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101.
The adsorption of HNO3/H2O mixtures on Ag(110) was investigated to learn more about the chemistry of the metal/electrolyte interface. The experiments were performed in ultrahigh vacuum (UHV) using thermal desorption spectroscopy (TDS), low energy electron diffraction (LEED), and electron stimulated desorption ion angular distribution (ESDIAD) over temperatures of 80–650 K and coverages of 0–10 monolayers (ML). As this is the first known study of HNO3 in UHV, the mass spectrometer cracking pattern for HNO3 is here reported. HNO3 adsorbs irreversibly on the clean surface at 80 K and loses its acidic proton to form an adsorbed surface nitrate (NO3) below 150 K. The saturation amount of adsorbed NO3 is 0.4 ± 0.1 ML for which adsorption occurs in either a normal or split c(2 × 2) structure. N03 is stable on the surface up to 450 K beyond which it decomposes directly to gaseous NO2 and NO and adsorbed atomic oxygen. NO3 decomposition is first order with an activation energy Ea = 151±4 kJ mol−1 and a pre-exponential factor of A = 1015.4±0.4s−1. NO3 stabilizes adsorbed H2O by about 8 kJ mol−1 and is hydrated by as many as three H2O molecules. Multilayers of HNO3/H2O desorb at 150–220 K and show evidence of extensive hydrogen bonding and hydration interactions. No evidence for HNO3-induced corrosion or other surface damage was detected in any of these experiments. 相似文献
102.
103.
Duane C. Hrncir Laura M. Barden Mark R. Wells Peter C. Stark 《Journal of inclusion phenomena and macrocyclic chemistry》1988,6(3):233-236
Tetrabutylammonium salts of the mixed haloindates, [Bu4N][InCl3X], X=Cl, Br, I, interact with aromatic solvents forming liquid inclusion compounds. The aromatic/cation ratio (A/C), a measure of the amount of guest aromatic, has been determined for a variety of simple aromatics. The values range from 2.6 to 0.4, substantially lower than the A/A of similar [Bu4N][Al2R6X] liquid clathrates. The ability of these liquid clathrates to function as catalysis media has been explored. The solubility of (Ph3P)2Rh(CO)Cl and (Ph3P)3RhCl in the various clathrates was determined. It was found that significant leaching of the catalyst into the bulk aromatic solvent occurred, ranging from 13 to 94%. A related liquid clathrate, [Li·12-crown-4][InCl4]·(C6H5CH3)2, had <1% of the dissolved catalyst leached. 相似文献
104.
本文报导了采用氩离子激光器来泵浦Pr3+:YLF晶体,应用声光调制器实现了主动锁模;同时应用振动─高反射平面镜也实现了被动锁模,两种锁模均得到了ps光脉冲.据作者了解这是这种晶体材料的第一次锁模运转. 相似文献
105.
Stetter M. Felsner P. Christiansen J. Frank K. Gortler A. Hintz G. Mehr T. Stark R. Tkotz R. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1995,23(3):283-293
The intention of this paper is to give an overview of recent experiments explaining the development and transition of the discharge phases in a pseudospark. The reported experiments include single gap pseudospark discharges in ultra-high-vacuum systems with hydrogen as working gas, as well as multigap pseudospark discharges in argon. Temporally and spatially resolved framing photography, spectrometry, raster electron microscopy and time resolved electrical measurements are presented. The experiments comprise a current range of some hundreds of amps to 60 kA. The results are used to specify the four characteristic phases of the pseudospark: Townsend-, hollow cathode-, high current- and metal vapor arc phase 相似文献
106.
C. W. Stark 《K-Theory》1991,5(4):333-354
We exhibit infinitely many commensurability classes of smooth closed manifolds M
m
, for all m 12, such that the universal cover of M is the product of a sphere and a Euclidean space and such that 1(M) contains finite dihedral subgroups. 相似文献
107.
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110.
THE AVAILABILITY OF SOLAR RADIATION BELOW 290 nm AND ITS IMPORTANCE IN PHOTOMODIFICATION OF POLYMERS
R. E. BARKER JR. 《Photochemistry and photobiology》1968,7(3):275-295
Abstract— On a percentage basis, ozone is a very minor component of the atmosphere; at STP it would make a layer only about 2 mm thick. On almost every other basis (biological, meteorological, paleontological, photochemical, etc.) it is a major component, due mainly to the tremendous reduction in solar ultraviolet flux which it causes in the 220–290 nm region. Since no data are available for Λ < 285 nm, a rational basis for estimating the flux reaching the earth's surface in this region is discussed. Variations in ozone concentration are of great importance, and it is possible to have more radiation with Λ < 270 nm fall on a surface in one extreme day than in several years of typical days. Often, persons involved in studies of polymer degradation by sunlight mention that a negligible fraction (1 ppm) of the radiant flux reaching the earth's surface is associated with wavelengths below 290 nm and infer that studies at shorter wavelengths will not be of much practical value. Such inferences are questionable for at least two reasons. (1) The quantum flux density below 290 nm is about 1016 photons cm-2 month-1 , so that considerable long-term damage is possible since most of the flux will be absorbed in a layer only a few microns thick. (2) Even if solar radiation below 290 nm were completely absent, the existence of correlations between absorption peaks in the near ultraviolet and visible, and in the infrared with ionization potentials typically 6–12 eV or 200-100 nm) is evidence that we may expect studies in the ultraviolet and extreme ultraviolet (EUV) to provide important clues to the problem of improving the resistance of polymers to sunlight. 相似文献