全文获取类型
收费全文 | 421篇 |
免费 | 5篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 36篇 |
大气科学 | 33篇 |
地球物理 | 88篇 |
地质学 | 188篇 |
海洋学 | 10篇 |
天文学 | 64篇 |
综合类 | 7篇 |
自然地理 | 4篇 |
出版年
2022年 | 11篇 |
2021年 | 7篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 36篇 |
2017年 | 25篇 |
2016年 | 18篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 39篇 |
2012年 | 18篇 |
2011年 | 15篇 |
2010年 | 14篇 |
2009年 | 23篇 |
2008年 | 18篇 |
2007年 | 18篇 |
2006年 | 14篇 |
2005年 | 10篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 3篇 |
1969年 | 1篇 |
排序方式: 共有430条查询结果,搜索用时 515 毫秒
21.
An attempt has been made to delineate different hydrogeomorphological units in and around the immediate environs of Jhansi city with a view to attempt a correlation between the well yields and hydrogeomorphic units using satellite remote sensing technique. In general, a positive correlation is observed between the geomorphic units and the borewell yields with overlapping yields at the margin. The pediment residual hill complex is observed to provide wells with discharges ranging from 100 gallons per hour (gph) to 5000 gph, while the wells drilled in shallow weathered, buried pediplain has yields in the range of 2000 to 10000 gph moderately weathered, buried pediplain has discharges in the range of 8000 to 12000 gph, and deeply weathered, buried pediplain has discharges in excess of 12000 gph. 相似文献
22.
Shwetambar Mishra 《Pure and Applied Geophysics》1973,104(1):523-529
Summary The solution of the title problem has been obtained for stress free boundaries of the layer. 相似文献
23.
In this paper we have taken an attempt to study the feasibility of scale invariant theory (Wesson, 1981a,b) in Bianchi type
VIII and IX space-times with a time dependent gauge function (Dirac Gauge i.e. βα
)and a matter field in the form of a perfect fluid. It is found that Bianchi type VIII (δ=1) space-time is feasible in this
theory whereas Bianchi type IX (δ=-1) space-time is not feasible. In this feasible case a radiating model is constructed and
its physical behaviour is discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
24.
An attempt has been made to solve the field equations with perfect fluid in an inhomogeneous space-time governed by the metric
in both Einstein and Barber's theories of gravitation. It is shown here that in both the theories the field equations are
reducible to a Laplace equation and the perfect fluid distribution does not survive. Moreover all the solutions represent
plane gravitational wave and the vacuum models in both the theories can be constructed by an arbitrary harmonic function iny and z coordinates.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
25.
K. K. Singh V. D. Mishra R. K. Garg 《Journal of the Indian Society of Remote Sensing》2007,35(3):243-251
Snow cover is an important variable for climatic and hydrologic models due to its effects on surface albedo, energy, and moisture budgets. Passive microwave sensors can be used to monitor temporal and spatial variations in large-scale snow cover parameters, avoiding problems of cloud cover and polar nights. In the present study, brightness temperature values were estimated (using calibration curves) for moist snow on natural and blackbody/metal surface. TB response on snow depth, density, SWE and angular variation from nadir were measured and found that TB decreases with increase of snow depth and with increase of angle from nadir. Empirical relations were used to estimate emissivity, dielectric constant and dielectric loss factor. It was observed that emissivity decreases with the increase of dielectric constant. The dielectric constant and dielectric loss factor both increases with the increase of density. Experiments were performed during winter of year 2005 at Dhundi and Solang (H.P.), India, using ground based passive microwave radiometer having 6.9 and 18.7 GHz antenna frequencies at dual polarization. 相似文献
26.
J. N. Mutemi L. A. Ogallo T. N. Krishnamurti A. K. Mishra T. S. V. Vijaya Kumar 《Meteorology and Atmospheric Physics》2007,95(1-2):87-113
Summary This study examines the predictability of weather over several regions in Africa using a multimodel superensemble technique
developed at the Florida State University, which is an objective means of combining daily forecasts from multilevel global
models. It is referred to as FSUSE and up to 7 different models are used to construct the superensemble. The benchmark reanalysis
fields used are the precipitation data sets from CMORPH and all other global fields from ECMWF daily operational analysis.
The FSUSE works by using multiple linear regression to derive weights from a comparison of each member model forecast to the
benchmark analysis during a training period of the most recent 120 days, and these weights are passed to the forecast phase.
This procedure removes the bias of each model and allows for an optimal linear combination of the individual model forecasts
by taking account of the relative skill of each model to give a consensus forecast that is superior to the ensemble mean and
all the members.
Results show that bad models and poor analysis fields used during the training phase degrade the skill of the FSUSE. In the
forecasts of rainfall events over all regions of Africa, the FSUSE root-mean-square (R M S) error, equitable threat skill
score (E T S), and bias on the daily forecasts of rainfall were invariably superior to the best member model. The skills deteriorate
as the forecast lead time in days increases, with the degradation being most significant beyond day 3. In all cases, the bias
score of the FSUSE was approximately 1, while the anomaly correlation scores were to the order of 0.9. These scores indicate
the robustness of the FSUSE forecasts. Over East Africa, the FSUSE forecasts were consistent with the spatial-temporal pattern
of the Intertropical Convergence Zone (ITCZ), the main rain bearing synoptic mechanism across tropical Africa. Thus, in addition
to superior forecasts, the use of FSUSE based data sets may provide a better understanding of the dynamical processes within
the ITCZ over the region.
