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681.
682.
A.M. Du W. Sun B.T. Tsurutani R.N. Boroyev A.V. Moiseyev 《Planetary and Space Science》2011,59(13):1551-1558
A new type of polar cap aurora, dawn–dusk aligned polar cap aurora (DDAPCA), was detected during the exceptionally intense January 21, 2005 substorm (AEmax=3504 nT). The DDAPCA was located at very high latitude (>85° MLAT) in the polar cap region. As the interplanetary magnetic field (IMF) GSM By component rotated from a positive to a negative value, the DDAPCA tilt angle relative to the dawn–dusk direction rotated anticlockwise and reached ∼45°. It is speculated that the DDAPCA arises from the formation of an X-line in the distant (>80RE) tail due to polar cap magnetic field reconnection under unusually high solar wind compression conditions. 相似文献
683.
684.
为满足水库抗震设计的震要,合成了50年超越概率5%和100年超越概率2%的基岩加速度时程曲线,考虑到吉林吉台电站所处的特殊地震环境和场地条件,分析其地震危险性认为:50年超越概率5%的地震动为远震影响;100年超越概率2%的地震动为近震影响,目前使用的基岩加带度反应谱衰关于关系的来源资料多少丢失一些高频成分,可能低估高频成分的地震动对基岩场地的影响,为此根据大震,远震的特征周期Tg较大这一规律,把两个概率水平的加速度反应谱的特征周期Tg都定为0.3s,并增加基岩反应谱高频成分控制,从而把基岩地震加速度反应谱处理成相应的规准谱,在此基础上通过拟合规准谱合成的基岩地震动时程曲线,较好地满足坝址的设防要求。 相似文献
685.
引潮力对显著地震触发作用与大震关系及在雅江地震预报中的应用 总被引:11,自引:2,他引:9
大地震的孕育和发生是震源区及其附近地壳应变能的积累和快速释放过程。当地震孕育到后期, 震源区及其附近应变能高度积累, 处于极不稳定的临界状态。因此, 地震短临预报方法必须基于临界状态的特点。临界状态的最重要特点是触发因素将起重要作用。固体潮的引潮力是一种重要的触发因素。笔者改进了过去仅用月亮固体潮引潮力的地方平太阴时方法, 而用月亮与太阳整个固体潮引潮力作为触发因素, 显然这样更为科学和合理。研究表明, 大地震前震源区及其附近发生的几次显著地震易受固体潮引潮力某个方位附近触发。并应用这一现象结合其他地震前兆方法成功预报了2001年2月23日四川雅江6. 0级地震。 相似文献
686.
Pter Kirly 《Journal of Astrophysics and Astronomy》2000,21(3-4):431-437
The heliosphere is the region filled with magnetized plasma of mainly solar origin. It extends from the solar corona to well
beyond the planets, and is separated from the interstellar medium by the heliopause. The latter is embedded in a complex and
still unexplored boundary region. The characteristics of heliospheric plasma, fields, and energetic particles depend on highly
variable internal boundary conditions, and also on quasi-stationary external ones. Both galactic cosmic rays and energetic
particles of solar and heliospheric origin are subject to intensity variations over individual solar cycles and also from
cycle to cycle. Particle propagation is controlled by spatially and temporally varying interplanetary magnetic fields, frozen
into the solar wind. An overview is presented of the main heliospheric components and processes, and also of the relevant
missions and data sets. Particular attention is given to flux variations over the last few solar cycles, and to extrapolated
effects on the terrestrial environment. 相似文献
687.
GRB 980519 is characterized by its rapidly declining optical and X-ray afterglows. Explanations of this behaviour include models invoking a dense medium environment, which makes the shock wave evolve quickly into the subrelativistic phase, a jet-like outflow, and a wind-shaped circumburst medium environment. Recently, Frail et al. found that the latter two cases are consistent with the radio afterglow of this burst. Here, by considering the transrelativistic shock hydrodynamics, we show that the dense medium model can also account for the radio light curve quite well. The potential virtue of the dense medium model for GRB 980519 is that it implies a smaller angular size of the afterglow, which is essential for interpreting the strong modulation of the radio light curve. Optical extinction arising from the dense medium is not important if the prompt optical–UV flash accompanying the γ -ray emission can destroy dust by sublimation out to an appreciable distance. Comparisons with some other radio afterglows are also discussed. 相似文献
688.
A model of gas-dynamical flow during gravitational collapse is analyzed mathematically by assuming its spherical symmetry and self-similarity. A shock wave diverging from the center emerges in this model. The physical requirements imposed on the post-shock flow at the center for the specified parameters at infinity unambiguously determine the shock front and the flow behind it. 相似文献
689.
P. W. May G. Pineau des Forêts D. R. Flower D. Field N. L. Allan J. A. Purton 《Monthly notices of the Royal Astronomical Society》2000,318(3):809-816
Sputtering yields are reported for the release of Mg, Fe, Si and O under impact of He, C, O, Si and Fe on grain material composed of Mg- and Fe-bearing silicates. The yields were derived using the trim code, which simulates the results of the transport of ions in matter by means of classical Monte Carlo techniques. The energetics of the sputtering process are a key factor in the sputtering calculations, and so detailed determinations have been made of the energy with which atoms are bound to the lattice, using solid-state simulation programs. The probability of ejection of an atom is computed at a given energy, for a number of angles of incidence, and integrated to obtain the mean yield at that energy. These numerical results are then fitted with a simple function of energy for convenience in subsequent applications.
A grid of C-type shock models has been computed, using our new sputtering yields, for pre-shock densities in the range 104 n H n (H)+2 n (H2 )106 cm−3 and shock speeds 20 v s 45 km s−1 . Sputtered fractions can be high, exceeding 50 per cent for shock speeds in excess of approximately 40 km s−1 . The column densities of Si and SiO were also computed, for comparison with observations. 相似文献
A grid of C-type shock models has been computed, using our new sputtering yields, for pre-shock densities in the range 10
690.