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排序方式: 共有263条查询结果,搜索用时 31 毫秒
191.
Song Yupu Zhao Guofan Doctor Professor Dalian University of Technology Dalian Professor Dalian University of Technology Dalian 《中国海洋工程》1994,(1)
Based on the experimental data, a stress variation model of the bond stress-slip relationship between steel bar and concrete is established. The characteristic of the model is that the boundary conditions are satisfied very well; the effects of the material properties, the concrete cover, the crack spacing and the distance from the cracked cross section are considered. Good agreement between measured and calculated bond stress-slip relationship is found. This model is useful for the study of the stiffness, deformation and crack width of reinforced concrete members, and for the nonlinear analysis of reinforced concrete structures by the finite element method. 相似文献
192.
Experiments with a set of electrolyte solutions have been carried out to investigate the effects of pore water composition changes on the stability conditions of methane hydrate in marine sediments. The results reveal that (1) SO42− and Cl− concentration changes can affect hydrate stability slightly, (2) the changes in both the type and the concentration of cations, which occur in normal diagenetic processes, do not exert a significant influence on the methane hydrate stability conditions, and (3) the shift of hydrate stability in pore water can be expressed as a function of the Cl− concentration only. Based on the results above, an empirical equation ΔT (K)=0.00206 Cl− (mmol/dm3) has been obtained for estimating the shift in the equilibrium temperature of methane hydrate in pore water at a given pressure. 相似文献
193.
Francesco Crea Alba Giacalone Antonio Gianguzza Daniela Piazzese Silvio Sammartano 《Marine Chemistry》2006,99(1-4):93
In this paper SIT and Pitzer models are used for the first time to describe the interactions of natural and synthetic polyelectrolytes in natural waters. Measurements were made potentiometrically at 25 °C in single electrolyte media, such as Et4NI and NaCl (for fulvic acid 0.1 < I /mol L− 1 < 0.75), and in a multi-component medium simulating the composition of natural waters at a wide range of salinities (for fulvic and alginic acids: 5 < S < 45) with particular reference to sea water [Synthetic Sea Water for Equilibrium studies, SSWE]. In order to simplify calculations, SSWE was considered to be a “single salt” BA, with cation B and anion A representing all the major cations (Na+, K+, Mg2+, Ca2+) and anions (Cl−, SO42−) in natural sea water, respectively. The ion pair formation model was also applied to fulvate and alginate in artificial sea water by examining the interaction of polyanions with the single sea water cation. Results were compared with those obtained from previous speciation studies of synthetic polyelectrolytes (polyacrylic and polymethacrylic acids of different molecular weights). Results indicate that the SIT, Pitzer and Ion Pairing formation models used in studies of low molecular weight electrolytes may also be applied to polyelctrolytes with a few simple adjustments. 相似文献
194.
下向分层进路充填采矿法中,进路充填顶板的稳定对回采过程安全性至关重要,而分层充填体叠加载荷计算一直是顶板稳定性分析的难点。在充分考虑采动岩体荷载、矿体倾角、相邻分层间回采进路的交错布置、充填体与围岩的接触等工程实际后,推导了进路顶板平衡微分方程,求解得到进路顶板静荷载的理论值。结合回采工艺建立了“多跨梁”力学模型,并得到了回采进路顶板拉应力的理论计算公式,分析得到影响进路顶板稳定性的4个重要理论因素:顶板上部载荷σ v、回采进路跨度l、1:4充填体的厚度h、充填体自身抗拉强度[σt]。为充分考虑进路顶板静载荷和回采爆破动载荷影响,利用FLAC3D对多因素影响下的顶板稳定性进行了数值模拟正交计算。根据模拟结果,分析了各因素对顶板拉应力的影响规律,利用多元非线性回归的方法建立了多因素组合影响下顶板稳定性评价模型。该模型应用到某铜矿试验采场的实际生产,具有较好的指导作用。 相似文献
195.
196.
罗布泊盐湖罗北区有着丰富的地下卤水资源,通过野外采集样品,室内试验检测,研究了罗布泊盐湖罗北区表层卤水主要离子的分布特征。采集卤水样品46件,通过分析,表明该区卤水矿化度范围在18.169~389.253g/L,略有中间高四周低的趋势。卤水中的阳离子主要为K+,Na+,Ca2+,Sr2+,B3+;阴离子主要为Cl-,SO24-,HCO3-,Br-,I-。其中K+,Na+,Li+,Cl-,SO24-,B3+的分布及含量均与矿化度呈正相关关系,Ca2+,Sr2+的分布及含量与矿化度呈负相关关系。HCO3-,Li+,Br-,I-,Mg2+的分布及含量与矿化度关系不明显。 相似文献
197.
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199.
Comparison of numerical simulation of solute transport with observed experimental data in a silt loam subsoil 总被引:1,自引:0,他引:1
Solute transport experiments were conducted on loamy soils of north-eastern Iowa, USA, and the results were compared with
a numerical solution of a classical advection-dispersion transport model developed in this study. Flow experiments in the
laboratory on undisturbed soil columns showed a flow rate of water much higher than was estimated from the soil properties
and grain-size analysis data, suggesting preferential flow regime in the soil. In contrast, the relative concentration peaks
of Cl– and Br– in the effluent were only approximately 70% of those predicted by the classical advection-dispersion equation (ADE). In addition,
the experimental breakthrough curves (BTCs) showed greater tailings of these ions than the model solution. These observations
suggest a loss of solute mass during transport from the dynamic flowing regions to a stagnant, immobile water phase in the
soil matrix. Experiments in small disturbed soil columns showed that movement of Cl– and Br– is in good agreement with predictions of the classical ADE when the tracers are applied as a continuous source. However,
in the case of a pulse source, the BTCs of Cl– and Br– matched the model only in the ascending part of the curves. Such variation indicates greater retardation of these ions than
that of simulation, probably caused by the decrease in soil permeability due to cation exchange reactions in the soil involving
monovalent and divalent cation pairs such as K+–Ca2+ and K+–Mg2+. In addition, retardation occurred as a result of the continuous saturation of soil columns which seemed to have caused an
expansion of clay minerals, thus resulting in decreased soil permeability. In both the continuous and the pulse-source experiments,
K+ was not detected in the effluent samples, which seemed to have been lost in exchange reactions and adsorption.
Received: 20 November 1998 · Accepted: 19 July 1999 相似文献
200.