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   443篇
  免费   12篇
  国内免费   5篇
安全科学   10篇
废物处理   34篇
环保管理   71篇
综合类   89篇
基础理论   100篇
污染及防治   95篇
评价与监测   37篇
社会与环境   19篇
灾害及防治   5篇
  2023年   6篇
  2022年   6篇
  2021年   13篇
  2020年   5篇
  2019年   6篇
  2018年   7篇
  2017年   10篇
  2016年   23篇
  2015年   17篇
  2014年   15篇
  2013年   50篇
  2012年   17篇
  2011年   19篇
  2010年   14篇
  2009年   20篇
  2008年   19篇
  2007年   20篇
  2006年   24篇
  2005年   15篇
  2004年   13篇
  2003年   14篇
  2002年   12篇
  2001年   11篇
  2000年   12篇
  1998年   3篇
  1997年   4篇
  1996年   2篇
  1995年   3篇
  1994年   5篇
  1992年   2篇
  1991年   7篇
  1990年   2篇
  1989年   3篇
  1988年   4篇
  1987年   6篇
  1986年   4篇
  1985年   4篇
  1984年   4篇
  1983年   4篇
  1982年   5篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1974年   2篇
  1971年   2篇
  1970年   2篇
  1969年   2篇
  1967年   4篇
  1938年   1篇
  1924年   1篇
排序方式: 共有460条查询结果,搜索用时 0 毫秒
361.
Composting toilets aim to recycle excrement into safe, stable humus. Preceding this, low costs, low risks, and mass reduction should be ensured. Source separating vermicomposting toilets (SSVCs) outperformed mixed latrine microbial composting toilets (MLMCs) in all categories. MLMCs: incurred ten times greater operational costs; created 10x more operator exposure; employed no proven pathogen reduction mechanism since solid end-products averaged 71,000 ± 230,000 CFU/g (fecal-origin) Escherichia coli and 24 ± 5% total solids, consistently failed NSF/ANSI Standard 41; failed to reduce volatile solids compared to raw fecal matter; increased total contaminated dry mass by 274%, and produced alkaline end-product (8.0 ± 0.7) high in toxic free ammonia (Solvita® 2.6 ± 1.5). SSVCs have low maintenance costs and risks; adequate worm density for pathogen destruction (0.03 ± 0.04 g-worm/g-material); reduced E. coli 200 ± 244 CFU/g in neutral (7.4 ± 0.3), stable (60 ± 10% volatile solids), and mature (4 ± 0 Solvita® NH3) end-product.  相似文献   
362.
To investigate whether the specificities of real jobs create distinctions in the performance of workers in different motor tests for the upper limbs, 24 participants were divided into two groups according to their specific job: fine and repetitive tasks and general tasks. Both groups reproduced tasks related to aiming movements, handling and strength of the upper limbs. There were no significant differences between groups in the dexterity and performance of aiming movements. However, the general tasks group had higher grip strength than the repetitive tasks group, demonstrating differences according to job specificity. The results suggest that a particular motor skill in a specific job cannot improve performance in other tasks with the same motor requirements. The transfer of the fine and gross motor skills from previous experience in a job-specific task is the basis for allocating training and guidance to workers.  相似文献   
363.
364.
This work presents a liquid disposal monitoring originated from uranium enrichment process at Aramar Experimental Center from 1990 to 1998. Assessment of uranium, fluorides, ammoniacal nitrogen, chemical oxygen demand, and pH measurements were made in water samples and compared with results achieved in other countries, as North America and India. The liquid disposal evaluation, generated by uranium enrichment process, showed low levels, considering most parameters established by Federal and State Legislation, aiming environmental pollution control. However, uranium levels were above the limits established by Conselho Nacional do Meio Ambiente, Environment Protection Agency and mainly by the World Health Organization.  相似文献   
365.
366.
