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911.
912.
Based on fracture mechanics,a large amount of practically observed data are analyzed in this paper,and it is disclosed that the earth resistivity stations around the epicenter of a strong event have shown seismically an anomalous earth resistivity suddenly changed sequence.The maximum sudden change in the sequence tends to shift backward with the increase of epicentral distance,while it shifts forward with the increase of the magnitude of the earthquake.Also,the maximum sudden change expands from the epicenter to the peripheral areas.The result of study has shown that the obviousness degree of the anomalies is related to the measuring direction.The lithological contrast around the stations also influences the time of the anomaly occurrence.The maximum sudden change of the sequence will be advanced while the rock resistance to pressure is not good.On the basis of these findings,the authors propose that it might be possible to predict the three key elements of forthcoming earthquakes by using the suddenly 相似文献
913.
Liu Wenlong Wu Peizhi and Chen YuweiSeismological Bureau of Annul Province Hefei China 《中国地震研究》1996,(3)
In this paper,a new method for determining the earthquake fracture feature is put forward.The generalized directional function DG is defined as the ratio of P waveamplitude spectrums recorded at station 1 and station 2 by comparisonof the recorded DG curve and the theoretical curve,the ratio of fracture lengths of a bilateral fracture in two opposite directions and the angle between station 1 and the main rupture propagating direction can be determined simultaneously.Theoretically speaking,only records of three stations distributed homogeneously are needed to determine the fracture feature of an earthquake.The main rupturing propagating direction of a strong aftershock(ML5.4)of the Tangshan earthquake(Ms7.8)has been obtained by using the new method and has been compared with the result of the earthquake source mechanism.This shows that this new method is effective. 相似文献
914.
According to the source mechanism of the main shock and the distribution feature of the aftershocks occurring in the southern
Taiwan Straits on Sept. 16, 1994, in this paper the authors analysed the source rupture feature of the major earthquake, demonstrated
that this seismic sequence possessed the characteristics of a large intraplate earthquake. And according to the seismotectonic
background and the historical seismicity in the area, the authors clarified the active characteristics of the seismically
active belts along northwestern direction and analysed preliminarily the earthquake circumstance in the southeastern coast
of China. 相似文献
915.
岩体节理形貌的分形维数与摩擦角的关系研究 总被引:1,自引:0,他引:1
在土木工程设计和施工中,岩体节理的摩角是一个重要参数,该值的获取既费时又费力。本文首先简要介绍节理形貌的描述方法和分形几何理论,然后将分形理论引人岩体节理摩擦角的研究中,得出了用分形维数表示摩擦角的经验公式。关键词 相似文献
916.
为了简化旋转针锥光下一光轴出露时测定2V的赤平投影法的绘图手续,设计了本图解,只要测取θ,R,R′与φ四值,就能更快地求得2V值。 相似文献
917.
A simplified multiple source model was constructed for the 1975 HawaiiM
s=7.2 earthquake by matching synthetic signals with three component accelerograms at two stations located approximately 45 km from the epicenter. Six major subevents were identified and located approximately. The signals of these are larger by factors of 1.4 to 3.2 than that of theM
L=5.9 foreshock which occurred 70 minutes before the main rupture and also triggered the SAM-1 recorders at the two stations. Dividing the rupture length (40 km) by the duration of strong ground shaking ( 50 sec) an, average rupture velocity of 0.8 km/sec (about 25% of S-velocity) is obtained. Thus it is likely that the rupture stopped between subevents. The approximate epicenters of the 6 major subevents, and of the foreshock, support the hypothesis that they were located in high stress asperities which rupture during the main shock, except for the last events which is interpreted as a stopping phase generated at a barrier. These asperities have been previously defined on the basis of differences in the precursor pattern before the mainshock. Thus, it appears that both the details of the precursors and of the main rupture depended critically on the heterogeneous tress distribution in the source volume. This suggests that main rupture initiation points and locations of high rupture accelerations may be identified before the mainshock occurs, based on precursor anomaly patterns. A satisfactory match of synthetic signals with the observations could be obtained only if the aximuth of the fault plane of subevents was rotated from N60°E to N90°E and back to N30°E. These orientations are approximately parallel to the nearest Kilauea rift segments. Hence the slip directions and greatest principal stresses were oriented perpendicular to the rifts everywhere. From this analysis and other work, it is concluded that this fault surface consisted of three types of segments with different strength: hard asperities (radius 5 km), soft but brittle segments between the asperities (radius 5 km), and a viscous half (10×40 km) which slipped during the mainshock, but where microearthquakes and aftershocks are not common. 相似文献
918.
This paper illustrates an approach for determining uniquely the dip angle of a faulted structure, approximated by two semi-infinite horizontal slabs, displaced vertically from each other, by making use of the maximum positive and the maximum negative gravity amplitudes. The method is simple and rapid, and it does not necessarily require computing facilities.Two field examples from Aberdeenshire, Scotland and from the Northern Eastern Desert of Egypt are presented in which the angles of dip of two geological contacts are estimated at 45 and 40 degrees, respectively, and verified from surface geology, gravity modeling, and seismic data. 相似文献
919.
920.
ZHONG Ningning Lu Shuangfang HUANG ZHILONG Zhang Yousheng XUE Haitao PAN Changchun 《中国科学D辑(英文版)》2004,47(Z2)
Through geological observation, simulation in laboratory and numerical modeling, the factors that control the changes in total organic content (TOC) of source rock have been studied. When the formula DTOC=(TOC0-TOC)/TOC0 (original organic carbon content in the rock) is used to measure the TOC (total organic carbon content) changes in the source rock through geological time, the degrees and directions of such changes are determined by losses and relative amounts both of organic and inorganic matter in the source rock. The DTOC equation, which is used to calculate the loss rate in the process of maturation for the source rock, is therefore obtained by analyzing the mass balance relations. For a certain type of source rock with a certain maturation history, the changes of its TOC respond only to the rates of hydrocarbon generation and expulsion. In actual cases of geological entities, DTOC generally ranges from -0.05 to 0.2, while the calculated reconversion coefficient (k) for organic carbon content remains between 0.90 and 1.25. Only in an ideal situation where there are extremely high rates of hydrocarbon generation and expulsion can the DTOC value experience significant changes, with k reaching up to 2.5. It is concluded, therefore, that the criterion for carbonates source rock assessment, based on reconverting the TOC to the value of its original state, may have overestimated the course of the "carbon-reduction", which is likely in many cases to make a poor source rock sound better. 相似文献