全文获取类型
收费全文 | 800篇 |
免费 | 259篇 |
国内免费 | 52篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 23篇 |
地球物理 | 689篇 |
地质学 | 306篇 |
海洋学 | 39篇 |
天文学 | 6篇 |
综合类 | 23篇 |
自然地理 | 19篇 |
出版年
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 18篇 |
2020年 | 18篇 |
2019年 | 25篇 |
2018年 | 24篇 |
2017年 | 36篇 |
2016年 | 39篇 |
2015年 | 49篇 |
2014年 | 59篇 |
2013年 | 45篇 |
2012年 | 34篇 |
2011年 | 51篇 |
2010年 | 21篇 |
2009年 | 55篇 |
2008年 | 54篇 |
2007年 | 53篇 |
2006年 | 48篇 |
2005年 | 37篇 |
2004年 | 50篇 |
2003年 | 46篇 |
2002年 | 23篇 |
2001年 | 21篇 |
2000年 | 27篇 |
1999年 | 29篇 |
1998年 | 29篇 |
1997年 | 21篇 |
1996年 | 34篇 |
1995年 | 26篇 |
1994年 | 19篇 |
1993年 | 17篇 |
1992年 | 6篇 |
1991年 | 11篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 17篇 |
1974年 | 1篇 |
1954年 | 2篇 |
排序方式: 共有1111条查询结果,搜索用时 218 毫秒
101.
岩石的应力松弛,应变硬化和应变软化 总被引:1,自引:0,他引:1
本文论述了岩石应力松弛的某些基本特征,分析了应力松弛测试的基本理论,特别就岩石应力松弛中的应变硬化和软化现象提出了作者的见解,并导出了其数据处理方法。 相似文献
102.
The Apuseni Mountains are located between the Pannonian Basin and the Transylvanian Basin along a direction of SE convergence with the Carpathian belt. A flexural model based on the cylindrical bending of a semi-infinite, isostatically supported, thin elastic plate is here examined with the Apuseni playing the role of flexural bulge, and under the assumption that the plate is deforming under the action of a vertical shear force and a bending moment applied at the end of the plate, beneath the Carpathians. The model yields estimates of the plate thickness ranging between 13 and 14.5 km, depending on the assumed density contrast between crust/sediments and mantle providing buoyancy. The vertical shear force which is necessary to bend the plate is in the range between 60 and 300 × 1011 N m− 1, depending on the assumed density contrast. This force is shown to be modelled by a gravitational ‘slab pull’ force, using model parameters derived from seismic tomography. If the height of the flexural bulge, after correction for erosion, is allowed to increase, the model yields an estimate of the horizontal strain rate at the top of the bulge. For example, 5 mm/yr vertical change of the flexural bulge of a 14 km thick plate results in a horizontal deformation rate of approximately 7 nanostrain/yr at the top of the bulge, a value which is at the threshold of sensitivity of continuous GPS measurements. Different vertical rates will change the horizontal strain rate almost proportionally. 相似文献
103.
S. Lafuerza N. Sultan M. Canals J. Frigola S. Berné G. Jouet M. Galavazi F. J. Sierro 《International Journal of Earth Sciences》2009,98(4):751-768
Data from in situ piezocone tests (CPTU) and laboratory analyses are utilized for the interpretation of the stress history
of Quaternary sedimentary sequences in the upper continental slope of the Gulf of Lion, northwestern Mediterranean Sea. A
CPTU based preconsolidation pressure profile referenced to the current effective stress indicates that the deposit is underconsolidated
from 12 meters below the seafloor (mbsf) down to at least 150 mbsf. Excess pore pressure below 12 mbsf is further supported
by results from oedometer and dissipation tests. Subseafloor pockmarks and indications of free gas in seismic reflection profiles
reveal four main overpressure sources (SI–SIV) with overpressure ratios >0.3 at subseafloor depths coinciding with levels
where the dominantly silty-clayey sediment contains increased proportions of sand. We relate the excess pore pressure related
to free gas due to gas exsolution processes and sea level variations driven by Pleistocene sea level changes. 相似文献
104.
Progressive failure mechanism in one-dimensional stability analysis of shallow slope failures 总被引:3,自引:0,他引:3
Chia-Nan Liu 《Landslides》2009,6(2):129-137
In many slopes, overstressed zones can develop where the shear stress is larger than the available shear strength. Along a
shear surface within a soil exhibiting a strain-softening behavior, the shear displacement increases while the available shear
strength decreases. The excess shear stress is transferred from the overstressed zone to the adjacent zones, providing more
shear strength. This stress-transferring mechanism induces stress redistribution within the slope and could enlarge the overstress
zone. A one-dimensional model that satisfies the strain compatibility and force equilibrium is proposed for the stability
analysis of a slope of strain-softening behavior. This paper’s objective is to facilitate the application of this model to
estimate stress distribution along the failure surface of a strain-softening slope and thereafter the stability status. The
study presents a set of specific solutions to this model by describing and demonstrating procedures to identify the pattern
of a stress state and to calculate stress distribution within a one-dimensional, strain-softening slope. The progressive failure
mechanism is also investigated by using the proposed approach. As the magnitude of released stress gets large enough, it induces
an overstressed zone adjacent to the initial unstable zone and progressive failure develops. The proposed approach is also
applied to study the pattern of stress redistribution. It is found that the pattern of stress redistribution is affected by
the magnitude of released stress. It is too complex to be reasonably expressed by simple models. Though some limitations exist,
the proposed approach serves as a simple tool for a better understanding of the progressive failure mechanism. 相似文献
105.
