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211.
212.
Md Soyeb Alam Dheeraj Kumar R. S. Chatterjee Vijay Upreti 《Journal of the Indian Society of Remote Sensing》2018,46(10):1569-1580
Differential interferometric synthetic aperture radar (DInSAR) is a novel remote sensing technique to measure earth surface deformation. It is capable of obtaining dense information related to the deformation of a large area efficiently, economically and effectively. Therefore, DInSAR is a promising technology for monitoring the earth surface deformation related to some natural hazardous events, such as earthquake, volcano eruption, land subsidence, landslide. In present study, Conventional DInSAR technique have been applied to a mineral rich zone, coming under the Khetri copper belt, a part of Northern Aravali range of hillocks in India, predominant with mining activities since late 1960’s to address the possibility of deformation phenomena due to hard rock underground metal mining. Four interferometric SAR data sets of Radarsat-2 was used for the study area to address the subsidence/uplift phenomena. Further, results obtained from conventional DInSAR technique using Radarsat-2 data sets compared with results obtained from ground based observation technique for its validity. In both the techniques, deformation results obtained in terms of average subsidence rate in mm (quarterly basis) of points under study within mining zone of Mine-A has well agreed to each other. Further, it has been observed that average subsidence rate in mm (quarterly basis) obtained from space based observation and ground based observation are 5.6 and 6.67, respectively over the points under study in mining zone of Mine-A. 相似文献
213.
The generation of internal gravity waves by barotropic tidal flow passing over a two-dimensional topography is investigated. Rather than calculating the conversion of tidal energy, this study focuses on delineating the geometric characteristics of the spatial structure of the resulting internal wave fields (i.e., the configurations of the internal beams and their horizontal projections) which have usually been ignored. It is found that the various possible wave types can be demarcated by three characteristic frequencies: the tidal frequency, ω0; the buoyancy frequency, N; and the vertical component of the Coriolis vector or earth's rotation, f. When different possibilities arising from the sequence of these frequencies are considered, there occur 12 kinds of wave structures in the full 3D space in contrast to the 5 kinds identified by the 2D theory. The constant wave phase lines may form as ellipses or hyperbolic lines on the horizontal plane, provided the buoyancy frequency is greater or less than the tidal frequency. The effect that stems from the consideration of the basic flow is also found, which not only serves as the reason for the occurrence of higher harmonics but also increases the wave strength in the direction of basic flow. 相似文献
214.
Hourly air temperature driven using multi-layer perceptron and radial basis function networks in arid and semi-arid regions 总被引:2,自引:0,他引:2
Mehdi Rezaeian-Zadeh Shahrookh Zand-Parsa Hirad Abghari Masih Zolghadr Vijay P. Singh 《Theoretical and Applied Climatology》2012,109(3-4):519-528
This study employed two artificial neural network (ANN) models, including multi-layer perceptron (MLP) and radial basis function (RBF), as data-driven methods of hourly air temperature at three meteorological stations in Fars province, Iran. MLP was optimized using the Levenberg–Marquardt (MLP_LM) training algorithm with a tangent sigmoid transfer function. Both time series (TS) and randomized (RZ) data were used for training and testing of ANNs. Daily maximum and minimum air temperatures (MM) and antecedent daily maximum and minimum air temperatures (AMM) constituted the input for ANNs. The ANN models were evaluated using the root mean square error (RMSE), the coefficient of determination (R 2) and the mean absolute error. The use of AMM led to a more accurate estimation of hourly temperature compared with the use of MM. The MLP-ANN seemed to have a higher estimation efficiency than the RBF ANN. Furthermore, the ANN testing using randomized data showed more accurate estimation. The RMSE values for MLP with RZ data using daily maximum and minimum air temperatures for testing phase were equal to 1.2°C, 1.8°C, and 1.7°C, respectively, at Arsanjan, Bajgah, and Kooshkak stations. The results of this study showed that hourly air temperature driven using ANNs (proposed models) had less error than the empirical equation. 相似文献
215.
