全文获取类型
收费全文 | 30890篇 |
免费 | 351篇 |
国内免费 | 472篇 |
专业分类
安全科学 | 976篇 |
废物处理 | 1461篇 |
环保管理 | 3807篇 |
综合类 | 5124篇 |
基础理论 | 8081篇 |
环境理论 | 19篇 |
污染及防治 | 8169篇 |
评价与监测 | 2103篇 |
社会与环境 | 1791篇 |
灾害及防治 | 182篇 |
出版年
2023年 | 136篇 |
2022年 | 322篇 |
2021年 | 318篇 |
2020年 | 244篇 |
2019年 | 287篇 |
2018年 | 488篇 |
2017年 | 480篇 |
2016年 | 755篇 |
2015年 | 579篇 |
2014年 | 897篇 |
2013年 | 2489篇 |
2012年 | 1077篇 |
2011年 | 1446篇 |
2010年 | 1177篇 |
2009年 | 1210篇 |
2008年 | 1469篇 |
2007年 | 1509篇 |
2006年 | 1287篇 |
2005年 | 1109篇 |
2004年 | 1009篇 |
2003年 | 1098篇 |
2002年 | 970篇 |
2001年 | 1251篇 |
2000年 | 875篇 |
1999年 | 531篇 |
1998年 | 355篇 |
1997年 | 364篇 |
1996年 | 365篇 |
1995年 | 430篇 |
1994年 | 453篇 |
1993年 | 356篇 |
1992年 | 386篇 |
1991年 | 358篇 |
1990年 | 391篇 |
1989年 | 348篇 |
1988年 | 304篇 |
1987年 | 282篇 |
1986年 | 231篇 |
1985年 | 254篇 |
1984年 | 276篇 |
1983年 | 271篇 |
1982年 | 251篇 |
1981年 | 229篇 |
1980年 | 191篇 |
1979年 | 199篇 |
1978年 | 181篇 |
1975年 | 142篇 |
1974年 | 118篇 |
1972年 | 130篇 |
1971年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
701.
702.
James M. Omernik 《Journal of the American Water Resources Association》2003,39(3):563-573
ABSTRACT: The use of watersheds to conduct research on land/water relationships has expanded recently to include both extrapolation and reporting of water resource information and ecosystem management. More often than not, hydrologic units (HUs) are used for these purposes, with the implication that hydrologic units are synonymous with watersheds. Whereas true topographic watersheds are areas within which apparent surface water drains to a particular point, generally only 45 percent of all hydrologic units, regardless of their hierarchical level, meet this definition. Because the area contributing to the downstream point in many hydrologic units extends far beyond the unit boundaries, use of the hydrologic unit framework to show regional and national patterns of water quality and other environmental resources can result in incorrect and misleading illustrations. In this paper, the implications of this misuse are demonstrated using four adjacent HUs in central Texas. A more effective way of showing regional patterns in environmental resources is by using data from true watersheds representative of different ecological regions containing particular mosaics of geographical characteristics affecting differences in ecosystems and water quality. 相似文献
703.
704.
J. Y. Kim M.-C. Shin J.-R. Park K. Nam 《Journal of Material Cycles and Waste Management》2003,5(1):0055-0062
The effect of the soil solids concentration in batch tests on the measured values of the partition coefficient (K
p) of organic pollutants in landfill liner-soil material was investigated. Since this study was based on the results of batch
and column tests conducted independently, there were limitations to the conclusions derived. The organic compounds tested
were benzene, methylene chloride, toluene, trichloroethylene, and p-xylene. The results of this study showed that as soil solids concentrations increased, the measured K
p values of these organic compounds strongly decreased. The observed values of K
p stabilized when the soil solids concentration was above a certain value. Typical K
p values obtained from batch tests conducted under high soil solids concentrations were close to those obtained from column
tests. It was concluded that the K
p values of organic compounds measured under low soil solids concentrations, i.e., less than 100 g/l, may not correctly simulate
the field situation. Consequently, the values of K
p obtained with low soil solids concentrations can result in an overestimation of the retardation factor of the landfill liner
material.
Received: March 14, 2002 / Accepted: August 25, 2002 相似文献
705.
