全文获取类型
收费全文 | 3535篇 |
免费 | 60篇 |
国内免费 | 33篇 |
专业分类
安全科学 | 203篇 |
废物处理 | 116篇 |
环保管理 | 945篇 |
综合类 | 323篇 |
基础理论 | 865篇 |
环境理论 | 7篇 |
污染及防治 | 785篇 |
评价与监测 | 224篇 |
社会与环境 | 130篇 |
灾害及防治 | 30篇 |
出版年
2023年 | 14篇 |
2022年 | 23篇 |
2021年 | 27篇 |
2020年 | 26篇 |
2019年 | 35篇 |
2018年 | 43篇 |
2017年 | 64篇 |
2016年 | 83篇 |
2015年 | 72篇 |
2014年 | 75篇 |
2013年 | 447篇 |
2012年 | 132篇 |
2011年 | 175篇 |
2010年 | 117篇 |
2009年 | 132篇 |
2008年 | 156篇 |
2007年 | 194篇 |
2006年 | 136篇 |
2005年 | 118篇 |
2004年 | 124篇 |
2003年 | 127篇 |
2002年 | 108篇 |
2001年 | 63篇 |
2000年 | 78篇 |
1999年 | 49篇 |
1998年 | 56篇 |
1997年 | 44篇 |
1996年 | 61篇 |
1995年 | 57篇 |
1994年 | 64篇 |
1993年 | 52篇 |
1992年 | 47篇 |
1991年 | 39篇 |
1990年 | 38篇 |
1989年 | 31篇 |
1988年 | 40篇 |
1987年 | 30篇 |
1986年 | 34篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 37篇 |
1982年 | 48篇 |
1981年 | 47篇 |
1980年 | 26篇 |
1979年 | 28篇 |
1978年 | 25篇 |
1977年 | 29篇 |
1976年 | 13篇 |
1974年 | 10篇 |
1972年 | 11篇 |
排序方式: 共有3628条查询结果,搜索用时 31 毫秒
121.
Kevin G. Boggs Robert W. Van Kirk Gary S. Johnson Jerry P. Fairley P. Steve Porter 《Journal of the American Water Resources Association》2010,46(6):1116-1132
Boggs, Kevin G., Robert W. Van Kirk, Gary S. Johnson, Jerry P. Fairley, and P. Steve Porter, 2010. Analytical Solutions to the Linearized Boussinesq Equation for Assessing the Effects of Recharge on Aquifer Discharge. Journal of the American Water Resources Association (JAWRA) 46(6):1116–1132. DOI: 10.1111/j.1752-1688.2010.00479.x Abstract: There is a need to develop a general understanding of how variations in aquifer recharge are reflected in discharge. Analytical solutions to the linearized Boussinesq equation governing flow in an unconfined aquifer provide a unified mathematical framework to quantify relationships among lag time, attenuation and distance between aquifer recharge and discharge and the effect of an up-gradient no-flow boundary. We applied this framework to three types of recharge: (1) instantaneous, (2) periodic, and (3) constant rate for a finite duration. When the temporal scale of recharge exceeds the diffusive aquifer time scale, recharge will be reflected in discharge quickly and with little attenuation. When aquifer time scale is large, most recharge events are shorter in scale than that of the aquifer, resulting in large attenuation. Attenuation is more sensitive to boundary effects than lag time, and boundary effects increase as recharge time scale increases. Boundary effects can often be ignored when the recharge source is farther than 1/3 of the domain length away from the no-flow boundary. We illustrate analytical results with application to the economically critical Eastern Snake River Plain Aquifer in Idaho. In this aquifer, detectable annual and decadal cycles in discharge can result from recharge no farther than 20 and 60 km away from the discharge point, respectively. The effects of more distant, long-term recharge can be detected only after a time lag of several decades. 相似文献
122.
Pietro A. Catizone Steven E. Zell Christopher R. Arrington Michael B. Newman Steven F. Weber Robert J. White 《Journal of the Air & Waste Management Association (1995)》2014,64(3):291-308
Detailed hourly precipitation data are required for long-range modeling of dispersion and wet deposition of particulate matter and water-soluble pollutants using the CALPUFF model. In sparsely populated areas such as the north central United States, ground-based precipitation measurement stations may be too widely spaced to offer a complete and accurate spatial representation of hourly precipitation within a modeling domain. The availability of remotely sensed precipitation data by satellite and the National Weather Service array of next-generation radars (NEXRAD) deployed nationally provide an opportunity to improve on the paucity of data for these areas. Before adopting a new method of precipitation estimation in a modeling protocol, it should be compared with the ground-based precipitation measurements, which are currently relied upon for modeling purposes. This paper presents a statistical comparison between hourly precipitation measurements for the years 2006 through 2008 at 25 ground-based stations in the north central United States and radar-based precipitation measurements available from the National Center for Environmental Predictions (NCEP) as Stage IV data at the nearest grid cell to each selected precipitation station. It was found that the statistical agreement between the two methods depends strongly on whether the ground-based hourly precipitation is measured to within 0.1 in/hr or to within 0.01 in/hr. The results of the statistical comparison indicate that it would be more accurate to use gridded Stage IV precipitation data in a gridded dispersion model for a long-range simulation, than to rely on precipitation data interpolated between widely scattered rain gauges.
