全文获取类型
收费全文 | 1790篇 |
免费 | 17篇 |
国内免费 | 23篇 |
专业分类
安全科学 | 46篇 |
废物处理 | 62篇 |
环保管理 | 244篇 |
综合类 | 401篇 |
基础理论 | 346篇 |
环境理论 | 1篇 |
污染及防治 | 512篇 |
评价与监测 | 95篇 |
社会与环境 | 109篇 |
灾害及防治 | 14篇 |
出版年
2023年 | 18篇 |
2022年 | 18篇 |
2021年 | 29篇 |
2020年 | 21篇 |
2019年 | 25篇 |
2018年 | 47篇 |
2017年 | 50篇 |
2016年 | 60篇 |
2015年 | 72篇 |
2014年 | 76篇 |
2013年 | 84篇 |
2012年 | 80篇 |
2011年 | 115篇 |
2010年 | 97篇 |
2009年 | 99篇 |
2008年 | 90篇 |
2007年 | 98篇 |
2006年 | 80篇 |
2005年 | 54篇 |
2004年 | 80篇 |
2003年 | 44篇 |
2002年 | 64篇 |
2001年 | 67篇 |
2000年 | 30篇 |
1999年 | 17篇 |
1998年 | 17篇 |
1997年 | 25篇 |
1996年 | 19篇 |
1995年 | 31篇 |
1994年 | 19篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 24篇 |
1990年 | 11篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1979年 | 9篇 |
1970年 | 6篇 |
1969年 | 4篇 |
1966年 | 3篇 |
1965年 | 4篇 |
1962年 | 3篇 |
1960年 | 4篇 |
1959年 | 3篇 |
1954年 | 3篇 |
排序方式: 共有1830条查询结果,搜索用时 375 毫秒
681.
The exchange of genetic information between coral reefs through the transport of larvae can be described in terms of networks that capture the linkages between distant populations. A key question arising from these networks is the determination of the highly connected modules (communities). Communities can be defined using genetic similarity or distance statistics between multiple samples but due to limited specimen sampling capacity the boundaries of the communities for the known coral reefs in the seascape remain unresolved. In this study we use the microsatellite composition of individual corals to compare sample populations using a genetic dissimilarity measure (FST) which is then used to create a complex network. This network involved sampling 1025 colonies from 22 collection sites and examining 10 microsatellites loci. The links between each sampling site were given a strength that was created from the pair wise FST values. The result is an undirected weighted network describing the genetic dissimilarity between each sampled population. From this network we then determined the community structure using a leading eigenvector algorithm within graph theory. However, given the relatively limited sampling conducted, the representation of the regional genetic structure was incomplete. To assist with defining the boundaries of the genetically based communities we also integrated the communities derived from a hydrodynamic and distance based networks. The hydrodynamic network, though more comprehensive, was of smaller spatial extent than our genetic sampling. A Bayesian Belief network was developed to integrate the overlapping communities. The results indicate the genetic population structure of the Great Barrier Reef and provide guidance on where future genetic sampling should take place to complete the genetic diversity mapping. 相似文献
682.
Simon L. Axelsen Alan Shapiro Evgeni Fedorovich Han van Dop 《Environmental Fluid Mechanics》2010,10(4):387-414
An analytical model for katabatic flow induced by cold strip of finite width in the cross-slope direction but of infinite
extent in the downslope direction is presented. The fluid is assumed to have a constant (eddy) viscosity, and the Coriolis
force is neglected. A numerical simulation has been used to verify the model, which is shown to revert to the classical Prandtl
model if the strip width goes to infinity. The effects of the strip width and slope angle on the katabatic flow are studied.
The buoyancy and downslope velocity reach maximum values at the centre of the strip, and spread outwards in the cross-slope
direction. The downslope wind maximum weakens for narrow strips and shallow slopes. In contrast to the Prandtl solution, which
shows a counter flow above the wind maximum, our model predicts the counter flow to occur outside the strip. The cross-slope
variation in the surface forcing induces cross-slope and slope-normal velocities, which are manifested in vortices at the
strip edges. Below the wind maximum, the fluid above the cooling surface descends and moves toward the strip edge where it
is detrained from the strip region. Replenishment of fluid into the strip region takes place above the wind maximum. 相似文献
683.
