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971.
The proteinoid cells are assembled of thermal polymers of amino acids. Typically, an appropriate mixture of amino acids containing
aspartic or glutamic acid is heated at 190°C for 6 h, stirred with water for 2 h, dialyzed during 2 d, and lyophilized. Spheroidal
cells are made from such polymer by dissolving it in the water by boiling, and then cooling. Many of them can be made by sonication
at room temperature.
These artificial cells, ranging from microns to tens of microns in diameter (depending on composition and preparation), have
double membranes and various internal compositions. The spherules can microencapsulate dyes, oxidant-reductant compounds or
acceptor-donor substances, and can be packed together.
Such spherules display electrical polarization and electrical discharges and respond to intra- and extracellular ionic and
electric influence upon membrane and action potential. These properties arise from the double membrane structure, asymmetric
membrane permeability, and channeling phenomena.
Such features as exponential dependence of the steady-state conductance and capacitance as well as negative resistance of
the membrane seem to be responsible for the flip-flop alternations of the membrane polarization, rhythmic electric oscillations,
and all-or-none action potentials.
The presence of such chromophores as pteridine and flavin in polymers constituting these cells is responsible for their photosensitivity. 相似文献
972.
The intermolecular reactivities of amino-substituted perchlorotriphenylmethyl radicals 1-3 were studied, with particular emphasis on electron transfer (ET) reactions. The natural fluorescence lifetimes and the rates of the electron-transfer quenching were studied with several electron donors and acceptors. Fluorescence quenching studies demonstrate the importance of the redox potentials of the ET pair on the observed steric and electronic properties. 相似文献
973.
The separation of coeluting congeners of Aroclor 1242, 1254, and 1260 on a DB-1 (low polarity) capillary gas chromatographic (GC) column is achieved when cuts of those peaks are transferred onto a smectic liquid crystalline column, which is commercially available. This procedure requires the use of a gas chromatograph equipped with two independent ovens for optimizing the temperature conditions of each column. Excellent base line separations are achieved on multicuts, up to six, of the same injection. This unique multidimensional/multimodal capillary GC system, in which the two separation modes of vapor pressure and molecule geometry are employed, is a powerful analytical technique for the separation of complex organic mixtures. 相似文献
974.
H. Yamashita H. Nishiguchi N. Kamada M. Anpo Y. Teraoka H. Hatano S. Ehara K. Kikui L. Palmisano A. Sclafani M. Schiavello M. A. Fox 《Research on Chemical Intermediates》1994,20(8):815-823
Photoinduced reduction of CO2 by H2O to produce CH4 and CH3OH has been investigated on wellcharacterized standard TiO2 catalysts and on a Cu2+ loaded TiO2 catalyst. The efficiency of this photoreaction depends strongly on the kind of catalyst and the ratio of H2O to CO2. Anatase TiO2, which has a large band gap and numerous surface OH groups, shows high efficiency for photocatalytic CH4 formation. Photogenerated Ti3+ ions, H and CH3 radicals are observed as reactive intermediates, by ESR at 77 K. Cu-loading of the small, powdered TiO2 catalyst (Cu/TiO2) brings about additional formation of CH3OH. XPS studies suggest that Cu+ plays a significant role in CH3OH formation. 相似文献
975.
K. Fox 《Journal of Quantitative Spectroscopy & Radiative Transfer》1970,10(12):1335-1342
A rigorous calculation of the quantum-mechanical rotational partition function for tetrahedral XY4 molecules yields Qr = (
)(2IY + 1)4π
-
exp(/4), where IY is the spin of the Y nucleus, and ≡ Bhc/kT. This result is accurate to 1 per cent or better for all values of B and T such that <
. 相似文献
976.
977.
The molecular structures of two carbaboranes, closo-2,3-C(2)B(9)H(11) and nido-2,9-C(2)B(9)H(13), were determined experimentally for the first time using gas-phase electron diffraction (GED). For closo-2,3-C(2)B(9)H(11), a model with C(2)(v)() symmetry was refined to give C-B bond distances ranging 158.3-167.0 pm and B-B distances ranging 177.4-200.0 pm. The structure of nido-2,9-C(2)B(9)H(13) was refined using a model with C(s)() symmetry to give C-B bond lengths ranging 160.3-171.9 pm and B-B lengths ranging 173.0-196.1 pm. Ab initio computations (up to MP2/6-311+G) were also carried out on these and the related nido-7,8-C(2)B(9)H(13), which was not sufficiently stable to allow determination of its molecular structure by GED. 相似文献
978.
