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71.
William R. Bidlake 《Journal of the American Water Resources Association》2002,38(1):197-211
ABSTRACT: Reliable estimates of evapotranspiration from areas of wildland vegetation are needed for many types of water-resource investigations. However, little is known about surface fluxes from many areally important vegetation types, and relatively few comparisons have been made to examine how well evapotranspiration models can predict evapotranspiration for soil-, climate-, or vegetation-types that differ from those under which the models have been calibrated. In this investigation at a prairie site in west-central Florida, latent heat flux (λE) computed from the energy balance and alternatively by eddy covariance during a 15-month period differed by 4 percent and 7 percent on hourly and daily time scales, respectively. Annual evapotranspiration computed from the energy balance and by eddy covariance were 978 and 944 mm, respectively. An hourly Penman-Monteith (PM) evapotranspiration model with stomatal control predicated on water-vapor-pressure deficit at canopy level, incoming solar radiation intensity, and soil water deficit was developed and calibrated using surface fluxes from eddy covariance. Model-predicted λE agreed closely with λE computed from the energy balance except when moisture from dew or precipitation covered vegetation surfaces. Finally, an hourly PM model developed for an Amazonian pasture predicted λE for the Florida prairie with unexpected reliability. Additional comparisons of PM-type models that have been developed for differing types of short vegetation could aid in assessing interchangeability of such models. 相似文献
72.
The covariance between hourly concentration (C) and depositionvelocity (V) for various atmospheric species may act to bias the dry deposition (D) computed from the product of the weeklyaverage C and V. This is a potential problem for the CASTNet filter pack (FP) species, nitric acid (HNO3). Using ozone (O3) behavior as a surrogate for HNO3, correctionfactors (CF) are developed to estimate this bias. Weekly CF for O3 depend on both site and season, and seasonal average weekly CF for O3 at a given site may be as high as 1.25.The seasonal magnitude of this CF is generally largest in summerand is ordered: summer fall spring > winter. The CF is drivento a large extent by the diurnal correlation between C andV (i.e., both are generally higher during the day and lower at night). However, since the diurnal C profile at elevated sites is relatively constant, the resulting correlation between C and V is small, and the CF at montane sites is generally negligiblysmall. The sampling protocol using daytime integrated sampling for a week and nighttime integrated sampling for a week capturesthe diurnal correlation between C and V adequately and may be used to aggregate relatively unbiased weekly D estimates. Day-night CF for O3 are close to unity, and limited results suggest similar behavior for HNO3. Using these limited FP results, the site- and seasonally-specific weekly CF forO3are refined to estimate the corresponding CF for HNO3. Worst-case adjustments for HNO3 as high as 30% are indicated for summer periods at a given site. 相似文献
73.
水喷淋控制烟气输运的大涡模拟研究 总被引:4,自引:0,他引:4
本文采用大涡模拟方法研究了烟气输运和水喷淋之间的相互作用问题。研究目的是探讨水喷淋(或细水雾)对烟气输运的控制和抑制的有效性和要行性。为了有效地模拟烟气输运过程,本文采用了低马赫数近似下的三维可压缩滤波形式的Navier-Stokes方程进行有限差分法数值求解。烟气的生成和运动采用携带燃烧反应热的Lagrangian粒子(热元模型)来模拟,同时喷淋器喷出的细水雾也采用模型模拟。在本文的研究中,烟气由一个独立的火池产生并且被一股来流(或风)驱动,从而在一个方形槽道里形成烟气输运,在火池下游槽道的顶部布置若干个喷淋器并喷出水雾,以便探讨水雾对烟气输运的控制作用。本文着重分析讨论了不同喷淋角和水雾半径下水雾对烟气输运的控制和抑制效果。 相似文献
74.
In this paper we analyse an ordination method in which spatial contiguity information is included. The original method, proposed by Ver Hoef and Glenn-Lewin (1989), is extended, using graphs to describe spatial contiguity for several sampling schemes where locations are given. Extensions for two dimensional grids and for the case of discrete measures of abundance are analysed. Applications to simulated transect frequency data and real data collected on a regular grid are reported. 相似文献
75.
采用瞬时烟线仪与迪沙(DISA)热线风速仪相结合的方法探测了山体的绕流区和尾流区结构。试验结果表明,山体的绕流和尾流对低架源排放的气态污染物扩散影响甚大,山体绕流可改变烟流的地面浓度分布.结果还表明,我们所用的探测流向的方法较为有效和准确. 相似文献
76.
77.
作者借助于卫星CCT数据进行了人-机对话式信息比值处理,获取了河口区高浓度的悬浮泥沙涡旋水体信息,并与现场考察资料相对证,发现其有规律的出现与输移。为此,结合毛蚶的生活习性,确认黄河入海泥沙扩散对黄河口及其邻近水域毛蚶的资源分布有直接的影响。预测了未来20年内研究区毛蚶场的扩大趋势及其范围。 相似文献
78.
ABSTRACT: Success in measuring turbulence in water has been achieved by replacing the hot-wire probe by the hot-film probe. Accordingly, these results have greatly increased knowledge and understanding of hydromechanics. However, there are few published measurements of turbulent properties of flow with suspended solid particles. With this in mind, the authors conducted measurements of turbulent properties of flow with suspended solid particles by using a quartz-coated, wedge-shaped hot-film probe. Turbulent intensities and macroscale of eddy change in the flow with suspended solid particles on a movable bed is discussed. 相似文献
79.
本文主要论述了依据絮凝动力学中涡旋理论设计的多极涡流管式混合器及其絮凝试验的研究结果,同时讨论了影响多极涡流管式混合器混合效能的管径及流量等因素,结果证实,该混合器适合于无机高分子絮凝剂的絮凝动力学反应特点,具有较高的工程推广和应用价值。 相似文献
80.
Montserrat Fuentes Arin Chaudhuri David M. Holland 《Environmental and Ecological Statistics》2007,14(3):323-340
We develop a spatial statistical methodology to design national air pollution monitoring networks with good predictive capabilities
while minimizing the cost of monitoring. The underlying complexity of atmospheric processes and the urgent need to give credible
assessments of environmental risk create problems requiring new statistical methodologies to meet these challenges. In this
work, we present a new method of ranking various subnetworks taking both the environmental cost and the statistical information
into account. A Bayesian algorithm is introduced to obtain an optimal subnetwork using an entropy framework. The final network
and accuracy of the spatial predictions is heavily dependent on the underlying model of spatial correlation. Usually the simplifying
assumption of stationarity, in the sense that the spatial dependency structure does not change location, is made for spatial
prediction. However, it is not uncommon to find spatial data that show strong signs of nonstationary behavior. We build upon
an existing approach that creates a nonstationary covariance by a mixture of a family of stationary processes, and we propose
a Bayesian method of estimating the associated parameters using the technique of Reversible Jump Markov Chain Monte Carlo.
We apply these methods for spatial prediction and network design to ambient ozone data from a monitoring network in the eastern
US. 相似文献