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601.
V. K. Dubrovich 《Astronomy Letters》2001,27(4):207-212
We consider the formation mechanisms of “negative”-intensity spots in the radio band for various astrophysical conditions. For wavelengths λ<1.5 mm, the regions of reduced temperature (relative to the cosmic microwave background radiation, CMBR) are shown to be produced only by high-redshift objects moving at peculiar velocities. The main processes are CMBR Thomson scattering and bremsstrahlung. We show that the effect δT/T can be ~10?5 in magnitude. We derive simple analytic expressions, which allow the redshifts, electron densities, and linear sizes of these regions to be estimated from observed spectral and spatial parameters. Additional observational methods for refining these parameters are outlined. 相似文献
602.
603.
A. S. N. Murty H. C. Tewari Prakash Kumar P. R. Reddy 《Pure and Applied Geophysics》2005,162(12):2409-2431
A 2-D subcrustal velocity model for the central Indian continental lithosphere has been derived by travel time and relative
amplitude modeling of a digitally normalized analog seismic record section of the Hirapur-Mandla DSS profile, using a ray-tracing
technique. Some prominent wave groups with apparent velocities slightly higher than the Moho reflection phase (PMP) are identified on the normalized record sections assembled with a reduction velocity of 6 km s−1. We interpret these phases as the wide-angle reflections from subcrustal lithospheric boundaries. Comparison of synthetic
seismograms with the observed record section shows that the observed phases cannot be explained either by multiples or by
the P-to-S converted phase (PMS) from the Moho. Subcrustal velocity models either with a velocity increase or with a single low velocity layer (LVL) also
do not provide a satisfactory fit. We infer that a subcrustal velocity model with two alternate LVLs (velocity 7.2 km s−1), separated by a 6-km thick high velocity layer (velocity 8.1 km s−1), can satisfy both the observed travel times and amplitudes. The prominent reflection phases are modeled at depths of 49,
51, 57 and 60 km. It is inferred that the subcrustal lithosphere in the central Indian region has a lamellar structure with
varying structural and mechanical properties. The alternating LVLs, occurring at relatively shallow depths below Moho, may
be associated with the zones of weakness and lower viscosity suggesting continued mobility, with a possible thermal source
in the upper mantle. This explains the source of observed high heat flow values in the central Indian region. 相似文献
604.
石化企业重大泄漏事故建模及GIS图形模拟的研究 总被引:1,自引:0,他引:1
有毒、有害物质泄漏是石化企业的重大事故,严重威胁企业和社会的安全.以石化企业乙二醇、丙烯腈装置产生的有毒、有害物质泄漏、扩散和污染范围的理论模型为根据,提出有毒、有害物质的地理信息系统(GIS)扩散图形模拟方法.通过对泄漏物质污染范围的确定,便于救援人员能够按照事故的影响范围,准确、及时的制定出救援方案,减少财产的损失. 相似文献
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608.
The popularly used viscoelastic models have some shortcomings in describing relationship between quality factor (Q) and frequency, which is not consistent with the observation data. Based on the theory of viscoelasticity, a new approach to construct constant-Q viscoelastic model in given frequency band with three parameters is developed. The designed model describes the frequency-independence feature of quality factor very well, and the effect of viscoelasticity on seismic wave field can be studied relatively accurate in theory with this model. Furthermore, the number of required parameters in this model has been reduced fewer than that of other constant-Q models, this can simplify the solution of the viscoelastic problems to some extent. At last, the accuracy and application range have been analyzed through numerical tests. The effect of viscoelasticity on wave propagation has been briefly illustrated through the change of frequency spectra and waveform in several different viscoelastic models. 相似文献
609.
We study the effects of possible deviations of fundamental physical constants on the yields of light nuclides, 2D, 3He, 4He, 7Li, and others during primordial nucleosynthesis. The deviations of fundamental constants from their current values are considered in the low-energy approximation of string theories; the latter predict the existence of a scalar field, which, apart from the tensor gravitational field, determines the space geometry. A two-parameter (η, δ) model is constructed for primordial nucleosynthesis: η = n B /n γ is the baryon-to-photon density ratio, and Ω is the relative deviation of fundamental physical constants at the epoch of primordial nucleosynthesis from their current values. A dependence of η on the deviation of coupling constants Ω has been derived on condition that the primordial helium abundance is Y p = f(η, δ) = const, where const corresponds to experimental values. We thus showed that the relative baryonic density (and hence ΩB could vary over a much wider range than allowed by the standard nucleosynthesis model. Considering this result, we discuss the recently found mismatch between ΩB obtained from an analysis of CMBR anisotropy and from the standard primordial nucleosynthesis model. 相似文献
610.
在全球政治经济变局和多尺度危机冲击语境下,区域经济韧性已成为当下经济地理学探究区域发展动态的核心议题。区域经济韧性不仅有关本地经济属性和适应力,更受到外部联系动态的影响,在范式上需融入多尺度网络动态观。本文将全球生产网络理论中的战略耦合概念纳入到演化经济地理学的区域经济韧性思想中,对两部分文献进行计量分析和梳理对比。在此基础上,以战略耦合不同模式(即耦合、去耦合、再耦合)为切入点,构建了一套基于“战略耦合演化”的区域经济韧性分析框架。研究结论:① 任何一种战略耦合模式,均是一种“战略性求变”和“语境应对”的能动行为过程,是理解区域经济韧性尺度性与能力来源的核心。② 两者在“连接度”“语境敏感性”“路径发展”概念上有较高的思想共性,相互融合可提升区域经济韧性的理论内涵。③ 战略耦合的能动主体、目的、嵌入性程度及方式是理解区域经济韧性特征和机制的关键,有助于从“地方-全球连接互动”的视角来综合分析区域经济韧性的初始属性(区域优势)、过程(恢复、更新和转型)、能力(恢复力、转型力和更新力)和结果(多元路径发展趋势)。本文认为战略耦合演化视角有利于破除以往“区域主义”韧性思想,能更科学地剖析区域经济韧性的多尺度语境依赖、多主体能动过程和多要素互动机制。此外,有利于推动关系与演化经济地理范式的融合创新,对“双循环”战略下中国企业决策和区域经济发展有重要现实意义。 相似文献