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41.
Nierengarten H Leize E Breuning E Garcia A Romero-Salguero F Rojo J Lehn JM Van Dorsselaer A 《Journal of mass spectrometry : JMS》2002,37(1):56-62
The self-assembly of the terdentate ligands 1a-h, based on terpyridine-like binding sites, with octahedrally coordinated metal ions, such as Fe(II), Co(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II), leads to the formation of the supramolecular grid-type complexes 2a-c(M(II)), 3d-g(M(II)) and 4h(M(II)). The structures and compositions of these coordination complexes in solution were deduced from electrospray mass spectrometry (ESMS) measurements. The results agree with the data available from x-ray radiocrystallography in the solid state and/or NMR spectroscopy in solution. ESMS may be applied in cases where other methods are difficult to use or inconclusive. This study stresses the power of ESMS in supramolecular chemistry. 相似文献
42.
Morilla ME Morfes G Nicasio MC Belderrain TR Mar Díaz-Requejo M Graiff C Tiripicchio A Sánchez-Delgado R Pérez PJ 《Chemical communications (Cambridge, England)》2002,(17):1848-1849
N,N, N',N'-Tetraethylethylenediamine undergoes simple or double intramolecular dealkylation reactions in the presence of the complexes [RuCl2(diene)]n (diene = cod, nbd) or trans-[RuCl2(diene)(morfoline)2 at 80 degrees C to afford chelating amine ligands which contains one or two N-H functionalities. 相似文献
43.
44.
Pasternack RF Gibbs EJ Bruzewicz D Stewart D Engstrom KS 《Journal of the American Chemical Society》2002,124(14):3533-3539
trans-Bis(N-methylpyridinium-4-yl)diphenylporphine forms extended, organized assemblies on DNA templates under appropriate conditions of concentration, ionic strength, and temperature. Addition of beta-cyclodextrin to these arrays leads to their disassembly as evidenced by changes in extinction, circular dichroism, and resonance light scattering spectra. The structure or flexibility of the polymer template has an effect on the rate of disassembly; the reaction is faster on a poly(dG-dC)(2) surface than on ct DNA. The kinetic profiles for the disassembly process can be fit with great precision with a two-kinetic parameter equation in which the rate constant is itself a function of time. The reaction rate, studied in the presence of excess beta-CD, shows a dependence on the mode of detection. A model is presented to account for these observations in which the arrays become increasingly reactive with time due to beta-CD attack at the interior of the porphyrin assemblies as well as the ends. 相似文献
45.
García-Herrero A Montero E Muñoz JL Espinosa JF Vián A García JL Asensio JL Cañada FJ Jiménez-Barbero J 《Journal of the American Chemical Society》2002,124(17):4804-4810
We show that the conformational features of the molecular complexes of E. coli beta-galactosidase and O-glycosides may differ from those formed with closely related compounds in their chemical nature, such as C- and S-glycosyl analogues. In the particular case presented here, NMR and ab initio quantum mechanical results show that the 3D-shapes of the ligand/inhibitor within the enzyme binding site depend on the chemical nature of the compounds. In fact, they depend on the relative size of the stereoelectronic barriers for chair deformation or for rotation around Phi glycosidic linkage. 相似文献
46.
García Ruano JL Alonso de Diego SA Martín MR Torrente E Martín Castro AM 《Organic letters》2004,6(26):4945-4948
[reaction: see text] Thermolysis of enantiopure sulfonyl pyrazolines 4 and 5, easily obtained from (Z)-3-p-tolylsulfinylacrylonitriles (1), afforded sulfonyl cyclopropanes (6, 7) in a completely stereoselective manner in almost quantitative yields. Both cyclopropanes and alkylidenecyclopropanes, containing one or two chiral carbon atoms, one of them being quaternary, were obtained by hydrogenolysis of the C-S bonding and under the conditions reported by Julia, respectively. The highly stereoselective extrusion of nitrogen suggests a concerted mechanism. 相似文献
47.
Esther Beneish 《Transactions of the American Mathematical Society》2004,356(4):1609-1622
Let be a finite group, let be a -lattice, and let be a field of characteristic zero containing primitive roots of 1. Let be the quotient field of the group algebra of the abelian group . It is well known that if is quasi-permutation and -faithful, then is stably equivalent to . Let be the center of the division ring of generic matrices over . Let be the symmetric group on symbols. Let be a prime. We show that there exist a split group extension of by a -elementary group, a -faithful quasi-permutation -lattice , and a one-cocycle in such that is stably isomorphic to . This represents a reduction of the problem since we have a quasi-permutation action; however, the twist introduces a new level of complexity. The second result, which is a consequence of the first, is that, if is algebraically closed, there is a group extension of by an abelian -group such that is stably equivalent to the invariants of the Noether setting .
48.
We have developed an aberro-polariscope that simultaneously measures spatially resolved polarization properties and wave-front aberration in a living human eye. The setup consists of an infrared Hartmann-Shack sensor that incorporates a polariscope. A series of four Hartmann-Shack images corresponding to independent polarization states were recorded. The corresponding wave-front aberration was computed from each image. Moreover, from each set of four images spatially resolved (over the pupil plane) parameters of polarization were also determined. This instrument allows useful information on both the optical and the biomechanical properties of the eye to be obtained. 相似文献
49.
Madrigal B Puebla P Peláez R Caballero E Medarde M 《The Journal of organic chemistry》2003,68(3):854-864
The methodology for the synthesis of podophyllotoxin and thuriferic acid-type lignans has been applied to derivatives carrying a naphthalene moiety. Starting from the 1,3-dithiane of 2-naphthaldehyde afforded the expected analogues in the 2,1-naphthalene series. The preferred conformations of these compounds are influenced by the bulky naphthalene system. By contrast, 1,8-bridged products were obtained from the 1,3-dithiane of 1-naphthaldehyde. In this series, polycyclic naphthalene lignan analogues were isolated after deprotection and/or desulfurization reactions. The cyclizations produced in this process are due to the proximity between the 3,4,5-trimethoxyphenyl moiety and the reacting C-2 of the 1,3-dithiane ring. 相似文献
50.