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91.
采用溶胶-凝胶法在玻璃衬底上制备ZnO/SiO2复合薄膜,分别用XRD、TEM、SEM对样品的结构和形貌进行表征,并研究了不同ZnO含量对复合薄膜透过率及荧光特性的影响。结果表明,样品经500 ℃退火处理生成了SiO2和ZnO,其晶粒尺寸为18.7 nm,薄膜具有双层结构。复合薄膜的透过率随着其中ZnO含量的增加而降低,禁带宽度减小,光学吸收边红移。样品在355 nm波长激发下产生了384 nm的紫外发射峰和440 nm的蓝光发射带,并随ZnO含量的增加而增强,它们分别来自ZnO的电子-空穴复合发光和缺陷发光,及ZnO/SiO2复合薄膜双层结构的缺陷发光。 相似文献
92.
一些实验表明, 实际大气会偏离理想Kolmogorov模型. 本文基于广义Huygens-Fresnel原理和Toselli等提出的非Kolmogorov湍流模型, 推导出部分相干双曲正弦-Gauss (HSG)涡旋光束通过非Kolmogorov大气湍流的解析传输公式, 并用以对两束部分相干HSG涡旋光束相干叠加和非相干叠加形成的合成相干涡旋在非Kolmogorov大气湍流中的动态演化进行了研究. 结果表明, 合成光束平均光强的演化过程与非Kolmogorov湍流的广义指数α, 源平面上叠加涡旋光束拓扑电荷的符号, 以及叠加方式有关. 合成相干涡旋在非Kolmogorov大气湍流中传输时会出现移动、产生和湮灭. 广义指数α, 拓扑电荷符号, 以及叠加方式都会影响其演化行为. 最后, 将本文所得结果与相关文献做了比较. 相似文献
93.
Polycrystalline ceramic samples of Bi2Sn2−xTixO7 (x=0.00, 0.2, 0.4, 0.6 and 0.8) have been synthesized by standard high temperature solid state reaction method. The effect of homovalent cation (titanium) substitution on the Sn-site on the structural and electrical properties of the pure Bi2Sn2O7 ceramic have been studied by X-ray diffraction followed by SEM, dielectric and dc conductivity studies. The structural analysis indicates that the increase of titanium contents do not lead to any secondary phase. The frequency and temperature dependent dielectric studies have been carried out. It is found that the Ti doping reduces the material particle size. The size of the particles are strongly influenced by the addition of titanium to the system. The substitution of Ti for Sn ions affected the degree of disorder and modified the dielectric properties leading to more resistive ceramic compounds. The activation energies of all the compounds were calculated using the relation σ=σ0exp(−Ea/kT). 相似文献
94.
G. Montagnoli S. Beghini F. Scarlassara A.M. Stefanini L. Corradi C.J. Lin G. Pollarolo Aage Winther 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):351-356
The two systems 40Ca + 90,96Zr have been studied by measuring nucleon transfer reactions at two energies near the Coulomb barrier, thus complementing
the available sub-barrier fusion cross-sections. Angular distributions for various transfer channels have been determined.
Significantly larger neutron transfer cross-sections are found for the target 96Zr that exhibits the larger enhancement in the sub-barrier fusion cross-sections. All data have been analyzed with a new model
for heavy-ion collisions that calculates simultaneously transfer cross-sections, fusion excitation functions and barrier distributions.
The model gives a good account of both transfer and fusion data.
Received: 2 May 2002 / Accepted: 4 June 2002 / Published online: 26 November 2002
RID="a"
ID="a"e-mail: montagnoli@pd.infn.it, Fax +39049 8277102, Tel. +39049 8277117.
RID="b"
ID="b"On leave from the China Institute for Atomic Energy, 102413 Beijing, China.
Communicated by C. Signorini 相似文献
95.
A molecular dynamics simulation of segregation behaviours of horizontally vibrated binary granular mixture 下载免费PDF全文
This paper performs the two-dimensional, soft-sphere
molecular dynamics simulations to study the granular segregation in
a binary granular mixture with the same size but different density
in the container with the sawtooth base under horizontal vibration.
