全文获取类型
收费全文 | 120篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 24篇 |
地球物理 | 20篇 |
地质学 | 33篇 |
海洋学 | 8篇 |
天文学 | 23篇 |
自然地理 | 13篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 6篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 6篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 2篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1977年 | 1篇 |
1970年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有124条查询结果,搜索用时 15 毫秒
81.
We summarize the results of numerical simulations of colliding gas-rich disk galaxies in which the impact velocity is set
parallel to the spin axes of the two galaxies. The effects of varying the impact speed are studied with particular attention
to the resulting gaseous structures and shockwave patterns, and the time needed to produce these structures. The simulations
employ an N-body treatment of the stars and dark matter, together with an SPH treatment of the gas, in which all components
of the models are gravitationally active. The results indicate that for such impact geometries, collisions can lead to the
very rapid formation of a central, rapidly rotating, dense gas disk, and that in all cases extensive star formation is predicted
by the very high gas densities and prevalence of shocks, both in the nucleus and out in the galactic disks. As the dense nucleus
is forming, gas and stars are dispersed over very large volumes, and only fall back towards the nucleus over long times. In
the case of low impact velocities, this takes an order of magnitude more time than that needed for the formation of a dense
nucleus.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
82.
83.
84.
85.
M. F. Cawley D. J. Fegan K. Harris A. M. Hillas P. W. Kwok R. C. Lamb M. J. Lang D. A. Lewis D. Macomb P. T. Reynolds D. J. Schmid G. Vacanti T. C. Weekes 《Experimental Astronomy》1990,1(3):173-193
Details are presented of an atmospheric Cherenkov telescope for use in very high energy gamma-ray astronomy which consists of a cluster of 109 close-packed photomultiplier tubes at the focus of a 10 meter optical reflector. The images of the Cherenkov flashes generated both by gamma-ray and charged cosmic-ray events are digitized and recorded. Subsequent off-line analysis of the images improves the significance of the signal to noise ratio by a factor of 10 compared with non-imaging techniques. 相似文献
86.
D. Lee G. Xia C. Daley A. Dubey S. Gopal C. Graziani D. Lamb K. Weide 《Astrophysics and Space Science》2011,336(1):157-162
FLASH is a publicly available astrophysical community code designed to solve highly compressible multi-physics reactive flows.
We are adding capabilities to FLASH that will make it an open science code for the academic HEDP community. Among many important
numerical requirements, we consider the following features to be important components necessary to meet our goals for FLASH
as an HEDP open toolset. First, we are developing computationally efficient time-stepping integration methods that overcome
the stiffness that arises in the equations describing a physical problem when there are disparate time scales. To this end,
we are adding two different time-stepping schemes to FLASH that relax the time step limit when diffusive effects are present:
an explicit super-time-stepping algorithm (Alexiades et al. in Com. Num. Mech. Eng. 12:31–42, 1996) and a Jacobian-Free Newton-Krylov implicit formulation. These two methods will be integrated into a robust, efficient, and
high-order accurate Unsplit Staggered Mesh MHD (USM) solver (Lee and Deane in J. Comput. Phys. 227, 2009). Second, we have implemented an anisotropic Spitzer-Braginskii conductivity model to treat thermal heat conduction along
magnetic field lines. Finally, we are implementing the Biermann Battery term to account for spontaneous generation of magnetic
fields in the presence of non-parallel temperature and density gradients. 相似文献
87.
88.
89.
Experimental evaluation of analytical and Lagrangian surface-layer flux footprint models 总被引:3,自引:1,他引:3
Three surface-layer flux footprint models have been evaluated with the results of an SF6 tracer release experiment specifically designed to test such models. They are a Lagrangian stochastic model, an analytical model, and a simplified derivative of the analytical model. Vertical SF6 fluxes were measured by eddy correlation at four distances downwind of a near-surface crosswind line source in an area of homogeneous sagebrush. The mean fluxes were calculated for 136 half-hour test periods and compared to the fluxes predicted by the footprint models. All three models gave similar predictions and good characterizations of the footprint over the stability range -0.01 < z
0/L < 0.005. The predictions of the three models were within the limits of the uncertainty of the experimental measurements in all but a few cases within this stability range. All three models are unconditionally recommended for determining the area defined by the footprint over short vegetative canopies in this range. They are also generally appropriate for estimating flux magnitudes within the limits of experimental uncertainties. Most of the mean differences observed between the measured and predicted fluxes at each of the four towers reflect a tendency for the measured fluxes to be greater than those predicted by the three models. Rigorous verification of the models in strongly stable conditions was complicated by the need to obtain very accurate measurements of small fluxes in only marginally stationary conditions. Verification in strongly unstable conditions was hampered by the limited number of appropriate data. 相似文献
90.
William M. Lamb 《Contributions to Mineralogy and Petrology》1993,114(3):379-394
The Carthage-Colton Zone (CCZ), located in the northwestern portion of the Proterozoic Adirondack terrane, forms the boundary between the Adirondack lowlands and highlands and is characterized by textures indicative of ductile deformation. Samples from three rock types have been collected from this zone: (1) pyroxene bearing syenite gneisses of the Diana igneous complex; (2) paragneiss samples from near the northwestern boundary of the Diana complex; (3) a quartz-rich metasediment. Feldspar geothermometry performed on the Diana metasyenites shows that porphyroclasts are relict igneous grains that formed atT900° C, while dynamic recrystallization occurred at temperatures as low as 470 to 550° C as shown by the compositions of feldspar neoblasts. All samples examined in this study from the CCZ contain a suite of CO2-rich fluid inclusions that are distinctive both texturally and in their microthermometric behavior (Th=-27.7 to-7.1° C) as compared to CO2-rich Adirondack fluid inclusions that do not lie within this zone (Th=-45.9 to +31.0° C). The results from fluid inclusion microthermometry and feldspar geothermometry restrict the conditions of dynamic recrystallization to temperatures and pressures of 400 to 550° C and 3 to 5 kbar. The retrograde pressure-temperature path must pass through these conditions. Similar fluid inclusion results have been obtained from the Parry Sound Shear Zone (PSSZ) which is a Grenvillian shear zone that is located in Southern Ontario (Lamb and Moecher 1992). However, the inferred retrogradeP-T paths for these two areas, the CCZ and the PSSZ, are different and this difference may be a result of late deformation along shear zones that are located between the two areas. 相似文献