
  1997年   538篇
  1996年   542篇
  1995年   543篇
  1994年   579篇
  1993年   464篇
  1992年   476篇
  1991年   439篇
  1990年   479篇
  1989年   443篇
  1988年   349篇
  1987年   323篇
  1986年   308篇
  1985年   315篇
  1984年   356篇
  1983年   346篇
  1982年   359篇
  1981年   361篇
  1980年   282篇
  1979年   305篇
  1978年   249篇
  1977年   237篇
  1974年   246篇
  1973年   232篇
  1972年   243篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
51.
The two studies reported further test reversal theory hypotheses concerning human psychological responses to different types of settings and environmental events on an Asian sample. In study 1, individuals in four settings representing different combinations of metamotivational state and arousal level (telic and paratelic/low arousal; telic and paratelic/high arousal) completed the telic state measure (TSM; Svebak & Murgatroyd, 1985). Significant differences between participants' mean scores across the four settings were obtained for TSM items serious–playful, planning–spontaneous, felt arousal, preferred arousal, effort and arousal discrepancy. In study 2 different environmental events in the same setting (changes in reading tasks), used in a crossover design, were used to induce reversals in individuals' operative metamotivational states. The results obtained from TSM scores pretask 1, between tasks and posttask 2. indicated significant time-of-testing interaction effects on the TSM serious–playful, planning–spontaneous and effort items. In addition, a main effect for TSM felt arousal was found. These results showed that reversals in metamotivational states were induced by the environmental event and that felt arousal scores increased across the three administrations of the TSM.  相似文献   
52.
53.
The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact.  相似文献   
54.
Peregrine falcons (Falco peregrinus) have been recorded nesting in Big Bend National Park, Texas, USA and other areas of the Chihuahuan Desert since the early 1900s. From 1993 to 1996, peregrine falcon productivity rates were very low and coincided with periods of low rainfall. However, low productivity also was suspected to be caused by environmental contaminants. To evaluate potential impacts of contaminants on peregrine falcon populations, likely avian and bat prey species were collected during 1994 and 1997 breeding seasons in selected regions of western Texas, primarily in Big Bend National Park. Tissues of three peregrine falcons found injured or dead and feathers of one live fledgling also were analyzed. Overall, mean concentrations of DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene], a metabolite of DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane], were low in all prey species except for northern rough-winged swallows (Stelgidopteryx serripennis, mean = 5.1 microg/g ww). Concentrations of mercury and selenium were elevated in some species, up to 2.5 microg/g dw, and 15 microg/g dw, respectively, which upon consumption could seriously affect reproduction of top predators. DDE levels near 5 microg/g ww were detected in carcass of one peregrine falcon found dead but the cause of death was unknown. Mercury, selenium, and DDE to some extent, may be contributing to low reproductive rates of peregrine falcons in the Big Bend region.  相似文献   
55.
56.
57.
58.
59.
60.
Sustainable development of the earth's limited water and land resources is of paramount importance because of rising world population and existing conflicting demands for these resources. Enormous capital investment has been made in developing these resources, but now there is irrefutable evidence that such developments have led to major resource degradation. This includes problems of salinisation and damages to ecosystems. The countries predominantly affected by human induced salinisation are located in arid and semi-arid regions of the world and include Australia, China, Egypt, India, Pakistan, USSR, and USA. This paper describes the processes of salinisation, its impacts and the use of quantitative methods in salinity investigation and management. Australia is used as a case study of typical salinity problems and as a demonstration of the fruitful application of quantitative methods. The paper concludes that quantitative methods such as surface water and groundwater models are powerful design, management and predictive tools in salinity investigation. However, application of some models, such as those for unsaturated flow and transport and groundwater solute transport, are not widespread due to uncertainties in describing the complexity of the processes and the lack of hydrodispersive data.  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