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   385篇
  免费   6篇
  国内免费   3篇
安全科学   13篇
废物处理   15篇
环保管理   69篇
综合类   60篇
基础理论   95篇
环境理论   2篇
污染及防治   98篇
评价与监测   22篇
社会与环境   12篇
灾害及防治   8篇
  2023年   5篇
  2022年   4篇
  2021年   5篇
  2020年   9篇
  2019年   4篇
  2018年   8篇
  2017年   16篇
  2016年   9篇
  2015年   10篇
  2014年   6篇
  2013年   48篇
  2012年   11篇
  2011年   24篇
  2010年   10篇
  2009年   10篇
  2008年   19篇
  2007年   13篇
  2006年   12篇
  2005年   8篇
  2004年   12篇
  2003年   18篇
  2002年   10篇
  2001年   7篇
  2000年   5篇
  1998年   5篇
  1997年   4篇
  1995年   5篇
  1994年   4篇
  1993年   4篇
  1991年   3篇
  1990年   7篇
  1989年   5篇
  1988年   3篇
  1987年   4篇
  1985年   2篇
  1984年   6篇
  1983年   6篇
  1982年   5篇
  1981年   4篇
  1979年   7篇
  1978年   2篇
  1977年   2篇
  1976年   3篇
  1975年   3篇
  1973年   3篇
  1972年   2篇
  1971年   2篇
  1968年   2篇
  1961年   3篇
  1959年   2篇
排序方式: 共有394条查询结果,搜索用时 15 毫秒
121.
We consider how ecosystem services can be incorporated into water infrastructure planning by studying the projected deepening of the Lower Weser river channel in Germany. We recalculate the project's benefit–cost ratio by integrating the monetary value of changes in different ecosystem services, as follows: (1) the restoration costs of a mitigation measure for a loss in fresh water supply for agricultural production in the estuary region, (2) the costs of a loss in habitat services, transferring the willingness to pay from a contingent valuation study to the area assessed in the environmental impact assessment, and (3) the benefits of emissions savings induced by more efficient shipping, taking a marginal abatement cost approach. We find that including monetary values for ecosystem service changes leads to a substantial drop in the benefit–cost ratio. On this basis, we argue for a reform of the standard cost–benefit analysis to facilitate more complete welfare assessments.  相似文献   
122.
123.
124.
125.
Long-term application of poultry (Gallus gallus domesticus) litter has built high levels of P in certain Coastal Plain soils of north Louisiana. However, soil P/runoff P relationships for soil and environmental conditions of the area have not been examined. This study measured soil P (total, Bray 1, Bray 2, Mehlich 3, resin-exchangeable, and water-extractable) and runoff P (dissolved P, DP; and total P, TP) at four pasture sites previously amended with poultry litter. Sites varied in soil P due to annual litter applications ranging from 1 to more than 20. Three replicated plots at each site were subjected to simulated rainfalls over 2 yr, and concentrations of DP and TP in runoff were measured and related to soil P. This allowed examination of soil P/runoff P relationships and their changes over time. Runoff DP was also related to DP desorbed from surface soil in a miscible displacement experiment. Among measures of soil P, only resin-exchangeable and water-extractable P showed significant decreases over 2 yr. These measures of soil P explained 54 to 64% of the variability in runoff DP data. However, the miscible displacement technique proved the best indicator of runoff DP, explaining 70% of the variability. Runoff varied among sites (decreasing with increasing years of litter application), limiting the predictive capability of the soil extraction methods. Linking runoff characteristics with miscible displacement data may be a useful predictive tool and warrants further examination.  相似文献   
126.
127.
128.
Effect of Experimental Selective Logging on Tropical Butterflies   总被引:6,自引:0,他引:6  
Abstract: I investigated the effects of an experimental selective logging regime on the assemblage of fruit-feeding butterflies in replicated experimental plots in the Chiquibul Forest, Belize. Over a 12-month period, I caught 1187 individuals of 49 species using fruit-baited traps. Selective logging at densities of six stems per ha 3 years before the study had little effect on butterfly species richness, the abundance of individual species, or the shape of species-abundance distributions. There was no tendency for taxa with restricted geographical ranges to be particularly sensitive to selective logging. Mark-release-recapture results suggest that most butterflies move relatively short distances, but that some dispersal occurs between plots separated by distances of ≥1 km. The apparent similarity of the fruit-feeding butterfly assemblage in selectively logged and unlogged forest contrasts with previous studies of butterfly assemblages but mirrors results for birds in the same plots. A possible explanation is the high frequency of natural disturbance—hurricanes and associated fires—in the Chiquibul Forest. The species present appear to be adapted to naturally disturbed habitats and may therefore be relatively unaffected by selective logging. Local studies of the effects of selective logging must take into account the history of natural and human disturbance in the study area. The results support the case for "ecological forestry," in which sustainable management regimes work within the limits imposed by natural disturbance.  相似文献   
129.
Several lines of evidence in the literature indicate that environmental stress such as starvation may initiate reallocation of sea urchin endoskeletal tissue. For example, Aristotle's lantern enlarges under conditions of starvation, and sea urchins tagged with tetracycline and then fed develop a distinct growth line, while starved individuals develop a diffuse pattern. We designed anin vivo system to examine stress-related changes in calcification in the purple sea urchinStrongylocentrotus purpuratus. SmallS. purpuratus (ca. 2 cm test diam) were collected from the Mission Bay jetty or Imperial Beach (San Diego, California, USA) in 1987.45Ca was incorporated from seawater into all body fractions including the organic tissue/coelomic fluid. In an initial experiment, sea urchins were fed or starved for 4 wk and then post-incubated in isotope. Overall, starved individuals deposited new calcite more slowly than did fed individuals; however, allocation was very different and calcification of teeth of starved sea urchins was nearly as great as in fed individuals. In a second experiment,S. purpuratus were first pre-labeled with isotope and then treated by feeding or starving. More of the labeled calcium was mobilized from the soft tissues and coelomic fluid into calcite in fed than in starved individuals. Growth of the teeth in starved sea urchins was significantly greater than in those fed. We conclude that starvation changes the metabolism of calcium in order to preferentially build teeth. However, we also found no evidence that calcium was resorbed from old skeletal calcite in order to build new skeleton.  相似文献   
130.
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