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211.
M. N. Das 《Geotechnical and Geological Engineering》1986,4(1):79-87
Conclusions The post-failure slope immediately after strength failure decreases on the negative side with the increase inw/h ratio. Atw/h equal to around 10 or 11 this slope becomes almost zero and then again the slope increases but on the positive side with further increase inw/h ratio.At loww/h ratios, the post-failure characteristic touches the abscissa ultimately. Forw/h greater than 4 or 6 after an initial fall, the broken mass starts reconsolidation on further loading due to high lateral constraints provided at the centre and the curve starts rising again. Forw/h ratios greater than 10 or 11, there is no loss in the post-failure strength. 相似文献
212.
Rock samples belonging to ten lithological types under different stages of weathering, were collected from different stratigraphical
horizons at Bhagalpur. Their densities and porosities were determined experimentally and the data obtained were fitted empirically
in a linear equation for each lithological type. The slopes of the curves, which were negative in each case, showed that the
increase in porosity for the same decrease in density were in the order, white sandstone > ferruginous sandstone > white claystone
> porphyritic gneiss > quartzite > pegmatite > amphibolite ≅ biotite gnejss > basalt ≅ dolerite. A new weathering potential
index based on the density-porosity data was proposed and the values for a specific stage of weathering for all the lithological
types studied fall within the same range. 相似文献
213.
Extraction and subsequent loss of silver from leach liquor during oxidative ammonia leaching of complex sulphide and chalcopyrite concentrates have been observed. The lost silver value from the leach liquor was unrecoverable when the residues were treated with ammonia-ammonium sulphate buffer (pH=9.5) solutions at 27°C. However, when the same slurry was heated to 75°C in an autoclave under an atmosphere of oxygen, almost all the silver value could be redissolved. The leach residues lost their silver absorbance property from ammoniacal solutions on repeatedly heating and cooling the leached slurries in the presence of oxygen. In this work, silver losses from ammoniacal solutions on various leach residues, synthetic iron oxides, and freshly precipitated Fe(II) and Fe(III) hydroxides are reported. None of the major constituents present in the leach residues were responsible for the silver losses but small amounts of Fe(II) associated with the residues could take up silver from the leach solutions. 相似文献
214.
This paper is an analysis of the historical change in city size distribution in India from the perspectives provided by Zipf and Jefferson. Rank-size distribution at national level and primate city-size distribution at regional levels are examined. India's national urban system is gradually evolving towards Zipf's rank-size distribution. But primate cities have persisted in three of the four macro-regions in India. The paper also examines, in the Indian context, the relation between rank-size distribution and an integrated urban system, and the normative nature of the latter as a spatial organization of human society. Finally, we have made a modest attempt to locate the research on city-size distribution, especially Berry's system-theoretic interpretation of rank-size distribution, on the realm of the political economy of urbanization. 相似文献
215.
The feasibility of differentiating four oil-seed crops viz., mustard, toria, yellow sarson and sunflower, based on their spectral reflectance in the visible and near infra red region was studied in a field experiment, The spectral vegetative index profiles, generated during the growth period of different oil seed crops indicated two vegetative growth peaks and a depression between the two peaks, due to the conspicuous yellow colour of flowers, which masked the green leaves. The magnitude of such depression in the spectral vegetation indices viz., ‘Greenness’ and ‘Perpendicular Vegetation Index’ (PVI), were of higher magnitude in yellow sarson. The flowering period parameters viz., flowering time, duration and intensity, deduced from the spectral vegetation indices were found to be beneficial in differentiating different oil-seed crops by remote sensing. A plot of ‘Brightness’ vs. ‘Greenness’ values determined during the growth of the crops formed typical clusters. The cluster representing toria crop was significantly different from the other crops, thereby making toria identifiable from others by remote sensing. 相似文献
216.
U. C. Mohanty N. V. Sam S. Das A. N. V. Satyanarayana 《Journal of Earth System Science》2003,112(2):147-163
Convective activity is one of the major processes in the atmosphere influencing the local and large-scale weather in the tropics.
The latent heat released by the cumulus cloud is known to drive monsoon circulation, which on the other hand supplies the
moisture that maintains the cumulus clouds. An investigation is carried out on the convective structure of the atmosphere
during active and suppressed periods of convection using data sets obtained from the Bay of Bengal and Monsoon Experiment
(BOBMEX). The cumulus convection though being a small-scale phenomenon, still influences its embedding environment by interaction
through various scales. This study shows the variation in the kinematic and convective parameters during the transition from
suppressed to active periods of convection. Convergence in the lower levels and strong upward vertical velocity, significant
during active convection are associated with the formation of monsoon depressions. The apparent heat source due to latent
heat release and the vertical transport of the eddy heat by cumulus convection, and the apparent moisture sink due to net
condensation and vertical divergence of the eddy transport of moisture, are estimated through residuals of the thermodynamic
equation and examined in relation to monsoon activity during BOBMEX. 相似文献
217.
