全文获取类型
收费全文 | 176篇 |
免费 | 95篇 |
国内免费 | 12篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 36篇 |
地球物理 | 192篇 |
地质学 | 27篇 |
海洋学 | 20篇 |
天文学 | 2篇 |
综合类 | 3篇 |
自然地理 | 2篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 7篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 8篇 |
2016年 | 4篇 |
2015年 | 11篇 |
2014年 | 18篇 |
2013年 | 10篇 |
2012年 | 8篇 |
2011年 | 10篇 |
2010年 | 12篇 |
2009年 | 26篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 20篇 |
2005年 | 12篇 |
2004年 | 4篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1977年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有283条查询结果,搜索用时 656 毫秒
71.
StudyontheThermalinternalBoundaryLayerandDispersionofAirPollutantinCoastalAreabyNumericalSimulation¥JiangWeimei(蒋维楣)andYuHong... 相似文献
72.
Following the collapse of the New York World Trade Center (WTC) towers on September 11, 2001, Local, State, and Federal agencies initiated numerous air monitoring activities to better understand the ongoing impacts of emissions from the disaster. The collapse of the World Trade Center towers and associated fires that lasted for several weeks resulted at times in a noticeable plume of material that was dispersed around the Metropolitan New York City (NYC) area. In general, the plume was only noticeable for a short period of time following September 11, and only apparent close to the World Trade Center site. A study of the estimated pathway which the plume of WTC material would likely follow was completed to support the United States Environmental Protection Agency’s 2002 initial exposure assessments. In this study, the WTC emissions were simulated using the CALMET-CALPUFF model in order to examine the general spatial and temporal dispersion patterns over NYC. This paper presents the results of the CALPUFF plume model in terms of plume dilution and location, since the exact source strength remains unknown. Independent observations of PM2.5 are used to support the general dispersion features calculated by the model. Results indicate that the simulated plume matched well with an abnormal increase (600–1000% of normal) in PM2.5 two nights after the WTC collapse as the plume rotated north to southeast, towards parts of NYC. Very little if any evidence of the plume signature was noted during a similar flow scenario a week after September 11. This leads to the conclusion that other than areas within a few kilometers from the WTC site, the PM2.5 plume was not observable over NYC’s background concentration after the first few days. 相似文献
73.
A barrier system based on the hydraulic trap design concept for a landfill was proposed. To study the field scenario in which
a clay liner is underlain by a granular layer functioning as a secondary leachate drain layer, a laboratory advection–diffusion
test was performed to investigate factors controlling the transport of contaminants in a two-layer soil system. The soils
used for this study were Ariake clay and, the underlying layer, Shirasu soil from the Kyushu region of Japan. Potassium (K+) was selected as the target chemical species with an initial concentration of 905 mg L−1. The effective diffusion coefficients (D
e) of K+ for Ariake clay and Shirasu soil were back-calculated using an available computer program, Pollute
V 6.3. Values of D
e derived from this experiment are consistent with previously published ones. The Ariake clay has lower D
e than the Shirasu soil. The hypothesis that mechanical dispersion can be considered negligible is reasonable based on both
the observation that the predicted values well fit the experimental data and the analyses of two dimensionless parameters.
Parametric analyses show that transport of K+ through soils is controlled by advection–diffusion rather than diffusion only, whereas at low Darcy velocity (i.e., ≤10−9 m s−1), transport of K+ will be controlled by diffusion. Applications of the test results and parametric analysis results in practical situations
were reviewed. 相似文献
74.
Large-eddy Simulation of the Dispersion of Solid Particles in a Turbulent Boundary Layer 总被引:2,自引:2,他引:2
Ivana Vinkovic Cesar Aguirre Michel Ayrault Serge Simoëns 《Boundary-Layer Meteorology》2006,121(2):283-311
A large-eddy simulation (LES) with the dynamic Smagorinsky-Germano subgrid-scale (SGS) model is used to study the dispersion of solid particles in a turbulent boundary layer. Solid particles are tracked in a Lagrangian way. The instantaneous velocity of the surrounding fluid is considered to have a large-scale part (directly computed by the LES) and a small-scale part. The SGS velocity of the surrounding fluid is given by a three-dimensional Langevin model written in terms of SGS statistics at a mesh level. An appropriate Lagrangian correlation time scale is considered in order to include the influences of gravity and inertia of the solid particle. Inter-particle collisions and the influence of particles on the mean flow are also taken into account. The results of the LES are compared with the wind-tunnel experiments of Nalpanis et al. (1993 J Fluid Mech 251: 661–685) and of Tanière et al. (1997 Exp in Fluids 23:463–471) on sand particles in saltation and in modified saltation, respectively. 相似文献
75.
Simultaneous measurement of coupled water, heat, and solute transport in unsaturated porous media is made possible with the multi-functional heat pulse probe (MFHPP). The probe combines a heat pulse technique for estimating soil heat properties, water flux, and water content with a Wenner array measurement of bulk soil electrical conductivity (ECbulk). To evaluate the MFHPP, we conducted controlled steady-state flow experiments in a sand column for a wide range of water saturations, flow velocities, and solute concentrations. Flow and transport processes were monitored continuously using the MFHPP. Experimental data were analyzed by inverse modeling of simultaneous water, heat, and solute transport using an adapted HYDRUS-2D model. Various optimization scenarios yielded simultaneous estimation of thermal, solute, and hydraulic parameters and variables, including thermal conductivity, volumetric water content, water flux, and thermal and solute dispersivities. We conclude that the MFHPP holds great promise as an excellent instrument for the continuous monitoring and characterization of the vadose zone. 相似文献
76.
77.
在前文[1]的基础上,进一步研究当海表温度存在经圈方向不均匀分布或偏离气候状态(距平)时,改变水分收支平衡及边界层的湿度辐合这一物理过程对Madden-Julian振荡的可能影响。结果表明,它对修正的Kelvin波和Rossby波的传播性质影响不大。但当海表温度为正距平时,修正后东传Kelvin波振幅不稳定增长到e倍的时间约减小了14.5%,其不稳定增长率随着热源特征宽度的增加而增加,当特征宽度为2倍Rossby变形半径时,不稳定增长率达极大,但当特征宽度继续增大时,其不稳定增长率又将减小。当海表温度为负距平时,修正后东传Kelvin波振幅不稳定增长到e倍的时间约增加20%,其不稳定增长率随着冷源特征宽度的增加而减小,当特征宽度为2倍Rossby变形半径时,其不稳定增长率达极小,此后;随着特征宽度的增加其不稳定增长率随之增加,但始终小于无海表温度异常的情形。经圈尺度较小的那支修正的Rossby波除波长极长的波段外,波仍是阻尼的;而经圈尺度较大的那支修正的Rossby波,在短的波段内仍是不稳定增长的。 相似文献
78.
79.
80.
基于有关粗糙界面的Rayleigh假设,讨论了平面声波按余弦规律快速变化的小尺度粗糙界面上的反射特征.研究表明:这类界面与位于该位置的一个过渡地层的作用相当.该过渡层的厚度为粗糙界面的起伏幅度,速度和密度为上下两层介质相应量的平均值.研究了埋藏很深的微粗糙界面所引起的地震反射(绕射)波的频散特性和走时的构成,即包含零炮检距反射时间、正常时差和界面粗糙时差三部分内容.该粗糙时差与空间坐标和时间坐标无关,与绕射波的阶次有关,绕射波尾随在反射波之后以某一固定的时差出现.且只有当界面的粗糙波长与地震波的波长相当时,才能观测到这类绕射波.该结论为粗糙界面地震反射资料的处理方法提供了理论依据. 相似文献