全文获取类型
收费全文 | 455篇 |
免费 | 16篇 |
国内免费 | 7篇 |
专业分类
测绘学 | 55篇 |
大气科学 | 20篇 |
地球物理 | 81篇 |
地质学 | 184篇 |
海洋学 | 16篇 |
天文学 | 105篇 |
综合类 | 8篇 |
自然地理 | 9篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 19篇 |
2017年 | 26篇 |
2016年 | 32篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 37篇 |
2012年 | 33篇 |
2011年 | 20篇 |
2010年 | 21篇 |
2009年 | 16篇 |
2008年 | 20篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 12篇 |
2004年 | 4篇 |
2003年 | 11篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 2篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3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 |
1961年 | 1篇 |
1928年 | 1篇 |
排序方式: 共有478条查询结果,搜索用时 46 毫秒
111.
In recent times, rapid urbanisation coupled with scarcity of land forces several structures to come up ever closer to each
other, which may sometime cause severe damage to the structures from both strength and serviceability point of view, and therefore,
a need is felt to devise simplified methods to capture the effect of footing interference. In the present study, an attempt
has been made to model the settlement behaviour of two strip footings placed in close spacing on layered soil deposit consisting
of a strong top layer underlying a weak bottom layer. Theory of elasticity is employed to derive the governing differential
equations and subsequently solved by the finite difference method. The perfectly rough strip footings are considered to be
resting on the surface of two-layer soil system, and the soil is assumed to behave as linear elastic material under a range
of static foundation load. The effect of various parameters such as the elastic moduli and thickness of two layers, clear
spacing between the footings and footing load on the settlement behaviour of closely spaced footings has been determined.
The variation of vertical normal stress at the interface of two different soil layers as well as at the base of the failure
domain also forms an important part of this study. The results are presented in terms of settlement ratio (ξδ), and their variation is obtained with the change in clear spacing between two footings. The present theoretical investigation
indicates that the settlement of closely spaced footings is found to be higher than that of single isolated footing, which
further reduces with increase in the spacing between the footings. 相似文献
112.
M. L. Ghosh 《Pure and Applied Geophysics》1973,111(1):2163-2176
Summary The diffraction of a pressure wave arising from the edge of the floating ice due to an incident wave of the formH[t–(xcos/)+ (ysin/)], whereH(t) is the Heaviside step function, has been studied. The ice sheet has been taken to be moving with a velocity much less than the velocity of sound in the liquid. The problem has been solved using an approximate method of solving Wiener Hopf problems. Finally, the pressure field at a large distance from the edge has been derived in a closed form evaluating the integrals by the saddle point method. 相似文献
113.
S. Ghosh 《Journal of Earth System Science》1993,102(1):265-270
Uptake of trace gases by (stratospheric aerosol can be significant particularly after large injections of volcanic sulphur.
A theoretical scheme is presented to quantify the rate at which trace gases diffuse into these aerosol droplets. Rate constants
for 19 trace gases are calculated and it is found that the rates vary from a value of 2.85 × 10-7s-1 for CC14 to 8.08 × 10-7s-1 for NO. The calculations are characterised by their ease of application and can be incorporated into stratospheric chemical
models. 相似文献
114.
A. K. Ghosh 《Mineralium Deposita》1972,7(3):292-313
The genesis of the copper ore deposits of the Singhbhum shear zone, India, has been worked out through a detailed geochemical examination of the ores and the country rocks. Following different techniques of atomic absorption, the abundances of Cu, Co, Ni, Pb, Zn, Cd, Ag, Mn and Hg were determined and the trace element characteristics of the principal rock units in and outside the shear zone have been compiled and critically evaluated. The data suggest that the ore deposits are the result of a sequence of long-continued and over-lapping geological processes culminating in intense shearing, syntectonic granitization and considerable mobilization of the ore elements. The Precambrian metasedimentary and metavolcanic rocks of the shear zone, as well as those enclosing it, served as the source, while diffusion of the ore constituents and their precipitation in physicochemically favourable structural traps, formed in response to shearing, resulted in the formation of the deposits.
