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   59236篇
  免费   596篇
  国内免费   729篇
安全科学   1791篇
废物处理   2436篇
环保管理   7621篇
综合类   10516篇
基础理论   15883篇
环境理论   41篇
污染及防治   15026篇
评价与监测   3872篇
社会与环境   2982篇
灾害及防治   393篇
  2022年   529篇
  2021年   505篇
  2020年   391篇
  2019年   504篇
  2018年   891篇
  2017年   856篇
  2016年   1287篇
  2015年   1025篇
  2014年   1516篇
  2013年   4543篇
  2012年   1878篇
  2011年   2603篇
  2010年   2104篇
  2009年   2163篇
  2008年   2551篇
  2007年   2648篇
  2006年   2354篇
  2005年   1979篇
  2004年   1921篇
  2003年   1939篇
  2002年   1790篇
  2001年   2296篇
  2000年   1596篇
  1999年   1019篇
  1998年   751篇
  1997年   756篇
  1996年   772篇
  1995年   852篇
  1994年   843篇
  1993年   708篇
  1992年   738篇
  1991年   708篇
  1990年   746篇
  1989年   723篇
  1988年   649篇
  1987年   546篇
  1986年   490篇
  1985年   547篇
  1984年   544篇
  1983年   569篇
  1982年   551篇
  1981年   508篇
  1980年   420篇
  1979年   466篇
  1978年   418篇
  1977年   341篇
  1976年   344篇
  1975年   335篇
  1974年   326篇
  1972年   351篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
221.
In the UK for the period 1994-99, a broad range of environmental projects were given financial support through the European Agriculture Guidance and Guarantee Fund under the Objective 1 and Objective 5b programmes. This paper is concerned with the ex-post evaluation of these projects set within a Sustainable Development framework. The aim was to identify project types or characteristics that offered the greatest return on investment. A classification of six broad project types was adopted. The evaluation revealed that there were significant differences between individual projects with respect to the type and scale, and temporal and social distribution of the benefits they delivered. In particular, as well as delivering environmental and economic benefits, many projects made a significant contribution to the development of human and social capital. The paper concludes that it is possible to improve the basis for future project selection in order to maximise the returns on environmental investments in the context of sustainable development.  相似文献   
222.
Much of the forest wealth on the plains and in the hilly areas of India has been foolishly destroyed, and the rich heritage of wildlife has been slaughtered mostly for only temporary gain. The wanton axing of the larger indigenous trees and the uprooting of other floristic elements in the hills and on the lower slopes of the mountains, gradually impoverishes them, and may be followed by erosion that ultimately leaves the slopes barren. These alarming threats to the chir (Pinus roxburghii) and fir (Abies pindrow) forests of Kashmir will have disastrous consequences. Once densely-forested, the mountain slopes in Kashmir have become largely naked through too-heavy tapping and cutting of the trees; with concomitant landslides, frequent floods, and loss of fertile topsoil. Unfortunately, the people living in the areas of the chir and fir trees, do not play a proper part in their protection, and the last two decades have witnessed, year by year, the rapid march of urbanization and manifold destructive activities which have taken a heavy toll on these precious species. Urgent conservation measures are essential to preserve these endangered trees in Kashmir.  相似文献   
223.
Most native polymers used in processing and application technologies are admittedly disposable from the environment in a biologic manner, but products possess low mechanical strength. One of the paths to increasing this attribute (if feasible) is their cross-linking, which may, however, affect their readiness to biodegradation. In the presented work this condition was observed on the example of waste protein (Hykol B) cross-linking by means of glutardialdehyde and glyoxal. Degree and course of cross-linking were determined through impedance spectroscopy. The objective of this work also was to obtain data for constructing a sensor capable of following the cross-linking course in real time, for potential industrial application of Hykol in continuous production. Impedance spectroscopy proved to be applicable even to this kind of material marked by considerable water content and exhibiting relatively high electric conductivity; so far it had been used only for materials of low conductivity. An aqueous environment inoculated with digested anaerobic sludge from a municipal wastewater treatment plant was selected for modeling anaerobic conditions. The relation was studied between cross-linking degree given by content of cross-linking agent (determined by impedance spectroscopy) and biodegradation degree under anaerobic conditions. It was confirmed that network density as given by quantity of added agent not only reduced breakdown degree but also slowed the course of the process. This fact is particularly obvious with cross-linking by means of glyoxal; network density is thus dependent on type of employed substance, which affect type and structure of created network. That not merely forms an obstacle during polymer swelling and dissolution but also prevents access of bacteria to source of metabolized organic carbon.  相似文献   
224.
 This paper deals with the present scenario of hazardous waste management practices in Thailand, and gives some insights into future prospects. Industrialization in Thailand has systematically increased the generation of hazardous waste. The total hazardous waste generated in 2001 was 1.65 million tons. It is estimated that over 300 million kg/year of hazardous waste is generated from nonindustrial, community sources (e.g., batteries, fluorescent lamps, cleansing chemicals, pesticides). No special facilities are available for handling these wastes. There are neither well-established systems for separation, storage, collection, and transportation, nor the effective enforcement of regulations related to hazardous wastes management generated from industrial or nonindustrial sectors. Therefore, because of a lack of treatment and disposal facilities, these wastes find their way into municipal wastewaters, public landfills, nearby dump sites, or waterways, raising serious environmental concern. Furthermore, Thailand does not have an integrated regulatory framework regarding the monitoring and management of hazardous materials and wastes. In addition to the absence of a national definition of hazardous wastes, limited funding has caused significant impediments to the effective management of hazardous waste. Thus, current waste management practices in Thailand present significant potential hazards to humans and the environment. The challenging issues of hazardous waste management in Thailand are not only related to a scarcity of financial resources (required for treatment and disposal facilities), but also to the fact that there has been no development of appropriate technology following the principles of waste minimization and sustainable development. A holistic approach to achieving effective hazardous waste management that integrates the efforts of all sectors, government, private, and community, is needed for the betterment of human health and the environment. Received: February 26, 2001 / Accepted: October 11, 2002  相似文献   
225.
