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81.
The present work aims to experimentally investigate the fire behaviour of water-filled E glass reinforced thermoset resin hybrid filament-wound composites tubes under static pressure. Heretofore, fire endurance tests have been conducted on single and adhesively bonded tubes manufactured by CTRA Company. Furthermore, internal pressure tests until failure have been performed on the burnt single and burnt joined tubes in order to quantify their abilities to contain the fluid after being exposed to heat flux. A comparison between the pressure behaviour of exposed to fire (burnt) and non-exposed tubes (single and joined) was also inspected. The identification of the fire-induced damage mechanisms of the tubes was performed through optical microscopy, Scanning Electron Microscopy (SEM) and X-ray tomographic observations. Finally, the thermal analysis was carried-out on burnt specimens in order to better understand the multiphysical phenomenon taking place during the fire endurance tests. The experimental results have revealed that the combustion process of both single and joined tubes was described in four steps namely tube heating, resin degradation, ignition and flame decay. Moreover, it was found that no leakage was witnessed on the tubes (single and joined) outer surfaces during the fire endurance tests. The comparison between the pressure behaviour of the burnt single tube and the burnt joined one has proved that the single tube is much resistant under internal pressure loading than the burnt joined tube. Finally, the fire-induced damage included matrix cracking and delamination between the tube plies which was noticed from microscopic observations. 相似文献
82.
Leonid V. Pastukhov Marc J. W. Kanters Tom A. P. Engels Leon E. Govaert 《Journal of polymer science. Part A, Polymer chemistry》2020,58(5):716-736
In this study, it is demonstrated that the apparent endurance (fatigue) limit for plasticity-controlled failure in poly(ether ether ketone) is related to an evolution of the yield stress. The increase of the yield stress has two separate causes: (a) stress- and temperature-accelerated physical aging of the amorphous phase and (b) strain hardening as a result of texture development. Yield stress evolution is monitored using thermomechanical treatments during which the material is exposed to temperature and load. The combined contributions of both temperature and applied stress to yield stress evolution (below T g) can be effectively modeled using an effective time approach employing an Arrhenius temperature-activation as well as Eyring stress activation. Combination of the yield stress evolution with a previously developed model for plasticity-controlled failure allows prediction of time-to-failure under both static and cyclic load, quantitatively capturing the observed apparent endurance limit. 相似文献
83.
Effects of ramp vibrational states on flexural intrinsic vibrations in Besocke-style scanners
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For both the vibrating and steady supporting surfaces of a scanning disk in a Besocke-style piezoelectric scanner, a theoretical model is given by considering the nonlinear lateral friction at the micro-contact interface between the positioning legs and the supporting surface. Numerical simulations demonstrate that unexpected flexural vibrations can arise from a vibrating ramp, and their frequencies are lower than the eigenfrequencies of the scanner in the linearly elastic regime. The vibrations essentially depend on 1) the vibrational states of the supporting ramp and the steel ball tips on the three piezo- electric positioning legs, and 2) the tribological characteristics of the contacts between the tips and the ramp. The results give an insight into the intrinsic vibrations of the scanners, and are applicable in designing and optimizing piezoelectric scanning systems. 相似文献
84.
85.
Peter C.Y.Lee 《Acta Mechanica Solida Sinica》2011,24(2):125-134
An infinite system of two-dimensional equations of motion of isotropic elastic plates with edge and corner conditions are deduced from the three-dimensional equations of elasticity by expansion of displacements in a series of trigonometrical functions and a linear function of the thickness coordinate of the plate. The linear term in the expansion is to accommodate the in-plane displacements induced by the rotation of the plate normal in low-frequency flexural motions. A system of first-order equations of flexural motions and accompanying boundary conditions are extracted from the infinite system. It is shown that the present system of equations is equivalent to the Mindlin’s first-order equations, and the dispersion relation of straight-crested waves of the present theory is identical to that of the Mindlin’s without introducing any corrections. Reduction of present equations and boundary conditions to those of classical plate theories of flexural motions is also presented. 相似文献
86.