Zusammenfassung Als Beitrag zur Klärung der Genese der Kupferlagerstätten in der Singhbhum Shear Zone, Indien, wurden geochemische Untersuchungen an Erzen und Nebengestein durchgeführt. Spurengehalte von Cu, Co, Ni, Pb, Zn, Cd, Ag, Mn, Hg wurden mit Hilfe der AAS bestimmt, ihre Verteilung innerhalb der Zone und der angrenzenden Gesteinstypen wird diskutiert. Auf Grund der vorliegenden geochemischen Daten wird folgende Deutung zur Entstehung der Erzlagerstätten gegeben: Die Bildung der Singhbhum-Erzvorkommen ist das Ergebnis einer Folge langandauernder und sich überschneidender geologischer Prozesse, wie intensiver Scherung, syntektonischer Granitisation und damit verbundener Mobilisierung der oben genannten Elemente. Die präkambrischen Metasedimente und Metavulkanite innerhalb der Scherzone und ihrer näheren Umgebung sind als Muttergesteine der erzbildenden Elemente anzusehen. Die Bildung der Lagerstätte ist das Resultat der Diffusion von Lösungen und ihres Absatzes in physikalisch-chemisch günstigen Struktur-Fallen, gebildet im Anschluß an die Scherung.相似文献
115.
Anjum Mahtab V. N. Sridhar Ranendu Ghosh 《Journal of the Indian Society of Remote Sensing》2004,32(3):261-268
Parametric kernel-based models for Bi-directional Reflectance Distribution Function (BRDF) of vegetated land surfaces attempt
to describe the BRDF as a linear superposition of a set of kernels describing basic angular shapes. The kernels and associated
model coefficients are derived as approximations to the underlying theories of radiative transfer as well as geometric-optical
scattering within vegetation canopies. In the present study, five kernels viz. Ross-Thick, Li-Sparse, Ross-Thin, Li-Dense
and Roujean geometric-optical (GO) kernels along with a purely empirical model were examined for their suitability in describing
the angular characteristics of two forest types (semi-evergreen and deciduous) during November 1996-March 1997 using ADEOS-1
POLDER data. The statistically significant kernels and their combinations with respect to red and NIR (near infra-red) wavelengths
were determined using correlation analysis. Atmospherically corrected POLDER measured reflectances at red and NIR wavelengths
were regressed with different kernels and their combinations. It is found that the best fitting volume and GO kernel combinations
depend on forest type, wavelength and date. 相似文献
116.
The Gondwana basins of peninsular India are traditionally considered as extensional-rift basins due to the overwhelming evidence
of fault-controlled synsedimentary subsidence. These basins indeed originated under a bulk extensional tectonic regime, due
to failure of the attenuated crust along pre-existing zones of weakness inherited from Precambrian structural fabrics. However,
disposition of the basins and their structural architecture indicate that the kinematics of all the basins cannot be extensional.
To maintain kinematic compatibility with other basins as well as the bulk lateral extension, some basins ought to be of strike-slip
origin. The disposition, shape and structural architecture of the Satpura basin, central India suggest that the basin could
be a pull-apart basin that developed above a releasing jog of a left-stepping strike-slip fault system defined by the Son-Narmada
south fault and Tapti north fault in consequence to sinistral displacement along WSW-ENE. Development of a sedimentary basin
under the above-mentioned kinematic condition was simulated in model experiments with sandpack. The shape, relative size,
stratigraphic and structural architecture of the experimental basin tally with that of the Satpura basin. The experimental
results also provide insights into the tectono-sedimentary evolution of the Satpura basin in particular and pull-apart basins
in general. 相似文献
117.
