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   15565篇
  免费   132篇
  国内免费   94篇
安全科学   402篇
废物处理   572篇
环保管理   1799篇
综合类   3424篇
基础理论   3916篇
环境理论   14篇
污染及防治   3902篇
评价与监测   900篇
社会与环境   771篇
灾害及防治   91篇
  2022年   126篇
  2021年   114篇
  2020年   99篇
  2019年   128篇
  2018年   232篇
  2017年   222篇
  2016年   307篇
  2015年   276篇
  2014年   370篇
  2013年   1053篇
  2012年   448篇
  2011年   660篇
  2010年   519篇
  2009年   582篇
  2008年   705篇
  2007年   671篇
  2006年   595篇
  2005年   523篇
  2004年   456篇
  2003年   457篇
  2002年   473篇
  2001年   536篇
  2000年   403篇
  1999年   251篇
  1998年   167篇
  1997年   189篇
  1996年   205篇
  1995年   228篇
  1994年   236篇
  1993年   184篇
  1992年   171篇
  1991年   197篇
  1990年   194篇
  1989年   184篇
  1988年   138篇
  1987年   132篇
  1986年   142篇
  1985年   113篇
  1984年   126篇
  1983年   129篇
  1982年   136篇
  1981年   134篇
  1980年   112篇
  1979年   128篇
  1978年   95篇
  1977年   102篇
  1976年   88篇
  1975年   94篇
  1973年   96篇
  1967年   91篇
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
431.
At the district heating plant of Kalmar, Sweden an on-line unit for production of granulated wood ash for nutrient recycling on forest soils is being applied. Currently, the granules are dried by hot air from an oil-fired burner. The objective of this work was to investigate how drying by flue gas affects the hardening of granules, or impacts their chemical composition and properties. Ninety-six granule samples were treated by flue gas from natural gas combustion in a laboratory pilot scale flue gas generator. CO2, CO, O2, C3H8 and NO concentrations were varied during the experiment. Additionally, some samples were treated by flue gas from combustion of sawdust at the heating plant in Kalmar. Drying by flue gases did not affect the chemical composition of granules, but minor effects were seen in their mineralogy. The carbonate content was slightly higher in granules treated with flue gas from natural gas combustion compared to the granules dried by hot air only, when measured by wet chemical methods. Results from XRD analysis imply that the calcite content is higher and the portlandite and arcanite content slightly less in granules treated with flue gas from sawdust combustion compared to the granules dried by hot air only. The results from this investigation showed no negative effects on ash granule composition or physical structure by the use of a flue as a drying medium.  相似文献   
432.
The creation of a cloned sheep from mammary tissue has raisedmajor social concern, and much talk about major ethical issuesoccasioned by this technology. It is necessary to separategenuine from spurious ethical issues here, a task made failureto initiate ethical discussion and explanation of new technologyas well as by fear reactions in society. As in geneticengineering of animals, issues about cloning fall into threecategories – suggestions that the technology is inherently wrong,risk emerging from the technology and harm to the creatureengendered. The issues regarding the cloning of humans can beanalyzed using the same categories.  相似文献   
433.
A pedagogic problem in forestry and landscape management is to visualize future landscape effects of forest growth and current management activities in the forest. This paper presents a method for forecasting digital image projections of forest landscape dynamics. Static nonlinear regression functions estimate the digital numbers in a Landsat Thematic Mapper image. Regressors used are forest stand variables. By estimating the future forest stand data, based on intermediate treatment and growth, future satellite digital images are created. In a case study example, the future landscape of a forest block in the province of Västernorrland, Sweden, is projected to demonstrate the application of this visualization technique.  相似文献   
434.
The California Environmental Quality Act (CEQA) has evolved from a mini-NEPA, first enacted in 1970, into a procedural act that affects the approval process of all large developments in California. In 1990, California local governments produced over 1600 environmental impact reports and 30,000 initial studies under CEQA. Because of its widespread use, CEQA has periodically drawn the attention of the state legislature, most recently in 1993, when over 60 CEQA reform bills were introduced. This paper describes the CEQA process and evaluates its success at meeting its explicit and implicit goals. The research includes a statewide survey of CEQA practice, sent to the planning departments of all 513 local governments in California in 1991. Survey respondents agreed that CEQA helps in evaluating environmental impacts, reducing impacts, informing the public, and coordinating public agency review. It is effective in reducing the environmental impacts of individual projects, but is not as effective in improving environmental quality on an areawide scale. This research concludes that CEQA has led to positive outcomes and is not as deeply flawed as many of its critics claim. Still, CEQA as currently designed may not be the optimal vehicle for ensuring environmental quality.  相似文献   
435.
The project on Biodiversity Uncertainties and Research Needs (BURN) ensures the advancement of usable knowledge on biodiversity by obtaining input from decision makers on their priority information needs about biodiversity and then using this input to engage leading scientists in designing policy-relevant research. Decision makers articulated concerns related to four issues: significance of biodiversity; status and trends of biodiversity; management for biodiversity; and the linkage of social, cultural, economic, legal, and biological objectives. Leading natural and social scientists then identified the research required to address the decision makers' needs and determined the probability of success. The diverse group of experts reached consensus on several fundamental issues, helping to clarify the role of biodiversity in land and resource management. The BURN participants identified several features that should be incorporated into policy-relevant research plans and management strategies for biodiversity. Research and assessment efforts should be: multidisciplinary and integrative, participatory with stakeholder involvement, hierarchical (multiple scales), and problem- and region-specific. The activities should be focused regionally within a global perspective. Meta-analysis of existing data is needed on all fronts to assess the state of the science. More specifically, the scientists recommended six priority research areas that should be pursued to address the information needs articulated by decision makers: (1) characterization of biodiversity, (2) environmental valuation, (3) management for sustainability—for humans and the environment (adaptive management), (4) information management strategies, (5) governance and stewardship issues, and (6) communication and outreach. Broad recommendations were developed for each research area to provide direction for research planning and resource management strategies. The results will directly benefit those groups that require biodiversity research to address their needs—whether to develop policy, manage natural resources, or make other decisions affecting biodiversity.  相似文献   
436.
In 1995 the authors spent a considerable amount of time conducting audits and audit training classes all over the world. In rolling out Colgate-Palmolive's reengineered environmental audit program, they coupled a two-day training program with a three-day audit. Whether in Asia-Pacific, South America, Europe, or the United States, auditors, especially those newly trained, always seemed to fall into the same traps time and again. In order to facilitate the learning process, the authors prepared a list of 20 tips to use at the beginning and end of all training programs and audits. In this article, the authors share the 20 “golden rules” to help all auditors improve the quality of their audits.  相似文献   
437.
438.
439.
440.
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