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21.
F2 color centers with a superhigh concentration (5000-cm–1 absorption coefficient at 450 nm) were formed by high-density electron beams in a layer of LiF crystals of micrometer thickness. The F2-centers excited by high-power nanosecond wide-band optical pulses (the “soft” pumping regime) efficiently amplified the laser radiation and showed high stability under these conditions. A low stability of F2-centers to laser radiation (the “hard” excitation regime) is explained by the dissociation of (F 2 + , F–) pairs induced by two-step ionization of F2-centers: (2hν > 4.5 eV) → F2 → (F2)* → F 2 + + e; F + e → F–; F 2 + + F– → 3F. 相似文献
22.
A new mechanism is presented to model the relaxation phenomena in pentagonal nanorods (PNRs) – elongated multiple twinned crystals. It is demonstrated that a shell possessing crystal mismatch with respect to the PNR core region will reduce the internal energy of the PNR associated with wedge disclinations of strength 7°20′ lying along the PNR axis. We predict the existence of an optimal magnitude for core/shell crystal lattice mismatch and an optimal shell thickness providing maximum energy release for this mechanism of mechanical stress relaxation. The considered relaxation mechanism can be realized by the diffusion of impurities in the shell region without change of the PNR radius or by growth of a thin mismatched shell layer with the corresponding thickening of PNR. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
23.
Shozo Kawamura Makoto Suzuki Hossain MD. Zahid Hirofumi Minamoto 《Applied Acoustics》2009,70(11-12):1393-1399
Machine condition monitoring and fault diagnosis of rotating machinery are very important because of the wide use of rotating machinery in industry. Couplings and gears are used in many mechanical systems to connect elements and transmit power. The system is usually modeled as a single-degree-of-freedom system with a piecewise linear spring property, where the mass of main machine is only considered. In the present study, the dynamic behavior of a system with an unsymmetrical nonlinearity and a significant mass of the connecting part was investigated both experimentally and by numerical simulation. In the experiment, a 1/3 sub-harmonic oscillation was observed, but this oscillation was not found in the simulation using a single-degree-of-freedom system, in which the mass of the connecting part was ignored. However, when a two-degrees-of-freedom system was used that considered both the mass of the connecting part and the impact property, the 1/3 sub-harmonic oscillation was observed. Thus it is recognized that an adequate mathematical model for diagnosis in the early stage of abnormality must be selected on the basis of the mass ratio between the connecting part and the main body. 相似文献
24.
E. D. Matveeva T. A. Podrugina I. N. Kolesnikova N. S. Zefirov 《Russian Chemical Bulletin》2010,59(2):411-417
Reactions of benzoylhydrazones derived from heterocyclic and aromatic aldehydes and aliphatic, heterocyclic, and aliphatic-aromatic
ketones with diethyl phosphite in the presence of [tetra(tert-butyl)phthalocyanine]aluminum chloride afford α-benzoylhydrazino phosphonates in high yields. 相似文献
25.
A. N. Mirskova G. G. Levkovskaya O. P. Kolesnikova O. M. Perminova E. V. Rudyakova S. N. Adamovich 《Russian Chemical Bulletin》2010,59(12):2236-2246
A general method for the synthesis of 1-alkyl(allyl)(benzyl)-substituted (indol-3-yl)-sulfanylalkanecarboxylic acids and hexane-1,6-diyl(1,4-phenylenemethylene)bisindol-3-ylsulfanylalkanecarboxylic
acids from the corresponding N-substituted indoles and bisindoles, thiourea, iodine, and halogencarboxylic acids was developed.
The oxidation of substituted (indol-3-yl)sulfanylalkanecarboxylic acids for the first time afforded their analogs containing
the sulfonyl group. New (2-hydroxyethyl)ammonium salts of 1-R-indol-3-ylsulfanyl(sulfonyl)-alkanecarboxylic acids, which are
structural analogs of highly active immunomodulators of indacetamin and VILIM, were synthesized. Among the studied (2-hydroxyethyl)ammonium
salts of 1-R-indol-3-ylsulfanylacetic and -sulfonylalkanecarboxylic acids, the compounds exhibiting high dose-dependent antiproliferative
activity by the ability to affect the spontaneous and mitogen-stimulated splenocyte proliferation of mice in vitro were found. 相似文献
26.
