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51.
Luke Sangalli 《电子设计技术》2009,16(10):72-72,55
最近出现了几篇文章.介绍了一些新奇的方法.旨在增加微处理器借助数量有限的引脚所能驱动的LED的数量(参考文献1)。标准的多路复用方法是由于多位七段显示器而流行起来.而在引脚稀少的设计方案中.它已让位于“Charlie多路复用(Charleplexing)”。 相似文献
52.
53.
T. H. Prettyman C. S. Cooper P. N. Luke P. A. Russo M. Amman D. J. Mercer 《Journal of Radioanalytical and Nuclear Chemistry》1998,233(1-2):257-264
A physics-based approach to gamma-ray response-function generation is presented in which the response of CdZnTe detectors
is modeled from first principles. Numerical modeling is used to generate response functions needed for spectrum analysis for
general detector configurations (e.g., electrode design, detector materials and geometry, and operating conditions). With
numerical modeling, requirements for calibration and characterization are significantly reduced. Elements of the physics-based
model, including gamma-ray transport, charge carrier drift and diffusion, and circuit response, are presented. Calculated
and experimental gamma-ray spectra are compared for a coplanar-grid CdZnTe detector. 相似文献
54.
Two solid-membrane methods exist for separating mixtures of organic liquids. They are pervaporation, in which the product phase is a vapour, and hyperfiltration in which feed and product phases are both liquid. Technically hyperfiltration is similar to reverse osmosis but, if that term is to be used at all, it should be restricted to dilute solutions of solutes to which the membrane is almost semi-permeable. The polymer membranes which have been found so far to give significant degrees of separation and fluxes with organic liquid mixtures have been crystalline polar polymers with high glass temperatures. The problems of membrane preparation are thus more severe than with almost amorphous, freely soluble polymers such as cellulose acetate.The absorption of liquids from a mixture by a polymer and their permeation in the polymer have received relatively little attention and it is not yet possible to infer the behaviour from that of the polymer towards each liquid alone. Nevertheless a theory of hyperfiltration can be developed based on Henry's and Fick's laws and neglecting any direct coupling of flows. The equations which predict the separation and fluxes are useful in the first place to predict the thermodynamic restraints on any potentially useful separation process. It turns out that relatively large pressures are required, 100 atm or more, and hyperfiltration is better adapted to further purifying a relatively good product than to recovering a small amount of a valuable substance from a large volume of waste.The equations lend themselves to a direct experimental test. An apparatus for doing this has been constructed and two liquid mixtures and membranes have been studied. They are toluene + n-heptane with an asymmetric polyacrylonitrile membrane and methanol + isobutanol with a uniform cellulose membrane. The mixtures were chosen as being thermodynamically close to ideal because this simplifies the interpretation of the data. Their nonideality has been taken fully into account.The results show that the simple theory accounts very well for the observed facts. For the first system the selectivity coefficient was about 2 and for the second, about 15.The mechanism of transport is found to be the normal solution-diffusion mechanism for permeation of organic solvents in polymers. There is some positive frictional coupling between the two liquids as a result of which the improvements in separation to be expected from an increase in the applied pressure are not achieved quantitatively. The increasing absorption of liquid by the membrane as the mole fraction of the preferentially absorbed liquid in the mixture is increased increases its permeability to both components by about 相似文献
55.
56.
Savici AT Fukaya A Gat-Malureanu IM Ito T Russo PL Uemura YJ Wiebe CR Kyriakou PP MacDougall GJ Rovers MT Luke GM Kojima KM Goto M Uchida S Kadono R Yamada K Tajima S Masui T Eisaki H Kaneko N Greven M Gu GD 《Physical review letters》2005,95(15):157001
Muon spin relaxation measurements in high transverse magnetic fields [FORMULA: SEE TEXT] revealed strong field-induced quasistatic magnetism in the underdoped and Eu-doped (La,Sr)2CuO4 and La1.875Ba0.125CuO4, existing well above Tc and TN. The susceptibility counterpart of Cu spin polarization, derived from the muon spin relaxation rate, exhibits a divergent behavior towards T approximately 25 K. No field-induced magnetism was detected in overdoped La1.81Sr0.19CuO4, optimally doped Bi2212, and Zn-doped YBa2Cu3O7. 相似文献
57.
