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631.
The scope of this study is to evaluate the parameters of the gypsum–anhydrite strata karstification under the influence of
the quarry exploitation of Jaziv sulphur field (West Ukraine) accompanying by drainage. The quarry drainage provoked the enormous
depression cone forming with 100 km2 in area and the corresponding intensification of chemical denudation of the gypsum–anhydrite strata. The gypsum karstification
rate for the 29-year period of the quarry drainage was 0.06% with the dissolved rock volume of 1,328,507 m3 that is about 80 times higher than in natural conditions. For the drainage period (29 years) the karst denudation rate was
17,952 m3/km2 against the natural background of 231.3 m3/km2. The absolute value of artificial denudation for the studied massif area is 1.79 cm for 29 years or 0.062 mm/year while the
denudation rate under natural conditions would be 0.231 cm for 29 years or 0.0008 mm/year. The forecasted volumes of the surface-evident
collapses are evaluated using the relationship between the calculated amount of dissolved sulphate rocks and volumes of the
current surface-evident collapses. According to this evaluation, the current collapses correspond to about 34% only from the
dissolved rocks volume calculated for the drainage period. 相似文献
632.
Application of neural network and MODIS 250m imagery for estimating suspended sediments concentration in Hangzhou Bay,China 总被引:1,自引:0,他引:1
Suspended sediments concentration (SSC) in surface water derived from bottom sediment resuspension or discharge of sediment-laden
rivers is an important indication of coastal water quality and changes rapidly in high-energy coastal area. Since artificial
neural networks (ANN) had been proven successful in modeling a variety of geophysical transfer functions, an ANN model to
simulate the relationship between surface water SSC and satellite-received radiances was employed. In situ SSC measurements
from the Hangzhou Bay and the Moderate-resolution Imaging Spectroradiometer (MODIS) 250 m daily products were adopted in this
study. Significant correlations were observed between in situ measurements and band 1–2 reflectance values of MODIS images,
respectively. Results indicated that application of ANN model with one hidden layer appeared to yield superior simulation
performance (r
2 = 0.98; n = 25) compared with regression analysis method. The RMSE for the ANN model was less than 10%, whereas the RMSE for the regression
analysis was more than 25%. Results also showed that different tidal situations affect the model simulation results to some
extent. The SSC of surface water in Hangzhou Bay is high and changes rapidly due to tidal flood and ebb during a tidal cycle.
The combined utilization of Terra and Aqua MODIS data can capture the tidal cycle induced dynamic of surface water SSC. This
study demonstrated that MODIS 250 m daily products and ANN model are useful for monitoring surface SSC dynamic within high-energy
coastal water environments. 相似文献
633.
夏季对流云人工增雨效果评价方法初探 总被引:8,自引:3,他引:5
由于对流云尺度小、生消快,降水时空分布不均匀等特点,对其进行人工增雨效果评价是十分困难的事.本文利用2003年在"江淮地区对流云人工增雨外场试验"试验区获取的对流云人工增雨监测资料,采用成对对流云试验方案,开展对对流云人工增雨效果进行评估.通过对催化云催化前后雷达特征量和地面雨量变化分析,以及催化云与非催化云自身对比分析和双比分析,初步得出:人工催化后10~20 min增雨效果不明显,人工催化30 min后才能产生明显的增雨效果,其效果在100%以上. 相似文献
634.
A new finite element scheme is proposed, in this paper, for solving two-dimensional wave propagation problems in multilayered soils resting on a rigid base. The multilayered soils are treated as multiple horizontal layers of lateral infinite extension in geometry. Since these horizontal layers can be truncated by two artificially truncated vertical boundaries, two high-order artificial boundary conditions are applied for propagating the incoming waves from the interior domain into the far field of the system. Both the semi-analytical method and the truncated boundary migration procedure are used to derive the high-order artificial boundary conditions, which are comprised of a physically meaningful dashpot and a generalized energy absorber. The main advantage of using the proposed finite element scheme is that the derived artificial boundary condition can be straightforwardly implemented in the finite element analysis, without violating the band/sparse structure of the conventional finite element equation. The related numerical examples have demonstrated that the proposed finite element scheme is of high accuracy in dealing with wave propagation problems in multiple horizontal layers. 相似文献
635.
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637.
Sediment flux sensitivity to climate change: A case study in the Longchuanjiang catchment of the upper Yangtze River, China 总被引:6,自引:0,他引:6
Climate change may affect the sediment generation and transportation processes and the consequent sediment flux in a river. The sensitivity of suspended sediment flux to climate change in the Longchuanjiang catchment is investigated with Artificial Neural Networks (ANNs). ANNs were calibrated and validated using sediment flux data from 1960 to 1990 during which the influence from human activities was relatively stable. The established ANN is used to predict the responses of sediment flux to 25 hypothetical climate scenarios, which were generated by adjusting the baseline temperature up to − 1, 1, 2 and 3 °C and by scaling the baseline precipitation by +/− 10% and +/− 20%. The results indicated when temperature remains unchanged, an increase in rainfall will lead to a rise in sediment flux; when rainfall level remains unchanged, an increase in temperature is likely to result in a decrease in sediment flux. Same percentage of changes in rainfall and temperature are likely to trigger higher responses in wetter months than in drier months. However, it is the combination of the change in temperature and rainfall that determines the change of sediment flux in a river. Higher sediment flux is expected to appear under wetter and warmer climate, when higher transport capacity is accompanied by higher erosion rate. 相似文献
638.
Rock mass failure is a particularly complex process that involves the opening and sliding of existing discontinuities and the fracturing of the intact rock. This paper adopts an advanced discretisation approach to simulate rock failure problems within the discontinuous deformation analysis (DDA) framework. The accuracy of this approach in continuum analysis is verified first. Then, the advanced discretisation approach for fracturing modelling is presented, and the discretisation strategy is discussed. Sample rock static failures are simulated and the results are compared with experimental results. Thereafter, with a generalised definition of the artificial joints, this approach is further extended and applied in the simulation of blast-induced rock mass failures in which the instant explosion gas pressure obtained by the detonation pressure equation of state is loaded on the main blast chamber walls and the induced surrounding connected fracture surfaces. In the simulation instance of rock mass cast blasting, the whole process, including the blast chamber expansion, explosion gas penetration, rock mass failure and cast, and the formation of the final blasting pile, is wholly reproduced. 相似文献
639.
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