全文获取类型
收费全文 | 33406篇 |
免费 | 362篇 |
国内免费 | 244篇 |
专业分类
安全科学 | 886篇 |
废物处理 | 1411篇 |
环保管理 | 4562篇 |
综合类 | 5476篇 |
基础理论 | 9258篇 |
环境理论 | 14篇 |
污染及防治 | 8558篇 |
评价与监测 | 2068篇 |
社会与环境 | 1553篇 |
灾害及防治 | 226篇 |
出版年
2022年 | 218篇 |
2021年 | 242篇 |
2019年 | 251篇 |
2018年 | 428篇 |
2017年 | 429篇 |
2016年 | 689篇 |
2015年 | 493篇 |
2014年 | 750篇 |
2013年 | 2588篇 |
2012年 | 934篇 |
2011年 | 1330篇 |
2010年 | 1100篇 |
2009年 | 1082篇 |
2008年 | 1375篇 |
2007年 | 1410篇 |
2006年 | 1297篇 |
2005年 | 1065篇 |
2004年 | 1091篇 |
2003年 | 1037篇 |
2002年 | 983篇 |
2001年 | 1282篇 |
2000年 | 916篇 |
1999年 | 549篇 |
1998年 | 441篇 |
1997年 | 438篇 |
1996年 | 453篇 |
1995年 | 520篇 |
1994年 | 516篇 |
1993年 | 451篇 |
1992年 | 468篇 |
1991年 | 443篇 |
1990年 | 482篇 |
1989年 | 461篇 |
1988年 | 403篇 |
1987年 | 375篇 |
1986年 | 338篇 |
1985年 | 331篇 |
1984年 | 400篇 |
1983年 | 355篇 |
1982年 | 403篇 |
1981年 | 363篇 |
1980年 | 297篇 |
1979年 | 323篇 |
1978年 | 281篇 |
1977年 | 233篇 |
1975年 | 229篇 |
1974年 | 251篇 |
1973年 | 240篇 |
1972年 | 247篇 |
1971年 | 215篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
791.
The exploration of offshore areas for hydrocarbons has involved new technical and economic considerations and has posed new problems, not the least of which has been the changing relationship between companies and governments. In this article, the authors present an analysis of the different perspectives and policies which emanate from national governments on the one hand and from transnational oil companies on the other. The issues examined include the considerations involved in establishing exploration legislation, post-discovery problems, the impact on revenues of increased production, the interests of companies in developing fields and the overall economic environment within which decisions have to be agreed. 相似文献
792.
Epidemiological procedures can be organised under disaster conditions by means of a simple surveillance system and with few personnel.
In the aftermath of the 4 February 1976 earthquake in Guatemala, an information system was organized by which the requisite information for decision-making was obtained with adequate speed and promptness.
The initial epidemiologic informution was based on reports collected during the early days on symptoms observed at hospitals and health centers and in localities and villages in the stricken area.
At a second, post-emergency stage a more elaborate surveillance system was instituted to provide guidance in the investigntwn of outbreaks, evaluate the health activities and establish basic criteria for preventive and control measures. 相似文献
In the aftermath of the 4 February 1976 earthquake in Guatemala, an information system was organized by which the requisite information for decision-making was obtained with adequate speed and promptness.
The initial epidemiologic informution was based on reports collected during the early days on symptoms observed at hospitals and health centers and in localities and villages in the stricken area.
At a second, post-emergency stage a more elaborate surveillance system was instituted to provide guidance in the investigntwn of outbreaks, evaluate the health activities and establish basic criteria for preventive and control measures. 相似文献
793.
The results of recent IAEA intercomparison programs are reviewed. 相似文献
794.
J.M.R. Hutchinson 《Environment international》1980,3(5):363-364
The development of traceability in low-level radioactivity measurements is discussed. The role that the development of large quantities of natural matrix standards can play is also discussed. 相似文献
795.
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
796.
797.
Resource estimates alone will not give advance warning of encroaching production difficulties. An analysis of the general stages in the evolution of petroleum production and discovery and of industry statistics provides an estimate of when the stage characterised by increasing production in the market economy countries outside the United States and Canada will end. The analysis indicates that the year of maximum production will be in the 1990s. Economic growth aggravates the difficulties accompanying the production decline by advancing the date of peak production and by increasing the adjustments that must be made as oil production declines. Des prévisions de ressources à elles seules ne constituent pas des signes précurseurs de difficultés croissantes de production. Une analyse des étapes générales marquant l'evolution de la découverte et de la production du pétrole ainsi que des statistiques industrielles nous permet de prévoir l'époque à laquelle prendra fin la phase de production accrue dans les pays à économie de marché en dehors des Etats-Unis et du Canada. Cette analyse révèle que l'année de production maximale se situera dans les années 90. La croissance économique accentue les difficultés qui accompagnent le déclin de la production de pétrole en avancant la date à laquelle cell-ci atteindra son plafond et en augmentant le nombre d'ajustements qui s'avèrent nécessaires au fur et à mesure qu'elle baisse. Las evaluaciones de recursos no dan por si solas un aviso anticipado de las dificultades de producción. Un análisis de las etapas principales en la evolución del descubrimiento y producción de petróleo y de las estadísticas industriales provee un estimado de cuando va a terminar la etapa caracterizada por un crecimiento de producción en los paises de economias de mercado otros que Estados Unidos y Canada. El análisis indica que el año de producción máxima se hallará en la década del 90. El crecimiento económico agrava las dificultades debidas a la declinación de la producción al adelantar la fecha de máxima producción (pico) y al aumentar los ajustes que deven hacerse cuando la producción de petróleos disminuye. 相似文献
798.
799.
800.