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71.
An ultra-high speed, time-resolved particle image velocimetry (PIV) system is developed to measure velocity fields created
by explosive detonators. When initiated into a gas, the detonators generate blast waves that propagate outwards from the origin
of initiation at supersonic speeds. The PIV system consists of a custom eight-pulse Nd:YAG laser system and an ultra-high
speed camera system comprising four dual-frame CCD cameras optically combined to share a single optic axis. The system is
capable of sampling the flow field four times at up to 333 MHz or eight times at up to 8 MHz. System development is discussed,
and preliminary application to the complex flow behind the blast wave from an exploding bridge wire detonator is demonstrated. 相似文献
72.
Maruthi Kumar Narayanam Yong Liang K. N. Houk Jennifer M. Murphy 《Chemical science》2016,7(2):1257-1261
Density functional theory (DFT) calculations and experiments in tandem led to discoveries of new reactivities and selectivities involving bioorthogonal sydnone cycloadditions. Dibenzocyclooctyne derivatives (DIBAC and BARAC) were identified to be especially reactive dipolarophiles, which undergo the (3 + 2) cycloadditions with N-phenyl sydnone with the rate constant of up to 1.46 M–1 s–1. Most significantly, the sydnone-dibenzocyclooctyne and norbornene-tetrazine cycloadditions were predicted to be mutually orthogonal. This was validated experimentally and used for highly selective fluorescence labeling of two proteins simultaneously. 相似文献
73.
Qingqing Gao Aijun Yang Xiaohua Wang Anthony B. Murphy Yunjia Li Chaojun Zhang Yanhui Lu Li Huan Zhaofang Zhu Mingzhe Rong 《Plasma Chemistry and Plasma Processing》2016,36(5):1301-1323
It has become increasingly clear that deviations from local thermodynamic equilibrium occur in thermal plasmas. This paper is devoted to investigating the non-equilibrium characteristics of CO2 thermal plasmas, which have wide application in industry. A two-temperature chemical kinetic model with a comprehensive chemical system is developed to calculate the non-equilibrium characteristics of CO2 thermal plasmas for a wide temperature range, from 12,000 to 500 K, at atmospheric pressure. The non-equilibrium results are compared to the equilibrium composition obtained by Gibbs free energy minimization, and significant deviations are found at lower temperatures. Based on the dependence of molar fractions on temperature, the dominant species are determined in three temperature ranges. The dominant reactions are then obtained by considering their contribution to the generation and loss of the dominant species. Using the dominant species and reactions, the full model is simplified into three simpler models and the accuracy of the simplified models is evaluated. It is shown that this approach greatly reduces the number of species and reactions considered, while showing good agreement with the full model, with a root-mean-square error of no more than 4 %. Thus, the complicated physicochemical processes in non-equilibrium CO2 thermal plasmas can be characterized by relatively few species and reactions. It is suggested that the two-temperature chemical kinetic model developed in this paper can be applied to the full range of pressures that occur in arc welding, arc quenching and other industrial applications. In addition, the simplified methods can be applied in multi-dimensional models to reduce the chemical complexity and computing time while capturing the main physicochemical processes in non-equilibrium CO2 thermal plasmas. 相似文献
74.
High-throughput approaches for the discovery and optimization of new olefin polymerization catalysts
Murphy V Bei X Boussie TR Brümmer O Diamond GM Goh C Hall KA Lapointe AM Leclerc M Longmire JM Shoemaker JA Turner H Weinberg WH 《Chemical record (New York, N.Y.)》2002,2(4):278-289
The discovery of new olefin polymerization catalysts is currently a time-intensive trial-and-error process with no guarantee of success. A fully integrated high-throughput screening workflow for the discovery of new catalysts for polyolefin production has been implemented at Symyx Technologies. The workflow includes the design of the metal-ligand libraries using custom-made computer software, automated delivery of metal precursors and ligands into the reactors using a liquid-handling robot, and a rapid primary screen that serves to assess the potential of each metalligand-activator combination as an olefin polymerization catalyst. "Hits" from the primary screen are subjected to secondary screens using a 48-cell parallel polymerization reactor. Individual polymerization reactions are monitored in real time under conditions that provide meaningful information about the performance capabilities of each catalyst. Rapid polymer characterization techniques support the primary and secondary screens. We have discovered many new and interesting catalyst classes using this technology. 相似文献
75.
