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961.
N. Mazars 《商业与工业应用随机模型》1989,5(3):203-231
Binary coherent system theory has played an important part in reliability. Its extension to (‘degradable’ or ‘multistate’ or) multinary systems has recently been considered in various papers, through various definitions. This paper studies the most general model for multinary systems, proposes a unified viewpoint on multinary coherent systems and gives unified arguments to apply and to investigate further the binary and multinary cases. In a more detailed way, the ‘helpful bridge’ lately proposed by Block and Savits1 between the binary and multinary cases is completed and multinary systems then can be studied in terms of monotone binary coherent systems, introduced in a companion paper.2 Through various results, multinary systems are examined in terms of structure functions and of life functions; fundamental relations for their analysis are obtained with their set characterizations; the main axis that can be retained among the numerous types of coherence is emphasized, in a unified way, through relevance; reliability models are examined through performance processes, life lengths and performance functions; and Birnbaum's factors of importance are thoroughly extended to the multinary case. Fundamental results proposed in previous studies are thus completed with a shorter unified approach. 相似文献
962.
Chromate conversion coatings are used on aluminium alloys, primarily for their renowned corrosion resistant properties. Although these coatings are in common industrial use, neither the protection mechanisms, nor the coating interation with the intermetallic precipitation phases are fully understood. Macroscopic models have been developed in order to represent the galvanic cells present in aluminium alloys due to the presence of such intermetallic particles. Particles modelled include CuAl2, FeAl3 and Cu2FeAl7, all know to be cathodic to the aluminium matrix. Variations in deposition, both in composition and thickness, are indicative of the mechanisms of deposition over each phase. Characterisation of the coating deposition was carried out using X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy, Auger electron spectroscopy, scanning electron microscopy with X-ray analysis. Depositional characteristics have been determined for each phase. The coating on the intermetallic phases is primarily Al oxide, and is significantly thinner than the coating on the matrix. This coating on the matrix consists mainly of a mixed Cr/Al oxide. The coating on the intermetallic phases was only one tenth the thickness of the matrix coating, and contained higher levels of Fe, Al and O. Matrix coating chemistry predominated with Cr, O, Fe and N, indicative of a chromate conversion coating. The mechanism for reduced rates of deposition over intermetallic phases was found to be affected by fluorine ion attack leading to intermetallic de-alloying and decomposition of Fe(CN)62− accelerator into amide groups on the matrix. 相似文献
963.
We have characterized the structural behaviour of ethanethiol self-assembled monolayers (SAMs) on Au(1 0 0) in 0.1 M H2SO4 as a function of electrode potential, using in-situ scanning tunneling microscopy (STM). After modification of the Au(1 0 0) electrode in an ethanolic solution of ethanethiol, STM images in air reveal a disordered thiol adlayer and a surface that is covered by 25% of monoatomic high gold islands, which originate from lifting of the (hex) reconstruction during thiol adsorption. In contrast to alkanethiol SAMs on Au(1 1 1), no vacancy islands are seen on the Au(1 0 0) surface. After contact of the SAM-covered Au(1 0 0) electrode with 0.1 M H2SO4 under potential control, two different structures are observed, depending on the potential range positive or negative of +0.3 V vs. SCE. In both cases the emerging ordered structures are quadratic, their unit cells being rotated by 45° with respect to the main crystallographic axes of the substrate. However, the ordered structure at negative potentials is more densely packed than the one at positive potentials, and in addition the surface reveals an almost 50% coverage of monoatomic high gold islands. The structure of the SAM changes reversibly with the electrode potential, the long range order gradually decreasing with each transition. Concomittant with this structure transition monoatomic deep holes are created when the potential is stepped from the cathodic to the anodic region. The experimental observations are rationalized by a high mobility of the gold thiolate moiety, causing the surface density of the SAM-covered gold to change drastically with potential. 相似文献
964.
When a laser source is used to illuminate a transmission hologram, the zero order beam is not utilised and is just wasted. The paper describes a new technique for economical utilisation of laser light by recycling the transmitted light to reconstruct a number of holograms simultaneously for viewing by a large number of observers. There is no danger to viewer who is exposed to the undiffracted laser beams transmitted through the hologram. The paper also discusses the diffraction efficiency requirement of successive hologram and the limit of number of holograms in the scheme. 相似文献
965.
We consider the superpositions of spin coherent states and study the coherence properties and spin squeezing in these states. The spin squeezing is examined using a new version of spectroscopic squeezing criteria. The results show that the antibuching effect can be enhanced and spin squeezing can be generated in the superpositions of two spin coherent states. 相似文献
966.
研究表明,保证经典轨道具有封闭性的Bertrand定理可以进一步推广,在适当的角动量下,仍存在着非椭圆的闭合轨道.对于屏蔽Coulomb场,可获得广义Runge-Lenz矢量.这种轨道封闭性与径向Schr?dinger方程因式分解相对应. 相似文献
967.
二元光学元件及其应用 总被引:3,自引:0,他引:3
叙述一种新型衍射光学元件──—二元光学元件的设计原理及其制造方法。分析二元光学元件的衍射效率和色差,讨论光刻法对其最小特征线宽的限制因素,阐明二无光学元件的特点及应用。 相似文献
968.
969.
X-ray photoemission spectra, resistivity and susceptibility of CeNi2Sb2 and CeCu2Sb2 were measured and are discussed. The results indicate that these alloys are Kondo systems. For comparison of the valence band properties, the spectra of the isostructural alloys of RT2X2-type with R = La, Gd, T = Cu, Ni and X = Sn, Sb were investigated, too. 相似文献
970.
Summary We discuss some recent theoretical studies of the kinetics of the collapse transition in homopolymers. An isolated polymer
is modelled using computer simulation, and a time-dependent mean-field theory. The mean-field theory is analysed analytically
for early stages, and for short polymers the equations are studied numerically. The results of simulation and theory are compared
yielding, we argue, a consistent physical picture. Quantitative comparisons are not yet given, but seem relatively promising.
Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4– 1994. 相似文献