The atmospheric correction bands 7 and 8 (765nm and 865nm respectively) of the Indian Remote Sensing Satellite IRS P4-0CM
(Ocean Colour Monitor) can be used for deriving aerosol optical depth (AOD) over the oceans. A retrieval algorithm has been
developed which computes the AOD using band 7 data by treating the ocean surface as a dark background after removing the Rayleigh
path radiance in the sensor-detected radiances. This algorithm has been used to detect marine aerosol distributions at different
coastal and offshore locations around India.
A comparison between OCM derived AOD and the NOAA operational AOD shows a correlation ∼0.92 while that between OCM derived
AOD and the ground-based sun photometer measurements near the coast of Trivandrum shows a correlation of ∼0.90. 相似文献
218.
Bearing capacity of strip foundation on geogrid-reinforced sand 总被引:1,自引:0,他引:1
E. C. Shin B. M. Das E. S. Lee C. Atalar 《Geotechnical and Geological Engineering》2002,20(2):169-180
Results of small-scale laboratory model tests to determine the ultimate bearing capacity of a strip foundation supported by sand with multiple layers of geogrid reinforcement are presented. Tests were conducted with only one type of geogrid and a sand compacted to one relative density. The embedment ratio of the foundation was varied from zero to 0.6. It is found that, for the given reinforcement-depth ratio, the bearing capacity ratio with respect to ultimate load increases with embedment. The relationship between the bearing capacity ratio at ultimate load and at limited levels of settlement (less than or equal to 5% of foundation width) is also presented. The bearing capacity ratio at limited levels of settlement is smaller than the value at ultimate load. 相似文献
219.
Anup Kumar Das Saumitra Mukherjee 《Journal of the Indian Society of Remote Sensing》2002,30(3):149-156
In the present study an attempt has been made in order to evaluate the weathering and erosional status of a part of the Konkan coast stretching between Mumbai and Rajpuri, using IRS-IB, LISS-II data supported by spectral reflectance and thin section study of the rock samples collected from the coastal plains. The study revealed that extensive erosion has been taking place in few pockets along the Konkan Coastal plain, which is evidenced by the presence of more weathered rocks in the coastal plains as compared to that of the hinterland, siltation of the coastal wetlands due to the deposition of eroded materials and high-suspended sediments in the coastal water. The thin section study of the basaltic rock samples collected from the coast also shows evidence of physical and chemical weathering. The lineaments of the coastal tract are found to exist in clusters mostly trending towards NNE—SSW and a few N—S trending, this supports the presence of a N-S trending fault parallel to the Konkan coast along the Western Ghats. It has also been found that remote sensing, in association with other conventional techniques is ideal for such type of studies. 相似文献
220.
D. Ray S. Ghosh H. Chennaoui Aoudjehane S. Das 《Meteoritics & planetary science》2019,54(12):3082-3088
The Agoudal IIAB iron meteorite exhibits only kamacite grains (~6 mm across) without any taenite. The kamacite is homogeneously enriched with numerous rhabdite inclusions of different size, shape, and composition. In some kamacite domains, this appears frosty due to micron‐scale rhabdite inclusions (~5 to 100 μm) of moderate to high Ni content (~26 to 40 wt%). In addition, all the kamacite grains in matrix are marked with a prominent linear crack formed during an atmospheric break‐up event and subsequently oxidized. This feature, also defined by trails of lowest Ni‐bearing (mean Ni: 23 wt%) mm‐scale rhabdite plates (fractured and oxidized) could be a trace of a pre‐existing γ–α interface. Agoudal experienced a very slow rate of primary cooling ~4 °C Ma?1 estimated from the binary plots of true rhabdite width against corresponding Ni wt% and the computed cooling rate curves after Randich and Goldstein (1978). Chemically, Agoudal iron (Ga: 54 ppm; Ge: 140 ppm; Ir: 0.03 ppm) resembles the Ainsworth iron, the coarsest octahedrite of the IIAB group. Agoudal contains multiple sets of Neumann bands that are formed in space and time at different scales and densities due to multiple impacts with shock magnitude up to 130 kb. Signatures of recrystallization due to postshock low temperature mild reheating at about 400 °C are also locally present. 相似文献