全文获取类型
收费全文 | 5757篇 |
免费 | 1774篇 |
国内免费 | 1195篇 |
专业分类
测绘学 | 77篇 |
大气科学 | 90篇 |
地球物理 | 3275篇 |
地质学 | 4194篇 |
海洋学 | 195篇 |
天文学 | 6篇 |
综合类 | 601篇 |
自然地理 | 288篇 |
出版年
2024年 | 18篇 |
2023年 | 62篇 |
2022年 | 171篇 |
2021年 | 253篇 |
2020年 | 183篇 |
2019年 | 323篇 |
2018年 | 259篇 |
2017年 | 265篇 |
2016年 | 306篇 |
2015年 | 296篇 |
2014年 | 342篇 |
2013年 | 377篇 |
2012年 | 351篇 |
2011年 | 329篇 |
2010年 | 310篇 |
2009年 | 428篇 |
2008年 | 425篇 |
2007年 | 374篇 |
2006年 | 409篇 |
2005年 | 317篇 |
2004年 | 362篇 |
2003年 | 284篇 |
2002年 | 249篇 |
2001年 | 258篇 |
2000年 | 258篇 |
1999年 | 170篇 |
1998年 | 194篇 |
1997年 | 171篇 |
1996年 | 170篇 |
1995年 | 161篇 |
1994年 | 157篇 |
1993年 | 129篇 |
1992年 | 105篇 |
1991年 | 50篇 |
1990年 | 41篇 |
1989年 | 47篇 |
1988年 | 37篇 |
1987年 | 29篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 21篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1954年 | 8篇 |
排序方式: 共有8726条查询结果,搜索用时 15 毫秒
71.
This paper reviews the data concerning the fracture network and the hydraulic characteristics of faults in an active zone of the Gulf of Corinth. Pressure gap measured through fault planes shows that in this area the active normal faults (Aigion, Helike) act, at least temporarily and locally, as transversal seal. The analysis of the carbonate cements in the fractures on both the hangingwall and the footwall of the faults also suggests that they have acted as local seals during the whole fault zone evolution. However, the pressure and the characteristics of the water samples measured in the wells indicate that meteoric water circulates from the highest part of the relief to the coast, which means it goes through the fault zones. Field quantitative analysis and core studies from the AIG-10 well have been performed to define both regional and fault-related fracture networks. Then laboratory thin section observations have been done to recognize the different fault rocks characterizing the fault zone components. These two kinds of approach give information on the permeability characteristics of the fault zone. To synthesize the data, a schematic conceptual 3D fluid flow modeling has been performed taking into account fault zone permeability architecture, sedimentation, fluid flow, fault vertical offset and meteoric water influx, as well as compaction water flow. This modeling allows us to fit all the data with a model where the fault segments act as a seal whereas the relays between these segments allow for the regional flow from the Peloponnese topographic highs to the coast. 相似文献
72.
Variability in Early Amazonian Tharsis stress state based on wrinkle ridges and strike-slip faulting
We present evidence for a decrease in the magnitude of Tharsis-circumferential compressive stress during the Late Hesperian to the Middle Amazonian based on chronologic changes in the predominant style of faulting in southern Amazonis Planitia. Using high-resolution MOLA topography, we identify a population of strike-slip faults that exhibit Middle Amazonian-aged displacements of regional chrono-stratigraphic units. These strike-slip faults are adjacent to an older population of previously documented Late Hesperian-aged thrust faults (wrinkle ridges). Along-strike orientations of these thrust and strike-slip faults reveal the Tharsis-radial stress to be the area's most compressive remote principal stress and that this stress orientation and magnitude persisted throughout the Late Hesperian to the Middle Amazonian. We show that the change in the predominant style of faulting from thrust faulting to strike-slip faulting during this time requires a decrease of the Tharsis-circumferential compressive stress to a magnitude less than lithostatic load, with negligible change in stress orientation. 相似文献
73.