Charge transfer (CT) interaction is described in semiconducting dispersions of TCNQ complex salt \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm Et}_3 {\rm NH}^+ ({\rm TCNQ})_2^{\cdot^{\hskip-3.7pt\hbox{--}}}$\end{document} with and without added TCNQ°, in poly(vinyl acetal) matrices in which the electron-donor moiety is varied. The extent of CT interaction was determined in films and in solution (DMF, acetonitrile, or methylene chloride) through the absorbances at 398 nm (\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm TCNQ}{\ }^{\cdot^{\hskip-3.7pt\hbox{--}}}$\end{document} and TCNQ°) and 857 nm \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm TCNQ}{\ }^{\cdot^{\hskip-3.7pt\hbox{--}}}$\end{document}. Resistivity of the conductive films was related to the stoichiometry of TCNQ species in the films and found to have a minimum at \documentclass{article}\pagestyle{empty}\begin{document}$[{\rm TCNQ}^\circ]/[{\rm TCNQ}{\ }^{\cdot^{\hskip-3.7pt\hbox{--}}}]\simeq 1$\end{document}. Lower resistivities were attained with films having a uniform, densely packed dispersion of microcrystallites which were obtained at a relatively slow solvent removal rate. With this particular complex salt, strong electron-donor polymers are found to be better matrices for semiconductivity. 相似文献
979.
The basic structure of benzaldehyde photopolymer (BPOL) consists of phenyl groups attached to a carbon-carbon and carbon-oxygen chain. The average BPOL molecule contains 12 monomer units. Relative rates for the BPOL photosensitized dimerization of 1,3-cyclohexadiene and the isomerizations of the 1,3-pentadienes, cis-1,2-dichloroethylene and cis-2-butene are reported. The BPOL photosensitized isomerizations of the 1,3-pentadienes in the visible (λ > 395 nm) proceed by a simple mechanism. Stern-Volmer plots are linear and the photostationary trans/cis ratio is 2.0, independent of 1,3-pentadiene pressure over the range 2–180 Torr. The energy of the BPOL triplet state is less than but near 53 kcal mol?1. It excites the s-cis 1,3-pentadiene rotamers exclusively. The decay ratio of the s-cis triplets is 3.75. 相似文献
980.
Electrical-conductance measurements have been made at 25° C up to concentrations of 0.06M in aqueous solutions of Na2SO4 at atmospheric pressure and as a function of pressure up to 2000 atm. Calculations of the change of the dissociation constant for the NaSO 4 ? ion pair with pressure indicate that the difference in partial molal volumes between products and reactants at infinite dilution is \(\Delta \bar V^ \circ \tilde = - 8.25{\text{ }}cm^3 /mole\) . Using the equation of Davies, Otter, and Prue, we found the average dissociation constants for five concentrations between 0.005 and 0.06 moles/liter to be 0.097, 0.131, and 0.165 at 1, 1000, and 2000 atm, respectively, with a standard deviation of ±0.003. The atmospheric-pressure value is 0.080±0.016 over the entire concentration range from 0.00005 to 0.06 moles/liter, about half that obtained by Jenkins and Monk. This is consistent with a value ofK=0.077±0.006 recalculated from the limited-concentration-conductance work of Jenkins and Monk, with a value ofK=0.073 obtained by Fisher from data of Kurtze and Tamm on ultrasonic absorption in MgSO4?NaCl solutions, and withK=0.067 calculated by Fisher from the potentiometric data of Pytkowicz and Kester at high ionic strength. The relationship of this work to sound absorption and ion pairing in seawater is discussed. The predicted pressure dependence of the NaSO 4 ? ion pair in seawater from this work differs substantially from earlier work by Kester and Pytkowicz and by Millero. 相似文献