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71.
基于ARM和SD卡的微动数据采集系统数据存储技术研究 总被引:1,自引:0,他引:1
为满足微动数据采集系统的大数据量、低功耗要求,用SD卡存储微动数据采集系统采集得到的数据。阐述如何实现SD卡在以三星ARM9-s3c2410为硬件平台、Linux操作系统为软件平台的微动数据采集系统中的存储功能。 相似文献
72.
Numerical ocean modelling is computationally very demanding. Traditionally, the hydrostatic approximation has been applied to reduce the computational burden. This approximation is valid in large scale studies with coarse grid resolution. With faster computers and gradually smaller grid sizes, we may expect that more studies will be performed with non-hydrostatic ocean models. In recent papers several methods for including non-hydrostatic pressure in c3;-coordinate models have been suggested. In this paper the sensitivity of the non-hydrostatic pressure field, the velocity fields, and the density fields to changes in the method for computing non-hydrostatic pressure in c3;-coordinate ocean models is addressed.The first test case used involves the propagation and breaking of an internal wave at an incline in a tank. The other test case concerns tidally driven flow over a sill in a stratified fjord. The results from our numerical exercises suggest that the velocity and density fields are very robust to the model choices investigated here. The differences between the model results are of the same order as the uncertainty due to the internal pressure gradient error, and they are smaller than an estimate of the uncertainty due to subgrid scale closure. 相似文献
73.
Performance of two-equation turbulence closures in three-dimensional simulations of the Red Sea overflow 总被引:2,自引:2,他引:0
Mehmet Ilcak Tamay M.
zgkmen Hartmut Peters Helmut Z. Baumert Mohamed Iskandarani 《Ocean Modelling》2008,24(3-4):122-139
Mixing of overflows released from polar and marginal seas is a key process shaping the structure of the meridional overturning circulation. Ocean general circulation models have difficulty in resolving the overflows, and therefore they must rely on parameterizations. In this study, the performance of a set of turbulence closures in reproducing mixing of an overflow is quantified. We simulate the Red Sea overflow by employing standard k–ε, k–c9; and Mellor–Yamada schemes with various stability functions, as well as a modified k–ε model that relies on the prescription of the turbulent Prandtl number rather than on stability functions. The simpler KPP mixing scheme and experiments without turbulent fluxes serve as useful references. To our knowledge, this is the first time that the performance of two-equation turbulence models has been examined so closely using data from an overflow.It is found that without turbulence closures, the hydrodynamic model has difficulty in reproducing the correct three-dimensional pathway of the Red Sea overflow, consisting of a distinct bifurcation into two diverging channels. All turbulence models capture the vertical structure of this overflow consisting of an interfacial layer, characterized by the density gradient, and a well-mixed bottom layer. Mean eddy diffusivity values from most closures are comparable those from observations. But we find that KPP leads to eddy diffusivity values that are too small while those from Mellor–Yamada with Galperin [Galperin, B., Kantha, L.H., Hassid, S., Rosati, A., 1988. A quasi-equilibrium turbulent energy model for geophysical flows. J. Atmos. Sci. 45, 55–62] stability functions are too large. Such high diffusivities lead to excessive mixing in the bottom layer of the overflow, ultimately resulting in a salinity deficit of approximately 1 psu in the product water mass. Salinity deviations between the models and observations are quantified using both data taken along the channels and two sections across the overflow. KPP and Mellor–Yamada with Galperin (1988) stability functions produce the largest deviations from the observations, while the modified k–ε exhibits the smallest deviations. The other four closures fall in between, showing results similar to one another. The performance of the Mellor–Yamada turbulence closure is improved considerably by using the stability functions by Kantha and Clayson [Kantha, L.H., Clayson, C.A., 1994. An improved mixed layer model for geophysical applications. J. Geophys. Res. 99 (December), 25235–25266], which allow for a stationary Richardson number of 0.21. In conclusion, we find that most turbulence closures lead to a satisfactory reproduction of the Red Sea overflow, within the temporal and spatial sampling uncertainties of the REDSOX data, provided that fairly high-resolution regional models are used. 相似文献
74.
