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941.
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中国滇西兰坪—思茅地洼盆地内中轴断裂带的初步研究 总被引:15,自引:0,他引:15
通过对中、新生代兰坪—思茅地洼盆地东、西部沉积特征、岩浆活动、地球物理场和卫星影像资料的综合研究与对比分析,论证了盆地内中轴断裂带的地质特征;讨论了中轴断裂带对盆地演化和成矿作用的重要意义。它是该区深部动力作用的主导构造 ,又是该区超大型、大型矿床形成的主要控制因素。 相似文献
945.
The depth to the top of magnetic dykes can be estimated from total field aeromagnetic data using the relation between the depth to magnetic sources and the autocorrelation function of magnetic data. By using synthetic anomalies we show that in the ideal case, depth can be determined to an accuracy of 10% or better, when the anomaly sources are two-dimensional dykes. However, the estimated depths depend on the width of the dykes. The estimated depth is about 0.6 times the actual depth to the top of thin dykes, and around the true depth for thick dykes having width-to-depth ratio around 3. The depth is considerably overestimated for very thick dykes (e.g., contacts, which is a special case of the thick dyke). Thus, the autocorrelation method requires that the width-to-depth ratio of the dyke is estimated independently to correctly estimate the depths. Alternatively, it must be assumed that the width-to-depth ratio for the two-dimensional source body is between 1.5 and 4. 相似文献
946.
Prakash P. Roday Gopal Maheshwari Narendra H. Vaghmarey 《Journal of Earth System Science》1990,99(2):321-338
Strain analysis of the Baraitha conglomerate is attempted by direct measurements on extracted pebbles and by micrometric analysis.
The overall deformation is of flattening type, with thek value lower by more than half in the matrix than in the pebbles. The viscosity contrast between pebbles and matrix (μ
i/μm) is in the ratio of 2:1 and the bulk deformation appears to be strongly controlled by Ci (concentration of pebbles expressed as percentage). The total shortening (≃35%) in the Baraitha conglomerate is comparable
with the shortening accomplished in the folding of the overlying Bijawar Group volcanosedimentary sequence. The bulk strain
axesX
t, Yt andZ
t, as determined from the analysis of the deformed conglomerate, are unsymmetrically oriented with reference to folds formed
by oblique flexural-slip with neitherX
t norY
tcoincident with the fold hinges. The lack of transection of folds by cleavage again suggests flattening deformation. The extension
in theY
tdirection is greater in the matrix than in the pebbles. 相似文献
947.
B. R. Arora 《Journal of Earth System Science》1990,99(4):693-716
Significant results from several array of magnetometers deployed in India to probe deep geoelectrical structures of the crust
and the upper mantle are reviewed in this paper. Emphasis is on critical appraisal of earlier results so that the article
summarizes what has been done so far and what caution is to be taken on future work.
Two large-scale arrays over northwest and peninsular India during 1979–80, have been followed up with six more linear or two-dimensional
arrays over different parts of the country.
“Trans-Himalayan” conductor aligned along the strike of Aravalli range, delineated by arrays over northwest India, essentially
represents one of the major continental induction anomalies mapped by electromagnetic methods. Efforts for quantifying the
induction effects through numerical models are shown to be constrained due to the large inter-station spacing, lack of information
on the regional background conductivity distribution and the non-inclusion of the frequency dependence of induction effects.
A more comprehensive modelling, not biased by these factors, enables approximating the Trans-Himalayan conductor as an asymmetric
domal upwarp in the middle and lower crust located between Delhi-Hardwar ridge and Moradabad fault. Numerical modelling results
for southern peninsular, despite the constraints, indicate that the strong and complex induction pattern can be adequately
attributed to the combination of conductors connected with triple junction between Indo-Ceylon Graben, Comorin ridge and the
west coast rifting.
Induction features derived from the Valsad array, operated over basalt-covered region of western India, demarcate an enhanced
conducting zone beneath Plume-associated triple junction in the Gulf of Cambay, apart from characterizing the presently active
seismic zone as a resistive block. 相似文献
948.
太仓—奉贤北西向活动断裂带及其地震地质意义初探 总被引:5,自引:0,他引:5
根据晚新生代以来沉积建造、沉积环境、岩浆活动、岸线变迁、地貌及现代地震等资料判断,太仓—奉贤北西向断裂带是上海及邻近地区一条重要的活动性断裂构造带。 相似文献
949.
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