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991.
Summary A capillary zone electrophoresis method for identification and determination of aesculin and aesculetin has been established
using borate-phosphate buffer containing 30% ethanol with on-column UV detection. A detailed investigation of the influence
of changes in borate concentration, pH, applied voltage, temperature and organic modifier was then carried out. For both aesculin
and aesculetin, a linear plot of migration time (MT) against borate concentration was obtained, and ln[measured peak area
(MA)] and lnMT both gave linear plots against ln(applied voltage) with correlation coefficient r>0.999, which also resulted
in a linear correlation between MA and MT (r≥0.9998) under varied voltage. Ethanol as organic modifier to the background electrolytes
helped in separating aesculin and aesculetin from other components in ash barks. The reproducibility with relative standard
deviation in MT and in normalized peak area(NA) and linearity based on NA against concentration were evaluated. Finally, the
method was successfully applied to monitor the quality of different ash barks and to compare the effect of sample preparation
on content of bioactive components in ash bark. Results indicate that CZE promises to be applicable to quality control of
traditional Chinese medicines containing aesculin and aesculetin. 相似文献
992.
Inductively coupled Argon Plasma Spectrometry is used for the indirect determination of sulphate in iron(III) chloride leach solution of Elliot Lake uranium ores via addition of a known amount of barium ions and analyzing for excess of barium. The ore contains approximately 7 wt% pyrite, FeS(2) as the major mineral which oxidizes to generate sulphate during leaching with fe(III). The effects of pH, the concentrations of Fe(III) and chloride ions and for presence of ethanol in the test samples on the accuracy of analysis are studied. It is found that unlike the Rhodizonate method, removal of iron(III) from or addition of ethanol to the test sample prior to analysis are not required. Linear calibration curves are obtained. 相似文献
993.
Z. Popova C. Dimitrov K. Aristirova R. P. Dimitrova L. Dukova G. Wendt 《Reaction Kinetics and Catalysis Letters》1988,36(1):85-90
Two series of nickel mordenite catalysts have been prepared on the basis of Na-mordenite and H-mordenite. Their catalytic activity in cyclohexane conversion has been studied. It has been found that the properties of the catalysts are strongly dependent on the acidity of mordenite.
NaM HM. .相似文献
994.
J. Moc Z. Latajka H. Ratajczak 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1986,4(2):185-188
Employing the STO-3G and 4–31 G basis sets within the unrestricted Hartree-Fock method the equilibrium structure of the CCl3 radical was calculated. The calculations predict the radical to be non-planar with both basis sets used. Using the UHF optimized geometries the SWXα calculations have been performed to calculate energy levels, ionization potentials and electron affinities of CCl3. 相似文献
995.
L. A. Srybnaya Z. Tulyabaev A. A. Sadykov D. N. Dalimov 《Chemistry of Natural Compounds》1990,26(3):347-348
A. S. Sadykov Institute of Bioorganic Chemistry, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 413–415,
May–June, 1990. 相似文献
996.
Ayorinde FO Bezabeh DZ Delves IG 《Rapid communications in mass spectrometry : RCM》2003,17(15):1735-1742
Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used for the simultaneous detection of sugars, ascorbic acid, citric acid, sodium and/or potassium benzoate in non-alcoholic beverages, with meso-tetrakis(pentafluorophenyl)porphyrin (MW 974) as a matrix. Using potassium hydroxide as dopant, fructose/glucose was detected as the potassiated molecule at m/z 219, whereas potassiated sucrose, [Sucrose. K](+), was detected at m/z 381. Using sodium hydroxide as dopant, the fructose and sucrose ions were detected at m/z 203 and 365, respectively. Citric acid generated multiple ions at m/z 269, 307, and 345, which were assigned to [Citricbond;H+2K](+), [Citricbond;2H+3K](+), and [Citricbond;3H+4K](+), respectively. However, a stored methanolic solution of citric acid produced additional ions at m/z 283, 297, and 321, which were attributed to [Citricbond;2H+CH(3)+2K](+), [Citricbond;3H+2CH(3)+2K](+), and [Citricbond;3H+CH(3)+3K](+), respectively, due to esterification that took place during storage. The limits of detection in water were: ascorbic acid, 0.30 wt%; citric acid, 0.5 wt%; and sodium benzoate, 0.001 wt%. In the beverage formulations, the limits of detection were: ascorbic acid 0.3 wt%, citric acid 0.3 wt%, and sodium benzoate 0.02 wt%. Spiking a water or beverage solution that contained ascorbic and/or citric acid with less than 0.6 wt% of tartaric acid lowered the detection limits of ascorbic and citric acids to 0.2 wt%. This study demonstrates the potential for using MALDI-TOFMS in the quality control analyses of non-alcoholic beverages, particularly with regard to the detection of low molecular weight organic acids in commercial beverage formulations. 相似文献
997.