Vivekananda S Sadílek M Chen X Adams LE Turecek F 《Journal of the American Society for Mass Spectrometry》2004,15(7):1068-1079
The title radical (1) is generated in the gas-phase by collisional neutralization of carbonyl-protonated oxolan-3-one. A 1.5% fraction of 1 does not dissociate and is detected following reionization as survivor ions. The major dissociation of 1 (approximately 56%) occurs as loss of the hydroxyl H atom forming oxolan-3-one (2). The competing ring cleavages by O[bond]C-2 and C-4[bond]C-5 bond dissociations combined account for approximately 42% of dissociation and result in the formation of formaldehyde and 2-hydroxyallyl radical. Additional ring-cleavage dissociations of 1 resulting in the formation of C(2)H(3)O and C(2)H(4)O cannot be explained as occurring competitively on the doublet ground (X) electronic state of 1, but are energetically accessible from the A and higher electronic states accessed by vertical electron transfer. Exothermic protonation of 2 also produces 3-oxo-(1H)-oxolanium cation (3(+)) which upon collisional neutralization gives hypervalent 3-oxo-(1H)-oxolanium radical (3). The latter dissociates spontaneously by ring opening and expulsion of hydroxy radical. Experiment and calculations suggest that carbohydrate radicals incorporating the 3-hydroxyoxolan-3-yl motif will prefer ring-cleavage dissociations at low internal energies or upon photoexcitation by absorbing light at approximately 590 and approximately 400 nm. 相似文献
58.
Vinyl acetate formation by the reaction of ethylene with acetate species on oxygen-covered Pd(111) 总被引:1,自引:0,他引:1
Stacchiola D Calaza F Burkholder L Tysoe WT 《Journal of the American Chemical Society》2004,126(47):15384-15385
The reaction pathway of vinyl acetate synthesis is scrutinized by reacting gas-phase ethylene (at an effective pressure of 1 x 10-4 Torr) with eta2-acetate species (with a coverage of 0.31 +/- 0.02 monolayer) on a Pd(111)-O(2x2) model catalyst surface in ultrahigh vacuum. It is found that the 1414 cm-1 infrared feature due to the symmetric OCO stretching mode of the acetate species decreases in intensity due to reaction with gas-phase ethylene, while temperature-programmed desorption experiments demonstrate that vinyl acetate is formed. The formation of ethylidyne species is detected when almost all of the acetate species have been removed. The experimental removal kinetics are reproduced by a model in which adsorbed acetates react with an ethylene-derived (possibly ethylene or vinyl) species, where ethylene adsorption is blocked by the acetate present on the surface. 相似文献
59.
Higham LT Kreher UP Mulder RJ Strauss CR Scott JL 《Chemical communications (Cambridge, England)》2004,(20):2264-2265
A member of a new class of novel macrocycles possessing both polyether and phenolic functionalities, forms dimers in both the solid-state and in solution when exposed to chloroform, dichloromethane or toluene, but does not self-associate in the presence of dimethyl sulfoxide. 相似文献
60.
Luke B. L. Pace P. E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2007,53(5):1759-1766
The robust symmetrical number system (RSNS) is a modular system formed using Nges2 integer sequences and ensures that two successive RSNS vectors (paired terms from all N sequences) differ by only one integer. This integer Gray-code property reduces the possibility of encoding errors and makes the RSNS useful in applications such as folding analog-to-digital converters (ADCs), direction finding antenna architectures, and photonic processors. This paper determines the length of combined sequences that contain no vector ambiguities. This length or longest run of distinct vectors we call the RSNS dynamic range (Mcirc). The position of Mcirc which is the starting point in the sequence is also derived. Computing Mcirc and the position of Mcirc allows the integer Gray-code properties of the RSNS to be used in practical applications. We first extend our two-sequence results to develop a closed-form expression for Mcirc for a three-sequence RSNS with moduli of the form 2r-1,2r,2r+1. We then extend the results to solving the N-sequence RSNS ambiguity locations in general 相似文献