全文获取类型
收费全文 | 493篇 |
免费 | 15篇 |
国内免费 | 6篇 |
专业分类
测绘学 | 55篇 |
大气科学 | 20篇 |
地球物理 | 87篇 |
地质学 | 203篇 |
海洋学 | 30篇 |
天文学 | 104篇 |
综合类 | 6篇 |
自然地理 | 9篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 22篇 |
2016年 | 32篇 |
2015年 | 25篇 |
2014年 | 27篇 |
2013年 | 45篇 |
2012年 | 35篇 |
2011年 | 24篇 |
2010年 | 26篇 |
2009年 | 20篇 |
2008年 | 21篇 |
2007年 | 14篇 |
2006年 | 12篇 |
2005年 | 13篇 |
2004年 | 5篇 |
2003年 | 12篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1977年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1970年 | 2篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1963年 | 1篇 |
1961年 | 2篇 |
1928年 | 1篇 |
排序方式: 共有514条查询结果,搜索用时 15 毫秒
21.
Spatio‐temporal prediction and forecasting of land surface temperature (LST) are relevant. However, several factors limit their usage, such as missing pixels, line drops, and cloud cover in satellite images. Being measured close to the Earth's surface, LST is mainly influenced by the land use/land cover (LULC) distribution of the terrain. This article presents a spatio‐temporal interpolation method which semantically models LULC information for the analysis of LST. The proposed spatio‐temporal semantic kriging (ST‐SemK) approach is presented in two variants: non‐separable ST‐SemK (ST‐SemKNSep) and separable ST‐SemK (ST‐SemKSep). Empirical studies have been carried out with derived Landsat 7 ETM+ satellite images of LST for two spatial regions: Kolkata, India and Dallas, Texas, U.S. It has been observed that semantically enhanced spatio‐temporal modeling by ST‐SemK yields more accurate prediction results than spatio‐temporal ordinary kriging and other existing methods. 相似文献
22.
Microtextural study of a single troilite‐metal nodule (TMN) from the Katol L6‐7 chondrite, a recent fall (May, 2012) in India suggests that the TMN is primarily an aggregate of submicron‐scale intergrowth of troilite and kamacite (mean Ni: 6.18 wt%) juxtaposed with intensely fractured silicates, mainly olivine (Fa: 25 mole%), low‐Ca pyroxene (Fs: 21.2 mole%), and a large volume of maskelynite. Evidence of shock textures in the TMN indicates a high degree of shock metamorphism that involves plagioclase‐maskelynite and olivine‐wadsleyite/ringwoodite transformations and formation of quenched metal‐sulfide melt textures due to localized shear‐induced frictional melting. It is inferred that the TMN formation is an independent, localized event by a high energy impact and its subsequent incorporation in the ejected chondritic fragment of the parent body. Katol chondrite has been calibrated with a peak shock pressure of S5 (~45 GPa) after Stöffler et al. (1991), whereas peak shock pressure within the TMN exceeds the shock facies S6 (>45 GPa) following Bennett and McSween (1996) and Stöffler et al. (1991). Overall, the shock‐thermal history of the Katol TMN is dissimilar as compared to the host chondrite. 相似文献
23.
Dwijesh Ray Dewashish Upadhyay Saumitra Misra Horton E. Newsom Sambhunath Ghosh 《Meteoritics & planetary science》2017,52(8):1577-1599
The Lonar impact crater, India, is one of the few known terrestrial impact craters excavated in continental basaltic target rocks (Deccan Traps, ~65 Ma). The impactites reported from the crater to date mainly include centimeter‐ to decimeter‐sized impact‐melt bombs, and aerodynamically shaped millimeter‐ and submillimeter‐sized impact spherules. They occur in situ within the ejecta around the crater rim and show schlieren structure. In contrast, non–in situ glassy objects, loosely strewn around the crater lake and in the ejecta around the crater rim do not show any schlieren structure. These non–in situ fragments appear to be similar to ancient bricks from the Daityasudan temple in the Lonar village. Synthesis of existing and new major and trace element data on the Lonar impact spherules show that (1) the target Lonar basalts incorporated into the spherules had undergone minimal preimpact alteration. Also, the paleosol layer as preserved between the top‐most target basalt flow and the ejecta blanket, even after the impact, was not a source component for the Lonar impactites, (2) the Archean basement below the Deccan traps were unlikely to have contributed material to the impactite parental melts, and (3) the impactor asteroid components (Cr, Co, Ni) were concentrated only within the submillimeter‐sized spherules. Two component mixing calculations using major oxides and Cr, Co, and Ni suggest that the Lonar impactor was a EH‐type chondrite with the submillimeter‐sized spherules containing ~6 wt% impactor components. 相似文献
24.
