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991.
Petroleum geological dynamics of Lower Paleozoic in the Ordos Basin, northwest China 总被引:2,自引:0,他引:2
Taking the hydrocarbon source rocks of Ordovician, Lower Paleozoic in the Ordos Basin as the main research object, the characteristics of petroleum geological dynamics about geohistory, geothermal history, hydrocarbon generation history and hydrocarbon expulsion history were studied by using the methods of basin numerical modeling dynamically and pool-forming dynamics. It is shown that the Ordovician strata had entirely undergone five stages of initial deposition, uplift and erosion, rapid subsidence, alternating uplift and subsidence, and differential uplift and erosion; that under the background of lower heat flow on the whole, the paleoheat flow of Ordovician strata in the basin could be divided into two large stages of relatively high heat flow values period before Cretaceous deposition and relatively low ones after it; that the thermal evolution of organic matters in the hydrocarbon source rocks of Ordovician had entered into high mature-postmature stage on the whole and the intensity of gas generated was greater than that of oil generated, the hydrocarbon being mainly natural gas; and that the curves of the intensity of oil and gas expulsion at each time unit showed the feature of multi-peak-type, the accumulative intensity of gas expulsion was greater than that of oil expulsion. Thus natural gas exploration potential is good. 相似文献
992.
The response wavelets for tether tension and the displacement of a package on the end of a tether are derived from a linear, frequency-domain model of vertically tethered systems using inverse fourier transform techniques. These wavelets are convolved with a record of ship displacement to predict the instantaneous tension and displacement to an accuracy of better than 20% for a typical system. Although snap loads are non-linear and the response cannot be calculated while the tether is slack, the onset of zero tension — a precursor to snap loads — is predicted by the wavelet. Thus, extreme and potentially hazardous conditions are foreseeable with the wavelet and this information can be used in real-time to guide operations at sea. 相似文献
993.
994.
Flattened Jaffe models for galaxies 总被引:1,自引:0,他引:1
Jiang Zhenglu 《Monthly notices of the Royal Astronomical Society》2000,319(4):1067-1078
This paper introduces a class of galactic models which extend Jaffe's spherical models to axisymmetric systems, and then studies the properties of their densities and two-integral even distribution functions. The models have finite total mass and finite densities which, at large distances, decay radially like r −4 except on the major axis, and like r −3 on the major axis. The more flattened the galaxy, the stronger is the dependence of the even distribution functions on the angular momenta of its stars. Their distribution functions can be obtained by using the maximum entropy principle or assuming the anisotropy of the models. In particular, some formulae analogous to those of Hunter & Qian are obtained to calculate two-integral odd distribution functions, and they can be applied to obtain the distribution functions under the assumption of anisotropy for the oblate models. 相似文献
995.
996.
P. M. S. Namboodiri 《Celestial Mechanics and Dynamical Astronomy》2000,76(1):69-77
Oscillations in galaxies have been investigated by numerical simulations. The various models used have density distributions
corresponding to that of polytrope of index n in the range 0 ≤ n ≤ 4 and their evolution has been followed for more than 70 crossing times. The kinetic energy shows regular and smooth oscillations
for models with n = 0, 1 and 2 whereas in other models it shows noisy oscillation. The oscillation in kinetic energy is observed to have a
period of 3 crossing time irrespective of the density and size of the galaxy. The amplitude of oscillation is seen to decrease
as the central density of the galaxy increases.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
997.
人为动力泥沙灾害类型及其特征初步研究 总被引:7,自引:3,他引:4
人为动力泥沙灾害是人类活动无意地导致地表物质侵蚀、输移、沉积过程中的渐近或超临界现象 ,它具有独特的社会学及灾害学属性。按人为驱动力形式、灾害所在地貌部位、灾害的表现形式及具体灾害现象 ,人为动力泥沙灾害系列可划分为 :流域水系、沟道坡面、河道及平原河口海岸四个泥沙灾害类 ;各灾害类包括侵蚀型、搬运型、堆积型、复杂型及关联型五种泥沙灾害型 ;共 54个灾害种。这是一种比较综合、系统的人为动力泥沙灾害类型划分。从流水地貌、泥沙运动及灾害学相结合出发 ,人为动力泥沙灾害具有以下特征 :1地理地带基础上的加剧性特征 ;2人文环境影响下的渐变性与急变性特征 ;3盲目性驱动下的无序性特征 ;4复杂性和非线性特征等。人文环境的变化是人为动力泥沙灾害产生的主要原因。只有加强管理力度 ,提高人民的环境保护意识 ,才能控制人为泥沙灾害的发生。 相似文献
998.
999.
We use high-spatial resolution (100 pc) rotation curves of 83 spiral galaxies to investigate the mass distribution of their innermost kpc. We show that, in this region, the luminous matter completely accounts for the gravitational potential and no dark component is required. The derived I-band disk mass-to-light ratios
agree well with those obtained from population synthesis models and correlate with color in a similar way. We find strict upper limits of 107 M for the masses of compact bodies at the center of spirals, ruling out that these systems host the remnants of the quasar activity. 相似文献
1000.
Edvige Corbelli Paolo Salucci 《Monthly notices of the Royal Astronomical Society》2000,311(2):441-447
We present the 21-cm rotation curve of the nearby galaxy M33 out to a galactocentric distance of 16 kpc (13 disc scalelengths). The rotation curve keeps rising out to the last measured point and implies a dark halo mass ≳5×1010 M⊙ . The stellar and gaseous discs provide virtually equal contributions to the galaxy gravitational potential at large galactocentric radii, but no obvious correlation is found between the radial distribution of dark matter and the distribution of stars or gas.
Results of the best fit to the mass distribution in M33 picture a dark halo which controls the gravitational potential from 3 kpc outward, with a matter density which decreases radially as R−1.3 . The density profile is consistent with the theoretical predictions for structure formation in hierarchical clustering cold dark matter (CDM) models, and favours lower mass concentrations than those expected in the standard cosmogony. 相似文献
Results of the best fit to the mass distribution in M33 picture a dark halo which controls the gravitational potential from 3 kpc outward, with a matter density which decreases radially as R