The development of structural elements and finite strain data are analysed to constrain kinematics of folds and faults at
various scales within a Proterozoic fold-and-thrust belt in Pranhita-Godavari basin, south India. The first order structures
in this belt are interpreted as large scale buckle folds above a subsurface decollement emphasizing the importance of detachment
folding in thin skinned deformation of a sedimentary prism lying above a gneissic basement. That the folds have developed
through fixed-hinge buckling is constrained by the nature of variation of mesoscopic fabric over large folds and finite strain
data. Relatively low, irrotational flattening strain (X:Z-3.1-4.8, k<1) are associated with zones of near upright early mesoscopic
folds and cleavage, whereas large flattening strain (X:Z-3.9-7.3, k<1) involving noncoaxiality are linked to domains of asymmetric,
later inclined folds, faults and intense cleavage on the hanging wall of thrusts on the flanks of large folds. In the latter
case, the bulk strain can be factorized to components of pure shear and simple shear with a maximum shearing strain of 3.
The present work reiterates the importance of analysis of minor structures in conjunction with strain data to unravel the
kinematic history of fold-and-thrust belts developed at shallow crustal level. 相似文献
118.
Debarchana Ghosh 《The Professional geographer》2006,58(3):278-293
The Government of India considers prenatal care programs as a priority activity for promoting safe motherhood and child survival. It relies heavily on electronic mass media, including radio, television, and cinema to educate mothers—two‐thirds of whom are illiterate—about prenatal check‐ups and timing, iron prophylaxis, and tetanus toxoid injections. This study evaluated the effect of mothers' exposure to electronic mass media on knowledge and use of prenatal care services, using data from India's 1998–1999 National Family Health Survey. Multivariate logistic regressions were used to estimate the effects of media exposure by calculating odds ratios of each of the four response variables (complete prenatal care services, prenatal check‐ups, tetanus toxoid injections, and iron prophylaxes) for exposure to mass media. The results indicated that exposure to mass media is related to the use of prenatal care services even when other likely causes of the relationships are statistically controlled at their mean. The effect also showed a north‐south divide among the Indian States, being stronger in northern states as compared with southern states. 相似文献
119.
Methodologies are presented for minimization of risk in a river water quality management problem. A risk minimization model is developed to minimize the risk of low water quality along a river in the face of conflict among various stake holders. The model consists of three parts: a water quality simulation model, a risk evaluation model with uncertainty analysis and an optimization model. Sensitivity analysis, First Order Reliability Analysis (FORA) and Monte–Carlo simulations are performed to evaluate the fuzzy risk of low water quality. Fuzzy multiobjective programming is used to formulate the multiobjective model. Probabilistic Global Search Laussane (PGSL), a global search algorithm developed recently, is used for solving the resulting non-linear optimization problem. The algorithm is based on the assumption that better sets of points are more likely to be found in the neighborhood of good sets of points, therefore intensifying the search in the regions that contain good solutions. Another model is developed for risk minimization, which deals with only the moments of the generated probability density functions of the water quality indicators. Suitable skewness values of water quality indicators, which lead to low fuzzy risk are identified. Results of the models are compared with the results of a deterministic fuzzy waste load allocation model (FWLAM), when methodologies are applied to the case study of Tunga–Bhadra river system in southern India, with a steady state BOD–DO model. The fractional removal levels resulting from the risk minimization model are slightly higher, but result in a significant reduction in risk of low water quality. 相似文献
120.
Many Large Eddy Simulation (LES) models use the classic Kessler parameterisation either as it is or in a modified form to model the process of cloud water autoconversion into precipitation. The Kessler scheme, being linear, is particularly useful and is computationally straightforward to implement. However, a major limitation with this scheme lies in its inability to predict different autoconversion rates for maritime and continental clouds. In contrast, the Berry formulation overcomes this difficulty, although it is cubic. Due to their different forms, it is difficult to match the two solutions to each other. In this paper we single out the processes of cloud conversion and accretion operating in a deep model cloud and neglect the advection terms for simplicity. This facilitates exact analytical integration and we are able to derive new expressions for the time of onset of precipitation using both the Kessler and Berry formulations. We then discuss the conditions when the two schemes are equivalent. Finally, we also critically examine the process of droplet evaporation within the framework of the classic Kessler scheme. We improve the existing parameterisation with an accurate estimation of the diffusional mass transport of water vapour. We then demonstrate the overall robustness of our calculations by comparing our results with the experimental observations of Beard and Pruppacher, and find excellent agreement. 相似文献