The segregation phase diagram is presented in the
acceleration-frequency space. When the acceleration is high enough
to result in relative motions of the particles, the system can be in
various states (mixed state, vertical and horizontal segregation
state), which depend on both acceleration and frequency. Due to the
sawtooth base there is stratified flow effect besides density
effect. The density effect raises the light particles. The
stratified flow drives the particles in the upper levels to the
right and the particles in the lower particles to the left, those
fact results in the appearance of the left segregation state. The
left segregation state can be changed to the right segregation by
changing the shape of the sawtooth. As the vibration frequency
increases, the stratified flow effect becomes weaker and weaker, so
at high vibration frequencies the vertical segregation state appears
instead of the left segregation state. 相似文献
96.
A simple model for the numerical determination of separation effects in seeded atomic gas flows is presented. The model is based on the known possibility to provide a statistically convergent estimate of the exact solution for a linear transport equation using the test particle Monte Carlo method. Accordingly, the flow field of the main gas is preliminary calculated and as a second step the linear transport equations obtained by fixing the target distribution in the collision term of the Boltzmann equation for both main and minority components are solved. Both solutions are based on appropriately devised test particle Monte Carlo methods. The second step, the critical one in evaluating the separation effects, is exact and thereby completely free of numerical diffusion. The model is described in details and illustrated by 2D test cases of atomic separation in shock fronts. 相似文献
97.
我国海域辽阔,各类船只的水上航行和作业安全密切关系到生命和财产的安全,需要可靠保障。由于海上险情发生的随机性和突发性,岸上险情监视力量必须全时、全天候地开设险情通信通道,接收海上遇险对象的遇险呼救信号并及时对遇险信息进行处理。因此,岸基必须建设遇险救生信息系统并规定必要的信息传输流程,保障险情报知通信的顺利完成。文章简要分析了目前海上救生的通信现状,对常用通信手段进行了分析与介绍,并提出了一种整合各通信手段的设计方法,实现了多种通信手段的综合使用以及统一调度,大幅提升险情信息的传输和处理效率,提高险情信息的保密性,为救援工作提供了精确可靠的问责手段。 相似文献
98.
R. Hrach P. Barto? V. Hrachová 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):417-423
The influence of the unevenness of substrates immersed into plasma important for plasma-based treatment of materials were
studied by computer experiment. The role of both substrate properties and plasma parameters was investigated. For this analysis
the combination of multidimensional fluid modelling and particle simulation was used. The fluid part of our model consisted
of continuity equations for all charged species, energy balance equation for electrons and Poisson equation. The basic scattering
processes were also included. The particle simulation technique was used both for the calculation of electron energy distribution
function and for the derivation of quantities characterising plasma-surface interaction. This approach enabled us to study
in detail the structure of the sheath and presheath near metal substrates with realistic geometries and finite dimensions.
The main attention was devoted to the influence of substrate geometry in both macroscopic and microscopic spatial scales on
the local electric fields in plasma. 相似文献
99.
Dehua Wang Kaiyun Huang Shenglu Lin 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(3):699-706
The ionization of Rydberg hydrogen atoms near a metal surface at different scaled energies above the classical saddle point
energy has been discussed by using the semiclassical method. The results show that the atoms ionize by emitting a train of
electron pulses. In order to reveal the chaotic and escape dynamical properties of this system in detail, the sensitive dependence
of the ionization rate upon the scaled energy is discussed. As the scaled energy is close to the saddle point energy, the
ionization process of the hydrogen atom is nearly the same as the case of hydrogen atom in an electric field. There is only
a single pulse of electrons, with an exponentially decaying tail. With the increase of the scaled energy, the ionization rates
are similar to the case of the hydrogen atom in parallel electric and magnetic field, a series of electron pulses appear in
the ionization process. This is caused by classical chaos, which occurs for the metal surface. Our studies also suggest that
the metal surface can play the role of both the electric and the magnetic fields. Our theoretical analysis will be useful
for guiding experimental studies of the ionization of atoms near the metal surface. 相似文献
100.
Han Wang Christoph Junghans Kurt Kremer 《The European physical journal. E, Soft matter》2009,28(2):221-229
We employ the inverse Boltzmann method to coarse-grain three commonly used three-site water models (TIP3P, SPC and SPC/E)
where one molecule is replaced with one coarse-grained particle with isotropic two-body interactions only. The shape of the
coarse-grained potentials is dominated by the ratio of two lengths, which can be rationalized by the geometric constraints
of the water clusters. It is shown that for simple two-body potentials either the radial distribution function or the geometrical
packing can be optimized. In a similar way, as needed for multiscale methods, either the pressure or the compressibility can
be fitted to the all atom liquid. In total, a speed-up by a factor of about 50 in computational time can be reached by this
coarse-graining procedure. 相似文献