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   50646篇
  免费   586篇
  国内免费   639篇
安全科学   1726篇
废物处理   2361篇
环保管理   6657篇
综合类   8142篇
基础理论   13315篇
环境理论   25篇
污染及防治   12762篇
评价与监测   3451篇
社会与环境   3105篇
灾害及防治   327篇
  2023年   226篇
  2022年   482篇
  2021年   531篇
  2020年   360篇
  2019年   443篇
  2018年   772篇
  2017年   796篇
  2016年   1188篇
  2015年   925篇
  2014年   1403篇
  2013年   4093篇
  2012年   1727篇
  2011年   2345篇
  2010年   1907篇
  2009年   1938篇
  2008年   2330篇
  2007年   2326篇
  2006年   2067篇
  2005年   1777篇
  2004年   1678篇
  2003年   1733篇
  2002年   1569篇
  2001年   1928篇
  2000年   1369篇
  1999年   832篇
  1998年   608篇
  1997年   618篇
  1996年   632篇
  1995年   749篇
  1994年   706篇
  1993年   593篇
  1992年   633篇
  1991年   619篇
  1990年   608篇
  1989年   570篇
  1988年   504篇
  1987年   449篇
  1986年   414篇
  1985年   425篇
  1984年   467篇
  1983年   441篇
  1982年   463篇
  1981年   386篇
  1980年   310篇
  1979年   340篇
  1978年   299篇
  1977年   228篇
  1975年   245篇
  1973年   232篇
  1972年   243篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
Although oil spill cleanup requirements have existed in the United States for years, recent increases in oil imports and marine transportation of petroleum products as well as growing environmental concern have exposed a new industry, the Oil Spill Cleanup Industry. This paper explores some of the microeconomic aspects of this industry which has come under increased scrutiny by the general public, big business, and the federal government.In addition to a brief history and definition, several basic questions about the economic viability of the oil spill cleanup industry are raised and explored, and the impact on the industry of cleanup from government sources is examined, both from the perspective of present operations and from apparent future increases in federal participation. The primary dilemma facing the industry, that of providing continued and immediate supply while confronted with stochastic demand, is discussed. The effects of the large spill on the industry both in terms of revenue and ability to meet cleanup requirements is also considered.Information for the paper is drawn from past and continuing involvement in the U.S. Coast Guard's Marine Environmental Protection Program by both authors. The statistical evidence presented here was compiled through personal interviews and from two computerized Coast Guard information systems; PIRS (the Pollution Incident Reporting System), and SKIM (the Spill Cleanup Equipment Inventory System).  相似文献   
182.
183.
184.
Natural gas may provide a major contribution to the world energy supply during the next few decades. The developing countries command about 50 per cent of the world proved natural gas reserves, with gas accounting for only 6 per cent of commercial primary energy production. The challenging task of expanding gas production and utilization in the developing countries, especially through effective use of gas associated with petroleum deposits and transportation of gas in liquefied form (LNG), will require long-term technical co-operation policy commitments with regard to investment, manpower and the transfer of technology. The article is intended to analyse the basic factors involved in these problems. Au cours des prochaines décennies, le gaz naturel peut constituer un apport considérable à l'approvisionnement énergétique mondial. Les pays en développement détiennent approximativement 50 pour cent des réserves mondiales prouvées de gaz naturel, le gaz représentant seulement 6 pour cent de la production d'énergie primaire commerciale. Le défi lancé par la production et l'utilisation croissantes de gaz dans les pays en développement, particulièrement par l'utilisation efficace du gaz lié aux gisements de pétrole et le transport du gaz liquéfié (GNL), requiert des engagements à long terme en matière de politique de coopération technique dans le domaine des investissements, de la main-d'oeuvre et du transfert de technologie. Cet article a pour but d'analyser les facteurs fondamentaux à prendre en considération lorsqu'on traite de ces problèmes. El gas natural podría representar una gran contribucíon a la oferta mundial de energía dentro de las próximas décadas. Los países en desarrollo poseen cerca del 50 porciento de la reserva provada mundial de gas y solamente el 6 porciento de la producción primaria de energía comercial proviene del gas. La tarea de expandir la producción y utilización de gas en los países en desarrollo, especialmente ia utilización efectiva en forma líquida (LNG) de gas asociado al petróleo, requiere de compromisos de cooperación técnica a largo plazo en lo referente a inversiones, recursos humanos y transferencia de tecnología. Este artículo intenta analizar los factores básicos pertinentes a dicha tarea.  相似文献   
185.
Sharlin SA  Mor-Barak M 《Disasters》1983,7(2):142-147
This paper describes the help given by the social services department of a shipping company to bereaved families following a shipping disaster. In the absence of clear, factual and prompt information from an authoritative source, there is a tendency for bereaved individuals to deny their loss and thereby delay the process of mourning and eventual recovery. Appropriate intervention and support can help to overcome this tendency as was seen in the Madasa case.  相似文献   
186.
Results of a recent intercomparison on the determination of trace elements in simulated air filter samples are reported. A large scatter of results is obtained for some elements and systematic differences between laboratories are observed. The performance of different methods, in particular neutron activation analysis and atomic absorption spectrophotometry, used by the various laboratories is discussed (air filter analysis; intercomparison; trace elements; control charts).  相似文献   
187.
188.
There is a growing recognition that knowledge of indigenous communities, based on accumulated observations and experience over time, is significant for sustainable environmental management in collaboration with modern scientific knowledge. A number of innovative policy initiatives are currently being implemented in New Zealand to enable indigenous Maori tribes and sub-tribes to rehabilitate and manage their local fisheries in accordance with customary values and practices. These policies are an important milestone from an historical perspective as they are meant to recognise and empower the role of Maori as Treaty partners. The fisheries management regime in New Zealand now provides for Maori representation at the local level within a co-management framework that enables local Maori communities to exercise their customary rights. These institutional arrangements have been crafted to facilitate Maori input, based on customary values and practices, to complement modern Western management practices for sustainable harvesting of marine resources. Nevertheless, the degree to which these initiatives constitute an adequate response to Maori Treaty aspirations is debatable. A major constraint in this respect is that the government is compelled to recognise the needs of other, economically and politically more dominant, non-Maori user-groups in allocating and managing access to fishery resources and the marine environment.  相似文献   
189.
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   
190.
Laboratory column experiments run for up to 13 days compared air sparging of groundwater contaminated by dissolved petroleum hydrocarbons in sterile and non-sterile aquifer sediments as well as uncontaminated sediments and groundwater. Loss of dissolved BTEX compounds in the contaminated columns was very rapid, occurring through volatilisation. The majority of the dissolved total organic carbon (TOC) persisted for much longer periods however. A direct comparison between losses from sterile and non-sterile columns suggested a negligible contribution of biodegradation to the removal of TOC. This was difficult to confirm through examination of O2 utilisation because oxidation of a small amount of reduced sulphur in the aquifer materials was the dominant sink for O2. Despite this, it was possible to conclude that less than 22% of the removal of TOC was through biodegradation during the first three days of air sparging.  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