Implications:
The current reliance on ground-based rain gauges for precipitation events and hourly data for modeling of dispersion and wet deposition of particulate matter and water-soluble pollutants results in potentially large discontinuity in data coverage and the need to extrapolate data between monitoring stations. The use of radar-based precipitation data, which is available for the entire continental United States and nearby areas, would resolve these data gaps and provide a complete and accurate spatial representation of hourly precipitation within a large modeling domain. 相似文献
123.
Grace B. Villamor Robert Gilmore Pontius Jr. Meine van Noordwijk 《Regional Environmental Change》2014,14(2):825-834
This paper examines the size and intensity of changes among five land categories during the two time intervals in a region of Indonesia that is pioneering negotiations concerning reducing emissions from deforestation and forest degradation (REDD). Maps at 1973, 1993, and 2005 indicate that land-cover change is accelerating, while carbon loss is decelerating in Jambi Province, Sumatra. Land dynamics have shifted from Forest loss during 1973–1993 to Agroforest loss during 1993–2005. Forest losses account for most reductions in aboveground carbon during the both time intervals, but Agroforest plays an increasingly important role in carbon reductions during the more recent interval. These results provide motivation for future REDD policies to count carbon changes associated with all influential land categories, such as Agroforests. 相似文献
124.
125.
Ralph E. George Robert L. Chass 《Journal of the Air & Waste Management Association (1995)》2013,63(6):392-395
The importance of fuels combustion was brought into sharp focus recently in a report on air pollution to the United States Senate in which it was stated, “These processes replace usable air with potentially harmful pollutants, and the capability of the atmosphere to disperse and dilute these pollutants—especially in urban areas where people, vehicles, and industries congregate in even greater numbers—is strictly limited.”1 The overwhelming burden of emissions of sulfur compounds, as well as nitrogen compounds and particulate matter in the U. S. today, originates from the burning of coal and fuel oil in stationary combustion sources. Thus, combustion has a large influence on the quality of the atmosphere in most urban areas. The air pollution effects of these contaminants are many and varied and all are objectionable and undesirable. Without a doubt, the most serious air pollution problem in the nation today is that created by the combustion of fossil fuels. 相似文献
126.
127.
Robert U. Ayres Stedman B. Noble 《Journal of the Air & Waste Management Association (1995)》2013,63(3):216-224
The study considers a range of possible effects on the transportation industry, satellite industries, the labor market, and the economy which may be anticipated in the event mass production of unconventional low emission automotive propulsion systems should occur, whether as a consequence of federal intervention, or not. A postulated 1 976 Otto Cycle Internal Combustion Engine equipped with a dual catalyst manifold reactor and other “conventional” emission control devices was compared in detail with a Regenerative Free Turbine Engine and a Rankine Cycle Engine, as specified by the contracting agency. Manufacturing costs, operating and ownership costs, consumer demand, inter-industry effects, employment, resource requirements, and international trade implications were analyzed in depth under a number of plausible sets of policy constraints and parametric variations. Principal conclusions are that conversion over a 10 year period is feasible, that manufacturing cost differentials are less critical than fuel consumption and cost differentials, that industry/employment impacts are minor, and that resource/trade effects are dominated by petroleum imports. Implications for federal policy are discussed. 相似文献
128.
Laurel J. Staley Marta K. Richards George L. Huffman Robert A. Olexsey Barry Dellinger 《Journal of the Air & Waste Management Association (1995)》2013,63(3):321-331
Measurements conducted on full-scale hazardous waste incinerators have occasionally shown a relationship between carbon monoxide (CO) emissions and emissions of toxic organic compounds. In this study, four mixtures of chlorinated C1 and C2 hydrocarbons were diluted in commercial-grade heptane and burned in a water-cooled turbulent flame reactor (TFR) under two different excess air levels. No correlation between CO and organic emissions could be discerned. Reasons for this lack of observable correlations are discussed in terms of combustion and chemical reaction kinetic theory. 相似文献
129.
Robert W. McMullen 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1057-1058
Calculations of pollutant concentrations at various downwind and crosswind distances from an elevated point source are frequently based on diffusion models and parameter values contained in Turner’s Workbook of Atmospheric Dispersion Estimates.1 These calculations can be made much more speedily on a computer or on a currentgeneration, programmable desk calculator, if the values of the horizontal and vertical standard deviations of plume concentrations distributions are stated explicitly as a mathematical function of downwind distance. The alternative is to read the values from Turner’s Figures 3-2 and 3-3 and input them into the calculation for each individual value of downwind distance. 相似文献
130.
Michael J. Massey Robert W. Dunlap 《Journal of the Air & Waste Management Association (1995)》2013,63(10):1019-1027
Two processes are currently being employed in North America for the desulfurization of coke oven gas, the Vacuum Carbonate System, and the Stretford System. A third, the Sulfi-ban Process, which was recently announced, now has several plants scheduled for construction. Overall operating requirements for each of these processes are considered in detail. Emphasis is placed on an identification of power and steam requirements, the types and amounts of solid and/or liquid waste streams produced together with methods for their treatment, and the net desulfurization efficiencies achieved by each process. Detailed estimates of capital and operating costs for desulfurization are considered, and equipment needs for environmental control requirements are discussed. 相似文献