S. L. Holmberg T. Claesson M. Abul-Milh B. -M. Steenari 《Resources, Conservation and Recycling》2003,38(4):3071
At the district heating plant of Kalmar, Sweden an on-line unit for production of granulated wood ash for nutrient recycling on forest soils is being applied. Currently, the granules are dried by hot air from an oil-fired burner. The objective of this work was to investigate how drying by flue gas affects the hardening of granules, or impacts their chemical composition and properties. Ninety-six granule samples were treated by flue gas from natural gas combustion in a laboratory pilot scale flue gas generator. CO2, CO, O2, C3H8 and NO concentrations were varied during the experiment. Additionally, some samples were treated by flue gas from combustion of sawdust at the heating plant in Kalmar. Drying by flue gases did not affect the chemical composition of granules, but minor effects were seen in their mineralogy. The carbonate content was slightly higher in granules treated with flue gas from natural gas combustion compared to the granules dried by hot air only, when measured by wet chemical methods. Results from XRD analysis imply that the calcite content is higher and the portlandite and arcanite content slightly less in granules treated with flue gas from sawdust combustion compared to the granules dried by hot air only. The results from this investigation showed no negative effects on ash granule composition or physical structure by the use of a flue as a drying medium. 相似文献
706.
707.
To date the transport solutions seeking to reduce traffic impacts have tended to focus on city/town centres. There has, however, been a substantial increase in traffic levels both in and to suburban areas and the location of large employment sites in such areas has had a significant impact. The typical policy response to traffic in these areas has been the introduction of traffic calming measures and residents' parking but such policies do not address the fundamental issue of travel generation and its consequences (including parking). Major employers should have an important role to play in the consideration of more sensible and sustainable uses of the car including the promotion of alternatives to car use. Using a case study at a large institution in Oxford this paper examines findings from a survey into staff travel behaviour in order to identify how staff currently behave. It explores the potential for transport and non-transport solutions to reduce car-based journeys to work and concludes that there is real potential to encourage a reduction in car-based travel. The paper seeks to widen the debate about who should take responsibility for achieving such a reduction. It argues that whilst travel awareness campaigns primarily push responsibility onto individuals an 'integrated package' is required with employers also assuming responsibility and thereby enabling individuals to adapt. 相似文献
708.
Lee H. Macdonald Donald M. Anderson William E. Dietrich 《Environmental management》1997,21(6):851-863
2 /yr, respectively. Geomorphic evidence indicates that plantation agriculture during the 18th and 19th centuries did not cause
severe erosion. Since about 1950 there has been rapid growth in roads and development due to increasing tourism and second-home
development. Our field investigations identified the approximately 50 km of unpaved roads as the primary source of anthropogenic
sediment. Field measurements of the road network in two catchments led to the development of a vector-based GIS model to predict
road surface erosion and sediment delivery. We estimate that road erosion has caused at least a fourfold increase in island-wide
sediment yields and that current sedimentation rates are unprecedented. Paving the dirt roads and implementing standard sediment
control practices can greatly reduce current sediment yields and possible adverse effects on the marine ecosystems surrounding
St. John. 相似文献
709.
/ Land use/land cover classifications for 1973 and 1991, derived from the interpretation of satellite imagery, are quantified on the basis of biophysical land units in a study area in southeastern Australia. Nutrient export potentials are estimated for each land unit based on their composition of land use/land cover classes. Spatial and temporal comparisons are made of the land units based on the calculated pollution hazard indicators to provide an insight into changes in the state of the environment and the regional significance of land use changes. For example, one ecosystem, unique to the study, showed a large increase in pollution hazard over the study period as a manifestation of an 11-fold rise in cleared area and an expansion of cropping activities. The benefits to environmental management in general are discussed.KEY WORDS: Land cover change; Nutrient export; Environmental condition; Pollution hazard; Agricultural pollution; Nonpoint source pollution; Diffuse pollution; Environmental degradation 相似文献
710.
TWO STRATEGIES FOR LEARNING A ROUTE IN A DRIVING SIMULATOR 总被引:2,自引:0,他引:2
Vlada Aginsky Catherine Harris Ronald Rensink Jack Beusmans 《Journal of environmental psychology》1997,17(4):317-331
The study of human navigation has long been dominated by the so-called stage theory, i.e. the notion that there are three distinct types of spatial knowledge (landmark, route, and survey knowledge), that are acquired sequentially during spatial learning and development. Based on the results of a route learning experiment in a driving simulator, an alternative to the stage theory is proposed. The authors suggest that subjects follow either a visually dominated or a spatially dominated strategy to solve a route-learning problem. In the visually dominated strategy, subjects base their wayfinding decisions on visually recognizing decision points along a route; the decision points are not integrated into any kind of survey representation. In the spatially dominated strategy, on the other hand, subjects represent the environment as a survey map right from the start; that is, they do not pass through a landmark or route stage. These strategies may be subserved by different cortical areas recently characterized in neurophysiological studies of animals solving maze problems. 相似文献