全文获取类型
收费全文 | 157篇 |
免费 | 2篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 4篇 |
地球物理 | 22篇 |
地质学 | 98篇 |
海洋学 | 1篇 |
天文学 | 16篇 |
自然地理 | 7篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 12篇 |
2017年 | 5篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 7篇 |
2009年 | 12篇 |
2008年 | 1篇 |
2007年 | 5篇 |
2006年 | 10篇 |
2005年 | 1篇 |
2004年 | 6篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 4篇 |
1971年 | 5篇 |
1968年 | 1篇 |
排序方式: 共有159条查询结果,搜索用时 515 毫秒
141.
The progressive deformation of the Singhbhum Shear Zone (SSZ) involved the initiation of a mylonitic foliation, its deformation
by three generations of reclined folds and superposition of two later groups of folds, i.e., a group of asymmetric folds with
subhorizontal or gently plunging axes and a group of gentle and open, transverse and more or less upright folds. The occurrence
of sheath folds and U-shaped deformed lineations indicate that the reclined folds were produced by rotation of fold hinges
through large angles. The total displacement along the SSZ was compounded of displacements along numerous mesoscopic shear
zones. The cleavages in the shear lenses and the mesoscopic shear zones cannot be distinguished as C and S surfaces. They
have the same kinematic significance and were produced by ductile deformation, although there were localized discontinuous
displacements along both sets,-of cleavages. A mylonitic foliation had formed before the development of the earliest recognizable
folds. Its time of formation and folding could be synchronous, diachronous or partly overlapping in time in the different
domains of the SSZ. 相似文献
142.
Many earthquakes have been recorded from the coastal margin of the Indian peninsular shield during the last 200 years. Largely made up of Precambrian assemblages with variable cover of Jurassic to Quaternary sedimentary rocks and Cretaceous-Eocene volcanics, the peninsular shield was long held to be aseismic. Recent measurements, however, show that this continental fragment is being pushed northeastward by the Carlsberg and Central Indian ridges; and the Indo-Myanmar subduction zone is exerting vigorous slab pull towards the east. Repeated cycles of sea level change during the Quaternary have also induced continuing hydro-isostatic adjustment due to variable melt water loading in the Bay of Bengal and the Arabian sea. All these forces produce space-time fluctuations of strain around many small to large faults, which occur in the upper crust of the shield. Some of the faults have been intermittently active (during the past 100 kyr); others were active earlier. Although the Shillong plateau and the associated hill ranges of northeastern India and Myanmar are subject to the maximum seismic hazard, the peninsular coast is also vulnerable to intermittent seismicity. We present illustrative evidence of some active faults, which are recognisable (a) on coastal land by displaced Pleistocene weathered cover, hot springs, leakages of native mercury and allochthonous geochemical anomalies of base metals and (b) offshore below the inner shelf by horst-shaped uplifted segments and intra-formational slump folds on and below the top shallow seismic (3.5 kHz) reflector. On the other hand, there are long stretches of the east coast at Vishakhapatnam and Manappad Point, which do not show active faults. Step-like marine terraces, which occur up to+6 m above the low tide level (LTL) preserve records of relative sea level fluctuations during the Holocene and the Last Interglacial. In such sectors, absence of tectonic disturbance during the last 100 ka is also corroborated by lateral continuity of shallow seismic reflectors below the inner shelf over many kilometers. Since authentic historical (200–1000 years B.P.) records of seismicity along the Peninsular coast are virtually unavailable, the likely recurrence interval between earthquakes in each sector cannot be gauged. We, therefore, propose a scale of seismic risk, based on geometry of the mappable faults and available seismic records of the last two centuries. These could be used in combination to rank the densely populated coastal tracts sector-wise. 相似文献
143.
A Hybrid Spatio-Temporal Data Model and Structure (HST-DMS) for Efficient Storage and Retrieval of Land Use Information 总被引:1,自引:0,他引:1
While the incorporation of geographical and environmental modeling with GIS requires software support for storage and retrieval of spatial information that changes over time, it continues to be an unresolved issue with modern GIS software. Two complementary approaches have been used to manage the spatial and temporal heterogeneity within datasets that use a field‐based representation of the world. Some researchers have proposed new data models that partition space into discrete elements on an as‐needed basis following each temporal event, while others have focused on eliminating duplication of repeated data elements present in spatio‐temporal information. It is proposed in this paper that both approaches have merit and can be combined to create a Hybrid Spatio‐Temporal Data Model and Structure (HST‐DMS) that efficiently supports spatio‐temporal data storage and querying. Specifically, Peuquet and Duan's (1995) Event‐based Spatio‐Temporal Data Model (ESTDM) and the Overlapping R‐tree (Guttman 1984, Tzourmanis et al. 2000) are utilized to create a prototype used to store information about urban expansion for the town of Carbondale, Illinois. 相似文献
144.
