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171.
Castro J Pérez RA Miguel E Sánchez-Brunete C Tadeo JL 《Journal of chromatography. A》2002,947(1):119-127
Rapid analytical methods for the determination of endosulfan isomers and endosulfan-sulfate in air and plant samples were developed. The insecticides were trapped from air using a column containing Florisil and extracted with a low volume of ethyl acetate, assisted by sonication. Pesticide residues were determined by gas chromatography with electron-capture detection using a nonpolar capillary column. Residue identities were confirmed by gas chromatography coupled with mass spectrometry. Recoveries of these compounds from air samples were always higher than 78% with an RSD lower than 11% and the detection limits obtained were at least 0.3 ng/l air. Leaf samples were homogenised with ethyl acetate and extracts cleaned-up on an aluminium oxide column. Pesticides were eluted with a hexane-ethyl acetate (80:20, v/v) mixture. Recoveries obtained from plant samples were higher than 78% with an RSD lower than 14% and detection limits in leaves were 0.02 microg/g for each pesticide. These methods were applied to study the volatilisation of endosulfan from tomato leaves under laboratory conditions. A volatilisation rate near 1% of the initial amount of endosulfan per hour was obtained during the first 24 h at room temperature. 相似文献
172.
The use of a rapid and specific (cross-reactivity<4%) enzyme-linked immunosorbent assay (ELISA) for the determination of alachlor residues in water and vegetable samples is addressed. The analytical method consists of a fast extraction procedure followed by an optimised ELISA. The detection limit was 0.44 microg l(-1), with a linear range from 0.89 to 143.2 microg l(-1). For alachlor extraction from water samples, different solid-phase cartridges (C, Ph, C8 and C2) were assayed using MeOH as eluent. Extracts were diluted (1:4) with distilled water before ELISA. This procedure gave recoveries close to 100% with RSDs<14%. For vegetable samples, alachlor was extracted directly with MeOH and the extracts diluted 1:40 (v/v) with saline buffer prior to ELISA. The results obtained by the proposed procedure correlate well with the reference method (multiresidue extraction-GC-MS) for vegetable samples (r>0.85). 相似文献
173.
174.
[structure: see text] Dicobalt-beta-pinene hybrids of types I and II have been prepared using a Nicholas reaction between propargyl derivatives, obtained from commercial (1R)-(-)-myrtenal, and different aromatic nucleophiles. The method is suitable for the preparation of densely functionalized bio-organometallic natural product-based hybrids, as demonstrated by the preparation of a beta-pinene-neoclerodane hybrid. 相似文献
175.
Antunes FE Lindman B Miguel MG 《Langmuir : the ACS journal of surfaces and colloids》2005,21(22):10188-10196
Rheology and phase separation were investigated for aqueous mixtures of two oppositely charged hydrophobically modified polyelectrolytes. The typical phase separation, normally seen for oppositely charged polymer mixtures, is dramatically reduced by the presence of hydrophobic modification, and phase separation is only detected close to the point of charge neutralization. While the two polyelectrolytes separately can give high viscosities and a gel-like behavior, a pronounced maximum in viscosity and storage modulus with the mixing ratio of the polyelectrolytes is observed; the maximum is located between the points of charge and hydrophobe stoichiometry and reflects a combination of hydrophobic and electrostatic association. Lowering the charge density of the anionic polymer leads to a strengthened association at first, but at lower charge densities there is a weakened association due to the onset of phase separation. The strength of the electrostatic interaction was modified by adding salt. Increased ionic strength can lead to phase separation and to increased or decreased viscosity depending on the polyelectrolyte mixing ratio. 相似文献
176.
Wang Mei Miguel Daniel Riera Víctor Bois Claudette Jeannin Yves 《Transition Metal Chemistry》2001,26(4-5):566-569
A novel dimolybdenum complex [(3-C3H5)(CO)2Mo(-S2CPCy3)Mo(3-CH2CMeCH2)(CO)2], obtained by reacting the [(CO)2(3-C3H5)Mo(-S2CPCy3)Mo(CO)3]– anion with an excess of ClCH2CMe=CH2, has been characterized by i.r., 31P{1H}, 1H- and 13C-n.m.r. spectroscopy and by elemental analysis. The crystal structure of the complex, determined by X-ray diffraction, shows a definite preference for the central carbon of the S2CPCy3 bridge to bind to the Mo(2) atom coordinated by 3-2-methylallyl, rather than the Mo(1) atom attached to unsubstituted 3-allyl ligand. 相似文献
177.