These results could be further improved if the daily series of operational analysis had included gauge data and if the resolution
were higher. It is hardly possible to get uniformly consistent and continuous daily observations over these diverse regions
of Africa. However, given the availability of the satellite based estimates of daily rainfall, such as CMORPH and global analysis
that are exchanged very fast nowadays, the FSUSE scheme for numerical weather predictions (N W P) provides useful medium range
weather forecasts in real-time. 相似文献
27.
D. Subrahmanyam M. K. Tandon L. George S. K. Mishra 《Pure and Applied Geophysics》1981,119(5):901-912
The role of barotropic processes in the development of a monsoon depression, formed on 5 July 1979 during MONEX observational period, is studied by considering it as a quasi-geostrophic divergent barotropic instability problem of zonal flow of 3 July 1979 at 700 mb level. Numerical solutions are obtained by initial value approach. The preferred wave has a wavelength of 2750 km, an e-folding time of 4.3 days, a period of 6.5 days and an eastward phase speed of 4.9 ms–1. Structure of preferred wave is found to be in good agreement with the observed horizontal structure of the depression at 700 mb. Poleward momentum transports are found to predominate over equatorward transports.Parts of this paper were presented at the National Symposium on Early Results of MONEX-1979. 9–12 March 1981, in New Delhi, India. 相似文献
28.
S.K. Mishra 《International Journal of Mineral Processing》1979,6(2):119-132
Electrokinetic and flotation studies on apatites and calcite show that under certain conditions these minerals are floatable with dodecylamine chloride (DDACl) and the possible mode of DDACl adsorption is due to Coulombic and Van der Waals forces. The results indicate hemi-micelle formation of dodecylamine ions and suggest involvement of neutral molecular amine in the hemi-micelle structure, the critical hemi-micelle concentration being influenced by the nature of charge at the mineral surface. 相似文献
29.
Ruchi Mishra 《Planetary and Space Science》2006,54(2):188-199
Dispersion relation, resonant energy transferred, growth rate and marginal instability criteria for the electrostatic ion-cyclotron wave with general loss-cone distribution in low-β anisotropic, homogeneous plasma in the auroral acceleration region are discussed by investigating the trajectories of the charged particles. Effects of the parallel electric field, ion beam velocity, steepness of the loss-cone distribution and temperature anisotropy on resonant energy transferred and growth rate of the instability are discussed. It is found that the effect of the parallel electric field is to stabilize the wave and enhance the transverse acceleration of ions whereas the effect of steepness of loss-cone, ion beam velocity and the temperature anisotropy is to enhance the growth rate and decrease the transverse acceleration of ions. The steepness of the loss-cone also introduces a peak in the growth rate which shifts towards the lower side of the perpendicular wave number with the increasing steepness of the loss-cone. 相似文献
30.
Bhoopesh Mishra Maxim Boyanov Shelly D. Kelly Jeremy B. Fein 《Geochimica et cosmochimica acta》2010,74(15):4219-9603
Bulk Cd adsorption isotherm experiments, thermodynamic equilibrium modeling, and Cd K edge EXAFS were used to constrain the mechanisms of proton and Cd adsorption to bacterial cells of the commonly occurring Gram-positive and Gram-negative bacteria, Bacillus subtilis and Shewanella oneidensis, respectively. Potentiometric titrations were used to characterize the functional group reactivity of the S. oneidensis cells, and we model the titration data using the same type of non-electrostatic surface complexation approach as was applied to titrations of B. subtilis suspensions by Fein et al. (2005). Similar to the results for B. subtilis, the S. oneidensis cells exhibit buffering behavior from approximately pH 3-9 that requires the presence of four distinct sites, with pKa values of 3.3 ± 0.2, 4.8 ± 0.2, 6.7 ± 0.4, and 9.4 ± 0.5, and site concentrations of 8.9(±2.6) × 10−5, 1.3(±0.2) × 10−4, 5.9(±3.3) × 10−5, and 1.1(±0.6) × 10−4 moles/g bacteria (wet mass), respectively. The bulk Cd isotherm adsorption data for both species, conducted at pH 5.9 as a function of Cd concentration at a fixed biomass concentration, were best modeled by reactions with a Cd:site stoichiometry of 1:1. EXAFS data were collected for both bacterial species as a function of Cd concentration at pH 5.9 and 10 g/L bacteria. The EXAFS results show that the same types of binding sites are responsible for Cd sorption to both bacterial species at all Cd loadings tested (1-200 ppm). Carboxyl sites are responsible for the binding at intermediate Cd loadings. Phosphoryl ligands are more important than carboxyl ligands for Cd binding at high Cd loadings. For the lowest Cd loadings studied here, a sulfhydryl site was found to dominate the bound Cd budgets for both species, in addition to the carboxyl and phosphoryl sites that dominate the higher loadings. The EXAFS results suggest that both Gram-positive and Gram-negative bacterial cell walls have a low concentration of very high-affinity sulfhydryl sites which become masked by the more abundant carboxyl and phosphoryl sites at higher metal:bacteria ratios. This study demonstrates that metal loading plays a vital role in determining the important metal-binding reactions that occur on bacterial cell walls, and that high affinity, low-density sites can be revealed by spectroscopy of biomass samples. Such sites may control the fate and transport of metals in realistic geologic settings, where metal concentrations are low. 相似文献