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   17093篇
  免费   172篇
  国内免费   149篇
安全科学   421篇
废物处理   724篇
环保管理   2011篇
综合类   2887篇
基础理论   4582篇
环境理论   4篇
污染及防治   4479篇
评价与监测   1137篇
社会与环境   1063篇
灾害及防治   106篇
  2022年   142篇
  2021年   132篇
  2020年   119篇
  2019年   133篇
  2018年   239篇
  2017年   274篇
  2016年   378篇
  2015年   333篇
  2014年   521篇
  2013年   1277篇
  2012年   560篇
  2011年   788篇
  2010年   688篇
  2009年   674篇
  2008年   749篇
  2007年   805篇
  2006年   658篇
  2005年   560篇
  2004年   593篇
  2003年   544篇
  2002年   547篇
  2001年   698篇
  2000年   497篇
  1999年   269篇
  1998年   188篇
  1997年   220篇
  1996年   221篇
  1995年   261篇
  1994年   245篇
  1993年   186篇
  1992年   207篇
  1991年   198篇
  1990年   215篇
  1989年   202篇
  1988年   155篇
  1987年   165篇
  1986年   155篇
  1985年   160篇
  1984年   153篇
  1983年   142篇
  1982年   137篇
  1981年   128篇
  1980年   118篇
  1979年   133篇
  1978年   102篇
  1977年   115篇
  1975年   90篇
  1974年   87篇
  1973年   98篇
  1972年   88篇
排序方式: 共有10000条查询结果,搜索用时 374 毫秒
991.
992.
993.
Anarchy, where honeybee workers produce males in the presence of a queen, is extremely rare in natural honeybee populations, suggesting that there are colony-level costs associated with being anarchistic. Yet, no significant costs have yet been identified. A possible reason for this may be that researchers have only focused on the behaviour of anarchistic workers, which have been shown to perform worker-tasks as do wild-type workers. Possibly, therefore, costs associated with anarchy should be sought in anarchistic queens and not workers. A potential cost could be a lower survival rate of eggs laid by anarchistic queens perhaps because their egg-marking signal is not as clear as that of a wild-type queen. In this paper, we determined the removal rate of eggs laid by anarchistic queens in standard worker-policing bioassays. Our results show that eggs laid by anarchistic queens are removed at a higher rate than eggs laid by wild-type queens. This does not seem to be due to differences in hydrocarbons found on the surface of eggs, as both egg types showed the same alkanes and alkenes in similar proportions. We postulate that higher removal rates of queen-laid eggs due to recognition errors may be one reason that anarchy is rare in natural honeybee populations.  相似文献   
994.
Abstract: Evaluating the relative amounts of water moving through the different components of the hydrological cycle is required for precise management and planning of water resources. An important aspect of this evaluation is the partitioning of streamflow into surface (quick flow) and base‐flow components. A prior study evaluated 40 different approaches for hydrograph‐partitioning on a field scale watershed in the Coastal Plain of the Southeastern United States and concluded that the Boughton’s method produced the most consistent and accurate results. However, its accuracy depends upon the proper estimation of: (1) the end of surface runoff, and (2) the fraction factor (α) that is function of many physical and hydrologic characteristics of a watershed. Proper identification of the end of surface runoff was accomplished by using a second derivative approach. Applying this approach to 12 years of separately measured surface and subsurface flow data from a field scale watershed (study area) proved to be accurate for 87% of the time. Estimation of the α value was accomplished in this study using two steps: (1) alpha was fitted to individual hydrographs: and, (2) a regression equation that determines these alpha values based on climatological factors (e.g., rainfall, evapotranspiration) was developed. Using these strategies improved the streamflow partitioning method’s performance significantly.  相似文献   
995.
Improving eco-efficiency in the steel industry: The ArcelorMittal Gent case   总被引:1,自引:0,他引:1  
In addition to CO2 released by the combustion of fossil fuel and leading to climate change, large steelworks emit pollutants that have other environmental impacts. ArcelorMittal Gent, an integrated steelwork producing ca. 5 × 106 tons of steel per year, not only decreased its specific energy consumption and CO2-emissions, but also reduced the environmental impact of its other emissions. This is illustrated by means of the evolution of 6 partial eco-efficiency indicators for the impact categories acidification, photo-oxidant formation, human toxicity, freshwater aquatic ecotoxicity, eutrophication and water use. The partial eco-efficiency indicators are eco-intensities, defined as the environmental impact in the respective impact category, divided by the amount of liquid steel produced. In the period 1995 – 2005 these indicators decreased by 45, 4, 52, 9, 11 and 33% respectively, whereas the steel production increased by 17%. The net impact of discharges of wastewater is negligible for human toxicity and is negative (concentrations lower than in the canal water used) for freshwater aquatic toxicity and eutrophication. For acidification, human toxicity (only emissions to air) and water use, the decoupling between environmental impact and production was absolute; for photo-oxidant formation, freshwater aquatic ecotoxicity (only emissions to air) and eutrophication, it was relative.  相似文献   
996.
997.
Innovations in water chain are discussed based on experiences in the Netherlands. The available and new technological options, as well as their dissemination in the Netherlands, are presented for the prevailing system with add-on technologies (elongation), and for the emerging separation system with technologies at the source. Numerous new options are available for both systems but these options are rarely used. The low use is explained using economic theories and with practical examples from the Netherlands. In order to foster innovations, the mainstream, evolutionary, and behavioral theories pinpoint respectively the pricing of common goods, broad support of concerted action, and support for innovators’ entry. These actions may all be needed. Experiences with a stakeholder cluster in water management suggest that markets for high value water use invoke innovations and low-cost technology adaptations. The systematic development of services that foster high value water-based activities is recommended.  相似文献   
998.
999.
This work reviews retrofitting new waste energy, carbon and water intensive technologies into existing industrial facilities (including electricity generators) to increase net energy, carbon, and water use efficiencies. The three applications reviewed are microalgal ponds consuming flue gasses and providing thermal power station cooling services, thermally driven membrane distillation desalination, and hydrometallurgical solution mining processes to indirectly remove water contaminants, and additional power station cooling. The aim of this work is to explore the unique challenge of site-specificity of retrofitting any or all of the reviewed technologies within existing facilities for commercial operations. The theoretical basis behind higher aggregated efficiencies is essentially vertical integration of infrastructure, energy, and material flows, reducing total costs, net waste, and associated potential environmental contamination. Whilst solution mining and some thermal desalination technologies are not necessarily new in isolation, new technical developments enable these technologies to use waste heat and waste water by operating in parallel with industrial facilities, and effectively subsidise microalgae biofuel water pumping and dewatering. This research determines three fundamental developments are required to enable wide-scale industrial co-located vertical integration efficiencies: (1) fundamental engineering, (2) monitoring system innovation, and (3) technology/knowledge transfer.  相似文献   
1000.
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