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111.
Natural Hazards - Dhanbad is the largest producer of coal in the state of Jharkhand, India, and hence, it is one of the most important cities in the country. Considering the present-day importance... 相似文献
112.
Landslide susceptibility map delineates the potential zones for landslides occurrence. The paper presents a statistical approach through spatial data analysis in GIS for landslide susceptibility mapping in parts of Sikkim Himalaya. Six important causative factors for landslide occurrences were selected and corresponding thematic data layers were prepared in GIS. Topographic maps,satellite image,field data and published maps constitute the input data for thematic layer preparation. Numerical weights for different categories of these factors were determined based on a statistical approach and the weighted thematic layers were integrated in GIS environment to generate the landslide susceptibility map of the area. The landslide susceptibility map classifies the area into five different landslide susceptible zones i.e.,very high,high,moderate,low and very low. This map was validated using the existing landslide distribution in the area. 相似文献
113.
S. S. De B. K. Sarkar B. Ghosh A. C. Sen S. Bandyopadhyay S. K. Adhikari 《Earth, Moon, and Planets》1991,53(1):1-10
Enhancement of conductivity tensor modification within the ionospheric plasma by electron density modulation through the temperature dependence of the recombination rates of different ionspecies caused due to electron temperature modulation during high-power wave propagation is studied. Variation of Hall and Pedersen conductivities of the ionosphere has been investigated in the height range between 85 km to 250 km. The generation of waves at the modulation frequency and its harmonics in the ELF, VLF bands in the process is discussed. 相似文献
114.
A new motion coordination algorithm for an autonomous underwater vehicle-manipulator system (UVMS) is proposed. This algorithm generates the desired trajectories for both the vehicle and the manipulator in such a way that the total hydrodynamic drag on the system is minimized. Resolution of kinematic redundancy of the system is performed at the acceleration level so that this algorithm can be incorporated into the system dynamics. The dynamics of the UVMS are modeled using a quasi-Lagrange approach. A state-space formulation of the system along with a model-based controller design for trajectory-following tasks that includes thruster dynamics is also presented. The computer simulation results demonstrate the effectiveness of this proposed method in reducing the drag on the system 相似文献
115.
Arnoldo Valle-Levinson Nandita Sarkar Rosario Sanay Doris Soto Jorge León 《Estuaries and Coasts》2007,30(1):113-126
Underway current velocity profiles were combined with temperature and salinity profiles at fixed stations to describe tidal
and subtidal flow patterns in the middle of the northernmost Chilean fjord, Estuario Reloncaví. This is the first study involving
current velocity measurements in this fjord. Reloncaví fjord is 55 km long, 2 km wide, and on average is 170 m deep. Measurements
concentrated around a marked bend of the coastline, where an 8-km along-fjord transect was sampled during a semidiurnal tidal
cycle in March 2002 and a 2-km cross-fjord transect was occupied, also during a semidiurnal cycle, in May 2004. The fjord
hydrography showed a relatively thin (<5 m deep), continuously stratified, buoyant layer with stratification values >4 kg
m−3 per meter of depth. Below this thin layer, the water was relatively homogeneous. Semidiurnal tidal currents had low amplitudes
(<10 cm s−1) that allowed the persistence of a surface front throughout the tidal cycle. The front oscillated with a period of ca. 2.5
h and showed excursions of 2 km. The front oscillations could have been produced by a lateral seiche that corresponds to the
natural period of oscillation across the fjord. This front could have also caused large (2 h) phase lags in the semidiurnal
tidal currents, from one end of the transect to the other, within the buoyant layer. Tidal phases were relatively uniform
underneath this buoyant layer. Subtidal flows showed a 3-layer pattern consisting of a surface layer (8 m thick, of 5 cm s−1 surface outflow), an intermediate layer (70 m thick, of 3 cm s−1 net inflow), and a bottom layer (below 80 m depth, of 3 cm s−1 net outflow). The surface outflow and, to a certain extent, the inflow layer were related to the buoyant water interacting
with the ambient oceanic water. The inflowing layer and the bottom outflow were attributed to nonlinear effects associated
with a tidal wave that reflects at the fjord's head. The weak subtidal currents followed the morphology of the bend and caused
downwelling on the inside and upwelling on the outside part of the bend. 相似文献
116.