Liu Y Liu C Zhang Z Wang C 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2001,57(1):35-39
The composite particles of Ag-TiO2 both in a nanocrystal form was prepared by photoreduction of AgNO3 in the rutile colloidal solution. The surface plasmon absorption (SPA) band of the silver clusters supported on the TiO2 nanocrystal was red shift, and a strong surface enhanced Raman scattering (SERS) effect for the composite particles of Ag-nanocrystalline TiO2 was observed. The SERS effect is relating to the red shift phenomenon of SPA band, which could be explained by induced-resonance effect. 相似文献
998.
G F Xie S L Li Z Z Wanc 《Science in China. Series B, Chemistry, life sciences & earth sciences》1992,35(4):429-436
The effects of reduction by DTT, oxidation by DTNB and treatment with NEM on the thiol contents and insulin binding to its receptor in mice liver membranes were studied. Reduction with DTT leads to a parallel increase in the thiol content and the specific binding of insulin to the membrane. Scatchard analysis of the results shows little change in the number of binding sites but a twofold increase of the binding constant. Washing the membrane with bound insulin by a DTT containing buffer results in a more marked increase in the release of bound insulin than washing with buffer alone, suggesting that part of the insulin is bound to its receptor by covalent disulfide linkages through a thiol-disulfide exchange reaction and reduction with DTT leads to a marked increase in this "disulfide-linked" insulin. Treatment with DTNB or NEM of the DTT-reduced membrane seems to reverse the effect of DTT reduction, although the reaction of the untreated membrane with DTNB or NEM had little or no effect on the specific binding of insulin. It is suggested that initially, part of the thiols responsible for the exchange reaction may not be available for reaction with DTNB and reduction with DTT generates further thiols leading to increased specific binding in general and increased insulin binding to the receptor through covalent disulfide linkages in particular. 相似文献
999.
The modification of a Ni-Cr oxide catalyst during reduction was studied by IR spectroscopy of adsorbed CO and NH3 probe molecules. It was determined that in the starting oxidized sample the nickel cations were in the form of oxide clusters distributed over the surface of chromium oxide. As a result of reduction, they were depleted in oxygen, and metal clusters were formed and enlarged. Effective oxidation, by water vapor, of part of the surface of the metallic-nickel clusters that formed during reduction was observed.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2718–2725, December, 1991. 相似文献
1000.
X-ray diffraction and spectral studies of 1-phenyl-3-methyl-4-(2′,4′-Dimethylphenylazo)-pyrazolone-5
L. G. Kuz'mina L. P. Grigor'eva Yu. T. Struchkov Z. I. Ezhkova B. E. Zaitsev V. A. Zaitseva P. P. Pron'kin 《Chemistry of Heterocyclic Compounds》1985,21(6):680-684
The molecular and crystal structures of 1-phenyl-3-methyl-4-(2,4-dimethyl-phenylazo) pyrazolone-5 were determined. In the crystal the molecule exists as the hydrazone tautomer. The pyrazole ring is planar, and the substituents are practically coplanar with it. The molecule contains an intramolecular NH...O hydrogen bond that closes a practically planar six-membered ring (N...O, 2.77 (I), H...O 2.14 Å, angle at H(N(4)) hydrogen 131 °). The x-ray diffraction data agree with the spectral data and with the CNO calculation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 816–821, June, 1985. 相似文献