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361.
Pollutant dispersion in wetland systems: Mathematical modelling and numerical simulation 总被引:1,自引:0,他引:1
In this paper we present and justify an original use of a diffusive-advective partial differential equation model, its discretization procedures and resulting numerical simulations for the dispersal of pollutants in an air2013;water system, with distinct behaviours in water and in air. The authors believe that the relevance of the developed work lies in its potential use in practical environmental assessment processes for the definition of both preventive and clean-up strategies. 相似文献
362.
Compensation for wildlife damages: Habitat conversion, species preservation and local welfare 总被引:1,自引:0,他引:1
We develop a model of hunting, farming and defensive action to study the environmental and economic consequences of introducing a program to compensate peasants of a small economy for the damage caused by wildlife. We show that the widespread belief that compensation induces wildlife conservation may be erroneous. Compensation can lower the wildlife stock, and may result in a net welfare loss for local people. 相似文献
363.
This paper explains the application of structural path analysis (SPA), an input2013;output-based technique for measuring flows in ecological and linked ecological2013;economic networks. Previous methods of input2013;output flow analysis have concluded with aggregate indexes relying on the summing feature of the Leontief inverse in order to completely account for throughflows along a multitude of inter-compartmental paths. This paper shows that for most linear dissipative networks, a manageable number of paths of limited length exist that cover in the order of 99% or more of total throughflow. These paths can be conveniently extracted, enumerated and ranked using SPA. 相似文献
364.
The species studied individually responded to different forms of mineral fertilizers introduced into the soil. Some species positively responded to the application of one nutrient (Easter-bell starwort, millet grass, and bilberry) or several nutrients (wood sorrel and hairy wood rush), whereas other species responded negatively. 相似文献
365.
The exchange of NO, NO2 and O3 at the soil surface wasmeasured with automatic dynamic chambers in a spruce forest and in abeech forest during periods of several months.NO was emitted from the soil at a rate of02013;8 ng N m-2 s-1(spruce) and 02013;15 ng Nm-2 s-1(beech), but there was no simple relationship between the flux andeither soil temperature or soil moisture. NO2 and O3 weredeposited at the soil surface. Deposition velocities forNO2were on average 0.3 mm s-1 (spruce) and 0.1 mms-1(beech), and the deposition velocities of O3 were on average 1.6 mm s-1 (spruce) and 1.4 mm s-1 (beech). The depositionvelocity of O3 is fairly constant whereas the deposition velocityof NO2 varies greatly, but the reasons remain to be investigated. 相似文献
366.
Udo E. Simonis 《The Environmentalist》2001,21(2):103-107
In the past, most of the attempts to improve the situation of the developing countries have focused on economic policy, on the conditions of international trade, on aid and direct investment. A debate on a New International Economic Order (NIEO) was launched in the 1970s (c.f. Tinbergen, 1976)—and largely failed (c.f. Simonis, 1989). This paper shows that environmental policy could be a more effective lever for improving the lot of the developing countries; the near future may see the evolution of a new international environmental order which is likely to better link environmental protection and economic development. 相似文献
367.
Partnerships between organisations in humanitarian crisis situations generally are challenging, but at the apex are those established as part of remote management in a context of extreme insecurity. To date, little systematic research has been conducted on arrangements between local organisations that have access to crisis‐affected populations and international organisations that hold the purse strings. This paper presents the findings of nine months of qualitative research conducted with five Syrian local organisations and their international partners engaging in humanitarian action across the Turkey–Syria border, and presents insights into the components of successful partnerships. It redefines capacity along organisational and operational lines, and unpacks how monitoring and evaluation and donor requirements create tension and, at times, place local organisations at risk. The paper highlights the centrality of trust in successful partnerships, and describes the personalisation of the conflict by local organisations. Based on a historical case study of civil society in northern Iraq, it closes with some suggestions for long‐term sustainability. 相似文献
368.
Modeling outcomes of approaches to sustained human and snow leopard coexistence 总被引:1,自引:0,他引:1
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The snow leopard (Uncia uncia) is in danger of extinction. Killing to protect livestock is among the primary causes of its decline. Efforts to mitigate this threat have focused on balancing the need to conserve the snow leopard with the needs of local people in snow leopard habitat, many of whom rely on raising livestock for their livelihoods. Conservation of the snow leopard has the characteristics of a public good, and outside funding is required to support conservation efforts. There are 5 commonly discussed approaches to resolving this issue: (1) direct payments for conservation, (2) investments in protection from predation, (3) damage compensation payments, (4) investments in better livestock husbandry, and (5) leases of pastureland for wild prey. After a review of these 5 conservation strategies, an economic–ecologic model, which includes the interactions between the snow leopard, its wild prey, and livestock, is used to evaluate the 2 most promising conservation strategies. The model reveals that investments in protection from predation and leases of pastureland for wild prey are effective but only in delaying the eventual extinction of the snow leopard. To preserve the snow leopard, these approaches must be applied more aggressively and new ones explored. 相似文献
369.
H. -W. Jacobi R. Weller A. E. Jones P. S. Anderson O. Schrems 《Atmospheric environment (Oxford, England : 1994)》2000,34(29-30)
Because investigations of PAN at higher southern latitudes are very scarce, we measured surface PAN concentrations for the first time in Antarctica. During the Photochemical Experiment at Neumayer (PEAN'99) campaign mean surface PAN mixing ratios of 13±7 pptv and maximum values of 48 pptv were found. When these PAN mixing ratios were compared to the sum of NOx and inorganic nitrate they were found to be equal or higher. Low ambient air temperatures and low PAN concentrations caused a slow homogeneous PAN decomposition rate of approximately 5×10−2 pptv h−1. These slow decay rates were not sufficient to firmly establish the simultaneously observed NOx concentrations. In addition, low concentration ratios of [HNO3]/[NOx] imply that the photochemical production of NOx within the snow pack can influence surface NOx mixing ratios in Antarctica. Alternate measurements of PAN mixing ratios at two different heights above the snow surface were performed to derive fluxes between the lower troposphere and the underlying snow pack using calculated friction velocities. Most of the concentration differences were below the precision of the measurements. Therefore, only an upper limit for the PAN flux of ±1×1013 molecules m−2 s−1 without a predominant direction can be estimated. However, PAN fluxes below this limit can still influence both the transfer of nitrogen compounds between atmosphere and ice, and the PAN budget in higher southern latitudes. 相似文献
370.
Robert G. McLaren Peter A. Forsyth Edward A. Sudicky Joel E. VanderKwaak Franklin W. Schwartz John H. Kessler 《Journal of contaminant hydrology》2000,43(3-4)
Recent discovery of bomb-related 36Cl at depth in fractured tuff in the unsaturated zone at the Yucca Mountain candidate high-level waste (HLW) repository site has called into question the usual modeling assumptions based on the equivalent continuum model (ECM). A dual continuum model (DCM) for simulating transient flow and transport at Yucca Mountain is developed. In order to ensure properly converged flow solutions, which are used in the transport simulation, a new flow solution convergence criteria is derived. An extensive series of simulation studies is presented which indicates that rapid movement of solute through the fractures will not occur unless there are intense episodic infiltration events. Movement of solute in the environs of the repository is enhanced if the properties of the tuff layer at the repository horizon are modified from current best-estimate values. Due to a large advective2013;dispersive coupling between the matrix and fractures, the matrix acts as a major buffer which inhibits rapid transport along the fractures. Consequently, fast movement of solutes through the fractures to the repository depth can only be explained if the matrix2013;fracture coupling term is significantly reduced from a value that would be calculated on the basis of data currently available. 相似文献