Assessment of groundwater potential zones using GIS technique 总被引:1,自引:0,他引:1
A case study was conducted to find out the groundwater potential zones in Kattakulathur block, Tamil Nadu, India with an aerial
extent of 360.60 km2. The thematic maps such as geology, geomorphology, soil hydrological group, land use / land cover and drainage map were prepared
for the study area. The Digital Elevation Model (DEM) has been generated from the 10 m interval contour lines (which is derived
from SOI, Toposheet 1:25000 scale) and obtained the slope (%) of the study area. The groundwater potential zones were obtained
by overlaying all the thematic maps in terms of weighted overlay methods using the spatial analysis tool in ArcGIS 9.2. During
weighted overlay analysis, the ranking has been given for each individual parameter of each thematic map and weights were
assigned according to the influence such as soil −25%, geomorphology − 25%, land use/land cover −25%, slope − 15%, lineament
− 5% and drainage / streams − 5% and find out the potential zones in terms of good, moderate and poor zones with the area
of 49.70 km2, 261.61 km2 and 46.04 km2 respectively. The potential zone wise study area was overlaid with village boundary map and the village wise groundwater
potential zones with three categories such as good, moderate and poor zones were obtained. This GIS based output result was
validated by conducting field survey by randomly selecting wells in different villages using GPS instruments. The coordinates
of each well location were obtained by GPS and plotted in the GIS platform and it was clearly shown that the well coordinates
were exactly seated with the classified zones. 相似文献
25.
Subimal Ghosh 《水文研究》2010,24(24):3558-3567
The rainfall patterns of neighbouring meteorological subdivisions of India are similar because of similar climatological and geographical characteristics. Analysing the rainfall pattern separately for these meteorological subdivisions may not always capture the correlation and tail dependence. Furthermore, generating the multivariate rainfall data separately may not preserve the correlation. In this study, copula method is used to derive the bivariate distribution of monsoon rainfall in neighbouring meteorological subdivisions. Different Archimedean copulas are used for this purpose and the best copula is selected based on nonparametric test and tail dependence coefficient. The fitted copula is then applied to derive the bivariate distribution, joint return period and conditional distribution. Bivariate rainfall data is generated with the fitted copula and it is observed with the increase of sample size, the generated data is able to capture the correlation as well as tail dependence. The methodology is demonstrated with the case study of two neighbouring meteorological subdivisions of North‐East India: Assam and Meghalaya meteorological subdivision and Nagaland, Manipur, Mizoram and Tripura meteorological subdivision. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
26.
Sumanta Dandapath Bishwajit Chakraborty Nicolas Maslov Siddaiah M. Karisiddaiah Dhrupad Ghosh William Fernandes Andrew Menezes 《Marine and Petroleum Geology》2012,29(1):115-128
Here we apply quantitative technique to describe the seafloor seepages based on the multi-beam backscatter and bathymetric investigations to characterize the pockmark morphology. The variable seafloor backscatter strength for coarser seafloor sediments are related to the diagenesis derived from biodegraded seepages. In this regard, box counting method is used to estimate ‘fractal dimension’ for backscatter imagery data of 398 blocks. These blocks are further sub-grouped into six classes depending on the spread of pockmark related seepages. The study area lies 102 km west off Marmagao along the central west coast of India which contains pre-dominantly (70%) gas-charged sediments. Comparison between the estimated self-similar fractals reveals that there is approximately 97% correlation between the box (Dbox) and information (Dinfo) dimensions. Box dimension–derived fractal dimension values, suggest that the seepages are more along the fault trace in deeper waters, in comparison to sparsely distributed shallow water seepages. Besides, this poor seepage is confined within the smooth to moderately rough seafloor. It is established that the high backscatter strength along the upper slope of the pockmark region having higher fractal dimensions reflects multifractal behavior of seepage distribution. Entire area indicates patchy seepage patterns as supported by estimated fractal values showing intermittent fluctuations, which emphasizes non-linear behavior. Estimated self organizing criticality (SOC) parameters for six representative blocks reveal that the nature of pockmark, fault trace, sediment nature coupled with slumping of pockmark’s wall, sediment movement due to bottom currents are controlling the dynamic balance in the area seepage system. Further, our study emphasizing the multifractal behavior of seepage blocks, clearly depicts the drift in the seepage pattern. 相似文献
27.
