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101.
Shao nan Zhang Knut Bj Φ rlykke 《沉积学报》2000,18(1):119-126
The timing and duration of
quartz cementation in sandstones have been mainly inferred from diagenetic texture,
relationship between pore filling minerals, fluid inclusions and isotopic data. Fluid
inclusion temperatures from North Sea reservoir sandstones indicate that most of the
quartz cement forms at temperature exceeding 90℃ and is continually proceeding after oil
emplacement, based on the fluid inclusion temperatures in quartz overgrowth which is
approaching the bottom-hole temperatures. The duration of quartz cement after oil
emplacement depends upon the saturation of porewater and the distribution of pore water
film and the property of water-wet or oil-wet of the reactants. The leaching of K-feldspar
by meteoric water requires pore water flow to move the released potassium and sodium and
silica out the solution, which suggests the mechanism does not appear to be a major source
of silica for quartz cementation. The quartz cementation coincidence with the compaction
and pressure solution suggests the major source of silica. The alteration of feldspar by
illitization of kaolinite may serve as another important source of silica at deep burial
depth. External sources are not need to call on for illustrating the quartz cementation,
because there is no evidences for large scale convection of pore water flow occurred in
the burial history of reservoir sandstones of middle Jurassic in the North Sea. 相似文献
102.
103.
F. Lucassen R. Becchio H. G. Wilke G. Franz M. F. Thirlwall J. Viramonte K. Wemmer 《Journal of South American Earth Sciences》2000,13(8):697
The Late Precambrian–Early Paleozoic metamorphic basement forms a volumetrically important part of the Andean crust. We investigated its evolution in order to subdivide the area between 18 and 26°S into crustal domains by means of petrological and age data (Sm–Nd isochrons, K–Ar). The metamorphic crystallization ages and tDM ages are not consistent with growth of the Pacific margin north of the Argentine Precordillera by accretion of exotic terranes, but favor a model of a mobile belt of the Pampean Cycle. Peak metamorphic conditions in all scattered outcrop areas between 18 and 26°S are similar and reached the upper amphibolite facies conditions indicated by mineral paragensis and the occurrence of migmatite. Sm–Nd mineral isochrons yielded 525±10, 505±6 and 509±1 Ma for the Chilean Coast Range, the Chilean Precordillera and the Argentine Puna, and 442±9 and 412±18 Ma for the Sierras Pampeanas. Conventional K–Ar cooling age data of amphibole and mica cluster around 400 Ma, but are frequently reset by Late Paleozoic and Jurassic magmatism. Final exhumation of the Early Paleozoic orogen is confirmed by Devonian erosional unconformities. Sm–Nd depleted mantle model ages of felsic rocks from the metamorphic basement range from 1.4 to 2.2 Ga, in northern Chile the average is 1.65±0.16 Ga (1σ; n=12), average tDM of both gneiss and metabasite in NW Argentina is 1.76±0.4 Ga (1σ; n=22), and the isotopic composition excludes major addition of juvenile mantle derived material during the Early Paleozoic metamorphic and magmatic cycle. These new data indicate a largely similar development of the metamorphic basement south of the Arequipa Massif at 18°S and north of the Argentine Precordillera at 28°S. Variations of metamorphic grade and of ages of peak metamorphism are of local importance. The protolith was derived from Early to Middle Proterozoic cratonic areas, similar to the Proterozoic rocks from the Arequipa Massif, which had undergone Grenvillian metamorphism at ca. 1.0 Ga. 相似文献
104.
浅析前岭井田4煤层层滑构造及薄化带展布特征 总被引:1,自引:0,他引:1
通过对前岭煤矿部分采区层滑构造形态特征及展布规律的观测和研究,分析了该地段主采煤层薄化带及增厚带的展布方向和幅度,揭示了31~5煤层组中,软弱夹层及滑动构造发育情况,指出4煤层变薄及增厚的规律性,为矿井安全提供了超前地质信息。 相似文献
105.
The instability of the vortex sheet along the shear line 总被引:13,自引:1,他引:12
Gao Shouting 《大气科学进展》2000,17(4):525-537
The traditional Kelvin-Helmholtz notion of studying the shear instability is not suitable for the case associated with shear line with the strong wind shear in the vortex sheet. Since then, the shear instability be-comes the instability of the vortex sheet. If the velocity is induced by the vortex sheet, the inequalities (1 – Rv + Rid)> 0 and U (y,t)> U{A(t)} become the criterion of the vortex sheet instability. This criterion indicates that 1) the disposition of environment field restrains the disturbance developing along the shear line. 2) There exist multi-scale interactions in the unstable process of the shear line. The calculation of the necessary condition for the instability is also presented in this paper. 相似文献
106.
G. Kallianpur V. G. Papanicolaou 《Stochastic Environmental Research and Risk Assessment (SERRA)》2000,14(1):33-49
We calculate explicitly some expectations (integrals over Hilbert spaces) of functionals of Gaussian random fields. Our work
is inspired by the formulas for the harmonic oscillator. We also show how to do similar calculations by considering continuum
limits of sequences of coupled harmonic oscillators. The results obtained in this work have applications in the study of random
media, renormalization and scaling, and in engineering perturbation analysis. 相似文献
107.
108.
A 3-D coupled ice sheet model, GLIMMER model is introduced, and an idealized ice sheet experiment under the EISMINT-1 criterion of moving boundary condition is presented. The results of the experiment reveal that for a steady-state ice sheet profile the characteristic curves describe the process of evolution which are accordant with theoretical estimates. By solving the coupled thermodynamics equations of ice sheet, one may find the characteristic curves which derived from the conservation of the mass, energy and momentum to the ice flow profile. At the same time, an agreement, approximate to the GLIMMER case and the confirmed theoretical results, is found. Present study is explorihg work to introduce and discuss the handicaps of EISMINT criterion and GLIMMER, and prospect a few directions of the GLIMMER model. 相似文献
109.
110.
LIU Lingyun GUO Haiyan SUN Qi 《中国海洋大学学报(英文版)》2006,5(3):269-272
Portal water injection sheet pile (PWISP), as a retaining wall, appeared in seashore engineering in 2000. Although there have been many systematic methods addressing the issue, there are very few focusing on the new structure because of the difficulties in defining the earth pressure between the two piles. A new method is proposed in this paper to obtain the earth pressure between the PWISPs. Stability analysis against overturning follows as a consequence. Using Finite Element Analysis (FEA) software ANSYS, both the nonlinear characteristics of the soil and those of the contact elements are taken into account to obtain the earth pressure distribution on the contact surface. Based on the results of the FEA, Rankin's theory and the slip plane theory, the formula of the earth pressure on the inner surfaces between the piles is given. Assuming the PWISP as the analysis object and the earth pressure as an outside force acting upon it, the equation of stability against overturning of the PWISP is presented. Finally, some parameters are discussed about the stability of the PWISP against overturning, such as the embedded depth of the front pile, the distance between the two rows of piles, the internal friction angle and the cohesion of the earth. The results show that the increase of the cohesion and the internal friction angle will decrease the distance and the embedded depth, and therefore enhance the stability against overturning. Specifically, when the distance is 1/3-2/3 of the maximal excavation depth, the two rows of piles give the best performance in stability. 相似文献