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   33419篇
  免费   341篇
  国内免费   243篇
安全科学   944篇
废物处理   1267篇
环保管理   4343篇
综合类   5237篇
基础理论   9474篇
环境理论   22篇
污染及防治   8646篇
评价与监测   2019篇
社会与环境   1842篇
灾害及防治   209篇
  2022年   249篇
  2021年   229篇
  2019年   244篇
  2018年   450篇
  2017年   447篇
  2016年   636篇
  2015年   531篇
  2014年   785篇
  2013年   2438篇
  2012年   963篇
  2011年   1416篇
  2010年   1175篇
  2009年   1188篇
  2008年   1418篇
  2007年   1491篇
  2006年   1351篇
  2005年   1134篇
  2004年   1135篇
  2003年   1097篇
  2002年   1061篇
  2001年   1414篇
  2000年   975篇
  1999年   610篇
  1998年   458篇
  1997年   475篇
  1996年   481篇
  1995年   524篇
  1994年   477篇
  1993年   439篇
  1992年   458篇
  1991年   416篇
  1990年   424篇
  1989年   451篇
  1988年   376篇
  1987年   340篇
  1986年   313篇
  1985年   330篇
  1984年   324篇
  1983年   357篇
  1982年   357篇
  1981年   292篇
  1980年   267篇
  1979年   291篇
  1978年   253篇
  1977年   218篇
  1976年   220篇
  1975年   208篇
  1974年   199篇
  1973年   194篇
  1972年   221篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
241.
This paper studies the scavenging efficiencies of aerosol emissions from coal-fired power plants under different removal mechanisms (coagulation, heterogeneous nucleation and gravitational settling) as a function of time. It also analyses the ‘health impact’ of the aerosol before and after the above dynamic mechanisms by comparing the respirable dust fractions. The well-known equations of evolution are applied to an average PSD that represents the exhaust particulate emissions from coal-fired power plants (i.e. Aboño power plant in Asturias that belongs to Hidrocantábrico Group, S.A.). From this study it is inferred that respirable dust is scavenged with the greatest difficulty and when compared with the initial volume of respirable dust, roughly 20% remains after 18 h of gravitational settling. Therefore, gravitational settling is the main removal mechanism of respirable dust compared to condensation and coagulation.  相似文献   
242.
Russian Journal of Ecology - It has been shown that the main drivers of the dynamics of cladoceran and copepod abundances can be predators (fish), the quantity and/or quality of food in terms of...  相似文献   
243.
Russian Journal of Ecology - Abstract—The study of the effect of mycorrhiza symbiosis on the transformation of carbon and nitrogen compounds in soils is important in view of the necessity to...  相似文献   
244.
Disaster management (DM) is a continuous, highly collaborative process involving governments, DM organisations, responders, the construction sector, and the general public. Most research approaches to DM include the development of information and communication technologies (ICT) to support the collaboration process rather than the creation of a collaboration process to provide information flows and patterns. An Intelligent Disaster Collaboration System (IDCS) is introduced in this paper as a conceptual model to integrate ICT into DM and the mitigation process and to enhance collaboration. The framework is applicable to the collaboration process at the local, regional and national levels. Within this context, the deployment of ICT tools in DM is explored and scenario-based case studies on flooding and terrorism—examples of natural and human-induced disasters, respectively—are presented. Conclusions are drawn regarding the differences found in collaboration patterns and ICT used during natural and human-induced disasters and the differences between currently available ICT and proposed ICT.  相似文献   
245.
Footprints for Sustainability: The Next Steps   总被引:21,自引:0,他引:21  
The concept of an ecological footprint is based on the understanding that every individual human appropriates a share of the productive and assimilative capacity of the biosphere. An ecological footprint corresponds to this exclusive biologically productive area that a defined population uses for all its resource requirements and wastes, and is expressed in terms of bioproductive space, with world-average productivity. Humanity's footprint or its aggregate ecological demand can only temporarily exceed the productive and assimilative capacity of the biosphere without liquidating and weakening the natural capital on which humanity depends fundamentally. Therefore, accounting tools for quantifying humanity's use of nature are essential for overall assessments of human impact as well as for planning specific steps towards a sustainable future.This paper discusses the strengths and weaknesses of the ecological footprint as an ecological accounting method, points out research needs for improvement of the analysis, and suggests potential new applications. The paper identifies ten new applications of the tool to make it applicable at various geographic scales and for a number of analytical and didactic purposes. Then nine methodological improvements are suggested that could refine the currently applied method, making assessments more sensitive to a larger number of ecological impacts. It concludes that many crucial questions pertinent to building a sustainable society can be addressed by current ecological footprint research. By making the method more complete, this tool could evolve from being largely of pedagogical use to become a strategic tool for policy analysis.  相似文献   
246.
247.
Concentrations of eight elements were measured in Chelonia mydas and Lepidochelys olivacea eggs collected along the Pacific coast of Panama. Manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd), and mercury (Hg) concentrations were similar to previous reports of these species from around the world, while lead (Pb) was lower than previous reports. Cd posed the highest health risk to people who regularly eat the eggs, with average consumption rates leading to target hazard quotients (THQ) of up to 0.35 ± 0.15. Our conclusions indicate that current turtle egg consumption in isolated, coastal Pacific communities may pose a health concern for young children, and that youth and young adults should limit their consumption of turtle eggs to reduce their total intake of nonessential metals.  相似文献   
248.
249.
Scrap preheating in foundries is a technology that saves melting energy, leading to economic and environmental benefits. The proposed method in this paper utilizes solar thermal energy for preheating scrap, effected through a parabolic trough concentrator that focuses sunlight onto a receiver which carries the metallic scrap. Scraps of various thicknesses were placed on the receiver to study the heat absorption by them. Experimental results revealed the pattern with which heat is gained by the scrap, the efficiency of the process and how it is affected as the scrap gains heat. The inferences from them gave practical guidelines on handling scraps for best possible energy savings. Based on the experiments conducted, preheat of up to 160 °C and a maximum efficiency of 70 % and a minimum efficiency of 40 % could be achieved across the time elapsed and heat gained by the scrap. Calculations show that this technology has the potential to save around 8 % of the energy consumption in foundries. Cumulative benefits are very encouraging: 180.45 million kWh of energy savings and 203,905 t of carbon emissions cut per year across the globe. This research reveals immense scope for this technology to be adopted by foundries throughout the world.  相似文献   
250.
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