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A general relationship between the volume fraction and the specific interfacial area for averaged dispersed two-phase flows is proposed. This relationship, expressed as a basic set of two scalar evolution equations and two vectorial non-uniformity state equations, is an analytical result obtained by a systematic approach using the derivatives of some generalized functions and a local volume-averaging technique. The proposed set of equations was expressed for measurable macroscopic parameters of the system and has the same generality as the averaged transport equations of two-phase flows. By combination of the basic set of equations, called the averaged topological equations (ATEs), second-order ATEs for the volume fraction were found. The second-order ATEs were expressed both by a Lagrangian formulation and by a Eulerian formulation. The importance and physical meaning of the ATEs developed in this study were clarified within the framework of the theory of kinematic waves. 相似文献
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Ángel E. Mercado-Pagán Yunqing Kang Dai Fei Elmer Ker Sangwon Park Jeffrey Yao Julius Bishop Yunzhi Peter Yang 《European Polymer Journal》2013
Here, we report the synthesis and characterization of a novel 4-arm poly(lactic acid urethane)-maleate (4PLAUMA) elastomer and its composites with nano-hydroxyapatite (nHA) as potential weight-bearing composite. The 4PLAUMA/nHA ratios of the composites were 1:3, 2:5, 1:2 and 1:1. FTIR and NMR characterization showed urethane and maleate units integrated into the PLA matrix. Energy dispersion and Auger electron spectroscopy confirmed homogeneous distribution of nHA in the polymer matrix. Maximum moduli and strength of the composites of 4PLAUMA/nHA, respectively, are 1973.31 ± 298.53 MPa and 78.10 ± 3.82 MPa for compression, 3630.46 ± 528.32 MPa and 6.23 ± 1.44 MPa for tension, 1810.42 ± 86.10 MPa and 13.00 ± 0.72 for bending, and 282.46 ± 24.91 MPa and 5.20 ± 0.85 MPa for torsion. The maximum tensile strains of the polymer and composites are in the range of 5–93%, and their maximum torsional strains vary from 0.26 to 0.90. The composites exhibited very slow degradation rates in aqueous solution, from approximately 50% mass remaining for the pure polymer to 75% mass remaining for composites with high nHA contents, after a period of 8 weeks. Increase in ceramic content increased mechanical properties, but decreased maximum strain, degradation rate, and swelling of the composites. Human bone marrow stem cells and human endothelial cells adhered and proliferated on 4PLAUMA films and degradation products of the composites showed little-to-no toxicity. These results demonstrate that novel 4-arm poly(lactic acid urethane)-maleate (4PLAUMA) elastomer and its nHA composites may have potential applications in regenerative medicine. 相似文献
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The growth of a prolate or oblate elliptic micro-void in a fiber reinforced anisotropic incompressible hyper-elastic rectangular thin plate subjected to uniaxial extensions is studied within the framework of finite elasticity. Coupling effects of void shape and void size on the growth of the void are paid special attention to. The deformation function of the plate with an isolated elliptic void is given, which is expressed by two parameters to solve the differential equation. The solution is approximately obtained from the minimum potential energy principle. Deformation curves for the void with a wide range of void aspect ratios and the stress distributions on the surface of the void have been obtained by numerical computation. The growth behavior of the void and the characteristics of stress distributions on the surface of the void are captured. The combined effects of void size and void shape on the growth of the void in the thin plate are discussed. The maximum stresses for the void with different sizes and different void aspect ratios are compared. 相似文献
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Void swelling is an important phenomenon observed in both nuclear fuels and cladding materials in operating nuclear reactors. In this work we develop a phase-field model to simulate void evolution and void volume change in irradiated materials. Important material processes, including the generation of defects such as vacancies and self-interstitials, their diffusion and annihilation, and void nucleation and evolution, have been taken into account in this model. The thermodynamic and kinetic properties, such... 相似文献
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As Reduced Activation Ferritic/Martensitic (RAFM) steel is considered the primary candidate for use as a structural material in fusion power reactors,many countries are developing different kinds of RAFM.China is developing new CLAM (China Low Activation Martensitic) steel.The study investigates microstructural changes in CLAM steel implanted with deuterium ions induced by 1250 keV electron irradiation from R.T.to 873 K,and observes both the growth and shrinkage of the defect clusters produced by deuterium ... 相似文献
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采用连续介质力学基唯象模型模拟分析了钽的平板撞击层裂行为。该模型包括了材料的非线性弹性(状态方程)、率相关塑性和孔洞的形核及生长等多种效应,并且采用一种对角隐式Runge-Kutta方法来求解本构率方程组,提高了热粘塑性本构关系计算的稳定性及精度。将数值模拟结果和相关实验数据进行了对比分析,结果表明,对于样品中的拉应力峰值明显高于材料层裂强度的实验(中、高速平板撞击实验),理论模型具有较好的预估能力,但对于临界层裂问题(低速平板撞击实验),该模型对材料损伤与失效过程的描述可能不够准确,需要进一步改进。 相似文献
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We demonstrate coded self-assembly in nanostructures using the code seeded at the component level through computer simulations.
Defects or cavities occur in all natural assembly processes including crystallization and our simulations capture this essential
aspect under surface minimization constraints for self-assembly. Our bottom-up approach to nanostructures would provide a
new dimension towards nanofabrication and better understanding of defects and crystallization process.
相似文献