全文获取类型
收费全文 | 1479篇 |
免费 | 118篇 |
国内免费 | 148篇 |
专业分类
安全科学 | 70篇 |
废物处理 | 20篇 |
环保管理 | 452篇 |
综合类 | 560篇 |
基础理论 | 120篇 |
环境理论 | 1篇 |
污染及防治 | 31篇 |
评价与监测 | 53篇 |
社会与环境 | 382篇 |
灾害及防治 | 56篇 |
出版年
2024年 | 8篇 |
2023年 | 16篇 |
2022年 | 38篇 |
2021年 | 49篇 |
2020年 | 29篇 |
2019年 | 45篇 |
2018年 | 45篇 |
2017年 | 63篇 |
2016年 | 67篇 |
2015年 | 63篇 |
2014年 | 47篇 |
2013年 | 103篇 |
2012年 | 97篇 |
2011年 | 121篇 |
2010年 | 84篇 |
2009年 | 69篇 |
2008年 | 61篇 |
2007年 | 91篇 |
2006年 | 76篇 |
2005年 | 59篇 |
2004年 | 71篇 |
2003年 | 58篇 |
2002年 | 54篇 |
2001年 | 32篇 |
2000年 | 55篇 |
1999年 | 43篇 |
1998年 | 15篇 |
1997年 | 22篇 |
1996年 | 22篇 |
1995年 | 28篇 |
1994年 | 26篇 |
1993年 | 16篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1975年 | 2篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1971年 | 2篇 |
排序方式: 共有1745条查询结果,搜索用时 703 毫秒
831.
David W. Watkins Greg A. Link Dennis Johnson 《Journal of the American Water Resources Association》2005,41(1):157-170
ABSTRACT: For regional precipitation frequency analyses, methods are needed to spatially interpolate or smooth point intensity duration frequency (IDF) estimates at gage sites for the purposes of visualization and estimation at ungaged sites. In this study to update IDF estimates for Michigan, the assumption is made that for practical purposes, the entire state may be treated as a homogeneous region in which annual maximum precipitation is identically distributed at each site apart from a site‐specific scaling factor, commonly known as the index flood. Several interpolation and smoothing techniques are evaluated for IDF estimation at ungaged sites, including trend surface analysis, thin plate splines, inverse distance weighting, and several kriging algorithms. Ordinary block kriging is recommended as a practical and objective method for smoothing the variability in the index flood values and developing isopluvial maps. 相似文献
832.
大西南的旅游资源丰富而独特,但开发程度低、经营粗放、发展整体性差、组合效益低.本文根据近年来的研究,从大西南的整体对其旅游资源进行分区及评价、并分析其开发的市场条件,提出了开发途径。 相似文献
833.
本文通过对四川省自然灾害分布规律的系统分析,提出其区划的原则和要求,并引入模糊聚类的方法,对四川省自然灾害进行分区划片,目的是为区域规划提供减灾的重点方向。 相似文献
834.
ABSTRACT: The geochemistry and nature of the flow of ground water not only control the supply potential but constitute clues to the whole geology of an area. A study has been made of the largest available assemblage of data from 161 wells for the Island of Montreal collected by the Geological Survey of Canada in 1951–53. Data indicated that the system is generally subartesian, flowing from the principal topographically high areas towards the shores of the Island. As the probable use is about 13% of the estimated recharge of 140 million liters per day, most wells could be supplied by local recharge. The study has confirmed the predominance of calcium bicarbonate ground water from the carbonate sequence. The waters appeared to be saturated with respect to CaCO3 in all but 10 wells. The presence of other types of waters suggests the effects of the igneous intrusions of the area, the post-glacial marine submergence and the upward movement of waters from deep sources through fault and other structural zones. Confirmation of the significant variations in chemical composition in some neighboring wells indicated the future need for repetitive sampling from specific horizons for chemical and isotopic analyses. 相似文献
835.
William H. Sander 《Journal of the American Water Resources Association》1980,16(2):189-193
ABSTRACT: The national and regional economic impact of the Bureau of Reclamation's Uncompahgre Project which was authorized in 1903 is assessed. Benefit-cost ratios for the project are calculated for a range of production cost estimates and discount rates. An economic base approach is used to estimate the project's regional economic impact. Although the project has been marginal in terms of an economic efficiency rationale it has been an important impetus to regional economic growth in the Uncompahgre Region over time. 相似文献
836.
J. Jeffrey Peirce 《Journal of the American Water Resources Association》1980,16(2):220-225
ABSTRACT: Strategies for controlling nonpoint sources of water pollution are discussed in terms of three representative states and eighteen regional agencies. The programs in Virginia, New York, and Wisconsin are seen to exhibit control options which range from voluntary action to strict regulation. Four conclusions are drawn from the analysis. First, nonpoint sources of pollution are a major component of the overall water pollution problem in the three states. Second, technical controls are generally available to solve the problems. Third, existing controls programs are not necessarily technologically sound or cost effective. Finally, existing control programs are capable of instituting solutions to the problems if and only if specified actions take place within the respective states and regions in the future. Critical research needs are identified which will assist states and regions in developing cost effective programs to control nonpoint source pollution. 相似文献
837.
论水资源格局与可持续发展 总被引:8,自引:0,他引:8
孟庆民 《中国人口.资源与环境》1999,9(2):26-30
以可持续发展理论为指导,分析了我国水资源自然格局及利用格局的现状与问题,提出了作为可持续发展重要支撑的水资源,其可持续利用的根本途径是建立可持续发展的水资源格局,即流域经济系统格局,并实现流域基础上的区域竞争与协作一体化 相似文献
838.
略论长江开发的战略思想 总被引:1,自引:0,他引:1
宋栋 《长江流域资源与环境》1999,8(4):339-344
当前长江开发所面临的最大问题是自然资源利用不合理所造成的资源严重浪费和生态环境恶化,其直接威胁到长江流域社会经济的可持续发展。长江流域既是我国自然资源的富集区,又是国民经济的核心主干区,其开发的成功与否直接关系到中国经济现代化的前途。因此,在经济体制与经济增长方式双重转型的过程中,长江的开发如何实现自然资源的利用与保护的相互协调,成为了我们的迫切需要解决的问题。 相似文献
839.
区域农业资源开发与可持续发展——以江苏为例 总被引:8,自引:1,他引:7
曲福田 《长江流域资源与环境》1999,8(3):282-287
我国系典型的人多地少国家,自然资源特别是农业资源对经济高速发展的支持能力相当薄弱,农业资源开发社会经济可持续发展中起着十分重要的作用。以江苏为例,探讨了农业资源开发与区域共同发展,经济国际化及科教兴省等战略实施之间的关系,对该区域主要农业资源开发前景进行分析,在此基础上提出了可持续发展战略下农业资源开发的途径与措施。 相似文献
840.
Gary D. Tasker Alan W. Burns 《Journal of the American Water Resources Association》1974,10(6):1133-1142
ABSTRACT: The empirical fit of an annual harmonic function to stream temperature measurements in central New England can be improved by considering a harmonic period of less than 365 days instead of 365 or 366 days. Generalized equations, developed using periodic temperature data from 27 streamflow stations, allow predictions of stream temperature at any site given (1) the mean basin altitude (E), in meters above mean sea level, and (2) station latitude (LAT), in degrees. Stream temperature t, in degrees Celsius, on day number d, in days starting with January 1, is estimated as: in which, M = 31.48 – 0.0025 (E) ? 0.4635 (LAT) with standard error of estimate of 0.62°C, and τ= 1228.88 – 21.01 (LAT) with standard error of estimate of 14.1 days. 相似文献