全文获取类型
收费全文 | 3202篇 |
免费 | 614篇 |
国内免费 | 896篇 |
专业分类
测绘学 | 288篇 |
大气科学 | 532篇 |
地球物理 | 737篇 |
地质学 | 1905篇 |
海洋学 | 424篇 |
天文学 | 164篇 |
综合类 | 267篇 |
自然地理 | 395篇 |
出版年
2024年 | 20篇 |
2023年 | 61篇 |
2022年 | 180篇 |
2021年 | 185篇 |
2020年 | 155篇 |
2019年 | 231篇 |
2018年 | 197篇 |
2017年 | 186篇 |
2016年 | 183篇 |
2015年 | 194篇 |
2014年 | 187篇 |
2013年 | 278篇 |
2012年 | 222篇 |
2011年 | 202篇 |
2010年 | 190篇 |
2009年 | 190篇 |
2008年 | 148篇 |
2007年 | 159篇 |
2006年 | 147篇 |
2005年 | 110篇 |
2004年 | 77篇 |
2003年 | 88篇 |
2002年 | 91篇 |
2001年 | 90篇 |
2000年 | 94篇 |
1999年 | 110篇 |
1998年 | 107篇 |
1997年 | 87篇 |
1996年 | 85篇 |
1995年 | 73篇 |
1994年 | 60篇 |
1993年 | 60篇 |
1992年 | 56篇 |
1991年 | 37篇 |
1990年 | 37篇 |
1989年 | 28篇 |
1988年 | 20篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 7篇 |
1984年 | 9篇 |
1983年 | 13篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 2篇 |
1968年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有4712条查询结果,搜索用时 671 毫秒
101.
102.
103.
Huawei Qin Zhen Cai Jianjun Wang Wei Ye Ying Chen 《Marine Georesources & Geotechnology》2016,34(5):403-408
The shortcomings of gravity corers in sampling marine sediments have been observed extensively in various field tests. In order to optimize the coring, this article provides an alternative numerical way to model the gravity coring and analyze the sampling effect. Based on this analysis, a new hydraulic hammer corer is devised. A coupled Eulerian-Lagrangian method with capability of simulating the problem involving extreme deformation, penetration is used to simulate the coring process. The results show that the hydrostatic pressure and deviator stress increase and reach their peak when the pile tip is slightly above or at the level of the observation point and then drop rapidly when the pile tip slides below the observation point. In addition, the stress path indicates that the soil element sustains plastic compression before yielding and then expands until recovering to the original state. The obvious “under-sampling” phenomenon is also well-captured by the finite element model. 相似文献
104.
105.
106.
107.
XIA Bin LU Ye YUAN Yajuan CHEN Weiyan ZHANG Xiao XU Chi YU Shengrui WAN Zhifeng 《《地质学报》英文版》2018,92(5):1753-1768
New zircon U–Pb ages, whole-rock geochemistry and zircon Hf isotopes from the Habo porphyry Western Yunnan, China, were determined to provide constraints on the timing of uplift of the Eastern Tibetan Plateau. The intrusive rocks consist of shoshonitic porphyry (syenite porphyry and monzonite porphyry). Zircon laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating indicates coeval emplacement ages of ~35 Ma. The porphyries have alkaline affinities, enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs) (e.g., Rb, Th, U, Pb), with depletion of high field strength elements (HFSEs) (e.g., Nb, Ti, Ta) and weak Eu anomalies. They display uniform Lu–Hf isotopic compositions with negative zircon εHf(t) values ranging from -3.9 to -0.6. The chemical characteristics of the syenite porphyries indicated that they most likely originated from the lower crust, with mantle-derived material involved in their generation. Geochemically, the monzonite porphyries are similar to the syenite porphyries; however, the lower MgO contents suggest that they were produced by different degrees of partial melting of the same lower crust source. Combined with the geochemical and isotopic data in this paper, imply that the alkali-rich porphyries of the Habo polymetallic deposit were derived from the partial melting of lower crust, enriched by mantle magma, formed in a conversion stage from stress extrusion (a strike-slip shear process) to local stress relaxation (a strike-slip pull-apart process) at the Ailaoshao tectonic zone. 相似文献
108.
109.
Timokhov L. A. Ivanov V. V. Kassens H. Lebedev N. V. Frolov I. Ye. Hölemann J. 《Doklady Earth Sciences》2018,480(1):685-688
Doklady Earth Sciences - According to historical oceanographic data, anomalies in the dynamic topography during the winter period were calculated and two climatic stages of dynamic condition of the... 相似文献
110.
Landslide-prone slopes in earthquake-affected areas commonly feature heterogeneity and high permeability due to the presence of cracks and fissures that were caused by ground shaking. Landslide reactivation in heterogeneous slope may be affected by preferential flow that was commonly occurred under heavy rainfall. Current hydro-mechanical models that are based on a single-permeability model consider soil as a homogeneous continuum, which, however, cannot explicitly represent the hydraulic properties of heterogeneous soil. The present study adopted a dual-permeability model, using two Darcy-Richards equations to simulate the infiltration processes in both matrix and preferential flow domains. The hydrological results were integrated with an infinite slope stability approach, attempting to investigate the hydro-mechanical behavior. A coarse-textured unstable slope in an earthquake-affected area was chosen for conducting artificial rainfall experiment, and in the experiment slope, failure was triggered several times under heavy rainfall. The simulated hydro-mechanical results of both single- and dual-permeability model were compared with the measurements, including soil moisture content, pore water pressure, and slope stability conditions. Under high-intensity rainfall, the measured soil moisture and pore water pressure at 1-m depth showed faster hydrological response than its simulations, which can be regarded as a typical evidence of preferential flow. We found the dual-permeability model substantially improved the quantification of hydro-mechanical processes. Such improvement could assist in obtaining more reliable landslide-triggering predication. In the light of the implementation of a dual-permeability model for slope stability analysis, a more flexible and robust early warning system for shallow landslides hazard in coarse-textured slopes could be provided. 相似文献