S. K. Nath P. Sengupta S. K. Srivastav S. N. Bhattacharya R. S. Dattatrayam R. Prakash H. V. Gupta 《Journal of Earth System Science》2003,112(3):441-462
Site response in and around Delhi is studied using digital seismograms recorded by a thirteen-station VSAT-based 24-bit digital
Delhi telemetry network of the India Meteorological Department. Nine local (M
l ≥ 2.3) and nine regional (M
l ≥ 3.9) earthquakes are selected for the estimation of site amplification factor using the classical standard spectral ratio
for regional events (Ridge Delhi Observatory being the reference station), normalized standard spectral ratio for local events,
horizontal-to-vertical spectral ratio or receiver function and the generalized inversion techniques in the frequency range
of 0.5 to 7.5 Hz. Site response curves at all the thirteen stations exhibit station to station variation of the site amplification
factor reflecting the changes in geologic/geotectonic/soil conditions. A comparison of the site response values obtained by
the generalized inversion with those computed using receiver function technique shows a large scatter even though the pattern
of the curves remain more or less similar. However, the site effects computed by generalized inversion and standard spectral
ratio exhibit a good 1:1 correspondence. The peaks yielded by all the methods have been observed to occur at the same frequencies.
It is evident that the softer fluvial deposits of the newer alluvium of the east Yamuna sector show steeper site amplification
gradient at lower frequencies, while the greater Delhi experiences moderate site amplification. The variation of site response
corroborates the abrupt changes in intensity from one location to another due to local site condition. 相似文献
145.
Environmental justice laws protect certain populations against discriminatory actions that may result from a myriad of enterprises, including transportation activities. Previous environmental equity studies examining the effects of transportation‐engendered externalities have been criticized on several points, including (1) that the choice of a reference population for comparison to the criterion variable may influence the outcome of research results and (2) that the selection and use of inappropriate methodologies intended to identify and characterize populations may foreordain research outcomes. This article examines the potentially confounding effects of selected spatial scale and population assignment strategies as applied to a study of excessive noise levels at a large Midwestern airport, finding that reported outcomes can vary significantly as a function of methodological choices. 相似文献
146.
S. Sengupta 《Pure and Applied Geophysics》1977,115(3):647-654
Fourier transforms of the theoretical gravity effect due to a two-dimensional asymmetrical triangular prism have been derived. Evaluation of the parameters from the analysis of the Fourier Spectra has been outlined. 相似文献
147.
148.
Sudipta Sengupta 《Journal of Earth System Science》1995,104(3):433-446
Drag patterns of foliation are graphically constructed around very competent dykes under bulk strain of pure shear, simple
shear and a combination of pure shear and simple shear. Four different types of drag patterns may be produced, depending on
the nature of the bulk deformation and the initial orientations of the dyke and the foliation. The drag pattern can be symmetric
or asymmetric, inward curving or outward curving. Both the magnitude and the sense of drag may vary along a dyke wall. A uniform
sense of drag develops all along a dyke wall only in certain special situations. The type of foliation drag near a dyke may
give us a rough idea of the nature of bulk deformation and the relative orientations of the dyke and the foliation with respect
to the bulk strain axes. 相似文献
149.
Plane strain tests were performed on seven kaolinite blocks, each of which developed shear bands. Anisotropy of magnetic susceptibility
(AMS) analysis of the kaolinite reveals a threshold degree of magnetic anisotropy (P′) exceeding which shear bands develop. Since P′ is a strain-intensity gauge and soils are known to develop shear bands prior to landsliding, it is concluded that soil in
every landslide-prone region must have its unique threshold P′ exceeding which it develops shear bands before failing. Therefore, AMS monitoring of soil in landslide prone regions is
proposed as a potential tool in the management of natural hazard zones. 相似文献
150.
M. Venkataramana K. Sengupta G. S. Bhat S. Ameenulla J. V. S. Raju 《Journal of Earth System Science》2000,109(2):239-247
This paper describes measurement of air-sea parameters and estimation of sensible and latent heat fluxes by the “Inertial-Dissipation”
technique over south Bay of Bengal. The data were collected on ORV Sagar Kanya during BOBMEX-Pilot cruise during the period
23rd October 1998 to 12th November 1998 over south Bay of Bengal. The fluxes are estimated using the data collected through
fast response sensors namely Gill anemometer, Sonic anemometer and IR Hygrometer. In this paper the analyses carried out for
two days, one relatively cloud free day on November 3rd and the other cloudy with rain on November 1st, are presented. Sea
surface and air temperatures are higher on November 3rd than on November 1st. Sensible heat flux for both the days does not
show any significant variation over the period of estimation, whereas latent heat flux is more for November 3rd than November
1st. An attempt is made to explain the variation of latent heat flux with a parameter called thermal stability on the vapor
transfer from the water surface, which depends on wind speed and air to sea surface temperature difference. 相似文献