Santanu Banerjee S.K. Bhattacharya Subir Sarkar 《Journal of Asian Earth Sciences》2007,29(5-6):823-831
Variations of carbon and oxygen isotopic ratios in response to cyclical sea level fluctuations have been documented from a Paleoproterozoic peritidal stromatolite succession. The upper division of the Kajrahat Limestone, Vindhyan Supergroup of central India consists of several shallowing upward stromatolite cycles identified by regular and systematic changes in stromatolite size. Normally, larger stromatolites are followed upward in the succession by smaller stromatolites and microbial laminites that occupy the top of the cycle. Desiccation cracks are found in all the facies indicating subaerial exposure. We investigated the stable isotope compositional variations across nine complete stromatolite cycles showing frequent subaerial emergence. Carbon and oxygen isotopic values of the limestones, in general, are comparable to contemporary marine values available from earlier studies but show regular depletion in response to shallowing of the water level. The δ13C and δ18O values of the limestones vary within an individual stromatolite cycle; depleted values characterize the topmost part of the cycles. The isotope pattern is explained by micritic carbonate deposition in different sub environments of the shallow marine domain having different salinity and variable duration of exposure. These variations also probably caused the observed scatter in δ13C and δ18O values of supratidal microbial laminites. 相似文献
117.
A statistical investigation has been made about the flare-process in relation to the photospheric magnetic field and configuration. It is understood from the analysis that the flare energy bears a linear relationship with the rate of change of flux of the longitudinal component of photospheric magnetic field. 相似文献
118.
119.
Combining neural network with fuzzy,certainty factor and likelihood ratio concepts for spatial prediction of landslides 总被引:6,自引:0,他引:6
The landslide studies can be categorized as pre- and postdisaster studies. The predisaster studies include spatial prediction
of potential landslide zones known as landslide susceptibility zonation (LSZ) mapping to identify the areas/locales susceptible
to landslide hazard. The LSZ maps provide an assessment of the safety of existing habitations and infrastructural/functional
elements and help plan further developmental activities in the hilly regions. Landslides are one of the natural geohazards
that affect at least 15% of land area of India. Different types of landslides occur frequently in geodynamical active domains
of the Himalayas. In India, various techniques have been developed and adopted for LSZ mapping of different regions. However,
the technique for LSZ mapping is not yet standardized. The present research is an attempt in this direction only. In our earlier
work (Kanungo et al. 2006), a detailed study on conventional, artificial neural network (ANN)- black box-, fuzzy set-based and combined neural and
fuzzy weighting techniques for LSZ mapping in Darjeeling Himalayas has been documented. In this paper, other techniques such
as combined neural and certainty factor concept along with combined neural and likelihood ratio techniques have been assessed
in comparison with combined neural and fuzzy technique for the preparation of LSZ maps of the same study area in parts of
Darjeeling Himalayas. It is observed from the present study that the LSZ map produced using combined neural and fuzzy approach
appears to be the most accurate one as in this case only 2.3% of the total area is found to be categorized as very high susceptibility
zone and contains 30.1% of the existing landslide area. This approach can serve as one of the key objective approaches for
spatial prediction of landslide hazards in hilly terrain. 相似文献
120.
Sudip Dey Chandrani Debbarma Prasamita Sarkar Muh Aris Marfai 《Arabian Journal of Geosciences》2011,4(5-6):899-906
This paper discusses an experiment on digital imaging and visualizing the surface condition of the sediment depositions. For that purpose, a part of South Tripura district was selected as sampling site. Physically, the selected area is located in a fold belt and preserves the history of Tertiary–Quaternary landform evolution in the main types of sediment depositions. Three samples, each from the different types of Tertiary depositions, were finally taken for thick section making, optical microscopy under reflected light, and soft computing. Geometric optical measurement and physical optical measurement were done to understand the surface condition of Bokabil, Tipam, and Duplitila samples by bidirectional reflectance distribution function and radiometric scales (within 0–255 digital number values). Maximum surface smoothness or near-perfect reflection surface was measured by brightness–contrast slicing operation. 相似文献