The NW-trending Bucaramanga fault links, at its southern termination, with the Soapaga and Boyacá faults, which by their NW trend define an ample horsetail structure. As a result of their Neogene reactivation as reverse faults, they bound fault-related anticlines that expose the sedimentary fill of two Early Jurassic rift basins. These sediments exhibit the wedge-like geometry of rift fills related to west-facing normal faults. Their structural setting was controlled further by segmentation of the bounding faults at approximately 10 km intervals, in which each segment is separated by a transverse basement high. Isopach contours and different facies associations suggest these transverse anticlines may have separated depocenters of their adjacent subbasins, which were shaped by a slightly different subsidence history and thereby decoupled. The basin fill of the relatively narrow basin associated with the Soapaga fault is dominated by fanglomeratic successions organized in two coarsening-upward cycles. In the larger basin linked to the Boyacá fault, the sedimentary fill consists of two coarsening-upward sequences that, when fully developed, vary from floodplain to alluvial fan deposits. These Early Jurassic rift fills temporally constrain the evolution of the Bucaramanga fault, which accommodated right-lateral displacement during the early Mesozoic rift event. 相似文献
74.
The evaluation of seismic site response in the urban area of Catania was tackled by selecting test areas having peculiar lithological
and structural features, potentially favourable to large local amplifications of ground motion. The two selected areas are
located in the historical downtown and in the northern part of Catania where the presence of a fault is evident. Site response
was evaluated using spectral ratio technique taking the horizontal- to-vertical component ratio of ambient noise. Inferences
from microtremor measurements are compared with results from synthetic accelerograms and response spectra computed at all
drillings available for this area. Such method is particularly suitable in urban areas where the nature of the outcropping
geological units is masked by city growth and anthropic intervention on the surface geology. The microtremor H/V spectral
ratios evaluated at soft sites located within the downtown profile tend to be smaller than that usually reported in the literature
for such soils. A tendency for amplifications to peaks near 2 Hz is observed only in some sites located on recent alluvial
deposits. Evidences for amplifications of site effects (frequency range 4–8 Hz) were observed in the sampling sites located
on the fault, with a rapid decrease of spectral amplitude just a few tenths of metres away from the discontinuity. Numerical
simulations evidenced the importance of geolithological features at depth levels even greater than 20–30 m. Besides this,
the results strongly confirm the importance of the subsurface geological conditions, in the estimate of seismic hazard at
urban scale. 相似文献
75.
The solution of two-dimensional problem of an interface breaking long inclined dip-slip fault in two welded half-spaces is
well known. The purpose of this note is to obtain the corresponding solution for a blind fault. The solution is valid for
arbitrary values of the fault-depth and the dip angle. Graphs showing the variation of the displacement field with the distance
from the fault, for different values of fault depth and dip angle are presented. Contour maps showing the stress field around
a long dip-slip fault are also obtained 相似文献
76.
77.
78.
79.
80.
CCSD主孔100-2950m榴辉岩类和片麻岩类叶理及微断层产状特征 总被引:1,自引:0,他引:1
CCSD主孔100~2950m榴辉岩、退变榴辉岩类岩石叶理倾角明显较片麻岩类岩石叶理倾角陡,前者总体倾角55°左右,后者28°左右,局部可见片麻岩类叶理切割榴辉岩类叶理,因此两者叶理可能形成于不同时期;两类岩石之间现部分为韧性剪切带接触关系,韧性剪切带形成于苏鲁地体折返主期自SEE向NWW的韧性剪切作用。榴辉岩、退变榴辉岩类岩石叶理产状对发育于该类岩石内的微断层产状有一定控制作用,而片麻岩类岩石叶理产状对发育于该类岩石内的微断层产状控制作用相对较弱。孔区脆性变形主要反映白垩纪以来SEE-NWW向伸展构造应力场的变形特征,主孔100~1620m倾伏向以SEE向占绝对优势的微正滑断层擦痕即为该期变形的产物。 相似文献