In different parts of the world, there is an urgent need for redesigning and innovating farming systems. Such a process may be supported by model-based explorations that enable ex-ante evaluation of a broad range of alternatives. Since a variety of viable patterns of farm development exists related to farm resource endowment and farmer's strategy, model-based explorations should be able to capture the existing variation in resource endowment and strategies in order to have impact on strategic farm management. In this paper, we present an overview of the model-based explorative method based on the MILP model Farm Images, applied to explore options for sustainable development of vegetable farms in Canelón Grande, Uruguay. The method is used to gain insight into the impact of current farm resource endowment on the possibilities for sustainable development and on the resource use efficiency at farm scale. We maximized farm income for 128 different farm types in an environment-oriented scenario and in an income-oriented scenario. Farm types were defined by combining 4 farm sizes, 2 labor endowments, 4 irrigation endowments, 2 soil quality combinations and 2 mechanization levels. The results demonstrate a strong impact of farm resource endowment on possibilities for sustainable development, as well as synergy between labor, land and irrigated area on resource-use efficiency at farm scale. Farms with 10ha of land or less, representing 47% of the farms in the Canelón Grande region, could only achieve a family income higher than the average income of Uruguayan families when the irrigated area was ca. 40% of the farm area. The achievement of environmental targets was less costly in terms of income on farms with a low rather than high labor availability per unit area and on farms with irrigation facilities. 相似文献
684.
Limited natural resources and landfill space, as well as increasing amounts of ash produced from incineration of bio fuel and municipal solid waste, have created a demand for useful applications of ash, of which road construction is one application. Along national road 90, situated about 20 km west of Sollefteå in the middle of Sweden, an experiment road was constructed with a 40 cm bio fuel ash layer. The environmental impact of the ash layer was evaluated from soil solutions obtained by centrifugation of soil samples taken on four occasions during 2001–2003. Soil samples were taken in the ash layer, below the ash layer at two depths in the road and in the ditch. In the soil solutions, pH, conductivity, dissolved organic carbon (DOC) and the total concentration of cations (metals) and anions were determined. Two years after the application of the ash layers in the test road, the concentrations in the ash layer of K, SO4, Zn, and Hg had increased significantly while the concentration of Se, Mo and Cd had decreased significantly. Below the ash layer in the road an initial increase of pH was observed and the concentrations of K, SO4, Se, Mo and Cd increased significantly, while the concentrations of Cu and Hg decreased significantly in the road and also in the ditch. Cd was the element showing a potential risk of contamination of the groundwater. The concentrations of Ca in the ash layer indicated an ongoing hardening, which is important for the leaching rate and the strength of the road construction. 相似文献
685.
Erik van Bergen Tad Dallas Michelle F. DiLeo Aapo Kahilainen Anniina L. K. Mattila Miska Luoto Marjo Saastamoinen 《Conservation biology》2020,34(6):1503-1511
The ecological impacts of extreme climatic events on population dynamics and community composition are profound and predominantly negative. Using extensive data of an ecological model system, we tested whether predictions from ecological models remain robust when environmental conditions are outside the bounds of observation. We observed a 10-fold demographic decline of the Glanville fritillary butterfly (Melitaea cinxia) metapopulation on the Åland islands, Finland in the summer of 2018 and used climatic and satellite data to demonstrate that this year was an anomaly with low climatic water balance values and low vegetation productivity indices across Åland. Population growth rates were strongly associated with spatiotemporal variation in climatic water balance. Covariates shown previously to affect the extinction probability of local populations in this metapopulation were less informative when populations were exposed to severe drought during the summer months. Our results highlight the unpredictable responses of natural populations to extreme climatic events. 相似文献
686.
Radium isotopes are widely used in marine studies (eg. to trace water masses, to quantify mixing processes or to study submarine groundwater discharge). While 228Ra and 226Ra are usually measured using gamma spectrometry, short-lived Ra isotopes (224Ra and 223Ra) are usually measured using a Radium Delayed Coincidence Counter (RaDeCC). Here we show that the four radium isotopes can be analyzed using gamma spectrometry. We report 226Ra, 228Ra, 224Ra, 223Ra activities measured using low-background gamma spectrometry in standard samples, in water samples collected in the vicinity of our laboratory (La Palme and Vaccarès lagoons, France) but also in seawater samples collected in the plume of the Amazon river, off French Guyana (AMANDES project). The 223Ra and 224Ra activities determined in these samples using gamma spectrometry were compared to the activities determined using RaDeCC. Activities determined using the two techniques are in good agreement. Uncertainties associated with the 224Ra activities are similar for the two techniques. RaDeCC is more sensitive for the detection of low 223Ra activities. Gamma spectrometry thus constitutes an alternate method for the determination of short-lived Ra isotopes. 相似文献
687.
Barend L. van Drooge 《Environmental pollution (Barking, Essex : 1987)》2010,158(9):2880-2887
The ambient air in Northern Italy is characterised by relatively high PAH and PM10 concentrations in relation to calm wind and intensive temperature inversions, especially during cold periods. These stagnant conditions are occasionally interrupted by North-Föhn events, which cause a drop in relative humidity and an increase in O3 levels, indicating the mixing of local and free troposphere air flows. In this study the influence of the North-Föhn on concentrations of tracer organic compounds, including polycyclic aromatic hydrocarbons (PAHs), PM10, O3 and black carbon (BC) was studied during a North-Föhn event in November 2007. Large fluctuations in the concentration of these compounds, as well as changes in PM10 composition due to daytime and night-time variations of local source emissions were observed. Although these events occur at low frequencies (6-10%) they can for short periods, strongly affect the regional air quality by quickly decreasing the concentrations of these tracer organic compounds. 相似文献
688.
