全文获取类型
收费全文 | 1030篇 |
免费 | 127篇 |
国内免费 | 400篇 |
专业分类
安全科学 | 32篇 |
废物处理 | 28篇 |
环保管理 | 229篇 |
综合类 | 895篇 |
基础理论 | 131篇 |
污染及防治 | 97篇 |
评价与监测 | 94篇 |
社会与环境 | 36篇 |
灾害及防治 | 15篇 |
出版年
2024年 | 15篇 |
2023年 | 37篇 |
2022年 | 55篇 |
2021年 | 57篇 |
2020年 | 65篇 |
2019年 | 70篇 |
2018年 | 54篇 |
2017年 | 57篇 |
2016年 | 76篇 |
2015年 | 77篇 |
2014年 | 82篇 |
2013年 | 99篇 |
2012年 | 95篇 |
2011年 | 84篇 |
2010年 | 70篇 |
2009年 | 49篇 |
2008年 | 39篇 |
2007年 | 54篇 |
2006年 | 52篇 |
2005年 | 54篇 |
2004年 | 24篇 |
2003年 | 48篇 |
2002年 | 40篇 |
2001年 | 27篇 |
2000年 | 19篇 |
1999年 | 32篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 14篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 6篇 |
1972年 | 8篇 |
1971年 | 7篇 |
1970年 | 1篇 |
排序方式: 共有1557条查询结果,搜索用时 843 毫秒
71.
72.
Thomas V. Belanger Donald F. Mikutel 《Journal of the American Water Resources Association》1985,21(2):265-272
Data from a study on East Lake Tohopekaliga, Florida, indicate that the seepage meter measurement method may often overestimate nutrient contributions to lakes. Nutrient loading data from this method and a method employing lakeside piezometer nutrient data and seepage meter flows were not comparable. Seepage nutrient loading from the meter and piezometer methods comprised 39 and 18 percent of the nitrogen budget and 38 and 9 percent of the phosphorus budget, respectively, for East Lake Tohopekaliga. In terms of water, groundwater seepage accounted for only 14 percent of the total input to the lake. It is felt that some of the past studies using the seepage meter method to estimate nutrient loading may be in error due to reasons related to the enclosure of lake sediments by the meter and the accompanying anaerobic conditions which quickly result. 相似文献
73.
Wendy A. Rice Steven M. Gorelick 《Journal of the American Water Resources Association》1985,21(6):919-930
A graphical inverse method for determining the regional transmissivity distribution was applied to three field problems. The study areas were the Hanford Site, Washington; the Rocky Mountain Arsenal, Colorado; and the Nevada Test Site, Nevada. This method can aid in flow system conceptualization by revealing the location of bedrock controls for groundwater flow. It is a valuable tool for aiding the hydrogeologist in asking questions about the nature of trends in the pattern of transmissivity values. Quantitative estimates of regional transmissivities can be used as starting points for further parameter refinement. Sensitivity analysis using Monte Carlo simulation shows that quantitative estimates of transmissivity can be obtained when measurement error in the hydraulic head does not cause a large error in the hydraulic gradient. 相似文献
74.
ABSTRACT: Although evidence of modern recharge in the North African and Arabian sedimentary basin aquifers exists, it is difficult to determine the volume of recharge. Also, from the evidence of regional groundwater gradients, the flow within the aquifers seems to be appreciably greater than one would intuitively expect. A hypotehtical model embodying the characteristics of the aquifers has been used to investigate the likely significance of various possible flow mechanisms. It is shown that while dewatering in the unconfined area can possibly contribute to flows for a considerable period of time, the maintenance of water levels in the unconfined zone must be the result of modern recharge. It is also shown that recharge depths of less than 10 mm per annum are sufficient given suitable aquifer parameters. Results for various combinations of aquifer parameters and configurations are given, including layered aquifers and the effects of restricted oufflows. Comparisons are made using a “bench mark” example. The work indicates that there is little point in carrying out conventional hydrological balance studies in hyper-arid areas and that, instead, more emphasis should be placed upon good groundwater hydrographic data and modeling. 相似文献
75.
