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761.
提供了土工格栅加筋砂土上的偏心受压条形基础极限承载力的室内模型试验结果。试验中只使用了一种相对压实密度的砂土和一种土工格栅,基础深度由0变化至B(基础宽度)。基于室内试验结果,提出了一个称为折减系数的经验关系,将偏心受压基础的极限承载力与中心受压基础的极限承载力联系起来。 相似文献
762.
Muriel Llubes Nicolas Florsch Jean-Paul Boy Martine Amalvict Pascal Bonnefond Marie-Noëlle Bouin Stphane Durand Marie-France Esnoult Pierre Exertier Jacques Hinderer Marie-Franoise Lalancette Frdric Masson Laurent Morel Joëlle Nicolas Mathilde Vergnolle Guy Wppelmann 《Comptes Rendus Geoscience》2008,340(6):379-389
We have organised afield study of ocean tide loading in the northwestern part of France, where tidal amplitudes are known to be among the highest in the world. GPS and gravimetric techniques have already proved their capability to measure such weak and high-frequency signals. In this study, these classical observations are complemented with less usual techniques, such as tiltmeter and Satellite Laser Ranging (SLR) measurements. We present here the preliminary results for a common period of observations spanning from 12–19 May 2004. Additional measurements from the French Transportable Laser Ranging Station (FTLRS) were available during September and October 2004. Observation residuals are computed as the difference between the observed and the predicted time signals. We obtain small RMS residuals for GPS measurements (2.5/3.1/4.5 mm for the eastward, northward and upward components), for absolute and relative gravimetry (9 nm/s2 and 13 nm/s2) and for tiltmeters (0.05 μrad for EW component). We also fit the amplitude of the main M2 tidal constituent to FTLRS observations and we find a value of 3.731 cm, which is comparable to the theoretical value. 相似文献
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765.
植物枝条失去50%水分传导时对应的水势(ψ50),称为枝的水分传导脆弱性。该指标是反映植物干旱适应能力的关键指标,也决定着植物沿降水梯度的分布。乔木和灌木枝水分传导脆弱性沿降水量递增的变化是否一致,有待揭示。基于已发表的文献,筛选出236种乔木、137种灌木,建立ψ50与分布地年均降水量及分布地干旱指数关系,来确认两大类植物的ψ50沿降水递增的变化的异同。结果表明:乔木和灌木的ψ50均随降水梯度、干旱指数的增加而增加,一元线性回归方程显著;ψ50与降水梯度、干旱指数回归方程的回归系数在乔木和灌木间差异不显著,但同一降水量下,乔木比灌木具有较低的ψ50值。我们认为灌木和乔木枝水分传导脆弱性对降水量和干旱指数递增具有相似的适应性。 相似文献
766.
A high-fidelity PC-based control system has been developed to improve the tracking characteristics of a small-scale seismic motion simulator used for testing structural control designs. This work outlines the development and testing of the control system. First, the simulator hardware is described in detail. The process of constructing a mechanistic model of the system and identifying model parameters is then described. Next, a closed-loop feedback/feed-forward control algorithm, based on an optimal receding horizon formulation, is developed. The control design was tested and the results indicate that the seismic shake table precisely tracked reference seismic motions. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
767.
A real-time hybrid experimental method, in which output from an actuator-excited vibration experiment and response calculation are combined on-line and conducted simultaneously in real time, is being developed as a new seismic experimental method for structural systems. In real-time hybrid experiments, however, there is an inevitable actuator-response delay, which has an effect equivalent to negative damping. To solve this problem, a real-time hybrid experimental system (including an actuator-delay compensation method) was developed. And seismic experiments were conducted in order to demonstrate the advantages of this system. Experimental results obtained using the developed hybrid experimental system were compared with exact results obtained using shaking-table experiments, and it was found that the two experimental methods gave almost identical results. It can therefore be concluded that the structural response can be obtained precisely by using the developed hybrid experimental system. Comparison of these experiments showed the advantages of the hybrid experiments; that is, they are simple and economical. This is because the hybrid experiment requires only a small structure as the excitation model, while a shaking-table experiment must consider the whole structural system. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
768.
M. F. Bransby 《国际地质力学数值与分析法杂志》1999,23(15):1909-1926
Two-dimensional finite element analysis has been used to find load–transfer relationships for translation of an infinitely long pile through undrained soil for a variety of soil-constitutive models. It has been shown that these load–transfer curves can be used as p–y curves in the analysis of single piles undergoing lateral pile head loading in undrained soils with non-linear stress–strain laws. Lateral pile response deduced from 2-D analysis input to the subgrade reaction method has been compared to the behaviour of a single pile analysed using three-dimensional finite element analysis. Good agreement between the two methods for non-linear soils suggests that the 2-D analysis may form a useful design method for calculation of p–y curves. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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770.
This paper describes results from a recent study concerning the numerical modelling of compound channel flow using two generalized two-dimensional finite element codes specifically adapted to floodplain studies: RMA-2 and TELEMAC-2D. By application to an 11 km reach of the River Culum, Devon, UK, simulations are developed to investigate the impact of numerical technique, mesh resolution and topographic parameterization on model results. The research is shown to raise a number of issues concerning the construction, calibration and validation of two-dimensional finite element models for this flow problem. © 1997 by John Wiley & Sons, Ltd. 相似文献