全文获取类型
收费全文 | 2645篇 |
免费 | 420篇 |
国内免费 | 861篇 |
专业分类
测绘学 | 69篇 |
大气科学 | 503篇 |
地球物理 | 1124篇 |
地质学 | 1251篇 |
海洋学 | 535篇 |
天文学 | 72篇 |
综合类 | 90篇 |
自然地理 | 282篇 |
出版年
2024年 | 18篇 |
2023年 | 47篇 |
2022年 | 92篇 |
2021年 | 96篇 |
2020年 | 129篇 |
2019年 | 133篇 |
2018年 | 119篇 |
2017年 | 138篇 |
2016年 | 153篇 |
2015年 | 147篇 |
2014年 | 157篇 |
2013年 | 178篇 |
2012年 | 152篇 |
2011年 | 151篇 |
2010年 | 154篇 |
2009年 | 191篇 |
2008年 | 209篇 |
2007年 | 186篇 |
2006年 | 200篇 |
2005年 | 156篇 |
2004年 | 142篇 |
2003年 | 130篇 |
2002年 | 99篇 |
2001年 | 117篇 |
2000年 | 103篇 |
1999年 | 93篇 |
1998年 | 110篇 |
1997年 | 72篇 |
1996年 | 73篇 |
1995年 | 49篇 |
1994年 | 28篇 |
1993年 | 26篇 |
1992年 | 19篇 |
1991年 | 18篇 |
1990年 | 8篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有3926条查询结果,搜索用时 0 毫秒
81.
沉积盆地流体—岩石相互作用研究的现状 总被引:17,自引:0,他引:17
沉积盆地流体-岩石相互作用研究主要是通过实验地球化学和岩石学,地球化学模拟方法开展的,综述了这一领域的研究现状,主要包括有机酸来源和分布及期 对矿物稳定性的影响,地层水成因与演化、烃类与岩石间的氧化还原反应、以及储层润湿性的变化等,并展望了其 发展趋势。 相似文献
82.
剪切带的流体-岩石相互作用 总被引:5,自引:1,他引:5
作为大陆岩石圈中的应变局部化带,剪切带中一般都渗透着大量流体。流体的来源与剪切带所处的构造背景、流变域和水文条件有关,而剪切带中流体的流动则受岩石的渗透率、孔隙度、孔隙性质、流体的扩散和渗透能力、环境的温压条件、应力或载荷的梯度等因素所制约。剪切带中流体的成分、通量及赋存状态或流动方式,直接影响着岩石的流变。由应变局部化及力学失稳所引起的化学不平衡和由流体与岩石的相互作用,使剪切带岩石的矿物成分和化学成分发生调整,其变异程度取决于原岩的性质、剪切的温压条件和流体的成分及通量等。由于流体的渗透流动和流体与岩石的相互作用使剪切带的体积有所变化,体积变化过程是一种自组织行为。较大的体积亏损,意味着剪切带中渗透过大量的流体,这对剪切带的流变行为、化学行为和成矿作用都有深刻的影响。 相似文献
83.
流体地质作用的构造效应 总被引:2,自引:1,他引:2
许多事实证明,在地壳及地球深部存在着大量的流体,它们以气体、液体、熔融体等形式存在于地球内部不同深度处。这些流体的活动在地壳及岩石圈运动演化过程中扮演着十分重要的角色,其作用贯穿于地壳与岩石圈运动演化的全过程,地球表面形成的各种构造与流体作用的参与有着密切的联系。 相似文献
84.
Todor Ganev Fumio Yamazaki Tsuneo Katayama Teruyuki Ueshima 《Soil Dynamics and Earthquake Engineering》1997,16(7-8):459-470
This paper presents results from forced vibration tests, microtremor observations and earthquake response analysis of a nuclear reactor containment model constructed on stiff soil in Hualien, Taiwan. The dynamic behavior of the soil-structure system is simulated successfully with two numerical models: a sway-rocking model, whose soil parameters are evaluated on the basis of the continuum formulation method, and a finite element model, using the program SASSI with the flexible volume substructuring approach. The dependences of the soil parameters of both models on the amplitudes of the different dynamic excitations are investigated in detail. An original numerical simulation of microtremor is performed. Comparison with results of a previous study involving a rigid tower on a soft soil site in Chiba, Japan is offered. 相似文献
85.
