全文获取类型
收费全文 | 10895篇 |
免费 | 2460篇 |
国内免费 | 3577篇 |
专业分类
测绘学 | 1146篇 |
大气科学 | 2535篇 |
地球物理 | 3509篇 |
地质学 | 5630篇 |
海洋学 | 1874篇 |
天文学 | 127篇 |
综合类 | 817篇 |
自然地理 | 1294篇 |
出版年
2024年 | 46篇 |
2023年 | 137篇 |
2022年 | 372篇 |
2021年 | 427篇 |
2020年 | 519篇 |
2019年 | 610篇 |
2018年 | 526篇 |
2017年 | 522篇 |
2016年 | 564篇 |
2015年 | 671篇 |
2014年 | 805篇 |
2013年 | 813篇 |
2012年 | 848篇 |
2011年 | 888篇 |
2010年 | 718篇 |
2009年 | 886篇 |
2008年 | 808篇 |
2007年 | 895篇 |
2006年 | 857篇 |
2005年 | 673篇 |
2004年 | 711篇 |
2003年 | 559篇 |
2002年 | 486篇 |
2001年 | 397篇 |
2000年 | 351篇 |
1999年 | 327篇 |
1998年 | 287篇 |
1997年 | 256篇 |
1996年 | 222篇 |
1995年 | 170篇 |
1994年 | 152篇 |
1993年 | 102篇 |
1992年 | 79篇 |
1991年 | 56篇 |
1990年 | 38篇 |
1989年 | 28篇 |
1988年 | 25篇 |
1987年 | 28篇 |
1986年 | 12篇 |
1985年 | 15篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1971年 | 4篇 |
1954年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
381.
382.
Modelling landslides in unsaturated slopes subjected to rainfall infiltration using material point method 下载免费PDF全文
This paper presents a dynamic fully coupled formulation for saturated and unsaturated soils that undergo large deformations based on material point method. Governing equations are applied to porous material while considering it as a continuum in which the pores of the solid skeleton are filled with water and air. The accuracy of the developed method is tested with available experimental and numerical results. The developed method has been applied to investigate the failure and post‐failure behaviour of rapid landslides in unsaturated slopes subjected to rainfall infiltration using two different bedrock geometries that lie below the top soil. The models show different failure and post‐failure mechanisms depending on the bedrock geometry and highlight the negative effects of continuous rain infiltrations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
383.
This paper discusses numerical results from three-dimensional large eddy simulations of an oscillating cylinder under prescribed movements in uniform flow. Six cases,namely pure in-line,pure cross-flow and two groups of 'Figure of Eight' oscillation patterns are under investigation at Reynolds number Re=24000. The 'Figure of Eight' pattern in each group is with identical shape but opposite orbital directions. The numerical results on hydrodynamic forces,higher order force components,and vortex shedding mode... 相似文献
384.
The present paper focuses on selected plasticity and damage‐plasticity models for describing the 3D material behavior of concrete. In particular, a plasticity model and a damage‐plasticity model are reviewed and evaluated. Based on the results of the evaluation, enhancements are proposed, aiming at improving the correspondence between predicted and observed material behavior and aiming at implementing a robust and efficient stress update algorithm in a finite element program for performing large‐scale 3D numerical simulations of concrete structures. The capabilities of the concrete models are demonstrated by 3D numerical simulations of benchmark tests with combined bending and torsional loading and combined compression and shear loading and by a large‐scale 3D finite element analysis of a model test of a concrete arch dam. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
385.
针对海洋测绘实践教学中,水深测量实习受场地、经费和安全因素影响大,难以开展的问题,设计并实现了模拟水深测量实习。该模拟实习能较为真实地模拟了水深测量的主要步骤,易于开展和推广。 相似文献
386.
在特高等级精密工程的测量范畴内,实现对超高层建筑的施工监测是一个非常重要的工作内容,GPS实时动态监测技术在监测中发挥着不可忽视的作用。本文首先对GPS监测技术做简要阐述,并分析了超高层建筑的特点;然后指出了GPS监测技术在施工监测中所发挥的作用;最后结合案例,具体分析了GPS监测技术在超高层建筑中的应用,以期为超高层建筑GPS实时动态监测技术的相关研究提供部分参考意见。 相似文献
387.
在捷联惯导(SINS)和GPS卫星接收机进行紧耦合的研究中,采用差分定位进行紧耦合的方法比较成熟,而关于精密单点定位(PPP)与捷联惯导紧耦合的研究还比较少。本文对精密单点定位与捷联惯导紧组合系统进行了Matlab仿真,利用数学解析的方法产生机载运动轨迹,通过设置系统的参数,获得仿真SINS和GPS数据;然后,通过PPP/SINS紧组合系统的仿真程序解算,将定位结果与PPP的结果比较,表明PPP/SINS紧组合导航定位的结果比PPP的精度和可靠性好,而且收敛的速度更快,同时也验证了算法的正确性。最后,分析了不同等级惯导对定位精度的影响。 相似文献
388.
以LandSat多时相影像为数据源,采用基于规则的面向对象分类方法,监测会理县2000~ 2015年地表覆盖变化.结合1∶50 000 DEM数据,分析了会理县地表覆盖构成与转移、变化动态度及潜在退耕地情况.监测分析结论能为会理县加强空间管制、促进土地资源集约利用、指导生态文明建设等提供决策信息支撑. 相似文献
389.
An alternative modelling for flexible membranes anchored to the ground for soil slope stabilisation is presented using Smoothed-Particle Hydrodynamics to model the unstable ground mass in a soil slope, employing a dynamic solve engine. A regression model of pressure normal to the ground, qsim, and also membrane deflection, fsim, have been developed using Design of Experiment. Finally, a comparison between the pressure obtained from numerical simulation and from a limit equilibrium analysis considering infinite slope has been carried out, showing differences in the results, mainly due to the membrane stiffness. 相似文献
390.
The summer Asian–Pacific Oscillation(APO) is a major teleconnection pattern that reflects the zonal thermal contrast between East Asia and the North Pacific in the upper troposphere. The performance of Beijing Climate Center Climate System Models(BCC CSMs) with different horizontal resolutions, i.e., BCC CSM1.1 and BCC CSM1.1(m), in reproducing APO interannual variability, APO-related precipitation anomalies, and associated atmospheric circulation anomalies, is evaluated.The results show that BCC CSM1.1(m) can successfully capture the interannual variability of the summer APO index. It is also more capable in reproducing the APO's spatial pattern, compared to BCC CSM1.1, due to its higher horizontal resolution. Associated with a positive APO index, the northward-shifted and intensified South Asian high, strengthened extratropical westerly jet, and tropical easterly jet in the upper troposphere, as well as the southwesterly monsoonal flow over North Africa and the Indian Ocean in the lower troposphere, are realistically represented by BCC CSM1.1(m), leading to an improvement in reproducing the increased precipitation over tropical North Africa, South Asia, and East Asia, as well as the decreased precipitation over subtropical North Africa, Japan, and North America. In contrast, these features are less consistent with observations when simulated by BCC CSM1.1. Regression analysis further indicates that surface temperature anomalies over the North Pacific and the southern and western flanks of the Tibetan Plateau are reasonably reproduced by BCC CSM1.1(m), which contributes to the substantial improvement in the simulation of the characteristics of summer APO compared to that of BCC CSM1.1. 相似文献