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961.
利用32位微处理器控制Σ-Δ型模数转换器ADS1248,实现了MEMS加速度传感器输出电压信号的模数转换,采集到的地震信号满足强震数据采集要求。 相似文献
962.
老挝东泰钾盐矿区矿床控矿因素探析 总被引:1,自引:0,他引:1
通过对区域地质、构造和岩相古地理的研究,从成矿阶段的角度,将控矿因素分为背景控矿因素、沉积控矿因素、改造控矿因素。得出:背景因素为区域性盆地沉积环境形成条件;沉积控矿因素直接控制了工区石盐矿层的层理形态;改造控矿因素中,局部构造对矿层的改造是矿区盐层多呈背斜分布且轴部较两翼矿层大幅变厚的原因,钾石盐出现在光卤石矿层顶部是因为上部裂隙水或者封存的老卤水向下侵蚀光卤石矿层顶部,溶蚀了溶解度相对较大的MgCl2,而溶解度相对较小的KCl被保留下来,从而多在上盐层光卤石矿顶部形成再生或次生钾石盐矿。 相似文献
963.
《世界地质(英文版)》2012,(3):210-215
Based on China National Standard of Soil Engineering Classification (GB/T 50145-2007) and the Unified Soil Classification System of American Society for Testing Materials (ASTM D-2478), two kinds of soil laboratory engineering classification methods were discussed and analyzed from the aspects of the definition in particle fraction, classification of soil type and evaluation standard for soil gradation. There is a same limit of fine grains fraction in the two standards, and there are three main types of soil in GB/T 50145-2007 and two in ASTM D-2487. Different evaluation standards of gradation are put forward for gravels and sands in ASTM D-2487. Same criteria of A line, B line and controlling value of plastic index are in the plasticity chart of both standards. 相似文献
964.
Neal Jackson Eran O. Ofek Masamune Oguri 《Monthly notices of the Royal Astronomical Society》2008,387(2):741-746
We report the discovery of a new gravitational lens system. This object, ULAS J234311.93-005034.0, is the first to be selected by using the new UKIRT Infrared Deep Sky Survey (UKIDSS), together with the Sloan Digital Sky Survey (SDSS). The ULAS J234311.93-005034.0 system contains a quasar at redshift 0.788 which is doubly imaged, with separation 1.4 arcsec. The two quasar images have the same redshift and similar, though not identical, spectra. The lensing galaxy is detected by subtracting point spread functions from R -band images taken with the Keck telescope. The lensing galaxy can also be detected by subtracting the spectra of the A and B images, since more of the galaxy light is likely to be present in the latter. No redshift is determined from the galaxy, although the shape of its spectrum suggests a redshift of about 0.3. The object's lens status is secure, due to the identification of two objects with the same redshift together with a lensing galaxy. Our imaging suggests that the lens is found in a cluster environment, in which candidate arc-like structures, that require confirmation, are visible in the vicinity. Further discoveries of lenses from the UKIDSS survey are likely as part of this programme, due to the depth of UKIDSS and its generally good seeing conditions. 相似文献
965.
On the variability and spectral distortion of fluorescent iron lines from black hole accretion discs
Andrzej Niedwiecki Piotr T. ycki 《Monthly notices of the Royal Astronomical Society》2008,386(2):759-780
We investigate the properties of fluorescent iron lines that arise as a result of the illumination of a black hole accretion disc by an X-ray source located above the disc's surface. We study in detail the light-bending model of the variability of the lines, extending previous work on the subject. We indicate that the bending of photon trajectories to the equatorial plane (a distinct property of the Kerr metric) is the most feasible effect underlying the reduced variability of the lines observed in several objects. A model involving an X-ray source with a varying radial distance, located within a few central gravitational radii around a rapidly rotating black hole, close to the disc's surface, may explain both the elongated red wing of the line profile and the complex variability pattern observed in MCG–6-30-15 by XMM–Newton . We also point out that illumination by radiation that returns to the disc (following the previous reflection) contributes significantly to the formation of the line profile in some cases. As a result of this effect, the line profile always has a pronounced blue peak (which is not observed in the deep minimum state in MCG–6-30-15), unless the reflecting material is absent within the innermost 2–3 gravitational radii. 相似文献
966.
Susan E. Thompson M. H. van Kerkwijk J. C. Clemens 《Monthly notices of the Royal Astronomical Society》2008,389(1):93-101
We present optical time series spectroscopy of the pulsating white dwarf star G 29-38 taken at the Very Large Telescope (VLT). By measuring the variations in brightness, Doppler shift and line shape of each spectrum, we explore the physics of pulsation and measure the spherical degree (ℓ) of each stellar pulsation mode. We measure the physical motion of the g modes correlated with the brightness variations for three of the eight pulsation modes in this data set. The varying line shape reveals the spherical degree of the pulsations, an important quantity for properly modelling the interior of the star with asteroseismology. Performing fits to the Hβ, Hγ and Hδ lines, we quantify the changing shape of the line and compare them to models and previous time series spectroscopy of G 29-38. These VLT data confirm several ℓ identifications and add four new values, including an additional ℓ= 2 and a possible ℓ= 4. In total, from both sets of spectroscopy of G 29-38, eleven modes now have known spherical degrees. 相似文献
967.
