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451.
R. C. Mehrotra Madhav Kumar Amit K. Ghosh K. Kumar Ritesh Arya 《Journal of the Geological Society of India》2014,83(6):647-652
Plant remains, including both mega and micro collected from the middle part of the Tharumsa Foramtion (early Miocene) are described for the first time from the Tharumsa village of the Kargil district, Jammu and Kashmir to reconstruct the palaeoenvironment. They indicate their affinities with Broussonetia of the Moraceae and Abies, Cedrus and Pinus of the Pinaceae. Their presence indicates warm and moist tropical to sub-tropical climate in the Kargil area during the depositional period against the cold and dry climate prevailing at present. 相似文献
452.
The theory of velocity dependent inertial induction, based upon extended Mach’s principle, has been able to generate many interesting results related to celestial mechanics and cosmological problems. Because of the extremely minute magnitude of the effect its presence can be detected through the motion of accurately observed bodies like Earth satellites. LAGEOS I and II are medium altitude satellites with nearly circular orbits. The motions of these satellites are accurately recorded and the past data of a few decades help to test many theories including the general theory of relativity. Therefore, it is hoped that the effect of the Earth’s inertial induction can have any detectable effect on the motion of these satellites. It is established that the semi-major axis of LAGEOS I is decreasing at the rate of 1.3 mm/d. As the atmospheric drag is negligible at that altitude, a proper explanation of the secular change has been wanting, and, therefore, this paper examines the effect of the Earth’s inertial induction effect on LAGEOS I. Past researches have established that Yarkovsky thermal drag, charged and neutral particle drag might be the possible mechanisms for this orbital decay. Inertial induction is found to generate a perturbing force that results in 0.33 mm/d decay of the semi major axis. Some other changes are also predicted and the phenomenon also helps to explain the observed changes in the orbits of a few other satellites. The results indicate the feasibility of the theory of inertial induction i.e. the dynamic gravitation phenomenon of the Earth on its satellites as a possible partial cause for orbital decay. 相似文献
453.
The propagation of nonlinear waves in a quantum plasma is studied. A quantum magnetohydrodynamic (QHD) model is used to take into account the effects of quantum force associated with the Bohm potential. Using the standard reductive perturbation technique, nonlinear Kadomtsev-Petviashvili (KP) equation is obtained to study the properties of ion acoustic waves (IAWs). For such waves the amplitude of the solitary waves is independent of the quantum parameter H (the ratio of the electron plasmon to electron Fermi energy), whereas the width and energy of the soliton increases with H. 相似文献
454.
Uday Narayan Ghosh Deb Kumar Ghosh Prasanta Chatterjee Mustapha Bacha Mouloud Tribeche 《Astrophysics and Space Science》2013,343(1):265-272
The properties of nonplanar (cylindrical and spherical) ion-acoustic solitary waves (IA SWs) in an unmagnetized, collisionless electron-positron-ion (e-p-i) plasma, whose constituents are q-distributed electrons and positrons and inertial ions, are investigated by deriving the modified Gardner (MG) equation. The well known reductive perturbation method is employed to derive the MG equation. The basic features of nonplanar IA Gardner solitons (GSs) are discussed. It is found that the properties of nonplanar IA GSs (rarefactive and compressive) are significantly affected by the particle nonextensivity. 相似文献
455.
Partha Pratim Ghosh Saibal Ray A. A. Usmani Utpal Mukhopadhyay 《Astrophysics and Space Science》2013,345(2):367-371
The concept of oscillatory Universe appears to be realistic and buried in the dynamic dark energy equation of state. We explore its evolutionary history under the framework of general relativity. We observe that oscillations do not go unnoticed with such an equation of state and that their effects persist later on in cosmic evolution. The ‘classical’ general relativity seems to retain the past history of oscillatory Universe in the form of increasing scale factor as the classical thermodynamics retains this history in the form of increasing cosmological entropy. 相似文献
456.
A Korteweg-de Vries (KdV) equation with a linear Landau damping term describing weakly nonlinear and weakly dispersive ion-acoustic
waves in an electron-positron-ion plasma is derived. It is found that the Landau damping causes the solitary wave amplitude
to decay with time. It is also found that in absence of Landau damping, both linear wave phase velocity and solitary wave
amplitude decrease with the increase of positron density, whereas, both increase with the increase of positron temperature.
On the other hand, the Landau damping rate decreases with the increase of both positron density and temperature. 相似文献
457.
G. Suresh R. Ananthanarayana R. C. Hanumanthu Subhasish Ghosh A. Anil Kumar K. V. S. Reddy 《Journal of the Geological Society of India》2010,75(4):576-595
Geological studies on saturated to oversaturated and subsolvus aegirine-riebeckite syenite bodies of the Pulikonda alkaline
complex and Dancherla alkaline complex were carried out. The REE distribution of the Dancherla syenite shows a high fractionation
between LREE and HREE. The absence of Eu anomaly suggests source from garnet peridotite. The Pulikonda syenite shows moderate
fractionation between LREE and HREE as reflected by enrichment of HREE and moderate enrichment of LREE. The negative Eu anomaly
indicates role of plagioclase fractionation.Three distinct co-eval primary magmas i.e. mafic syenite-, felsic syenite- and
alkali basalt magmas — all derived from low-degrees of partial melting of mantle differentiates and enriched metasomatised
lower crust played a major role in the genesis and emplacement of the syenites into overlying crust along deep seated regional
scale trans-lithospheric strike-slip faults and shear zones following immediately after late-Archaean calc-alkaline arc magmatism
at different time-space episodes i.e. initially at craton margin and later on into the thickened interior of the Eastern Dharwar
craton. The ductile sheared and folded Pulikonda alkaline complex was evolved dominantly from the magmas derived from partial
melting of lower crust and minor juvenile magmas from mantle. Differentiation and fractionation by liquid immiscibility of
mafic magma and commingling-mixing of intermediate and felsic magmas followed by fractionational crystallisation under extensional
tectonics during waning stages of calc-alkaline arc magmatism nearer to the craton margin were attributed as the main processes
for the genesis of Pulikonda syenite complex. Commingling and limited mixing of independent mantle derived mafic and felsic
syenitic magmas and accompanying fractionation resulting into soda rich and potash rich syenite variants was tentatively deduced
mechanism for the origin of Dancherla, Danduvaripalle, Reddypalle syenites and other bodies belonging to Dancherla alkaline
complex at the craton interior. The Peddavaduguru syenite was formed by differentiation of alkali mafic magma (gabbro to diorite)
and it’s simultaneous mingling with fractionated felsic syenitic magma under incipient rift. Vannedoddi and Yeguvapalli syenites
were derived due to desilicification and accompanying alkali feldspar mestasomatism of younger potash rich granites along
Guntakal-Gooty fault and along Singanamala shear zone respectively. 相似文献