全文获取类型
收费全文 | 2070篇 |
免费 | 43篇 |
国内免费 | 24篇 |
专业分类
安全科学 | 74篇 |
废物处理 | 64篇 |
环保管理 | 382篇 |
综合类 | 877篇 |
基础理论 | 349篇 |
环境理论 | 4篇 |
污染及防治 | 247篇 |
评价与监测 | 80篇 |
社会与环境 | 48篇 |
灾害及防治 | 12篇 |
出版年
2023年 | 14篇 |
2022年 | 16篇 |
2021年 | 18篇 |
2020年 | 24篇 |
2019年 | 16篇 |
2018年 | 43篇 |
2017年 | 45篇 |
2016年 | 67篇 |
2015年 | 47篇 |
2014年 | 46篇 |
2013年 | 122篇 |
2012年 | 65篇 |
2011年 | 88篇 |
2010年 | 57篇 |
2009年 | 61篇 |
2008年 | 63篇 |
2007年 | 67篇 |
2006年 | 49篇 |
2005年 | 34篇 |
2004年 | 47篇 |
2003年 | 46篇 |
2002年 | 38篇 |
2001年 | 15篇 |
2000年 | 18篇 |
1999年 | 18篇 |
1998年 | 29篇 |
1997年 | 23篇 |
1996年 | 15篇 |
1995年 | 64篇 |
1994年 | 53篇 |
1993年 | 50篇 |
1992年 | 41篇 |
1991年 | 34篇 |
1990年 | 34篇 |
1989年 | 27篇 |
1988年 | 38篇 |
1987年 | 37篇 |
1986年 | 27篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 13篇 |
1973年 | 10篇 |
1919年 | 47篇 |
1918年 | 44篇 |
1917年 | 36篇 |
1916年 | 53篇 |
1915年 | 37篇 |
1914年 | 71篇 |
1913年 | 106篇 |
排序方式: 共有2137条查询结果,搜索用时 15 毫秒
171.
Integrated BIosphere Simulator (IBIS) yield and nitrate loss predictions for Wisconsin maize receiving varied amounts of nitrogen fertilizer 总被引:1,自引:0,他引:1
Agriculture in the U.S. Midwest faces the formidable challenge of improving crop productivity while simultaneously mitigating the environmental consequences of intense management. This study examined the simultaneous response of nitrate nitrogen (NO3-N) leaching losses and maize (Zea mays L.) yield to varied fertilizer N management using field observations and the Integrated BIosphere Simulator (IBIS) model. The model was validated against six years of field observations in chisel-plowed maize plots receiving an optimal (180 kg N ha(-1)) fertilizer N application and in N-unfertilized plots on a silt loam soil near Arlington, Wisconsin. Predicted values of grain yield, harvest index, plant N uptake, residue C to N ratio, leaf area index (LAI), grain N, and drainage were within 20% of observations. However, simulated NO3-N leaching losses, NO3-N concentrations, and net N mineralization exhibited less interannual variability than observations, and had higher levels of error (20-65%). Potential effects of 30% higher (234 kg N ha(-1)) and 30% lower (126 kg N ha(-1)) fertilizer N use (from optimal) on NO3-N leaching loss and maize yield were simulated. A 30% increase in fertilizer N use increased annual NO3-N leaching by 56%, while yield increased by only 1%. The NO3-N concentration in the leachate solution at 1.4 m below the soil surface was 30.7 mg L(-1). When fertilizer N use was reduced by 30% (from optimal), annual NO3-N leaching losses declined by 42% after seven years, and annual average yield only decreased by 8%. However, NO3-N concentration in the leachate solution remained above 10 mg L(-1) (11.3 mg L(-1)). Clearly, nonlinear relationships existed between changes in fertilizer use and NO3-N leaching losses over time. Simulated changes in NO3-N leaching were greater in magnitude than fertilizer N use changes. 相似文献
172.