MD. Daloar Hossain Le Thi Bao Tran Jong Myung Park Kwon Taek Lim 《Journal of polymer science. Part A, Polymer chemistry》2010,48(22):4958-4964
A new, efficient method for synthesizing stable nanoparticles with poly(ethylene oxide) (PEO) functionalities on the core surface, in which the micellization and crosslinking reactions occur in one pot, has been developed. First, amphiphilic PEO‐b‐PS copolymers were synthesized by reversible addition fragmentation chain transfer (RAFT) radical polymerization of styrene using (PEO)‐based trithiocarbonate as a macro‐RAFT agent. The low molecular weight PEO‐b‐PS copolymer was dissolved in isopropyl alcohol where the block copolymer self‐assembled as core‐shell micelles, and then the core‐shell interface crosslink was performed using divinylbenzene as a crosslinking agent and 2,2′‐azobisisobutyronitrile as an initiator. The design of the amphiphilic RAFT agent is critical for the successful preparation of core‐shell interface crosslinked micellar nanoparticles, because of RAFT functional groups interconnect PEO and polystyrene blocks. The PEO functionality of the nanoparticles surface was confirmed by 1H NMR and FTIR. The size and morphology of the nanoparticles was confirmed by scanning electron microscopy, transmission electron microscopy, and dynamic laser light scattering analysis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献
27.
L. E. Kitaev E. E. Kolesnikova E. N. Biryukova N. V. Kolesnichenko S. N. Khadzhiev 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2013,87(4):668-673
The structural changes and acid characteristics of the zeolite ZSM-5 modified with titanium and sulfur were studied. The modifier components were chemically bonded to the zeolite structure. The acid characteristics of zeolite changed and superacid centers appeared. A physicochemical study showed that treatment of zeolite with titanium tetrachloride and sulfuryl chloride did not change its structure and molecular-sieve properties. 相似文献
28.
MD. Anwarul Hasan Carlos F. Lange Malcolm L. King 《ournal of non Newtonian Fluid Mechanics》2010,165(21-22):1431-1441
The effect of viscoelastic properties and surface tension of artificial mucus simulant samples on the size distribution and volume concentration of bioaerosol droplets generated during simulated coughing was investigated through in vitro experiments. The mucus simulant samples had viscoelastic properties in a similar range as those of real human airway mucus. The mucus simulant gels were prepared by mixing various proportions of 0.5–1.7% locust bean gum solution and 0.1 M sodium tetraborate (XLB) solution. Surface tension of one set of samples was varied by adding different amounts of SDS (sodium dodecyl sulfate) surfactant while the measurement of surface tension was performed using ADSA (axisymmetric drop shape analysis) method. The viscoelastic properties of the samples were measured using a Bohlin Gemini 200 HR (Malvern, UK) nano-rheometer with peltier plate assembly. An artificial cough machine was used to simulate human cough, generating aerosol droplets in a model trachea attached to the front of the cough machine. The size distribution and volume concentration of the droplets generated through simulated cough were measured using a laser diffraction particle sizer (SprayTec, Malvern, USA). The surface tension was found to have negligible effect on the characteristic of generated droplets within the range of this investigation. The experimental results showed a decrease in particle size as the samples changed from a viscous fluid type to a viscoelastic to an elastic solid type sample. The volume concentration also changed significantly as the viscoelasticity of the samples was varied. 相似文献
29.
The effect of a conducting liquid lubricant on the heating of a rail and projectile (armature) is studied theoretically and
experimentally. It is shown that both the Joule and friction heating of the accelerated body can be reduced significantly
by using resistive liquid films. When the contact resistance of the film is high, its temperature is determined by two competing
processes: Joule heating and heat removal by the moving film. As a result, the dependence of the film temperature on the magnetic
Reynolds number, its thickness, and its resistance is nonmonotonic. In the limiting case where the velocity skin effect is
completely suppressed and the magnetic Reynolds number is sufficiently high, the film temperature is extremely low. In intermediate
cases, however, the film temperature can turn out to be rather high and exceed the melting point of the armature. Viscous
dissipation in the liquid film has no significant effect on the temperature of the rail-armature interface until the melting
of the armature is determined by Joule heating within it. In the case where the velocity skin effect is strongly suppressed,
viscous dissipation along with Joule heating in the resistive film can become one of the major factors controlling the attainable
velocity of bodies in railguns.
Zh. Tekh. Fiz. 69, 117–125 (October 1999) 相似文献
30.
The possibility of using a disclination approach to describe the structure and properties of fullerenes is discussed. It is
shown that the conversion of a planar carbon monolayer into a spherical macromolecule can be viewed as the result of introducing
12 disclinations with power π/3 into the original layer.
Fiz. Tverd. Tela (St. Petersburg) 40, 1178–1180 (June 1998) 相似文献