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   337篇
  免费   6篇
  国内免费   4篇
安全科学   10篇
废物处理   9篇
环保管理   56篇
综合类   88篇
基础理论   70篇
环境理论   1篇
污染及防治   81篇
评价与监测   19篇
社会与环境   9篇
灾害及防治   4篇
  2023年   4篇
  2022年   4篇
  2021年   3篇
  2020年   4篇
  2019年   6篇
  2018年   13篇
  2017年   17篇
  2016年   13篇
  2015年   7篇
  2014年   14篇
  2013年   15篇
  2012年   9篇
  2011年   15篇
  2010年   15篇
  2009年   10篇
  2008年   25篇
  2007年   15篇
  2006年   17篇
  2005年   9篇
  2004年   12篇
  2003年   11篇
  2002年   10篇
  2001年   5篇
  2000年   4篇
  1999年   3篇
  1998年   5篇
  1997年   2篇
  1996年   3篇
  1995年   8篇
  1992年   4篇
  1988年   2篇
  1987年   4篇
  1986年   5篇
  1985年   2篇
  1984年   2篇
  1983年   2篇
  1981年   2篇
  1975年   2篇
  1974年   2篇
  1972年   2篇
  1969年   2篇
  1963年   4篇
  1961年   2篇
  1958年   5篇
  1957年   2篇
  1955年   5篇
  1954年   5篇
  1939年   2篇
  1938年   2篇
  1926年   1篇
排序方式: 共有347条查询结果,搜索用时 140 毫秒
91.
The conventional gausslan plume equation for ground level concentrations was used to estimate hourly average sulfur dioxide concentrations at selected points in Louisville, KY, on specific days during 1973. Area emission sources were not included in the model since they are not substantial. The trajectory of the emissions from each continuous point source was calculated by a procedure that allowed for spatial variability in wind direction. All other meteorological parameters were held constant during each hour. The twenty-four individual hourly estimates at each location for a given day were arithmetically averaged yielding a daily mean. The model predictions were compared to actual measurements conducted by Jefferson County Air Pollution Control District personnel using the West-Gaeke sampling procedure. The sample correlation coefficient for all predictions was low, but after only about 30% of the predictions were eliminated on statistical grounds, the sample correlation coefficient was increased to 0.72. The statistical analysis appeared to discard a reasonable number of predictions on the basis of observed variability in the measured air quality.  相似文献   
92.
93.
94.
A reduction in the legitimacy of top-down governance approaches has resulted in many government agencies using decentralised governance approaches, including localism. However, the effective implementation of localism is challenging. Localism aims to encourage innovative context-based solutions; however unanticipated implementation problems often constrain localism outcomes. There is a significant gap in our understanding of localism in practice, with a better understanding essential to improve localism design and implementation. This paper contributes to addressing this gap through an empirical examination of localism in action. Using the CLEAR framework, we evaluate the decentralised governance of environmental water in the Australian state of New South Wales, a contentious, uncertain and multi-level governance environment. Qualitative interviews with 58 Environmental Water Advisory Group members identified barriers to an effective localism approach, including issues of access and capacity development, transparency of decision-making outcomes and power inequities. This understanding enables the development of strategies for improved localism practice.  相似文献   
95.
96.
To investigate the effects of Cd on tolerance and antioxidant activities of castor, two different castor(Ricinus communis L.) cultivars(Zibo No. 5 and Zibo No. 8) were used for a hydroponic experiment(0, 1 and 2 mg/L Cd) and a pot experiment using Cd-contaminated soil(34 mg/kg) with the addition of ethylenedinitrilotetraacetic acid(EDTA). The results indicated that there were significant differences between the two cultivars with respect to Cd uptake in shoots(113–248 mg/kg for Zibo No. 5 and 130–288 mg/kg Zibo No. 8), biomass tolerance indexes(64.9%–74.6% for Zibo No. 5 and 80.1%–90.9% for Zibo No. 8) in the hydroponic experiment and survival rates(0% for Zibo No. 5 and 100% for Zibo No. 8)determined by the addition of EDTA in the pot experiment, suggesting that Zibo No. 8 has higher tolerance than Zibo No. 5. Moreover, the castor cultivars have low bioconcentration factors(4.80% for Zibo No. 5 and 5.43% for Zibo No. 8) and low translocation factors(〈1%).Consequently, Zibo No. 8 can participate in Cd phytostabilization in highly Cd-polluted areas. The results indicated that glutathione(GSH) as a non-enzymatic antioxidant, and antioxidant enzymes including superoxide dismutase(SOD), catalase(CAT) and guaiacol peroxidase(GPX), were cultivar- and dose-dependent. The higher tolerance of Zibo No. 8compared with Zibo No. 5 can be attributed to the higher GSH levels in the root and higher GPX activity in the leaf.  相似文献   
97.