Christopher M. Smemoe E. James Nelson Alan K. Zundel A. Woodruff Miller 《Journal of the American Water Resources Association》2007,43(2):359-371
Abstract: The U.S. Federal Emergency Management Agency (FEMA) flood maps depict the 100‐year recurrence interval floodplain boundary as a single line. However, because of natural variability and model uncertainty, no floodplain extents can be accurately defined by a single line. This article presents a new approach to floodplain mapping that takes advantage of accepted methodologies in hydrologic and hydraulic analysis while including the effects of uncertainty. In this approach, the extents of computed floodplain boundaries are defined as a continuous map of flood probabilities, rather than as a single line. Engineers and planners can use these flood probability maps for viewing the uncertainty of a floodplain boundary at any recurrence interval. Such a flood probability map is a useful tool for visualizing the uncertainty of a floodplain boundary and represents greater honesty in engineering technologies that are used for flood mapping. While institutional barriers may prevent adoption of such definitions for use in graduated flood insurance rates (as most other insurance industries use to account for relative risks), the methods open the door technically to such a reality. 相似文献
173.
Whenever a short-term or local need in the exploitation of a scarce natural resource must be pitted against its long-term use or the needs of the larger community, the commons dilemma arises. The study of commons dilemmas originated in agricultural economies but has importance in all resource management areas. Psychologists have recently found it to be a useful paradigm in the study of decision-making behavior.This paper reviews the commons dilemma as it has been used in three areas of psychological research: games theory, animal and human territorial behavior, and behavior reinforcement. In the first area, results show how communication within groups operates in cooperation/competition situations. In the second, the effects of social and political ideologies are examined. In the third, the implications of the commons dilemma with regard to breaking out of social traps are discussed. Throughout, the relevance of this basic psychological research to rational resource management is made clear. An extensive bibliography of relevant original research is provided. 相似文献
174.
The future supplies of iron ore, coking coal and ferrous scrap are discussed. There is no likelihood of the resources of iron ore being exhausted until well into the twenty-first century. Coking coal, on the other hand, is in shorter supply but it is being eked out by blending with non-coking coal and by making blast furnaces more efficient. Briquettes made completely from non-coking coal will play a part in iron making in the future. To ensure greater flexibility in steel making, hydrocarbons are being considered as possible substitutes for coal. Scrap has always played an important part in steel making and the amount recycled is increasing every year. But more effort is needed, for example, to ensure that the steel in car scrap is fully utilised and that refuse is efficiently recycled. Steel making increasingly demands the scrap to have few impurities and to be in uniform sized pieces. A cryogenic method of preparing such scrap is described. A futuristic way of extracting iron, non-ferrous metals and other saleeable by-products from refuse, by using redundant blast furnaces, is also discussed. 相似文献
175.
176.
The drivers for increasing incineration of sewage sludge and the characteristics of the resulting incinerated sewage sludge ash (ISSA) are reviewed. It is estimated that approximately 1.7 million tonnes of ISSA are produced annually world-wide and is likely to increase in the future. Although most ISSA is currently landfilled, various options have been investigated that allow recycling and beneficial resource recovery. These include the use of ISSA as a substitute for clay in sintered bricks, tiles and pavers, and as a raw material for the manufacture of lightweight aggregate. ISSA has also been used to form high density glass–ceramics. Significant research has investigated the potential use of ISSA in blended cements for use in mortars and concrete, and as a raw material for the production of Portland cement. However, all these applications represent a loss of the valuable phosphate content in ISSA, which is typically comparable to that of a low grade phosphate ore. ISSA has significant potential to be used as a secondary source of phosphate for the production of fertilisers and phosphoric acid. Resource efficient approaches to recycling will increasingly require phosphate recovery from ISSA, with the remaining residual fraction also considered a useful material, and therefore further research is required in this area. 相似文献
177.
Incorporating Geological Effects in Modeling of Revegetation Strategies for Salt-Affected Landscapes 总被引:1,自引:0,他引:1
Christopher J. Clarke Richard W. Bell Richard J. Hobbs Richard J. George 《Environmental management》1999,24(1):99-109
The work highlights the difficulties of using standard sampling and statistical techniques to investigate regional phenomena
and presents an integrated approach combining small-scale sampling with broad-scale observations to provide input into a modeling
exercise. It is suggested that such approaches are vital if landscape- and regional-scale processes are to be understood and
managed. The way in which the problem is perceived (holistically or piecemeal) affects the way treatments are designed and
their effectiveness: past approaches have failed to integrate the various scales and processes involved. Effective solutions
require an integrated holistic response. 相似文献
178.
