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171.
172.
V. A. Sarychev A. Guerman P. Paglione 《Celestial Mechanics and Dynamical Astronomy》2003,87(3):219-239
We consider the equilibria of a satellite in a circular orbit under the action of gravitational and constant torques. The number of equilibria depending on the parameters of the problem is found by the analysis of an algebraic equation of order 6. The domains with different numbers of equilibria are specified, and the equations of boundary curves are determined in function of values of the components of constant torque. Classification of different distributions of number of equilibria is made for arbitrary values of the parameters. 相似文献
173.
Shortly the vacuum component of the Universe from the geometry point of view and from the point of view of the standard model of physics of elementary particles is discussed. Some arguments are given to the calculated value of the cosmological constant (Zel’dovich’s approximation). A new component of space vacuum (the gravitational vacuum condensate) is involved the production of which has fixed time in our Universe. Also the phenomenon of vacuum selforganization must be included in physical consideration of the Universe evolution. 相似文献
174.
A mathematical model describing the hydraulic head distribution for a constant‐head test performed in a well situated at the centre of a patchy aquifer is presented. The analytical solution for the mathematical model is derived by the Laplace transforms and the Bromwich integral method. The solution for the hydraulic head has been shown to satisfy the governing equations, related boundary conditions, and continuity requirements for the hydraulic head and flow rate at the interface of the patch and outer regions. An efficient numerical approach is proposed to evaluate the solution, which has an integral covering an integration range from zero to infinity and an integrand consisting the product and square of the Bessel functions. This solution can be used to produce the curves of dimensionless hydraulic head against dimensionless time for investigating the effect of the contrast of formation properties on the dimensionless hydraulic head distribution. Define the ratio of outer‐region transmissivity to patch‐region transmissivity as α. The dimensionless hydraulic head for α=0.1 case is about 2.72 times to that for α=10 case at dimensionless large time (e.g. τ?106) when the dimensionless distance (ρ) equals 10. The results indicate that the hydraulic head distribution highly depends on the hydraulic properties of two‐zone formations. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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176.
工业测量全站仪坐标测量精度检定方法 总被引:1,自引:0,他引:1
全站仪坐标测量在航空航天、大型设备制造业、特种异形工程和计量检测等领域有广泛应用,其坐标测量误差是最受关注的精度指标。与激光跟踪仪、关节臂等坐标测量技术不同,全站仪的标称精度指标并未直接给出点位坐标误差,而是分别给定测角和测距误差。由于国内外目前还缺乏将测角和测距精度对应到坐标精度的相应规范,这就导致不能直观反映全站仪的实际坐标测量精度,给具体测量工作的坐标精度估算带来一定难度。基于以上现状,提出了基于点对点长度测量和三维坐标测量误差的检定模型;并利用3种不同类型的工业测量全站仪进行了实验测试,验证了该检定模型的可行性。 相似文献
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178.
土壤盐渍化对区域经济和生态可持续发展产生负面影响。微波介电常数是微波遥感探测土壤的关键因素,然而介电常数与盐分的关系仍不清晰。为分析盐分类型及含盐量对土壤介电常数的影响,在0.3~20.0 GHz频率下,测量了新疆典型的2种盐渍土类型(硫酸盐-氯化物型: ;氯化物-硫酸盐型: )的介电常数,探讨含水量、含盐量、盐分类型及质地对土壤介电特性的影响。结果表明:(1) 含盐量对湿润土壤、干燥粉壤土的复介电常数实部( )和虚部( )均产生影响。(2) 对于同等级的2种湿润盐渍土在0.3 GHz频率下,整体上 > 。(3) 虚部的电模量( )与含盐量的关系更紧密,且0.3~5.0 GHz是重要的频率范围。研究结果可为复杂下垫面下土壤盐渍化的微波遥感监测提供科学支持。 相似文献
179.
《Geomechanics and Geoengineering》2013,8(3):237-244
An infilled rock joint is likely to be the weakest plane in a rock mass. The presence of infill material within the joint significantly reduces the friction of the discontinuity boundaries (i.e. rock to rock contact of the joint walls). The thicker the infill, the smaller the shear strength of the rock joint. Once the infill reaches a critical thickness, the infill material governs the overall shear strength, and the joint walls (rock) play no significant role. Several models have been proposed to predict the peak shear strength of soil-infilled joints under both constant normal load (CNL) and constant normal stiffness (CNS) boundary conditions, taking into account the ratio of infill thickness (t) to the height of the joint wall asperity (a). CNS models provide a more realistic picture of the soil-infilled joint behaviour in the field. This paper presents a critical review on the existing mathematical models for predicting the shear strength of soil-infilled rock joint and verifies the normalised peak shear stress model with further laboratory investigations carried out on idealised saw-tooth rock joints at the University of Wollongong. Based on the prediction of the experimental data, the normalised peak shear stress model is slightly modified by the authors. A simplified approach for using this model in practice is presented and a new expression for prediction of dilatation at peak shear stress is suggested. 相似文献
180.
This study investigated the degradation kinetics, formation of disinfection by‐products (DBPs), and degradation pathways during monochloramination of oxytetracycline (OTC). The degradation kinetics can be well described by a second‐order kinetic model, first‐order in monochloramine (NH2Cl), and first‐order in OTC. Reaction of OTC with NH2Cl shows a high reactivity, with the apparent rate constant of 17.64/M/s at pH 7. The apparent rate constant declined as pH increased from 5 to 10. Six DBPs were detected during monochloramination of OTC, including chloroform (CF), 1,1‐dichloro‐2‐propanone (1,1‐DCP), 1,1,1‐trichloro‐2‐propanone (1,1,1‐TCP), dichloroacetonitrile (DCAN), trichloronitromethane (TCNM), and N‐nitrosodimethlyamine (NDMA). CF, DCAN and NDMA had the maximum yields at neutral pH, while 1,1‐DCP and 1,1,1‐TCP had the maximum yields at pH 4. However, TCNM concentration increased as pH increased. Degradation pathways of OTC monochloramination were then proposed. Hydroxylation and Cl‐substitution are found to be the dominant mechanisms in monochloramination of OTC. 相似文献