全文获取类型
收费全文 | 1800篇 |
免费 | 41篇 |
国内免费 | 15篇 |
专业分类
安全科学 | 62篇 |
废物处理 | 61篇 |
环保管理 | 373篇 |
综合类 | 195篇 |
基础理论 | 503篇 |
环境理论 | 2篇 |
污染及防治 | 432篇 |
评价与监测 | 109篇 |
社会与环境 | 103篇 |
灾害及防治 | 16篇 |
出版年
2022年 | 21篇 |
2021年 | 22篇 |
2020年 | 23篇 |
2019年 | 20篇 |
2018年 | 46篇 |
2017年 | 33篇 |
2016年 | 73篇 |
2015年 | 53篇 |
2014年 | 55篇 |
2013年 | 167篇 |
2012年 | 62篇 |
2011年 | 110篇 |
2010年 | 67篇 |
2009年 | 77篇 |
2008年 | 81篇 |
2007年 | 88篇 |
2006年 | 72篇 |
2005年 | 65篇 |
2004年 | 53篇 |
2003年 | 57篇 |
2002年 | 57篇 |
2001年 | 50篇 |
2000年 | 28篇 |
1999年 | 31篇 |
1998年 | 20篇 |
1997年 | 20篇 |
1996年 | 22篇 |
1995年 | 39篇 |
1994年 | 21篇 |
1993年 | 23篇 |
1992年 | 15篇 |
1991年 | 25篇 |
1990年 | 22篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 26篇 |
1983年 | 11篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 7篇 |
1977年 | 15篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1971年 | 7篇 |
排序方式: 共有1856条查询结果,搜索用时 15 毫秒
61.
ABSTRACT: A procedure of estimating instantaneous flood flows for various return periods on the Island of Newfoundland is presented. The procedure is based on annual maximum instantaneous flows rather than annual maximum daily-mean flows, as the latter requires the conversion of estimated daily-mean flows into instantaneous flows. Regression equations were developed for each of three homogeneous regions for the desired return periods. The flood flow estimation capability of the presented procedure is demonstrated to be better than any other currently available procedure on the Island. 相似文献
62.
Zachary A. Smith 《Journal of the American Water Resources Association》1987,23(5):873-877
ABSTRACT: Federal-state relations over the management and regulation of ground water resources have undergone a number of changes in recent years. There are a variety of reasons that the role of the federal government in ground water management may increase in the future. One important reason federal policymakers may become involved concerns the extent of competition for ground water resources that cross state and national borders. This article summarizes reasons that interstate and international competition for ground water resources may provide the impetus for federal intervention in ground water management and presents the results of a survey conducted to determine the extent of that competition. 相似文献
63.
R. A. Smith 《Safety Science》1995,18(4)
Work undertaken to quantify the relationships between crowd velocities, flow rates and densities for uni-directional motion is reviewed. Most of the available data has been generated for underground stations in the UK; similar work for commuter stations in Japan is introduced and developed. Maximum observed flow rates from this work are compared with those suggested in the ‘Green Guide’ for the evacuation of sports grounds. The ‘Green Guide’ figures are higher than the maximum values obtained from the work reviewed. 相似文献
64.
65.
Taiye B. Sangoyomi Benjamin L. Harding 《Journal of the American Water Resources Association》1995,31(5):925-938
ABSTRACT: We evaluated the effects of institutional responses developed for coping with a severe sustained drought (SSD) in the Colorado River Basin on selected system variables using a SSD inflow hydrology derived from the drought which occurred in the Colorado River basin from 1579–1616. Institutional responses considered are reverse equalization, salinity reduction, minimum flow requirements, and temporary suspension of the delivery obligation of the Colorado River Compact. Selected system variables (reservoir contents, streamflows, consumptive uses, salinity, and power generation) from scenarios incorporating the drought-coping responses were compared to those from Baseline conditions using the current operating criteria. The coping responses successfully mitigated some impacts of the SSD on consumptive uses in the Upper Basin with only slight impacts on consumptive uses in the Lower Basin, and successfully maintained specified minimum streamflows throughout the drought with no apparent effect on consumptive uses. The impacts of the coping responses on other system variables were not as clear cut. We also assessed the effects of the drought-coping responses to normal and wet hydrologic conditions to determine if they were overly conservative. The results show that the rules would have inconsequential effects on the system during normal and wet years. 相似文献
66.