Laikre L  Palme A  Josefsson M  Utter F  Ryman N 《Ambio》2006,35(5):255-261
Introduction of alien species is a major threat to biological diversity. Although public attention typically focuses on the species level, guidelines from the Convention of Biological Diversity define alien species to include entities below species level. This inclusion recognizes that release of nonlocal populations of native species may also result in negative effects on biodiversity. In practice, little is known about the extent, degree of establishment, or the effects on natural gene pools of such releases. Existing information on the releases in Sweden shows that alien populations are spread to a great extent. The most commonly released species include brown trout, Atlantic salmon, Arctic char, common whitefish, Scots pine, Norway spruce, mallard duck, gray partridge, and pheasant. Although millions of forest trees, fish, and birds are released annually, poor documentation makes the geographic and genetic origin of these populations, as well as the sites where they have been released, largely unclear. We provide recommendations for urgently needed first steps relating to the risks and problems associated with release of alien populations.  相似文献   
98.
Background Due to the bovine spongiform encephalopathy (BSE), specified risk material (SRM) as well as animal meat and bone meal (MBM) are banned from the food and feed chain because of a possible infection with pathogenic prions (PrPSc). Nowadays, prions are widely accepted to be responsible for TSE(transmissible spongiform encephalopathies)-caused illnesses like BSE and scrapie, and especially for the occurrence of the new variant of CJD in humans. Presently, SRM and MBM are burnt under high temperatures to avoid any hazards for humans, animals or the environment. The aim of this study was to evaluate a method using animal fat separated from Category I material which includes SRM and the carcasses of TSE-infected animals, or animals suspected of being infected with TSE, as a source for producing biodiesel by transesterification, analogous to the biodiesel process using vegetable oil. Methods For this purpose, animal fat was spiked with scrapie-infected hamster brain equivalents – as representative for a TSE-infected animal – and the biodiesel manufacturing process was downscaled and performed under lab-scale conditions. Results and Discussion The results analysed by Western blotting showed clearly that almost each single step of the process leads to a significant reduction of the concentration of the pathogenic prion protein (PrPSc) in the main and side-products. Conclusion The data revealed that the biodiesel production, even from material with a high concentration of pathogenic prions, can be considered as safe. Recommendations and Outlook The obtained results indicated that biodiesel produced from prion-contaminated fat was safe under the tested process conditions. However, it has to be pointed out that the results cannot be generalized because a different process control using other conditions may lead to different results and then has to be analysed independently. It is clear that the production of biodiesel from high risk material represents a more economic usage than the combustion of such material.  相似文献   
99.
100.
An assessment of recent trends in primary NO2 emissions has been carried out for ten case study locations across the European Union. Estimates of the percentage of NOx from road traffic emitted as primary NO2 (f-NO2) have been derived for 1995, 2000 and 2005 by combining the results of a literature survey of primary NO2 emission factors for different vehicle types and technologies with an emission inventory. Estimates of f-NO2 have also been derived from ambient monitoring data at roadside sites in each case study location using a model.The results of the analysis of trends show that f-NO2 has increased in recent years and that the rate of increase has been greatest since 2000. f-NO2 has increased from 8.6% in 2000 to 12.4% in 2004 as an average across the monitoring sites and from an average of 6.3% in 2000 to 10.6% in 2005 as an average of the emission inventory based calculations for the case study countries. f-NO2 is predicted to increase further to an average of 19.6% in 2010 and 32.0% in 2020 as a result of the further penetration of exhaust after treatment technologies for diesel vehicles in the fleets. This increase is expected to be offset by the large reduction in NOx emissions over this period, resulting in an increase in NO2 emissions from road traffic to 2015, followed by a decline to close to 2004 levels by 2020. Estimates of future ambient NO2 concentrations have also been calculated for the roadside monitoring sites included in the study. At 29 out of 45 of these sites the annual mean NO2 limit value is predicted to be exceeded in 2010. At 22 of these sites, the annual mean concentration is expected to remain above the limit value until 2020 and beyond.  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