采用静电自组装方法在五氧化二钽(Ta2O5)介质氧化膜上制备了聚二烯丙基二甲基氯化铵(PDDA)/聚苯乙烯磺酸钠(PSS)和聚二烯丙基二甲基氯化铵/聚-3,4-乙烯二氧噻吩-聚苯乙烯磺酸钠(PEDOT-PSS)超薄膜.研究了两种自组装超薄膜在Ta2O5介质氧化薄膜上的组装特性.结果表明两种自组装膜能够稳定地组装于Ta2O5介质膜表面,并有效降低薄膜的表面粗糙度.进一步研究了两种自组装超薄膜修饰的Ta2O5电容结构的电性能.结果表明静电自组装膜对Ta2O5介质膜表面进行修饰后,有效地隔离了介质氧化膜中的缺陷,降低了电容的漏电流并提高耐电压能力;研究还发现不同厚度的超薄膜对Ta2O5电容结构的耐压特性有不同程度的影响,较厚的薄膜可以更好地提高电容的耐压能力并降低漏电流,但会增加电容的等效串联电阻(ESR).另外,在相同薄膜层数的情况下,聚合物电解质PEDOT-PSS良好的导电性能降低了复合超薄膜的电阻,使得PDDA/PEDOT-PSS修饰的电容结构ESR值较低. 相似文献
87.
Biodegradable composites made from bagasse fiber and biodegradable resin were fabricated and the flexural properties of the composites investigated in terms of the effects of fiber length, fiber volume fraction, and different alkali treatments of the bagasse fibers. The flexural properties of the composites increased with the increase in fiber length but decreased below the critical fiber length. The flexural properties increased with the increase in fiber volume fraction. The scanning electron microscope (SEM) micrographs showed that compression of the cellulose structure of bagasse fiber after preparation could have caused enhancement in the flexural properties. Furthermore, when comparing the effects of different alkali treatments of the bagasse fibers, maximum improvement in the flexural properties was observed for the 1% NaOH solution treated fiber composites. After alkali treatment, fibrillation occurred and the surface of the treated fibers became finer; this could contribute to improvement in the fiber‐matrix adhesion and result in enhancing the flexural properties. 相似文献
88.
《Composite Interfaces》2013,20(3):247-258
In this study, a flexible interphase than matrix resin is studied. The fabrication method of unidirectional CFRP laminates with flexible fiber/matrix interphase has been established. The influence of the flexible interphase thickness on the flexural modulus and strength are experimentally investigated. The influence on the vibration properties are also investigated. It has been concluded that the flexible interphase with the optimized thickness could improve both the static and dynamic properties. 相似文献
89.
90.
Baljinder K. Kandola S. Ilker Mistik Wiwat Pornwannachai A. Richard Horrocks 《Molecules (Basel, Switzerland)》2021,26(15)
Biocomposites comprising a combination of natural fibres and bio-based polymers are good alternatives to those produced from synthetic components in terms of sustainability and environmental issues. However, it is well known that water or aqueous chemical solutions affect natural polymers/fibres more than the respective synthetic components. In this study the effects of water, salt water, acidic and alkali solutions ageing on water uptake, mechanical properties and flammability of natural fibre-reinforced polypropylene (PP) and poly(lactic acid) (PLA) composites were compared. Jute, sisal and wool fibre- reinforced PP and PLA composites were prepared using a novel, patented nonwoven technology followed by the hot press method. The prepared composites were aged in water and chemical solutions for up to 3 week periods. Water absorption, flexural properties and the thermal and flammability performances of the composites were investigated before and after ageing each process. The effect of post-ageing drying on the retention of mechanical and flammability properties has also been studied. A linear relationship between irreversible flexural modulus reduction and water adsorption/desorption was observed. The aqueous chemical solutions caused further but minor effects in terms of moisture sorption and flexural modulus changes. PLA composites were affected more than the respective PP composites, because of their hydrolytic sensitivity. From thermal analytical results, these changes in PP composites could be attributed to ageing effects on fibres, whereas in PLA composite changes related to both those of fibres present and of the polymer. Ageing however, had no adverse effect on the flammability of the composites. 相似文献