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   370篇
  免费   21篇
  国内免费   65篇
安全科学   8篇
废物处理   3篇
环保管理   91篇
综合类   167篇
基础理论   53篇
污染及防治   29篇
评价与监测   26篇
社会与环境   62篇
灾害及防治   17篇
  2024年   2篇
  2023年   5篇
  2022年   8篇
  2021年   18篇
  2020年   12篇
  2019年   8篇
  2018年   6篇
  2017年   16篇
  2016年   24篇
  2015年   19篇
  2014年   11篇
  2013年   32篇
  2012年   23篇
  2011年   26篇
  2010年   14篇
  2009年   22篇
  2008年   23篇
  2007年   32篇
  2006年   19篇
  2005年   22篇
  2004年   13篇
  2003年   13篇
  2002年   9篇
  2001年   12篇
  2000年   6篇
  1999年   12篇
  1998年   7篇
  1997年   8篇
  1996年   4篇
  1995年   2篇
  1994年   8篇
  1993年   3篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1987年   2篇
  1985年   2篇
  1979年   1篇
  1977年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
排序方式: 共有456条查询结果,搜索用时 15 毫秒
401.
铁路运输安全的产权分析   总被引:1,自引:0,他引:1  
由于我国铁路运输安全的复杂性 ,运输安全在改革过程中极有可能沦为“公地悲剧” ,对安全进行产权分析确有必要。分析了一些国家保证铁路运输安全的产权制度安排 ,如英国的“网运分离”后的私有产权路网公司完全负责制、美国的垂直一体化私有产权铁路公司负责和政府安全监管体制、瑞典的非赢利性组织管理和政府安全监管体制以及我国的垂直一体化国有垄断企业 (政府部门 )负责制。笔者认为我国铁路在改革过程中 ,不能忽视运输安全的产权问题 ,应建立适当的运输安全管制体系 ,政府更应该在确保铁路运输安全方面发挥重要作用。  相似文献   
402.
彭州市土地利用变化及驱动力分析   总被引:3,自引:1,他引:3  
陈国慧  樊宏  刘亚迪  张念华 《四川环境》2005,24(4):70-73,76
依据1992~2003土地利用变更数据,分析彭州市土地利用动态、土地利用程度和土地利用区域差异等变化情况。总结了引起土地利用变化的主要驱动力是地形条件、人口增长、工业化和城镇化、第三产业的发展、交通条件、政策因素等六个方面,并针对目前土地利用中存在的主要问题,提出相应的措施,以期对彭州市社会经济发展提供参考。  相似文献   
403.
成都市区植被变化的遥感动态监测   总被引:4,自引:1,他引:4  
利用1987年和2000年的TM影像,对成都市区植被动态变化进行了分析.首先, 利用1:25万数字地形图对2000年的TM影像进行几何校正,并将1987年的TM影像与其配准.其次,利用TM影像的第四和第三波段计算植被指数,根据植被指数提取植被.第三,对成都市区1987~2000年的植被进行了动态变化分析.研究表明,1987~2000年成都市区植被有增有减,但总的趋势是减少:增加部分集中在老城区,是人工绿化的结果;减少部分主要集中在市区西北和西南的面状区域以及因城市道路扩展而占用的线状区域,这是城市化的必然结果.  相似文献   
404.
This paper provides a complete case study analysis of environmental impact assessment (EIA) implementation in China from planning to legal challenge, which is typical but rarely reported. The analysis takes an historical perspective on the regulatory and institutional structures through which EIA has been implemented in China, in order to evaluate the extent to which EIA has matured over the last 10 years. The case study relates to a proposed recreation/tourist development at Dianshan Lake, a protected water resource for Shanghai. Legal and administrative challenge began in 1993, when the case was initiated with a letter from the public, and concluded in 1996, when the case was decided in a court judgment. More recent follow-up research indicates that many issues have continued to be problems for EIA implementation in China. Policy implications in terms of regulatory structure, institutional arrangement, EIA procedure, EIA practitioners, and public participation can be drawn, and lessons learned for both the government and the developers. The study emphasizes the problem of relying on reorientation of existing institutions to promote new (environmental) priorities.  相似文献   
405.
ABSTRACT: Snow course surveys in late winter provide stream‐flow forecasters with their best information for making water supply and flood forecasts for the subsequent spring and summer runoff period in mountainous regions of western North America. Snow survey data analyses are generally based on a 30‐year “normal” period. It is well documented that forest cover changes over time will affect snow accumulation on the ground within forests. This paper seeks to determine if forest cover changes over decades at long term snow courses decrease measured peak snow water equivalent (SWE) enough to affect runoff prediction. Annual peak SWE records were analyzed at four snow courses in two different forest types having at least 25 years of snowpack data to detect any decreases in SWE due to forest growth. No statistically significant decreases in annual peak SWE over time were found at any of these four snow courses. The wide range of annual winter precipitation and correspondingly highly variable peak snowpack accumulation, as well as many other weather and site variables, masked any minor trends in the data.  相似文献   
406.
ABSTRACT: Experimental cuttings on two small, hardwood-forested watersheds in New England showed that annual streamflow can be increased as much as 41 percent. Most of the increase occurred in summer and early autumn when additional streamflow is most needed. Revegetation caused the annual increases to nearly disappear within 4 years after complete forest clearing.  相似文献   
407.
陕西未来50年区域旱涝气候预测研究   总被引:7,自引:0,他引:7  
栗珂  叶殿秀 《灾害学》1998,13(3):23-27
用陕西省近526a的旱涝等级资料,根据超低频气候振动理论和尺度对应原理,通过旱涝气候对天体物理、太阳活动等周期,特别是ENSO对天体物理显著敏感的周期响应关系的物理统计分析,选取周期概率显著的周期,进行外延叠加集成预测,给出了未来50a陕西省不同区域旱涝趋势的预测结果.  相似文献   
408.
The results of long-term stationary research on the assessment of aboveground phytomass and soil moisture dynamics in a steppe pasture are presented. An analysis of annual and interannual variation in meteorological parameters over the study period has been performed, and, on this basis, the dependence of productivity on climatic changes has been determined.  相似文献   
409.
In China, farmland property rights characterized by the household-responsibility system (HRS) have been improved since the reform and opening-up. The rights of use, transfer and gain become more stable, authorized and complete. This paper firstly analyzes the impact on farmland productivity, which comes from the improvement of farmland property rights. Then, an economet-ric model is built to test the above analysis. It concludes that changes of property rights will affect farmland performance in China. In the end, some policy implications are explored for fur-ther reforms.  相似文献   
410.
The operational designing of Environmentally Sustainable Economic Development (ESED) emerges as an urgent and demanding task. Even though ESED has paved the way for thought-provoking and constructive scientific dialogue, appeal for designing an operational ESED is still lagging behind the needs of contemporary societies, leaving much to be desired. With this in mind, the present paper will aim at delineating principles for the operational application of ESED. First, the preservation of crucial properties of environmental functions and ecosystems, emerges as a prime condition of ESED. The second condition concerns the provision of the economic process with sufficient natural inputs; in this context, the paper intends to trace certain operational tenets governing the use of natural resources. Finally, the appropriate institutional settings for the operational design of ESED are traced. Readers should send their comments on this paper to BhaskarNath@aol.com within 3 months of publication of this issue  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