Anoop Kumar Mishra Rakesh M. Gairola Vijay K. Agarwal 《Journal of the Indian Society of Remote Sensing》2012,40(1):65-74
In the present study an attempt has been made to improve the rainfall estimation technique developed recently by Mishra et
al. (2009a, 2009b) based on KALPANA and Tropical Rainfall Measuring Mission (TRMM)-Precipitation Radar (PR) data over the Indian land and oceanic
region. The algorithm for rainfall estimation was basically based on synergistically analyzing the thermal infra-red radiances
from Kalpana/INSAT data along with the high resolution, horizontal and vertical rainfall estimates from PR. Presently the
augmentation is based on the data base of precipitable water and relative humidity from National Centre for Environmental
Prediction-Global forecast System (NCEP-GFS) data as a background field to correct for the biases in earlier algorithm. The
algorithm is tested for many case studies of monsoon rainfall over India and adjoining oceanic regions. The rainfall from
the present scheme is compared with the standard TRMM-3B42 rain product. The validation with the Automatic Weather Station
(AWS) rain gauge and the Global Precipitation and Climatology Project (GPCP) version 2 rain products shows that the present
scheme is able to retrieve the rainfall with a very good accuracy. These studies are aimed at the rainfall retrievals in near
future from both INSAT-3D and Megha-Tropiques, IR and MW imagers respectively. 相似文献
216.
A radio survey, using the Very Large Array at 20 and 90 cm λ has been carried out in the direction of 46 distant Abell clusters
(0.1 ≲ z ≲ 0.3) dominated by a cD galaxy (clusters classified to be Bautz-Morgan I type). A radio source coincident with the
cD galaxy was detected in 16 clusters. We find that the radio luminosity function of the cD galaxies at 20cm λ, and below
the luminosityP
1.4ghz ≲ 1024.5 W Hz-1, is similar to that of brightest ellipticals in less clustered environments. Above this luminosity, the cDs seem to have
a higher probability of becoming radio sources. The effect of optical brightness on radio emission is shown to be the same
for the two classes. No significantly large population of very-steep-spectrum sources with spectral index α >1.2 (flux density
∝ frequency-α) was found to be associated with cD galaxies. A significant negative correlation is found between the radio luminosity of
the cD galaxy and the cooling-time of the intra cluster medium near the galaxy. We also present evidence that the probability
of radio emission from first-ranked galaxies is dependent upon their location relative to the geometrical centres of clusters
and thus related to the morphological class and the evolutionary state of the clusters. We argue that both these effects are
primarily caused by the dynamical evolution of these distant clusters of galaxies. 相似文献
217.
Here the stability of triangular libration points when both the attracting bodies are radiating as well has been investigated under the non-resonance cases. It is found that except for some cases for all values of the radiation reduction factors and for all values of <0.0285954..., the motion will be stable. 相似文献
218.
We investigate the stability of the triangular libration points when both the attracting bodies are radiating under the resonance conditions 1 = 22 and 32. 相似文献
219.
Settlement of compacted ash fills 总被引:1,自引:0,他引:1
The coal ash is a by-product of coal-fired thermal power station. It is extensively used as a geo-material for landfill. The
compacted ash is used as a structural fill if it is properly characterized for load-bearing capacity and settlement. The main
objective of the present work is to characterize ash material and to evaluate its settlement characteristics. The ash is normally
compacted by vibration at or near optimum moisture for its performance as structural fill. The overt characteristics of ashes
are viewed similar to cohesionless soils. However, the mass behavior may have differences due to the subtle influence of chemical
and physical processes involved in its formation. The empirical and analytical methods predicting settlement of footing under
static loading require direct or indirect measurement of density and stress state in the deposit. In the present work, experimental
investigations for settlement prediction were carried out on compacted coal ash produced at Ropar thermal power station in
India, which was conveniently classified as ASTM class F ash. The settlement was experimentally obtained for the rigid plates having least dimension more than 0.3 m on ashes compacted
at varying degree of compaction. The predicted settlement based on the observed data of coal ash using conventional techniques
for soils was found to be conservative. A relationship between settlement and foundation size is proposed at varying compaction
to obtain the settlement of compacted ash. At a higher degree of compaction, the settlement of a foundation may not exceed
the allowable settlements in the working stress range. 相似文献
220.
Vijay P. SINGH 《国际泥沙研究》2003,18(3)
Hydraulic geometry is of fundamental importance in planning, design, and management of river engineering and training works. Although some concepts of hydraulic geometry were proposed toward the end of the nineteenth century, the real impetus toward formulating a theory of hydraulic geometry was provided by the work of Leopold and Maddock (1953). A number of theories have since been proposed. Some of the theories are interrelated but others are based on quite different principles. All theories, however, assume that the river flow is steady and uniform and the river tends to attain a state of equilibrium or quasi-equilibrium. The differences are due to the differences in hydraulic mechanisms that the theories employ to explain the attainment of equilibrium by the river. 相似文献