安徽省桐城市地质环境复杂,是安徽省地质灾害多发频发的地区之一,尤其以小规模的崩塌、滑坡为主,给桐城市人民造成了巨大经济损失和人员伤亡,并严重威胁当地居民的生命财产安全。本文在地质灾害调查的基础上,对桐城市地质灾害发育规律及特征做进一步的分析研究,以期对桐城市地质灾害防治工作有所借鉴。 相似文献
106.
Stress Measurement by Overcoring at Shallow Depths in a Rock Slope: the Scattering of Input Data and Results 总被引:1,自引:0,他引:1
C. Clément V. Merrien-Soukatchoff C. Dünner Y. Gunzburger 《Rock Mechanics and Rock Engineering》2009,42(4):585-609
This paper describes a field experiment of stress measurement using the overcoring method performed in a rock slope, called
Rochers de Valabres (located in France’s Southern Alps Region), a field laboratory site prone to rockfalls. Six measurements were conducted at
shallow depths from the surface, moving deeper along a sub-horizontal borehole. The experiment was conducted in heterogeneous
and anisotropic gneiss, with the overcored rock elastic properties, as evaluated by biaxial and uniaxial tests, being widely
scattered. Since stress calculations are sensitive to all input data uncertainties, strain inversion was, thus, performed
using an experimental device and Monte Carlo simulations. The experimental device allows the assessment of rather broad confidence
intervals for both stress magnitude and orientation. The results indicate that the stress state in the surface area is quite
heterogeneous and may be correlated with topography. The measurements show a nonlinear stress distribution with distance to
the free surface, along with high values of principal stresses, despite the vicinity of the surface. Although influenced by
local topography, orientations of the principal computed stresses are characterized by a high turnover due to local heterogeneities.
The results are roughly in accordance to a 2D finite element model of the site. 相似文献
107.
108.
Thermal convective precipitation (TCP) often occurs over mainland China in summer when the area is dominated by the western Pacific subtropical high (WPSH). It is well known that the WPSH often brings about large scale subsidence, then why could deep moist convection occur and where does the water vapor come from? In this paper, a deep convective precipitation case that happened on 2 August 2003 is studied in order to address these two questions. First, the characteristics of the TCP event are analyzed using the Tropical Rainfall Measuring Mission (TRMM) satellite data, automatic weather station observations, and the data from the US National Centers for Environmental Prediction (NCEP). Second, water vapor sources are identified through examining surface evaporation, water vapor advection, and water vapor flux divergence calculated by using a regionally averaged water vapor budget equation. Furthermore, using an Advanced Regional Eta-coordinate Model (AREM), contributions of sensible and latent heat fluxes to the TCP are compared through four sensitivity experiments. The results show that in the regions controlled by the WPSH, surface temperature rises rapidly after sunrise. Upon receiving enough sensible heat, the air goes up and leads to convergence in the lower atmosphere. Then the water vapor assembled from the surroundings and the ground surface is transported to the upper levels, and a favorable environment for the TCP forms. A model data diagnosis indicates that about half of precipitable water comes from the convergence of horizontal fluxes of water vapor, and the other half from surface evaporation, while little is from advection. Additional sensitivity experiments prove that both sensible and latent heating are essential for the onset of the TCP. The sensible heat flux triggers thermodynamic ascending motion, and the latent heat flux provides water vapor, but the contribution to TCP from the latter is a little smaller than that from the former. 相似文献
109.
利用1948-2006年NCEP/NCAR逐日再分析资料分析了南亚高压的移动路径、特征及其触发机制。根据高压的移动情况及其环流等特征发现,南亚高压的移动路径分为东路型,南路型和西路型。对比不同路径的温度场、风场及热源整层积分场等特征,发现不同路径之间存在很大差异。通过SVD分析以及合成分析发现,高原附近热源强弱配置的差异是造成路径差异的可能原因;同时,高原地区热力、动力作用造成的中低纬度的大气长波波型配置对路径的影响也至关重要。 相似文献
110.
新型人工引雷专用火箭及其首次引雷实验结果 总被引:2,自引:2,他引:0
成功研制了一种新型的人工引雷专用火箭, 火箭箭体结构采用了新型复合材料, 质量轻, 并具有空中抛伞和放线功能。利用新型火箭和全新的雷电流及同步电磁场测量技术, 在2009年的山东人工引雷实验 (SHATLE2009) 中成功引发负极性云对地放电过程3次, 共包括6次大电流回击过程, 采用0.5 mΩ的大功率同轴分流器和宽带光纤传输技术测量到了0.1 μs时间分辨率的雷电流波形、以及距雷电通道30 m、60 m和480 m处的电磁场和6000 f/s的高速摄像观测资料。6次回击的电流峰值分布范围为11.2~16.3 kA, 几何平均值12.8 kA; 半峰值宽度为7.4~34.9 μs, 几何平均值21.6 μs; 10%~90%峰值的上升时间为0.5~1.4 μs, 几何平均值1.0 μs。成功的人工引发雷电实验证明新型引雷火箭安全性能好、可靠性高, 其成功研制为雷电物理过程和效应的研究, 以及雷电流波形资料的积累提供了重要的技术手段, 对制定具有我国自主知识产权的雷电防护标准等具有重要的应用价值。 相似文献