J.N. Cape L.J. Sheppard A. Crossley N. van Dijk Y.S. Tang 《Environmental pollution (Barking, Essex : 1987)》2010,158(9):2926-2933
The content of organic N has been shown in many studies to increase during the passage of rain water through forest canopies. The source of this organic N is unknown, but generally assumed to come from canopy processing of wet or dry-deposited inorganic N. There have been very few experimental studies in the field to address the canopy formation or loss of organic N. We report two studies: a Scots pine canopy exposed to ammonia gas, and a Sitka spruce canopy exposed to ammonium and nitrate as wet deposition. In both cases, organic N deposition in throughfall was increased, but only represented a small fraction (<10%) of the additional inorganic N supplied, suggesting a limited capacity for net organic N production, similar in both conifer canopies under Scottish summertime conditions, of less than 1.6 mmol N m−2 mth−1 (equivalent to 3 kg N ha−1 y−1). 相似文献
689.
Joris Koornneef Andrea Ramirez Toon van Harmelen Arjan van Horssen Wim Turkenburg Andre Faaij 《Atmospheric environment (Oxford, England : 1994)》2010,44(11):1369-1385
This study quantifies the trade-offs and synergies between climate and air quality policy objectives for the European power and heat (P&H) sector. An overview is presented of the expected performance data of CO2 capture systems implemented at P&H plants, and the expected emission of key air pollutants, being: SO2, NOX, NH3, volatile organic compounds (VOCs) and particulate matter (PM). The CO2 capture systems investigated include: post-combustion, oxyfuel combustion and pre-combustion capture.For all capture systems it was found that SO2, NOx and PM emissions are expected to be reduced or remain equal per unit of primary energy input compared to power plants without CO2 capture. Increase in primary energy input as a result of the energy penalty for CO2 capture may for some technologies and substances result in a net increase of emissions per kWh output. The emission of ammonia may increase by a factor of up to 45 per unit of primary energy input for post-combustion technologies. No data are available about the emission of VOCs from CO2 capture technologies.A simple model was developed and applied to analyse the impact of CO2 capture in the European P&H sector on the emission level of key air pollutants in 2030. Four scenarios were developed: one without CO2 capture and three with one dominantly implemented CO2 capture system, varying between: post-combustion, oxyfuel combustion and pre-combustion.The results showed a reduction in GHG emissions for the scenarios with CO2 capture compared to the baseline scenario between 12% and 20% in the EU 27 region in 2030. NOx emissions were 15% higher in the P&H sector in a scenario with predominantly post-combustion and lower when oxyfuel combustion (?16%) or pre-combustion (?20%) were implemented on a large scale. Large scale implementation of the post-combustion technology in 2030 may also result in significantly higher, i.e. increase by a factor of 28, NH3 emissions compared to scenarios with other CO2 capture options or without capture. SO2 emissions were very low for all scenarios that include large scale implementation of CO2 capture in 2030, i.e. a reduction varying between 27% and 41%. Particulate Matter emissions were found to be lower in the scenarios with CO2 capture. The scenario with implementation of the oxyfuel technology showed the lowest PM emissions followed by the scenario with a significant share allocated to pre-combustion, respectively ?59% and ?31%. The scenario with post-combustion capture resulted in PM emissions varying between 35% reduction and 26% increase. 相似文献
690.
Prepared for climate change? A method for the ex-ante assessment of formal responsibilities for climate adaptation in specific sectors 总被引:1,自引:0,他引:1
H. A. C. Runhaar C. J. Uittenbroek H. F. M. W. van Rijswick H. L. P. Mees P. P. J. Driessen H. K. Gilissen 《Regional Environmental Change》2016,16(5):1389-1400
Climate change-related risks encompass an intensification of extreme weather events, such as fluvial and pluvial flooding, droughts, storms, and heat stress. A transparent and comprehensive division of responsibilities is a necessary—but not the only—precondition for being prepared for climate change. In this paper, we present, and preliminarily test, a method for the ex-ante assessment of the division of public and private responsibilities for climate adaptation in terms of comprehensiveness, transparency, legitimacy, and effectiveness. This method proofs particularly suited for the assessment of adaptation responsibilities in combination with a sectoral approach. It helps identifying a number of shortcomings in divisions of responsibilities for climate adaptation. We conclude that this method is useful as a diagnostic tool for identifying the expected climate change preparedness level, and recommend to combine this with ex-post analyses of real-life cases of extreme events in order to assess the actual preparedness for climate change. Besides the scientific purpose of providing a generally applicable assessment method, with this method, we also intend to assist policy-makers in developing and implementing adaptation plans at various levels. 相似文献