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401.
AlN films grown on sputter-deposited and annealed AlN buffer layer by high temperature hydride vapor phase epitaxy(HVPE)have been fabricated and structurally characterized.The crystalline quality and surface morphology of as-grown AlN films with various V/III ratios were studied and compared.The XRD results showed that the crystalline quality of the AlN film could be optimized when the growth V/III ratio was 150.At the same time,the full width at half-maximum(FWHM)values of(0002)-and(10ˉ12)-plane were 64 arcsec and 648 arcsec,respectively.As revealed by AFM,the AlN films grown with higher V/III ratios of 150 and 300 exhibited apparent hillock-like surface structure due to the low density of screw threading dislocation(TD).The defects microstructure and strain field around the HVPE-AlN/sputtered-AlN/sapphire interfaces have been investigated by transmission electron microscopy(TEM)technique combined with geometric phase analysis(GPA).It was found that the screw TDs within AlN films intend to turn into loops or half-loops after originating from the AlN/sapphire interface,while the edge ones would bend first and then reacted with others within a region of 400 nm above the interface.Consequently,part of the edge TDs propagated to the surface vertically.The GPA analysis indicated that the voids extending from sapphire to HVPE-AlN layer were beneficial to relax the interfacial strain of the best quality AlN film grown with a V/III ratio of 150. 相似文献
402.
为了研究靶前高功率束流的物理特性,欧洲散裂中子源计划研制一套靶前多丝束流剖面监测器及束晕监测器样机,样机的在线测试将在日本质子加速器研究设施的3 GeV质子束传输束线上进行。针对此束线现场安装管道狭小、监测器样机传动机构行程大的特点,提出一种适用于小通道的多点定位多丝束流剖面探头,将其与束晕探头集成在一个样机上,结构紧凑,可实现双探头的独立驱动。使用ANSYS workbench对探头及传动杆进行了变形分析,完成了样机的研制,通过丝间距光学影像测量、真空检漏、小孔通过性测试及通断检测,确保了样机的可靠性。 相似文献
403.
为提高独立学院教育资源配置效率,基于数据包络分析理论,构建了独立学院相对办学效益测评指标体系及模型,将独立学院所在地区经济、人口和母体高校声誉等环境因素视为不可控投入要素纳入其中,分析了这些环境因素对45所独立学院办学效益的影响,得出了一个有趣的结论:即使环境因素对独立学院的办学效益不起主要作用,但是,可能会显著影响其投入与产出的改进量. 相似文献
404.
405.
牛庠均 《应用数学和力学(英文版)》1983,4(2):261-268
Based on[1 ],we have further applied the variational princi-ple of the variable boundary to investigate the discretizationanalysis of the solid system and derived the generalized Ga-lerkin’s equations of the finite element.the boundary varia-tional equations and the boundary integral equations.These e-quations indicate that the unknown functions of the solid sys-tem must satisfy the conditions in the element S_a or on the boun-dariesГ_a.These equations are applied to establishing the discreti-zation equations in order to obtain the numerical solution ofthe unknown functions.At a time these equations can be usedas the basis for the simplified calculation in various corres-ponding cases.In this paper,the results of boundary integral equationsshow that the calculation of integration is not accurate alongthe surfaceГ_a of interior element S_a by J-integral suggestedby Rice[2]. 相似文献
406.
Volume fraction condition is a true constraint that must be taken into consideration in deducing the thermodynamic restrictions
of mixture theory applying the axiom of dissipation. For a process to be admissible, the constraints imposed by the volume
fraction condition include not only the equation obtained by taking its material derivative with respect to the motion of
a given phase, but also those by taking its spatial gradient. The thermodynamic restrictions are deduced under the complete
constraints, the results obtained are consistent for the mixtures with or without a compressible phase, and in which the free
energy of each phase depends on the densities of all phases. 相似文献
407.
Photoluminescence of Self-Assembled InAs/GaAs Quantum Dots Covered by InAlAs and InGaAs Combination Strain-Reducing Layer 下载免费PDF全文
Self-assembled lnAs/GaAs quantum dots covered by the 1-nm InxAI(1-x)As (x = 0.2, 0.3) and 3-nm In0.2Ga0.8As combination strain-reducing layer are fabricated, whose height can take up to 30-46 nm. The luminescence emission at a long-wavelength of 1.33μm and the energy separation between the ground and the first-excited state of 86meV are observed at room temperature. Furthermore, comparative study proves that the energy separation can increase to 91 meV by multiple stacking. 相似文献
408.
A straight magnetic filtering arc source is used to deposit thin films of titanium nitride. The properties of the films depend strongly on the deposition process. TiN films can be deposited directly onto heated substrates in a nitrogen atmosphere or onto unbiased substrates by condensing the Ti^+ ion beam in about 300 eV N2^+ nitrogen ion bombardment. In the latter case, the film stoichiometry is varied from an N:Ti ratio of 0.6-1.1 by controlling the arrival rates of Ti and nitrogen ions. Meanwhile, simple models are used to describe the evolution of compressive stress as function of the arrival ratio and the composition of the ion-assisted TiN films. 相似文献
409.
利用微乳液方法合成出粒径为4 nm的核-壳结构ZnS∶Tb/CdS纳米晶。用XRD、TEM及荧光光谱等手段对合成的纳米晶的结构、形态和光学特性分别进行了表征。将ZnS∶Tb/CdS纳米晶制作成有机-无机杂化结构电致发光器件,其结构为ITO/poly(3,4-ethylene d ioxythiophene)∶poly(styrene sulfonate)(PEDOT-PSS)(70 nm)/poly(vinylcobarzale)(PVK)(100 nm)/ZnS∶Tb/CdS纳米晶(120 nm)/2,9-d im ethyl-4,7-d iphenyl-1,10-phenanthroline(BCP)(30 nm)/L iF(1.0 nm)/A l(100 nm)。当驱动电压为13 V时,可以测到Tb3+离子的两个特征峰。在电致发光光谱中未测到聚合物PVK的发光,说明电子和空穴是在纳米晶层上复合的。当驱动电压为25 V时,得到器件的最大亮度为19 cd/m2。 相似文献
410.