Computation of the seismic stability of rock wedges 总被引:1,自引:0,他引:1
Summary Newmark's concept of computing the permanent displacement under seismic loads has been combined with the conventional limit equilibrium analysis to compute the displacements of a rock wedge. The rock wedge formed by the intersecting planes may or may not have a tension crack in the upper slope surface. As the static analysis of a rock wedge is available from the literature, only the seismic problem is treated theoretically in more details.A computer program has been developed to compute the displacements from the digitised input data of the acceleration-time-history. The program can take into account the water pressure on the intersecting planes and on the planes of the tension crack. The effect of rock anchors if present is also taken care of in addition to static surcharge loads. The program calculates the conventional static factor of safety, remaining resistance against sliding, the critical acceleration, exciting force, relative velocity with time and the cumulative displacements.Two model examples are presented: one with simple sinusoidal acceleration and the other one with actual earthquake data considering the different systems of forces acting on the wedge. The results are critically discussed with respect to the different parameters e. g. anchor forces, water pressure and cohesion influencing the magnitude of displacements under seismic loads. It is shown that the critical acceleration is a better index for the seismic stability than the conventional factor of safety.The critical acceleration presented in this paper serves as a very handy tool for a site engineer to get the first hand information about the stability of the wedge for a given acceleration-time-history without going into the details of dynamic analysis.Notations
A, B
Inclined intersecting planes
-
C, D
Geometric points on the intersection ofA andB
-
a
cr
Critical acceleration
-
a
h
Horizontal acceleration
-
a
v
Vertical acceleration
-
a
r
Relative acceleration of the wedge
-
DF
Driving force
-
DF
dyn
Dynamic driving force
-
DF
st
Static driving force
-
FS
Factor of safety
-
g
Acceleration due to gravity
-
m
Mass of the wedge
-
RF
Resisting force
-
RF
dyn
Dynamic resisting force
-
RF
st
Static resisting force
-
RS
Remaining resisting force against sliding
-
RS
dyn
Total seismic induced force
-
RS
st
Remaining static resisting force against sliding
-
s
r
Cumulative relative displacement of the wedge
-
TRS
Total remaining resisting force against sliding
-
v
r
Relative velocity of the wedge
-
W
Weight of the wedge
-
W
A
,W
B
Weight of the wedge in the planeA andB
-
Dip of line of intersection of the planesA andB
-
Average friction angle
-
A
,
B
Friction angle of planeA andB
- I, II, III, IV
Points in the curve shown in Fig. 6 相似文献
28.
Rekha Ghosh 《Journal of the Indian Society of Remote Sensing》1993,21(3):119-126
Jharia coalfield, the chief storehouse of prime coking coal in India, has lost the original controls of ground water conditions. Here, ground water level is dependent mainly upon the presently existing topography, geomorphic features such as abandoned channels, confluence of channels, losing streams etc. and human-induced recharge conditions. These features are reflected by the soil moisture content and presence of vegetative cover. The ground water map of Jharia coalfield has been prepared from the aerial photographs using the grey tone and vegetation cover as the criteria. The observations are supported with field checks. The ground water map prepared will be very much useful to the society because some parts of the coalfield suffer from severe drought during summer. 相似文献
29.
D. K. Ghosh 《Environmental Geology》1990,16(1):15-22
Geological contributions to the stability of rockcut caves and evaluation of stone block as a construction material are discussed. Rock alteration and microfissuring are proposed to be coded by a deterioration index and usable stone blocks are evaluated on joint frequency measured in the field. 相似文献
30.