Christopher De Sousa 《Journal of Environmental Planning and Management》2000,43(6):831-853
This paper examines the nature of the economic costs and risks involved in brownfield versus greenfield redevelopment in the Greater Toronto Area (Ontario, Canada) from a private sector perspective, and assesses the potential effectiveness of different policies and programmes designed to attenuate associated costs and risks. Through interviews, case-studies and an analysis of hypothetical development scenarios, it has been found that the perception that brownfield redevelopment is less cost-effective and entails greater risks than greenfield development, on the part of the private sector, is true for industrial projects in the province, but not for residential ones, which were found to be feasible, given the assumptions of the present study. Furthermore, the study has found that the attractiveness of residential brownfield projects can increase considerably with minor policy changes, but that promoting industrial redevelopment will require a more vigorous approach that employs a variety of environmental policy and economic development measures. 相似文献
179.
Francis K Wiese Julia K Parrish Christopher W Thompson Christina Maranto 《Ecological applications》2008,18(3):681-700
Predator-prey relationships are often altered as a result of human activities. Where prey are legally protected, conservation action may include lethal predator control. In the Columbia River basin (Pacific Northwest, USA and Canada), piscivorous predators have been implicated in contributing to a lack of recovery of several endangered anadromous salmonids (Oncorhynchus spp.), and lethal and nonlethal control programs have been instituted against both piscine and avian species. To determine the consequences of avian predation, we used a bioenergetics approach to estimate the consumption of salmonid smolts by waterbirds (Common Merganser, California and Ring-billed Gull, Caspian Tern, Double-crested Cormorant) found in the mid-Columbia River from April through August, 2002-2004. We used our model to explore several predator-prey scenarios, including the impact of historical bird abundance, and the effect of preserving vs. removing birds, on smolt abundance. Each year, <1% of the estimated available salmonid smolts (interannual range: 44,830-109,209; 95% CI = 38,000-137,000) were consumed, 85-98% away from dams. Current diet data combined with historical gull abundance at dams suggests that past smolt consumption may have been 1.5-3 times current numbers, depending on the assumed distribution of gulls along the reaches. After the majority (80%) of salmonid smolts have left the study area, birds switch their diet to predominantly juvenile northern pikeminnow (Ptychocheilus oregonensis), which as adults are significant native salmonid predators in the Columbia River. Our models suggest that one consequence of removing birds from the system may be increased pikeminnow abundance, which--even assuming 80% compensatory mortality in juvenile pikeminnow survival--would theoretically result in an annual average savings of just over 180,000 smolts, calculated over a decade. Practically, this suggests that smolt survival could be maximized by deterring birds from the river when smolts are present, allowing bird presence after the diet switch to act as a tool for salmonid-predator control, and conducting adult-pikeminnow control throughout. Our analysis demonstrates that identifying the strength of ecosystem interactions represents a top priority when attempting to manage the abundance of a particular ecosystem constituent, and that the consequences of a single-species view may be counterintuitive, and potentially counterproductive. 相似文献
180.
Costas A. Velis David C. Wilson Christopher R. Cheeseman 《Waste management (New York, N.Y.)》2009,29(4):1282-1290
The material recovery methods used by dust-yards in early 19th century London, England and the conditions that led to their development, success and decline are reported. The overall system developed in response to the market value of constituents of municipal waste, and particularly the high coal ash content of household ‘dust’. The emergence of lucrative markets for ‘soil’ and ‘breeze’ products encouraged dust-contractors to recover effectively 100% of the residual wastes remaining after readily saleable items and materials had been removed by the thriving informal sector. Contracting dust collection to the private sector allowed parishes to keep the streets relatively clean, without the need to develop institutional capacity, and for a period this also generated useful income. The dust-yard system is, therefore, an early example of organised, municipal-wide solid waste management, and also of public–private sector participation. The dust-yard system had been working successfully for more than 50 years before the Public Health Acts of 1848 and 1875, and was thus important in facilitating a relatively smooth transition to an institutionalised, municipally-run solid waste management system in England. The dust-yards can be seen as early precursors of modern materials recycling facilities (MRFs) and mechanical–biological treatment (MBT) plants; however, it must be emphasised that dust-yards operated without any of the environmental and occupational health considerations that are indispensable today. In addition, there are analogies between dust-yards and informal sector recycling systems currently operating in many developing countries. 相似文献