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121.
122.
Magnetic properties of tidal flat sediments of the Yangtze Estuary and its relationship with particle size 总被引:6,自引:0,他引:6
Since the 1970s, environmental magnetism has found extensive applications in diverse research areas of geoscience[1]. In China, a lot of environmental magnetic studies have been carried out on loess, lake and marine sediments for the purpose of paleoclima… 相似文献
123.
The distinct element method (DEM) has been used successfully for the dynamic analysis of rigid block systems. One of many
difficulties associated with DEM is modeling of damping. In this paper, new procedures are proposed for the damping modeling
and its numerical implementation in distinct element analysis of rigid multi-block systems. The stiffness proportional damping
is constructed for the prescribed damping ratio, based on the non-zero fundamental frequency effective during the time interval
while the boundary conditions remain essentially constant. At this time interval, the fundamental frequency can be estimated
without complete eigenvalue analysis. The damping coefficients will vary while the damping ratio remains the same throughout
the entire analysis. A new numerical procedure is developed to prevent unnecessary energy loss that can occur during the separation
phases. These procedures were implemented in the development of the distinct element method for the dynamic analyses of piled
multi-block systems. The analysis results for the single-block and two-block systems were in a good agreement with the analytic
predictions. Applications to the seismic analyses of piled fourblock systems revealed that the new procedures can make a significant
difference and may lead to much-improved results. 相似文献
124.
P. P. Hallan Sanjay Jain K. B. Bhatnagar 《Celestial Mechanics and Dynamical Astronomy》2000,77(3):157-184
The non-linear stability of L
4 in the restricted three-body problem has been studied when the bigger primary is a triaxial rigid body with its equatorial
plane coincident with the plane of motion. It is found that L
4 is stable in the range of linear stability except for three mass ratios:
where A1, A2 depend upon the lengths of the semi axes of the triaxial rigid body.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
125.
A numerical model based on smoothed particle hydrodynamics (SPH) was developed and used to simulate immiscible and miscible fluid flows in porous media and to study effects of pore scale heterogeneity and anisotropy on such flows. 相似文献
126.
P. I. A. Kinnell 《地球表面变化过程与地形》2006,31(3):355-367
Rain‐impacted flows dominate sheet and interrill erosion and are important in eroding soil rich in nutrients and other chemicals which may have deleterious effects on water quality. Erosion in rain‐impacted flow is associated with raindrop detachment followed by transport either by the combination of flow velocity and raindrop impact (raindrop‐induced flow transport, RIFT) or the inherent capacity of the flow to transport detached material. Coarse particles tend to be transported by RIFT, while fine particles tend to be transported without any assistance from raindrop impact. Because the transport process associated with coarse particles is not 100 per cent efficient, it generates a layer of loose particles on the soil surface and this layer protects the underlying soil from detachment. Simulations were performed by modelling the uplift and downstream movement of both fine and coarse particles detached from the soil surface by individual raindrop impacts starting with a surface where no loose material was present. The simulations produced a flush of fine material followed by a decline in the discharge of fine material as the amount of loose material built up on the bed. The decline in the discharge of fine material was accompanied by an increase in the discharge of coarse material. The relative amounts of coarse and fine material discharged in the flow varied with flow velocity and cohesion in the surface of the soil matrix. The results indicate that the discharge of various sized sediments is highly dependent on local soil, rain and flow conditions and that extrapolating the results from one situation to another may not be appropriate. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
127.
128.
水敏现象在石油、岩土和环境工程等领域广泛存在。有效地控制水敏现象的发生,不仅具有科学意义,还有一定的经济价值。本文在广泛查阅国内外研究成果的基础上,总结了水敏性在石油、岩土和环境工程方面应用的研究进展,并在此基础上提出了水敏性研究的发展方向。 相似文献
129.
An approximate analytical solution for the deposition of heavy particles released from an elevated line source 总被引:1,自引:1,他引:1
This work re-examines and further develops an analytical solution for the deposition swath of heavy particles released in
the atmosphere from an elevated source over uniform terrain, correcting the particle diffusivity for the crossing trajectory
effect. The revised (approximate) analytical solution proves to be accurate within 20% over a wide range of micrometeorological
conditions and particle size, despite its neglect of the turbulence component of the deposition flux. It compares very satisfactorily
with experimental data and with the simulations of a Lagrangian stochastic model, provided the variable U(H)/w
g
≤7 (ratio of the mean horizontal wind speed at source height to the particle settling velocity). In this domain of validity,
simple formulae relating the statistics of the deposition swath to U(H)/w
g
are derived. 相似文献
130.
纳米级微粒测量是寻找隐伏矿的新方法,选取实地模拟实验和在已知隐伏矿区,利用液态捕集剂和等离子体质谱分析测试样品,进行重复测量试验,研究结果表明,不同成矿元素,在地表形成异常的运移富集速率不同,其运移速率主要取决于纳米级微粒本身的地球化学性质,地下上升气流、断裂等裂隙有利于微粒的上升运移富集;纳米级微粒地球化学重复测量时,异常可具有良好的重现性,但异常重现较常规气体缓慢,通常需要2~3个月。 相似文献