Understanding Managers’ Views of Global Environmental Risk   总被引:1,自引:0,他引:1  
This research investigated managers’ views of two global environmental risks: climate change and loss of biodiversity. The intent was to understand why different managers place varying levels of attention and priority on these issues. The data came from in-depth interviews with 28 senior corporate managers across Canada and a range of sectors, although most were employed in the energy sector. Approximately half had direct environmental responsibilities and half had other management duties. Grounded theory was used to collect and analyze the data. From the results, a theoretical framework was constructed to explain important factors that can influence managers’ mental models of environmental risk. Four factors relevant to managers’ appraisal of the threat of environmental risk include: (1) salience, (2) intrinsic value of nature, (3) knowledge, and (4) perceived resilience of nature. In addition, four factors relevant to managers’ view of the appeal of a particular response strategy were: (1) avoidability, (2) perceived costs and benefits, (3) fairness and equity, and (4) effectiveness. The time horizon for decision making was seen as being important in both portions of the mental model.  相似文献   
367.
Mount Washington, NH in the White Mountain National Forest, is flanked to the north-northeast and south by two Class I Wilderness areas, the Great Gulf and Presidential Range-Dry River Wildernesses, respectively. The Clean Air Act protects Class I Area natural resource values from air pollution. Aerosol sulfate, a fine particulate component that is often transported long distances, is a known contributor to visibility degradation and acidic deposition. We examined summertime fine particulate aerosol mass and sulfate, strong acidity and ammonium concentrations from 1988 to 2007 on Mount Washington at two elevations, 452 and 1540 m (msl). The former site is often within, and the latter at the interface of, the planetary boundary layer. Comparisons of sampling interval durations (10 and 24 h) and site vs. site are made. We also examine the extent to which aerosol sulfate is neutralized.Ten hour (daytime) compared to 24 h samples have higher mass and aerosol sulfate concentrations, however paired samples are well correlated. Fine mass concentrations compared between the 452 m and 1540 m sites (standard temperature and pressure corrected) show a weak positive linear relationship with the later being approximately 32% lower. We attribute the lack of a strong correlation to the facts that the 1540 m site is commonly at the interface of and even above the regional planetary boundary layer in summer and that it can intercept different air masses relative to the 452 m site. Sulfate is ~18% lower at the higher elevation site, but comprises a greater percentage of total fine mass; 42% compared to 37% for the high and low elevation site, respectively. Aerosol strong acidity was found to increase with increasing sulfate concentrations at both sites. Further the ratio of hydrogen to sulfate ion was greater in 24 h than 10 h samples at the higher elevation site likely due to overnight transport of fresh acidic aerosols.  相似文献   
368.
化学沉淀法除去废水中的氨氮及其反应的探讨   总被引:29,自引:0,他引:29  
研究了化学沉淀法处理含氨氮废水,实验研究了不同操作条件,如溶液pH值、沉淀剂种类和配比、废水中的初始氨浓度等对氨的处理效率的影响,在适宜的操作条件下,可除去废水中的氨高达99%,处理后残液中氨浓度小于1mg/L(1ppm),探讨了化学沉淀反应过程的机理。  相似文献   
369.
370.
The aim of the present study was to investigate tebuconazole sorption on common soil minerals (birnessite, ferrihydrite, goethite, calcite and illite) and humic acids (representing soil organic matter). Tebuconazole was used (i) in the commercial form Horizon 250 EW and (ii) as an analytical grade pure chemical. In the experiment with the commercially available tebuconazole, a significant pH-dependent sorption onto the oxides was observed (decreasing sorption with increasing pH). The highest sorption was found for ferrihydrite due to its high specific surface area, followed by humic acids, birnessite, goethite and illite. No detectable sorption was found for calcite. The sorption of analytical grade tebuconazole on all selected minerals was significantly lower compared to the commercial product. The sorption was the highest for humic acids, followed by ferrihydrite and illite and almost negligible for goethite and birnessite without any pH dependence. Again, no sorption was observed for calcite. The differences in sorption of the commercially available and analytical grade tebuconazole can be attributed to the additives (e.g., solvents) present in the commercial product. This work proved the importance of soil mineralogy and composition of the commercially available pesticides on the behavior of tebuconazole in soils.  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