R. Usón L.A. Oro D. Carmona M.A. Esteruelas C. Foces-Foces F.H. Cano S. García-Blanco A.Vázquez De Miguel 《Journal of organometallic chemistry》1984,273(1):111-128
A new series of cationic areneiridium(I) complexes of formula [Ir(barrelene)(arene)]+ or [Ir(barrelene)(PhNRPh)]+ (R= Ph or H) have been synthesized from neutral iridium complexes of the type [IrY(barrelene)]x (barrelene = Me3TFB, Y = Cl or OMe (x = 2), Y = acac (x = 1); barrelene = TFB, Y = OMe (x = 2), Y = acac (x = 1)). The crystal structures of [Ir(Me3TFB)(1,4-C6H4Me2)]ClO4 and [Ir(TFB)(PhNPh2)]BF4·CH2Cl2 have been determined by X-ray diffraction. They crystallize in the space groups Pbca and Pna21 respectively with lattice constants of 17.6947(11), 15.8072(10), 16.0019(11) Å and 9.8059(2), 20.8097(9), 14.3367(4) Å. Final R factors were 0.063 and 0.042 for the observed data. Both complexes show a staggered arrangement between the arene and the TFB moieties and deviation from planarity of the coordinated arene ligands. In the second complex the IrC and NC distances, the CNC angle, the type of arene puckering, and the spectroscopic data indicate a distortion of the coordinated arene towards a η5-coordinated iminocyclohexadienyl form. 相似文献
178.
Miguel F. Braa María L. Lpez Rodríguez Concepcin Rodríguez Amando Garrido-Pertierra 《Journal of heterocyclic chemistry》1986,23(4):1019-1022
Reaction of N-(4-pyridylmethyl)benzamide N-oxides 2a-f with ethyl cyanoacetate in the presence of acetic anhydride yield dimerization compounds 3a-f and (E)-ethyl 2-cyano-3-(4-pyridyl)-3(benzoylamino)acrylates 4a-f , which react with hydrazine to give 4-cyano-3-(4-pyridyl)-3-pyrazolin-5-one 9 and the corresponding benzamides 10a-f . 相似文献
179.
Miguel A. Esteso Luis Fernandez-Merida Felipe F. Hernandez-Luis 《Journal of Electroanalytical Chemistry》1987,230(1-2)
Values of the emf for the cell: Na-glass|Na2Succ(m), Hg2Succ|Hg, have been measured. These values of E have been used with Hückel's extended Debye and Hückel equation to obtain the mean ionic activity coefficient values for Na2Succ in aqueous solutions of several concentrations, m. The values of γ± thus obtained have been adjusted to Pitzer's equation, with b = 1.2 and α = 2.0 to find Pitzer's parameters and then the values for both the osmotic coefficients and the activity of water. Finally, the standard potential of the Hg2Succ|Hg electrode has been determined and from this value the solubility-product equilibrium constant for mercurous succinate has also been calculated. 相似文献
180.
The three-dimensional structure of a complex tubular uranyl phosphonate, (UO(2))(3)(HO(3)PC(6)H(5))(2)(O(3)PC(6)H(5))(2).H(2)O, was determined ab initio from laboratory X-ray powder diffraction data and refined by the Rietveld method. The crystals belong to the space group P2(1)2(1)2(1), with a = 17.1966(2) ?, b = 7.2125(2) ?, c = 27.8282(4) ?, and Z = 4. The structure consists of three independent uranium atoms, among which two are seven-coordinated and the third is eight-coordinated. These metal atoms are connected by four different phosphonate groups to form a one-dimensional channel structure along the b axis. The phenyl groups are arranged on the outer periphery of the channels, and their stacking forces keep the channels intact in the lattice. The determination of this structure which contains 50 non-hydrogen atoms in the asymmetric unit, from conventional X-ray powder data, represents significant progress in the application of powder techniques to structure solution of complex inorganic compounds, including organometallic compounds. 相似文献