Jessica Sargent‐Michaud Kevin J. Boyle Andrew E. Smith 《Journal of the American Water Resources Association》2006,42(5):1237-1245
ABSTRACT: This study was undertaken to investigate the cost effectiveness of selected arsenic avoidance methods. Annual costs of reverse osmosis (RO), activated alumina (AA), bottled water, and rented and purchased water coolers for various household sizes in Maine were compared. Relative ranking of systems shows that RO ($411 annually) is the most cost effective, followed by AA ($518) and one‐gallon jugs of water ($321 to $1,285), respectively, for households larger than one person. One‐gallon jugs ($321) followed by 2.5‐gallon jugs ($358) of water were found to be the most cost effective for households of one person or for households with arsenic III concentrations of 0.02 to 0.06 mg/L and arsenic V concentrations of 0.08 to 1.0 mg/L. Point‐of‐entry systems and water coolers were not found to be cost effective under any of the study's conditions. The research reported here will help states make more definitive treatment recommendations to households regarding the cost effectiveness of alternative treatment systems to reduce arsenic concentrations below 0.01 mg/L. While arsenic removal technologies are improving, which enhances removal rates and reduces costs, the major insights from this analysis appear to be reinforced by technological improvements. 相似文献
67.
68.
Katherine C. Ewel Joel E. Smith 《Journal of the American Water Resources Association》1992,28(2):299-304
ABSTRACT: We measured diurnal changes in water levels in three swamps dominated by pondcypress trees (Taxodium distichum var. nuans) in central Florida for four years in order to obtain additional documentation of relatively low evapotranspiration (ET) rates. Two of these swamps were monitored for another three years after one of them was clearcut. Estimated annual ET from undisturbed cypress swamps varied from 38 cm/yr to 86 cm/yr, averaging 60 cm (not including interception). Faster ET rates may have been related to faster pondcypress growth rates, a greater proportion of hardwoods in the canopy, and clearcutting in the surrounding pine plantation. The average ET rate was considerably lower than ET rates that have been estimated for north Florida pine plantations. However, incorporating estimates of interception indicates that overall ET rates in pondcypress swamps may be only slightly lower than ET from pine plantations. ET decreased only 5 percent in one swamp after it was clearcut, indicating that this management practice is not likely to affect regional water balances. 相似文献
69.
70.
DEVELOPMENT OF WATERSIIED MODELS FOR TWO SIERRA NEVADA BASINS USING A GEOGRAPHIC INFORMATION SYSTEM1
Anne E. Jeton J. LaRue. Smith 《Journal of the American Water Resources Association》1993,29(6):923-932
ABSTRACT: Techniques were developed using vector and raster data in a geographic information system (GIS) to define the spatial variability of watershed characteristics in the north-central Sierra Nevada of California and Nevada and to assist in computing model input parameters. The U.S. Geological Survey's Precipitation-Runoff Modeling System, a physically based, distributed-parameter watershed model, simulates runoff for a basin by partitioning a watershed into areas that each have a homogeneous hydrologic response to precipitation or snowmelt. These land units, known as hydrologic-response units (HRU's), are characterized according to physical properties, such as altitude, slope, aspect, land cover, soils, and geology, and climate patterns. Digital data were used to develop a GIS data base and HRIJ classification for the American River and Carson River basins. The following criteria are used in delineating HRU's: (1) Data layers are hydrologically significant and have a resolution appropriate to the watershed's natural spatial variability, (2) the technique for delineating HRU's accommodates different classification criteria and is reproducible, and (3) HRU's are not limited by hydrographic-subbasin boundaries. HRU's so defined are spatially noncontiguous. The result is an objective, efficient methodology for characterizing a watershed and for delineating HRU's. Also, digital data can be analyzed and transformed to assist in defining parameters and in calibrating the model. 相似文献