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751.
A study of surface dynamics of polymers. III. Surface dynamic stabilization by plasma polymerization
T. Yasuda K. Yoshida T. Okuno H. Yasuda 《Journal of Polymer Science.Polymer Physics》1988,26(10):2061-2074
As demonstrated in Part II of this series of studies, the hydrophobic character of CF4 plasma-treated Nylon 6 and poly(ethylene terephthalate) (PET) decay with time of water immersion, and the rate of decay can be used as a measure for the surface mobility of (substrate) polymers. The same method of using fluorine-containing moieties introduced by CF4 plasma treatment as surface labeling is applied to investigate the influence of a thin layer of plasma polymer of methane applied onto the surface of those polymers. An ultrathin layer of plasma polymer provides a barrier to the rotational and diffusional migration of the introduced chemical moieties from the surface into the bulk of the film. The influence of operational parameters of plasma polymerization on the surface dynamic stability are examined by measuring the decay rate constants for (subsequently) CF4 plasma-treated samples. The rate constant was found to decrease sharply with increasing value of plasma energy input manifested by J/kg monomer, and no decay was observed as the energy input reached a threshold value (about 6.5 GJ/kg for PET, about 7.0 GJ/kg for Nylon 6), indicating that unperturbable surfaces can be created by means of plasma polymerization. 相似文献
752.
Polarization versus electric field double hysteresis loops along the b-axis of TID2PO4 were observed. From this fact and the permittivity versus temperature characteristic, the low temperature phase of TID2PO4 was confirmed to be antiferroelectric. 相似文献
753.
An attempt is made to analyze the relationship between salt rejection and water flux of nonionic polymer membranes in reverse osmosis on the basis of the movement of water in the membranes. The salt rejection Rs is a consequence of transport depletion of salt in relation to water flux. The transport depletion can be quantitatively expressed through knowledge of the mode of water transport and by application of free-volume theory to membrane transport phenomena. Water permeation can be characterized by a parameter ω = RTK1/P1v1, K1 denoting hydraulic permeability, P1 diffusive water permeability, v1 the molar volume of water. Thus polymer membranes can be classified in three categories: ω = 1 (diffusion membranes); ω > 1 (diffusion-flow membranes); and ω ? 1 (flow membranes). Salt rejection Rs can be expressed in terms of P1, the diffusive salt permeability P2, and the effective pressure (Δp ? Δπ): Experimental results obtained with various hydrophilic polymers are presented as the dependence of Rs on the logarithm of water flux. Good agreement was found between the experimental data and the calculated curve. Excessive swelling of membranes results in bulk flow of water (high ω) with coupled transport of salt. Hence the salt rejection decreases quickly as water flux in creases beyond a threshold value above which water flux can be characterized as bulk flow. 相似文献
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The interaction of atomic hydrogen with a-Si:H films was studied by means of in situ ESR during H plasma treatment. H diffuses into the a-Si:H film and creates additional Si dangling bonds ( approximately 10(13) cm (-2)). We observed a high diffusion coefficient (>10(-10) cm (2) s (-1)) at the very initial stage of H treatment (<1 s). The resulting additional dangling bonds are spatially distributed ( approximately 100 nm) into the bulk film. The characteristic depth of dangling bond (db) distribution decreases with increasing H treatment temperature. The activated rate constants of db creation and annihilation reactions determine the distribution of additional dangling bonds at different treatment temperatures. 相似文献
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759.
Porous semiconductor compound nanoparticles have been prepared by a new technique utilizing electronic excitation. The porous structures are formed in GaSb particles, when vacancies are efficiently introduced by electronic excitation and the particle size is large enough to confine the vacancy clusters. The capture cross section of the surface layer in particles for the vacancies is smaller than that for the interstitials. Under the condition of supersaturation of vacancies in the particle core, porous structures are produced through the vacancy clusters to a void formation. 相似文献
760.
Effects of light irradiation on growth processes in the initial stage of growth of Ge films on (100)Si substrates by gas source molecular beam epitaxy using GeH4 have been investigated by in-situ RHEED observations. It has been found that the growth rate is enhanced by an Ar+ ion laser and a D2 lamp irradiation, and, moreover, that the growth process sequence of the Ge films irradiated by the Ar+ laser and D2 lamp is the same as that without irradiation. The irradiation effect on the photolysis of GeH4 gas has been examined by mass spectroscopy. The increase of the growth rate is due to the photolysis of GeH4 and the excitation of substrate surfaces by vacuum-ultraviolet light in the D2 lamp irradiation, and is due to only the excitation of substrate surfaces in the Ar+ laser irradiation. 相似文献