Kuehn K Mehta S Fu H Genio E Murphy D Liu F Liu Y Ahlers G 《Physical review letters》2002,88(9):095702
We report new measurements in four cells of the thermal boundary resistance R between copper and (4)He below but near the superfluid-transition temperature T(lambda). For 10(-7)< or =t identical to 1-T/T(lambda))< or =10(-4) fits of R = R(0)t(-x(b))+R(B) to the data yielded x(b) approximately equal to 0.18, whereas a fit to theoretical values based on the renormalization-group theory yielded x(b) = 0.23. Alternatively, a good fit of the theory to the data could be obtained if the amplitude of the prediction was reduced by a factor close to 2. The results raise the question whether the boundary conditions used in the theory should be modified. 相似文献
76.
The preparation and physical properties of the layered VS2, MyV1?yS2 (M = Fe or Cr), and their lithium intercalation adducts are described. These compounds were prepared by oxidative delithiation of LiMyV1?yS2 with iodine. Crystallographic distortions present in LixVS2 (0.25 ? x ? 0.6) are suppressed by Fe or Cr substitution for V. The electrochemical sluggishness of Li/Li+/VS2 cells is reduced by the substitution. 相似文献
77.
Activated aryl aroylcyclopropanes cyclise with Lewis acids under mild conditions to 1-aryltetralones. 相似文献
78.
H. V. Murphy 《The Journal of the Operational Research Society》1969,20(1):59-79
Quantitative methods are derived to assist buyers purchasing commodities in fluctuating price markets. Demand is known whilst price is a stochastic variable which may contain trends or seasonal fluctuations. The essential feature of the problem is that the buyer has many opportunities to make a purchase.Mathematical models are formulated to describe particular commodity buying problems. The optimal purchasing policy is derived by using dynamic programming. It consists of a set of discrete price breaks at each buying opportunity together with the associated stock levels the buyer should aim to achieve at each price break with his purchase at this opportunity. The price breaks are dependent on the probability density functions of future prices and the number of future buying opportunities. Recurrence relations are derived to calculate these price breaks. The case of restrictions on the purchase quantity at each price offer, either because of supply limitations or by the buyer as a policy decision, and price discounts are also considered.A case study illustrating the techniques is given and the methods are extended to purchasing for a blending problem with substitutable commodities. 相似文献
79.
A new stable product from the reaction of nitrosobenzene and N-ethoxycarbonylazepine is shown to be a 1,4-cycloadduct. 相似文献
80.
Murphy CJ Sau TK Gole AM Orendorff CJ Gao J Gou L Hunyadi SE Li T 《The journal of physical chemistry. B》2005,109(29):13857-13870
This feature article highlights work from the authors' laboratories on the synthesis, assembly, reactivity, and optical applications of metallic nanoparticles of nonspherical shape, especially nanorods. The synthesis is a seed-mediated growth procedure, in which metal salts are reduced initially with a strong reducing agent, in water, to produce approximately 4 nm seed particles. Subsequent reduction of more metal salt with a weak reducing agent, in the presence of structure-directing additives, leads to the controlled formation of nanorods of specified aspect ratio and can also yield other shapes of nanoparticles (stars, tetrapods, blocks, cubes, etc.). Variations in reaction conditions and crystallographic analysis of gold nanorods have led to insight into the growth mechanism of these materials. Assembly of nanorods can be driven by simple evaporation from solution or by rational design with molecular-scale connectors. Short nanorods appear to be more chemically reactive than long nanorods. Finally, optical applications in sensing and imaging, which take advantage of the visible light absorption and scattering properties of the nanorods, are discussed. 相似文献