利用线粒体细胞色素 c 氧化酶Ⅰ亚基(COI)部分序列研究了南海区鲳属鱼类(Pampus)银鲳(P. ar-genteus)、珍鲳(P. minor)和中国鲳(P. chinensis)的系统进化与种群遗传结构.通过 PCR 扩增与序列测定获得了长度为643 bp 的 COI 基因片段,其 A、T、G、C 碱基的平均含量分别为25.4%、33.6%、18.9%和22.1%, A+T 含量高于 G+C 含量.64条序列共定义了20种单倍型,包含152个变异位点,简约信息位点148个,单变异位点4个,产生169个点突变.结果表明,银鲳与中国鲳的遗传差异最小,银鲳与珍鲳的其次,而珍鲳与中国鲳的遗传差异最大,3种鲳属鱼类的遗传多样性均呈现较低的水平,应采取有效的保护措施,以避免其遗传多样性水平的进一步丧失.本研究结果为鲳属鱼类资源保护和合理开发利用提供必要的参考 相似文献
75.
This paper deals with seismic analysis of plan‐asymmetric r/c frame multi‐storey buildings. Non‐linear numerical analyses are carried out by using a lumped plasticity model for beams and a multi‐spring model for columns, the latter one introduced to account for axial force–biaxial bending moment interaction. A comparison between numerical analyses and experimental test results is reported in order to calibrate the numerical model, showing that the adopted model is very suitable. In order to study the effects of the earthquake orthogonal component, the seismic response of the modelled structure under uni‐directional excitation is compared to the one under bi‐directional excitation. Such comparison shows that the maximum base shear and the top displacement are not very sensitive to the presence of the orthogonal component, which, conversely, leads to large increase in the column plastic excursions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
76.
????Sato???????????????????????????????о?????-???????????β??Qc???仯?????????Qc???????仯????Qc(f)=19.63??4.81f 1.183 8??0.094 5?? ??2005??12??3??ML3.9????????????????????ε????Q0???????仯?????????????????????????????????к?????ε????Q0???????仯?????????????????????????????? ?????????п?????ζ????????????????н???????????Ρ? 相似文献
77.
78.
79.
Results of simultaneous spectral and photometric monitoring of the Ae Herbig star WW Vul in the neighborhoods of the Ha line
and the sodium NaI D resonance doublet are reported. It is shown that the spectral variability of the star is caused mainly
by the anisotropic disk wind, whose high velocity component forms in the inner region of the accretion disk. The circumstellar
gas in footpoint of the wind shows the variability of the density and velocity, that is in good agreement with the results
of modeling of an accretion and outflows around young stars controlled by the stellar and/or disk magnetic field. An analysis
of the variability of the parameters of the Ha emission line also showed that the density of the gas in the inner region of
the accretion disk varies over a time scale exceeding 10 years.
__________
Translated from Astrofizika, Vol. 49, No. 2, pp. 171–185 (May 2006). 相似文献
80.
随着含煤岩系沉积学从最初的旋回层理论到沉积模式,再到现阶段层序地层学理论的发展,中国学者已经在含煤岩系沉积学研究领域取得了显著的成果。(1)层序地层格架下基于可容空间增加速率与泥炭堆积速率之间平衡关系的厚煤层聚集模式受到重视,层序地层学提供了等时性地层单元,用于中国六大聚煤区等时性层序地层格架下岩相古地理的重建,为预测各聚煤期聚煤中心及富煤带的分布起到指导性作用。随着层序地层学理论的深入研究,煤相及沉积有机相的发育特征、研究方法以及划分方案也取得了新的进展。(2)近年来,煤系共伴生矿产已经成为当今煤地质学研究的热点问题之一,含煤盆地的煤层气、页岩气、天然气水合物、铀矿、三稀矿产、石墨等矿产资源具有重要的经济价值,部分共伴生矿产潜在的价值甚至超过煤炭本身。古地理作为研究煤系矿产资源的先决条件,与之联系密切,为这些矿产的研究和勘探提供极大的帮助。(3)煤作为泥炭地的产物和重要的沉积载体,其中蕴藏着丰富的ȁc;深时”古气候信息。以米兰科维奇旋回作为地层时间的ȁc;度量”工具,可以通过分析煤中碳的聚集速率,进而分析泥炭地的碳聚集速率、净初级生产力以及大气CO2的变化趋势;而随着对煤中惰质组成因的重新认识,蕴含在煤中的古野火信息越来越受到重视,基于煤中惰质组的含量对地质历史中古泥炭地野火事件以及大气氧含量的估算也成为古环境研究的新方向。中国聚煤模式及聚煤古地理今后的研究需进一步加强对不同构造背景下含煤盆地的层序地层模式、各聚煤期的聚煤古地理及聚煤规律、有益煤系共伴生矿产的古地理重建、含煤岩系ȁc;深时”古气候信息以及大数据驱动下的含煤岩系古地理定量化研究等方面的探索。 相似文献