Mao-Li Ma Xin-Wu Cao Dong-Rong Jiang Min-Feng Gu 《天体物理学报》2008,8(1):39-49
The Konigl inhomogeneous jet model can successfully reproduce most observational features of jets in active galactic nuclei (AGN), when suitable physical parameters are adopted. We improve Konigl's calculations on the core emission from the jet with a small viewing angle θ0 - φ (φ is half opening angle of the conical jet). The proper motion of the jet component provides a constraint on the jet kinematics. Based on the inhomogeneous jet model, we use the proper motion data of the jet component to calculate the minimal kinetic luminosity of the jet required to reproduce the core emission measured by the very-long- baseline interferometry (VLBI) for a sample of BL Lac objects. Our results show that the minimal kinetic luminosity is slightly higher than the bolometric luminosity for most sources in the sample, which implies that radiatively inefficient accretion flows (RIAFs) may be in those BL Lac objects, or/and the properties of their broad-line regions (BLRs) are significantly different from flat-spectrum radio-loud quasars. 相似文献
968.
Model-Synthesized Rate of Type Ia Supernovae and its Influence on the Chemical Enrichment of the ISM
Using Hurley's rapid binary stellar evolution code, we have studied the model-synthesized rate of Type Ia Supernovae (SNe Ia) and its influence on the chemical enrichment of the interstellar medium ejected by stellar populations. We adopt two popular scenarios, i.e., single degenerate scenario (SD) and double degenerate scenario (DD), for the progenitors of SNe Ia to calculate the rates of SNe Ia. Rates calculated in this work agree with that of Hachisu et al. and Han & Podsiadlowski, but are different from that usually adopted in chemical evolution models of galaxies. We apply the rates of SNe Ia to the chemical enrichment (especially Fe enrichment), then compare the results with previous studies. As known SNe Ia slightly affect the enrichment of C, N, O and Mg elements, while significantly affect the enrichment of Fe. We find that the occurrence and the value of the Fe enrichment in our models are earlier and smaller than that commonly adopted in chemical evolution models. We also study the evolution of [Mg/Fe] ratios, which are almost reciprocals of the Fe enrichment. The study may provide constraints on the free parameters of chemical evolution models of galaxies and evolutionary population synthesis. 相似文献
969.
讨论了激光测距仪测距本领的限制因素,找出了诸多限制因素的内在联系,得出了影响测距能力的关键因素是目标的照明概率.在前人已有的对激光测距仪最佳发散角的选取方法基础上,对其进行了改进.新得到的方法在选取最佳发散角时具有快速、简洁和精确度高等特点,并利用多项式拟合对其进行了简化,使其可用于粗略估算.最后,利用数值模拟对新方法进行了验证分析. 相似文献
970.
The power spectrum of the two-degree Field Galaxy Redshift Survey (2dFGRS) sample is estimated with the discrete wavelet transform (DWT) method. The DWT power spectra within 0.035 < k < 2.2 h Mpc-1 are measured for three volume-limited samples de-fined in consecutive absolute magnitude bins -19 ~-18, -20~ -19 and -21~-20. We show that the DWT power spectrum can effectively distinguish ACDM models of σs = 0.84 and σ8 = 0.74. We adopt maximum likelihood method to perform three-parameter fitting of the bias parameter b, pairwise velocity dispersion σpv and redshift distortion parame-ter β = Ω0.6m/b to the measured DWT power spectrum. The fitting results state that in a σ8= 0.84 universe the best-fit values of σm given by the three samples are mutually consis-tent within the range 0.28 ~ 0.36, and the best fitted values of σpv are 398 35-27475 37-29 and 550 ± 20km s-1 for the three samples, respectively. In the model of σ8 = 0.74, our three samples give very different values of Ωm. We repeated the fitting using the empirical formula of redshift distortion. The result of the model of low σ8 is still poor, especially, one of the best-fit values of σpv is as large as 103 km s-1. We also repeated our fitting by incorporating a scale-dependent galaxy bias. This gave a slightly lower value of Ωm. Differences between the models of σ8 = 0.84 and σ8 = 0.74 still exist in the fitting results. The power spectrum of 2dFGRS seems to disfavor models with low amplitude of density fluctuations if the bias parameter is assumed to be scale independent. For the fitting value of Ωm to be consistent with that given by WMAP3, strong scale dependence of the bias parameters is needed. 相似文献