Dinshaw N. Contractor 《Journal of the American Water Resources Association》1983,19(5):745-751
ABSTRACT This paper deals with the application of a two-dimensional, saltwater intrusion model to the aquifer in Northern Guam. The model used finite element theory and the Galerkin, weighted-residual technique as its basis. The Northern Guam lens was discretized into 299 linear, triangular elements and 189 nodes. The model was calibrated using 1978 hydrologic data. The output of the model was compared with measured water levels in six observation wells. The calibrated values of permeability and porosity were then used to verify the model using 1979 data. A calibrated and verified model can be used to make an infinite variety of management and planning studies. In this study, three applications are provided that would be considered typical management runs. Steady state runs were made to compare the four conditions of no pumping, 1978 pumping levels, twice 1978 pumping levels, and five times 1978 pumping levels. The water levels due to these conditions are shown in plan and in cross sections of the aquifer. The effect of zero recharge to the aquifer is next demonstrated for the pumping levels existing during 1978. The final run shows how long the aquifer takes to reach steady state when the pumping rate is increased from the 1978 pumping level to twice that value. The program can be used for numerous other studies for management and planning purposes. 相似文献
76.
中国工程物理研究院核 物理与化学研究所原工作地点(老点)存在两个放射性废物库537-1和537-2。年内分别在库周围取地下水(或土)6次,对537-1得到地下水和泥土中的铀含量大约为1.27μg/L和3.0μg/L,对537-2得到的地下水中的90Sr含量约为5.35×10-3Bq/L。上列数据与本底无明显差异。可见,537-1废物库周围地下水中铀含量与生活区河水中含量无明显差异,537-2废物库周围地下水中锶含量与生活区河水中含量也无明显差异。至今未监测到两个废物库中的放射性核素对周围地下水中的明显 影响。 相似文献
77.
78.
Morton W. Bittinger E. Bruce Jones 《Journal of the American Water Resources Association》1972,8(2):386-390
Many important groundwater aquifers cross state and national boundaries. The flow of water in these aquifers is not influenced by the boundaries but may be materially influenced by mans activities on one or both sides of a boundary. Interstate and international problems may develop because of excessive groundwater lowering on one side of a boundary affecting water users on the opposite side of the line. Similarly, intensive groundwater development along a surface stream may influence the amount of surface water that flows across a boundary. A third type of problem may develop when pumping on one side of the boundary induces poor quality water into an aquifer on the other side of the boundary. Several specific interstate and international aquifer problems are briefly described. 相似文献
79.
Jack E. McKee 《Journal of the American Water Resources Association》1971,7(4):740-749
ABSTRACT There are several possible ways in which wastewater from municipalities may be reclaimed and reused so as to minimize the need for imported water in North Central Texas. The rationale for reuse is enhanced by the fact that new water quality requirements in the Trinity River system will necessitate a very high degree of treatment at municipal sewage plants, just for discharge to surface streams. The largest potential market for municipal effluent is the steam-electric power industry. Within the next decade the generating capacity for electric power in North Central Texas will have to be more than doubled to meet increasing demand. Adequate supplies of condenser cooling water for such expansion will be difficult to obtain and assure. New large power stations might advantageously be located adjacent to municipal wastewater treatment plants, to utilize effluent as make-up water for cooling towers. Experience elsewhere has shown that well-treated wastewater can be used for cooling tower make-up with a minimum of trouble, with a considerable saving in overall cost, and with conservation of pristine water for other uses. 相似文献
80.
Yawn M. Sternberg 《Journal of the American Water Resources Association》1971,7(3):447-456
ABSTRACT A discussion of the various tools and techniques available for evaluation of aquifers is presented. Data for evaluation studies can be obtained from laboratory experiments, geological maps, well logs and field studies. Such data can be used in analytic or electric analog models to determine the sustained yield of the aquifer under various operating conditions. 相似文献