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Based on a comprehensive analysis of the October 25, 1994 event, we consider the balance of energetic particles in a type-IV solar radio emission source with a zebra-type fine structure (in a coronal magnetic loop). The zebra pattern is formed through the injection of fast electrons into a trap and the formation of a ring-type nonequilibrium electron distribution function. We estimated the characteristic zebra-pattern lifetime, which is determined by the escape of fast particles from the trap into the loss cone. In addition, we determined the number of fast particles that must be injected into the trap to provide the observed radio brightness temperature in zebra-pattern stripes by analyzing the plasma emission mechanism responsible for the zebra-pattern generation. As a result, we estimated the efficiency of the electron acceleration mechanism in coronal magnetic loops at the post-flare evolutionary phase of an active region. 相似文献
805.
Data from the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses and synoptic maps from Kitt Peak are used to analyze the polar coronal holes of solar activity cycles 22 and 23 (from 1990 to end of 2003). In the beginning of the declining phase of solar cycles 22 and 23, the north polar coronal holes (PCHs) appear about one year earlier than the ones in the south polar region. The solar wind velocity and the solar wind ionic charge composition exhibit a characteristic dependence on the solar wind source position within a PCH. From the center toward the boundary of a young PCH, the solar wind velocity decreases, coinciding with a shift of the ionic charge composition toward higher charge states. However, for an old PCH, the ionic charge composition does not show any obvious change, although the latitude evolution of the velocity is similar to that of a young PCH. 相似文献
806.
胡景耀 《中国天文和天体物理学报》1991,(3)
本文首次提出了从观测得到的具有星周尘埃壳层的恒星的能谱分布求取星周尘埃云的消光,并由此可通过改正星周消光改正后的星际消光法求得恒星距离的方法。 相似文献
807.
Hari Om Vats M. R. Deshpande O. P. N. Calla N. M. Vadher B. M. Darji V. Sukumaran 《Earth, Moon, and Planets》1996,75(2):127-133
In this article we report the peculiar oscillations in the intensity of microwave (4.15 GHz) emission seen during the impact of K fragment of comet Shoemaker-Levy 9 on July 19, 1994. The oscillations begin at 10h 13m 25s UT suddenly with a frequency of ~0.3 Hz and gradually the frequency of these oscillations increases to ~ 1 Hz. The oscillations are not due to local atmosphere or the radio interference from signals of geostationary satellite. They are intrinsic to the microwave emission from Jupiter during the impact of K fragment. Peak-to-peak amplitude of the oscillations is about 34% of the total microwave emission from Jupiter. If we assume that only 50% of the microwave emission is non-thermal and only the non-thermal emission suffered oscillations, then the oscillations are about 68% of the non-thermal emission from Jupiter. The observations also indicate that there are three continuum enhancements during this event and periodic oscillations almost all through. The third enhancement was the largest and during this enhancement there were some additional aperiodic variations. The aperiodic variations were of the order of few minutes and were possibly generated by the gravity waves. The periodic oscillations could be synchrotron emission modulated by the plasma oscillation in the outer magnetosphere. kg]Key words 相似文献
808.
弱磁化相对论电子束注入等离子体时,由非共振波粒相互作用激发的束-等离子体不稳定性可以直接放大电磁波,计算结果表明:在偏离共振条件的区域,电磁波仍可在较宽的频率范围被放大,并在每个共振峰下形成平台结构。随着谐波数的增高,增长率峰值逐渐变小,峰宽也变窄。本文还分析了电磁波的增长率随背景参数ω_(pe)/Ω_e及高能电子的入射方向和辐射方向的变化规律,在典型的日冕条件下,此类不稳定性所放大的电磁波的增长率大小、带宽、方向性、偏振及谐波等性质,可以用来解释太阳Ⅲ型射电爆发现象,本文的研究亦可用来解释其他天体等离子体辐射。 相似文献
809.
J. Cantó R. F. González A. C. Raga E. M. de Gouveia Dal Pino A. Lara J. A. González-Esparza 《Monthly notices of the Royal Astronomical Society》2005,357(2):572-578
In this paper we present a simple, analytic model for the dynamical evolution of supersonic velocity fluctuations at the base of the ambient solar wind. These fluctuations result in the formation of dense working surfaces that travel down the wind. It is shown how the initial parameters of the fluctuations (velocity, density and duration) are related to the characteristics of the working surfaces far from the Sun (for instance at the Earth). We apply the model to the evolution of the coronal mass ejections in the IP medium, finding that the model is in good agreement with satellite observations of these phenomena, thus providing physical insight into their dynamical evolution. Our model may contribute to future 'space weather forecasting' on the Earth, based on detailed satellite monitoring of the solar corona. 相似文献
810.
M. H. Gokhale 《Journal of Astrophysics and Astronomy》1986,7(4):241-257
We present preliminary results of a spherical-harmonic-Fourier analysis of sunspot activity during the twenty-two years 1933–1954.
The results indicate that the sunspot activity might be originating in global solar oscillations with periods of years and
decades. However, except for the axisymmetric mode of degree 6, the set of other axisymmetric modes showing ∼ 11 yr periodicities
are different from one sunspot cycle to another. A more detailed analysis, preferably with larger data series, will be needed
to arrive at a more definite conclusion. 相似文献