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   16443篇
  免费   222篇
  国内免费   163篇
安全科学   483篇
废物处理   603篇
环保管理   2297篇
综合类   3183篇
基础理论   4119篇
环境理论   13篇
污染及防治   4030篇
评价与监测   1000篇
社会与环境   966篇
灾害及防治   134篇
  2022年   143篇
  2021年   144篇
  2020年   119篇
  2019年   157篇
  2018年   224篇
  2017年   262篇
  2016年   361篇
  2015年   305篇
  2014年   400篇
  2013年   1384篇
  2012年   497篇
  2011年   664篇
  2010年   527篇
  2009年   590篇
  2008年   657篇
  2007年   682篇
  2006年   642篇
  2005年   518篇
  2004年   497篇
  2003年   514篇
  2002年   446篇
  2001年   556篇
  2000年   436篇
  1999年   249篇
  1998年   207篇
  1997年   193篇
  1996年   211篇
  1995年   221篇
  1994年   212篇
  1993年   210篇
  1992年   219篇
  1991年   205篇
  1990年   206篇
  1989年   177篇
  1988年   158篇
  1987年   133篇
  1986年   159篇
  1985年   162篇
  1984年   162篇
  1983年   165篇
  1982年   159篇
  1981年   162篇
  1980年   152篇
  1979年   146篇
  1978年   110篇
  1977年   124篇
  1974年   109篇
  1973年   92篇
  1972年   109篇
  1971年   88篇
排序方式: 共有10000条查询结果,搜索用时 927 毫秒
231.
This paper describes a method for determining reductions of SO2 emissions from coal- and oil-fired power stations, oil refineries and large industrial units in the UK taking into account their pollution potential. The method is based on the use of two gridded data sets: critical loads, which represent the sensitivity of the environment to acid deposition and modelled estimates of total (wet + dry) sulphur deposition for 646 point sources within the UK. An iterative method is used to identify and subsequently reduce emissions from point sources that contribute most to areas of critical loads exceedance. This paper demonstrates how the method may be used to determine an optimal allocation of emissions across the UK which yields the maximum amount of environmental protection per unit of emission.The paper then goes on to consider the changes that will have to take place within the UK power generation industry in order to meet the revised EC Large Combustion Plant Directive which comes into force on 1 January 2008. Particular emphasis is placed upon proposed emissions trading schemes and the environmental implications of allowing trading between stations with high and low pollution potentials. The paper concludes by suggesting that the emissions trading process should take into account the pollution potential of each source, irrespective of whether the proposed emission is within the plant's agreed emission limit. An approach based entirely on minimizing environmental damage rather than one which takes cost into account, as in current integrated assessment modelling, could provide an interesting approach across the rest of Europe.  相似文献   
232.
Sustainable resource management is the critical agricultural research and development challenge in sub-Saharan Africa. The accumulated knowledge on soil management gathered over the last 10 years, combined with solid crop improvement and plant health research at farmers’ level, has brought us to a stage where we can now address with confidence the intensification of cereal–grain–legume-based cropping systems in the dry savanna of West Africa in a sustainable and environmentally positive manner.Two sustainable farming systems that greatly enhance the productivity and sustainability of integrated livestock systems have been developed and implemented in the dry savanna of Nigeria. These are: (i) maize (Zea mays L.)–promiscuous soybean [Glycine max (L.) Merr.] rotations that combine high nitrogen fixation and the ability to kill large numbers of Striga hermonthica seeds in the soil; and (ii) miflet [Eleusine coracana (L.) Gaerth] and dual-purpose cowpea [Vigna unguiculata (L.) Walp.]. Improvement of the cropping systems in the dry savanna has been driven by the adoption of promiscuously nodulating soybean varieties (in particular TGx 1448-2E) and dual-purpose cowpea. The rate of adoption is very high, even in the absence of an efficient seed distribution system. The number of farmers cultivating the improved varieties increased by 228% during the last 3 years. Increased production of promiscuous soybean has been stimulated by increased demand from industries and home utilization. Production in Nigeria was estimated at 405,000 t in 1999 compared to less than 60,000 t in 1984. Economic analysis of these systems shows already an increase of 50–70% in the gross incomes of adopting farmers compared to those still following the current practices, mainly continuous maize cultivation. Furthermore, increases in legume areas of 10% in Nigeria (about 30,000 ha in the northern Guinea savanna) and increases of 20% in yield have translated into additional fixed nitrogen valued annually at US$ 44 million. This reflects, at the same time, an equivalent increase in land-use productivity, and with further spread of the improved crops, there are excellent prospects for additional economic and environmental benefits from a very large recommendation domain across West Africa.  相似文献   
233.
234.
235.
236.
237.
238.
239.
The product service systems’ (PSS) sustainability potential is described in the framework of the new types of stakeholder relationships and/or partnerships, producing new convergence of economic interests, and a potential concomitant systemic resources optimization.In this perspective, it is argued that the design competencies should move towards those of the ‘strategic design’, thus introducing the concept of ‘strategic design for sustainability’: the design of an innovation strategy, shifting the business focus from designing (and selling) physical products only, to designing (and selling) a system of products and services which are jointly capable of fulfilling specific client demands, while re-orienting current unsustainable trends in production and consumption practices.Some examples of PSS are presented and discussed using the PSS categories ‘services providing added value to the product life cycle’, ‘services providing final results to customers’, and ‘services providing enabling platforms for customers’. The cases derive from an analysis of the ‘environmental friendly innovation’ yearly endowed prize submissions. The Politecnico di Milano University together with the Bocconi University and Legambiente (an environmental NGO) promotes the initiative in Italy.  相似文献   
240.
We describe a new method for the post-mortem examination of the fetal central nervous system. The brain is immobilized in gelatin prior to ultrasonic examination. Correlation with prenatal ultrasound is excellent and subsequent pathological examination is enhanced and facilitated.  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