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991.
A method was developed for the recovery and determination of cyanide ion in organic sample matrices. To facilitate the solubilization of cyanide ions, cetyltrimethylammonium bromide (CTAB) was added at concentrations above the critical micelle concentration. Sample cyanation reaction products consisted of solvent mixtures of a hydroxynitrile in DMF-toluene or DMF-isopropylacetate (IPAC). Spectrophotometric determination of cyanide ion at 578 nm by the pyridine-barbituric acid method was automated by flow injection analysis. Recovery of cyanide ion from spiked samples was 93.2% in DMF-IPAC solvent matrix and 93.9% in DMF-toluene. Low alkali concentration was observed to favor solubilization of cyanide ion in the micellar solution. 相似文献
992.
N. N. Chipanina A. M. Shulunova T. I. Yushmanova L. I. Volkova V. A. Lopyrev Yu. L. Frolov 《Russian Chemical Bulletin》1987,36(10):2182-2183
Conclusions An IR spectroscopic study showed that the C=0 values in the spectra of N,N-dimethylhydrazides of aromatic acids, RCONHN(Me)2, correlate linearly with a regression equation obtained for the unsubstituted hydrazides of aromatic acids, RCONHNH2. This dependence differs significantly from that for N-methyl-N-aroylhydrazines, in which ,-conjugation in the RC(O)N group is more pronounced.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2353–2355, October, 1987. 相似文献
993.
The total phospholipids of kenaf of variety Opytnyi-1847 and homogeneous fractions of them have been studied. A known law has been confirmed — positions 2 of the main fractions of phospholipids are esterified predominantly with unsaturated fatty acids and in N-aceylated phospholipids the amide-bound acids are more saturated than the O-acyls.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 775–777, November–December, 1980. 相似文献
994.
A method to observe the phosphorescence emissions from the spin sublevels of low emissivity is proposed, and its application to quinoxaline is attempted. The newly observed phosphorescence spectra from the Tx and Ty sublevels differ considerably in vibrational structures from the usually observed phosphorescence from the Tz sublevel. 相似文献
995.
Yu. N. El'kin A. I. Kalinovskii B. V. Rozynov T. I. Vakorina N. I. Shul'ga A. K. Dzizenko 《Chemistry of Natural Compounds》1976,10(4):463-465
Summary GLC-MS results have been obtained for acetates of partially methylated methyl 6-deoxyhexopyranosides that permit the positions of the OMe groups to be determined unambiguously and assignment to a definite stereoisomer to be made by means of T values.Pacific Ocean Institute of Bioorganic Chemistry, Far-Eastern Scientific Center, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 457–459, July–August, 1974. 相似文献
996.
A.A. Ischenko T.G. Strand A.V. Demidov V.P. Spiridonov 《Journal of Molecular Structure》1978,43(2):227-243
The pentachlorides of niobium and tantalum have trigonal bipyramidal structures (D3hsymmetry) with thermal average axial bonds, rα, longer than the equatorial ones by 0.097(9) and 0.142(5) Å, respectively. The equatorial bonds are r(Nb—Cl) = 2.241(4) and r(Ta—Cl) = 2.227(3) Å. Standard deviations are given. Calculated amplitudes of vibration for the e' type of bending frequencies assigned as v6 (equatorial in-plane bend) < v7 (axial—equatorial bend) agree significantly better with the experimental vibrational amplitudes than do amplitudes computed for the opposite assignment. Assuming an analytical quartic-harmonic potential for the pseudorotational motion of the molecules, barriers to pseudorotation of 1.5(0.7) and 1.2(0.6) kcal mol?1 are estimated from the electron diffraction data for NbCl5 and TaCl5, respectively. Effects from interatomic multiple scattering are included in the theoretical intensities, and are found to be of some importance to the results. 相似文献
997.
By deuteration of the OH group, it has been shown that two bands, at 1665 and 1630 cm−1 (CCl4), in the IR spectra of 5-hydroxychromones are associated with the H-bonded CO stretching vibration. Nuclear deuteration of 5-hydroxy-2-methylchromone (1) under acidic conditions gave a tri- and a hexadeutero derivative; the latter, isotopically substituted at C-3, shows a single CO band at 1649 cm−1. Hydrolysis of 3-acetyl-5-hydroxy-2-methylchromone with sodium carbonate in deuterium oxide furnished 5-hydroxy-2-trideuteromethylchromone-3-d which also exhibits a single CO absorption. Partial incorporation of O18 into the CO group of 1 results in a single νC=O18 at 1593 cm−1. It is suggested that the doublet CO absorption of 5-hydroxychromones arises from a Fermi resonance involving a low-energy vibrational mode of the vinyl proton on the nuclear C-3 position. 相似文献
998.
An indirect spectrophotometric method is proposed for the determination of cyanide down to 0.2 ppm. It is based on the fact that cyanide prevents the formation of the strongly absorbing ternary complex between silver(I), 1,10-phenanthroline and Bromopyrogallol Red in nearly neutral aqueous solution. Among 17 cations examined, only mercury(II) could not be tolerated. Zinc, cadmium and cobalt interfered only when present in large amounts. A 1000-fold molar excess (over cyanide) of 14 anions can also be tolerated. Bromide, iodide and thiocyanate interference is overcome by addition of lead nitrate, ammonium sulphate and barium nitrate, followed by centrifugation. 相似文献
999.
Peak distortion in the column liquid chromatographic determination of omeprazole dissolved in borax buffer. 总被引:1,自引:0,他引:1
Injection of a sample containing omeprazole dissolved in borax buffer (pH 9.2) into a reversed-phase liquid chromatographic system consisting of a mixture of acetonitrile and phosphate buffer (pH 7.6) as the mobile phase and a C18 surface-modified silica as the solid phase resulted under special conditions in split peaks of omeprazole. The degree of peak split and the retention time of omeprazole varied with the concentration of borax in the sample solution and the ionic strength of the mobile phase buffer as well as with the column used. Borax is eluted from the column in a broad zone starting from the void volume of the column. The retention is probably due to the presence of polyborate ions. The size of the zone varies with the concentration of borax in the sample injected. In the borax zone the pH is increased compared with the pH of the mobile phase, and when omeprazole (a weak acid) is co-eluting in the borax zone its retention is affected. In the front part and in the back part of the borax zone, pH gradients are formed, and these gradients can induce the peak splitting. When the dissolving medium is changed to a phosphate buffer or an ammonium buffer at pH 9 no peak distortion of omeprazole is observed. 相似文献
1000.
Rat luteinizing hormone /LH/ was labelled with125I by the Chloramine T method.125I-LH, used as tracer in radioimmunoassay, was separated from the labelling reaction mixture by gel filtration. By using the proper protein/radioiodine ratio in the labelling reaction mixture the specific activity of125I-LH was adjusted to 2.5–20.5 MBq g–1. The influence of the specific activity on the assay parameters as well as on the tracer stability was investigated. 相似文献