This article does not focus on adaptation or mitigation policy directly but on an allied opportunity that exists for the Pacific Islands via the auspices of the Climate Convention, because the existing very costly energy systems used in the Pacific Island region are fossil-fuel dependent. It is argued here that efforts can be made towards the development of energy systems that are ecologically sustainable because Pacific Island nations are eligible to receive assistance to introduce renewable energy technology and pursue energy conservation via implementation mechanisms of the Climate Convention and, in particular, through transfer of technology and via joint implementation. It is contended that assistance in the form of finance, technology, and human resource development from developed countries and international organizations would provide sustainable benefits in improving the local Pacific Island environments. It is also emphasized that mitigation of greenhouse gas emissions is not the responsibility of the Pacific Islands as they contribute very little on a per capita global scale and a tiny proportion of total global greenhouse gas emissions.  相似文献   
226.
Recent research has suggested that health damage from air pollution—most notably from inhalable particulate matter and lead—is a serious concern in many cities in developing countries. A comparative risk assessment conducted in Cairo in 1994 found these two pollutants to be especially worrisome, and an analysis of the potential economic benefits associated with controlling these pollutants suggests that their economic damage is significant. Control strategies to reduce ambient pollutant levels are under development, with point source controls on major industrial facilities—especially in the secondary lead smelling industry—a cost-effective initial step.  相似文献   
227.
More than 20000 handling manoeuvres in loading or unloading trailers in a large transportation company were observed. The aim of the study was to determine the frequency and nature of the incidents occurring whilst handling. The incidents were recorded and interpreted from a double perspective, namely as risk factors and as activity regulation factors. The study showed that on average, one incident occurred in every seven handling manoeuvres: 71% of them were related to the environment, and 29% to the activity. While numerous, the environment-related incidents were generally without consequences. In this respect, the activity incidents appeared more risky; also, the majority of these incidents occurred during the load positioning phase. The study also showed that loads are re-handled twice as often in unloading as in loading, the frequency of re-handlings varying widely from one handler to another. The reasons why so few of the observed incidents are reported in accident studies and their significance in the understanding of handling problems are discussed.  相似文献   
228.
This paper describes a novel technology for the removal of solidified radioactive waste from underground storage tanks at the DOE Hanford site in southeast Washington. The process involves the use of a unique high pressure system which pulverizes the hardened saltcake with stainless steel pellets to a powder for easy vacuum removal. The steel pellets can be magnetically separated from the waste material for re-use. Specifically this study analyzes the effects of various steel abrasives, pressure of the air stream, and stand-off distance on removal rates and penetration depth on simulated saltcake samples using the high pressure technique. A full-scale test set-up and protocol were implemented to allow for comprehensive testing. To insure reproducibility of the method, tests were then run for the optimum removal parameters. A time-dependent test was also conducted to determine the relationship of removal rates to length of pressure blasts. The results of these tests revealed that stand-off distance and pressure could be positively correlated to removal volumes. Additionally, a statistical analysis confirmed that nozzle angle is independent of removal rate. This study demonstrated that the pellet ‘blaster’ technique is a safe, effective method for removal of radioactive wastes without any increase in either waste mass or volume.  相似文献   
229.
Corporations own approximately 25% of all private land in the United States and, therefore, play an essential role in protecting biodiversity and maintaining natural habitats. The Wildlife Habitat Council (WHC) is a unique joint venture between conservation organizations and corporations to utilize corporate lands for ensuring biodiversity. The following case studies demonstrate how corporations have helped ensure healthy ecosystems and provided critical leadership in regional efforts. Amoco Chemical Company's Cooper River Plant has been instrumental in developing a cooperative project that involves numerous corporations, plantation owners, private citizens, nonprofit organizations, government agencies, and community groups to develop a comprehensive, ecosystem-based management plan for part of the Cooper River in Charleston, South Carolina, USA. The second case focuses on the Morie Company, a national sand quarry operator headquartered in southern New Jersey, USA. Morie Company is working with WHC, community groups, the Pinelands Commission, and other state regulatory agencies to explore sustainable development opportunities for companies within the Pinelands regulations. The third case takes us to DuPont Company's Asturias, Spain, site. A win—win success story of improved habitat and cost savings is the result of DuPont's concern for the environment, ability to work with a variety of groups, and willingness to consider innovative restoration techniques. The fourth case discusses Consumers Power Company's Campbell Plant in West Olive, Michigan, USA. In addition to implementing projects that contribute to biodiversity, Consumers Power has developed an environmental education field station to teach others about the importance of natural habitats. The final case highlights Baltimore Gas & Electric Company's efforts to maintain habitat for endangered species at their Calvert Cliffs site in Maryland.  相似文献   
230.
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