By means of barotropic model, the characteristic and initial value problems are investigated to reveal the local two-dimensional
barotropic instability of the nonuniform current to the dynamic mechanism of the formation of the Yangtze-Huaihe River severe
storm in July 1991. Analytical theory and numerical experiment show that (i) the unstable developing modes are chiefly the
two periods of about 44 d and 10 d, which are fundamentally consistent with that of the precipitation change of the Yangtze-Huaihe
River. (ii) The growth rate of the local perturbation is dominated by the meridional wave numbern = 1–5 and zonal wave numberk = 1–12, i.e. the severe storm over the Yangtze-Huaihe River results from the interaction of the systems at different latitudes
and waves of different scales, (iii) The perturbation over the Yangtze-Huaihe River possesses the property of local intensification,
which slowly migrates westward over the lower and middle reaches of the Yangtze-Huaihe River. (iv) The growth rate of the
instability, especially the propagation velocity of the perturbation, is sensitive to the external parameters ū and α.
Project supported by the National Natural Science Foundation of China. 相似文献
86.
The validity of the Winkler foundation model is investigated by predicting the experimentally measured displacement transfer functions and strain spectra of a single pile embedded in a sandbox and supporting a single-degree-of-freedom superstructure. The foundation-superstructure system is a scale model and was subjected to shake table excitations. The distributed springs and dashpots of the Winkler foundation model are frequency dependent and the calibrated model predicts satisfactorily the displacement transfer function at different depths for both fixed- and free-tip pile conditions. On the other hand, the pile-axial-strains are substantially underestimated when expressed in terms of the second derivative of the computed elastic line of the pile. It is shown that a much more dependable prediction is achieved when pile-axial-strains are expressed in terms of the inertial forces acting along the pile-superstructure system. 相似文献
87.
88.
Zhang Sheng Li Tongjin Wang LiankuiGuangzhou Institute of Geochemistry Chinese Academy of SciencesWushan Guangzhou 《《地质学报》英文版》1997,71(4):433-445
The Changkeng gold-silver deposits consist of a sediment-hosted, disseminated gold deposit and a replacement-type silver deposit. The mineralizations of gold and silver are zoned and closely related to the silicification of carbonate and clastic rocks, so that siliceous ores dominate in the deposit. The mineralizing temperature ranges mainly from 300 to 170℃, and K+, Na+, Ca2+, Mg2+, and Cl- are the major ions in the ore-forming fluid. Calculations of distribution of metal complexes show that gold is mainly transported by hydrosulphide complexes, but chloride complexes of silver, iron, lead, and zinc, which are transformed into hydroxyl and hydrosulphide complexes under neutral to weak-alkaline circumstances in the late stage, predominate in the ore-forming solutions. Water-rock interaction is confirmed to be the effective mechanism for the formation of silver ores by computer modelling of reaction of hydrothermal solution with carbonate rocks. The solubility analyses demonstrate that the precipitation 相似文献
89.
90.
Shintaro Yao Koichi Kobayashi Nozomu Yoshida Hiroshi Matsuo 《Soil Dynamics and Earthquake Engineering》2004,24(5):572-409
Shaking table tests were conducted by means of a large-scale laminar box with 4 m in length, 2 m in width and 2 m in height in order to investigate behavior of a soil-pile-superstructure system in liquefiable ground. A model two-storey structure, supported by a pile group, was set in a saturated sand deposit, and subjected to a sinusoidal base motion with increasing amplitude. Discussions are focused on the transient behavior until soil liquefaction occurs. Main interests are characteristics of springs used in a sway-rocking model and a multi-freedom lumped mass (MFLM) model that are frequently used in soil–pile interaction analysis. The spring constant in the sway-rocking model is represented by restoring force characteristics at the pile head, and that in the MFLM system is represented by an interaction spring connecting the pile to the free field. The transient state prior to soil liquefaction is shown to be important in the design of a pile because dynamic earth pressure shows peak response in this state. The reduction of the stiffness due to excess porewater generation and strain dependent nonlinear behavior is evaluated. 相似文献