全文获取类型
收费全文 | 29071篇 |
免费 | 328篇 |
国内免费 | 251篇 |
专业分类
安全科学 | 783篇 |
废物处理 | 1151篇 |
环保管理 | 3727篇 |
综合类 | 5204篇 |
基础理论 | 7658篇 |
环境理论 | 14篇 |
污染及防治 | 7279篇 |
评价与监测 | 1889篇 |
社会与环境 | 1734篇 |
灾害及防治 | 211篇 |
出版年
2022年 | 230篇 |
2021年 | 217篇 |
2020年 | 187篇 |
2019年 | 219篇 |
2018年 | 367篇 |
2017年 | 444篇 |
2016年 | 604篇 |
2015年 | 505篇 |
2014年 | 753篇 |
2013年 | 2343篇 |
2012年 | 884篇 |
2011年 | 1213篇 |
2010年 | 1040篇 |
2009年 | 1057篇 |
2008年 | 1212篇 |
2007年 | 1279篇 |
2006年 | 1125篇 |
2005年 | 920篇 |
2004年 | 910篇 |
2003年 | 926篇 |
2002年 | 848篇 |
2001年 | 1084篇 |
2000年 | 824篇 |
1999年 | 465篇 |
1998年 | 339篇 |
1997年 | 367篇 |
1996年 | 389篇 |
1995年 | 414篇 |
1994年 | 401篇 |
1993年 | 368篇 |
1992年 | 382篇 |
1991年 | 359篇 |
1990年 | 370篇 |
1989年 | 331篇 |
1988年 | 286篇 |
1987年 | 271篇 |
1986年 | 283篇 |
1985年 | 287篇 |
1984年 | 297篇 |
1983年 | 284篇 |
1982年 | 266篇 |
1981年 | 259篇 |
1980年 | 244篇 |
1979年 | 252篇 |
1978年 | 198篇 |
1977年 | 217篇 |
1975年 | 153篇 |
1974年 | 181篇 |
1973年 | 172篇 |
1972年 | 182篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
681.
Based upon two recent periods of fieldwork among a spontaneously resettled population of cattle herders in southwestern Ethiopia, this paper is an attempt to illustrate, by a particular case, the general proposition that external aid, if it is not to be counter-productive, must meet people's needs as they themselves define them. The people in question, the Mursi, have experienced, since 1970, their worst period of drought and hunger in living memory. They have responded to this experience with resilience and inventiveness and largely without external assistance. The paper concentrates on a recent, drought induced, migration of Mursi to higher land, outside their traditional territory, and shows how the migrants are adapting to a new way of life which brings them into direct conflict with some of their most cherished cultural traditions. 相似文献
682.
683.
684.
685.
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
686.
687.
Various suggested definitions of the term “traceability” are discussed from the standpoint of proposed adoption and use of the concept by the International Organization of Legal Metrology. 相似文献
688.
Deposition velocities have been determined for corn and soybeans in the first 4–6 weeks of growth in a full-scale study of canopy flow in a wind tunnel. Particles of 1, 5, 10 and 15 μm aerodynamic diameter made of sodium florescein were injected into the Environmental Wind Tunnel Facility at Colorado State University. Deposition velocities were determined as a function of free stream velocity (183, 305 and 610 cm/s) and approach flow turbulence intensity (~1% and 8%). Plants were arranged in realistic field configurations. Hot-wire anemometer studies confirmed that the fluid velocity profiles developed in the wind tunnel were similar to the flow realized in canopies in natural fields. An increase in velocity and turbulence intensity was found to decrease the deposition velocities. A minimum deposition velocity was observed at a particle diameter of 5 μm. 相似文献
689.
690.