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11.
Pentacarbonyl-rhenate and -manganate react with the cationic complexes [cpMo(CO)2(diene)]+, [cpMo(CO)2(cyclopentadiene]+, [cpMo(CO)2(cyclohexadiene)]+, [cpMo(CO)2(trimethylenemethane]+, [(OC)3Mo(η7-C7H7)]+, [cp(OC)-(Ph3P)Mo(alkyne)]+ to give the corresponding heteronuclear hydrocarbon-bridged complexes. 相似文献
12.
Hans-Joachim Böhm 《Journal of computer-aided molecular design》1992,6(1):61-78
Summary A new computer program is described, which positions small molecules into clefts of protein structures (e.g. an active site of an enzyme) in such a way that hydrogen bonds can be formed with the enzyme and hydrophobic pockets are filled with hydrophobic groups. The program works in three steps. First it calculates interaction sites, which are discrete positions in space suitable to form hydrogen bonds or to fill a hydrophobic pocket. The interaction sites are derived from distributions of nonbonded contacts generated by a search through the Cambridge Structural Database. An alternative route to generate the interaction sites is the use of rules. The second step is the fit of molecular fragments onto the interaction sites. Currently we use a library of 600 fragments for the fitting. The final step in the present program is the connection of some or all of the fitted fragments to a single molecule. This is done by bridge fragments. Applications are presented for the crystal packing of benzoic acid and the enzymes dihydrofolate reductase and trypsin. 相似文献
13.
Hans-Joachim Arnold 《Results in Mathematics》1995,28(3-4):195-208
To characterize E. D. Sontag’s system of axioms for control-systems in a more operative manner we consider an equivalent algebraic structure, which we name Regel- Relative. 相似文献
14.
Described is an asymmetric synthesis of new Delta(3a,4)-unsaturated, fused bicyclic proline analogues from cyclic bis(allylsulfoximine)titanium complexes and N-tert-butylsulfonyl imino ethyl ester. Treatment of the enantiomerically pure five-, six-, seven-, and eight-membered cyclic bis(allylsulfoximine)titanium complexes with the imino ester gave mixtures of the corresponding (E,syn)- and (Z,syn)-configured, delta-sulfoximine substituted, cyclic gamma,delta-unsaturated alpha-amino acid esters with high regio- and diastereoselectivities in good yields. Activation of the N-methyl sulfoximine group of these amino acid derivatives through methylation with Me(3)OBF(4) afforded in nearly quantitative yields the corresponding (dimethylamino)sulfoxonium salts. A novel migratory cyclization of these salts with DBU gave via an isomerization to the corresponding allylic (dimethylamino)sulfoxonium salts and an intramolecular substitution of the (dimethylamino)sulfoxonium group the enantio- and diastereomerically pure, bicyclic, N-tert-butylsulfonyl protected proline analogues having a six- and eight-membered unsaturated carbocyclic ring. Cyclization of the alkenyl (dimethylamino)sulfoxonium salts was independent of the configuration of the double bond. N,N-Dimethylphenylsulfinamide of > or =99% ee was obtained in good yield as a further reaction product. Conversion of the sulfinamide to N,S-dimethyl-S-phenylsulfoximine of > or =99% ee, the starting material for the synthesis of the allylic sulfoximines, had been accomplished previously. Finally, cleavage of the tert-butylsulfonyl protecting group with anhydrous acid furnished the fused bicyclic proline analogue containing an unsaturated six-membered ring in high yield. 相似文献
15.
George Hohlneicher Harald Pulm Hans-Joachim Freund 《Journal of Electron Spectroscopy and Related Phenomena》1985,37(2):209-224
First, we show that the quantity Δβ(i) = ΔEA(kii) + 2ΔEB(i) — ΔEB(k) is directly related to the final state relaxation contribution ΔER(i) of the binding energy shift ΔEB(i). ΔEA(kii) is the kinetic energy shift of the Auger transition which corresponds to the decay of a hole state with a hole in level k into a final state with two holes in level i. The shift parameter Δβ(i), which is based on information on two binding energies, is conceptually similar to Wagner's Auger parameter. To establish the relation between Δβ(i) and ΔR(i) one needs, however, less drastic approximations than in the case of Auger parameter shifts. The only approximation necessary is the assumption that ΔR(i) is determined by coulomb contributions.Secondly, we use Δβ (i) to analyse the experimental data of eighteen gaseous phosphorus-containing compounds obtained by Sodhi and Cavell1. It is shown that ΔR(P2p) is strongly related to changes in the polarizability of the ligands. The initial state effects derived from our study deviate from those expected on the basis of simple electronegativity considerations. 相似文献
16.
17.
A general algorithm allowing the numerical modeling of the time and space dependence of product formation in spherical reaction volumes is described. The algorithm is described by the complete set of mass balance equations. On the basis of these equations, the effects of the diffusion coefficient, reaction rate, bead size, reagent excess, and packing density of the resin beads on the overall reaction rates are determined for second-order reactions. Experimental data of reaction progress are employed to calculate reaction rates and diffusion coefficients in polymer-supported reactions. In addition, the conditions for shell-like product formation are determined, and various strategies for the radial patterning of resin beads are compared. The effect of diffusion on polymer-supported enzyme-catalyzed reactions of the Michaelis-Menten type is treated, as well. Finally, the effects of typical nonideal solid-phase phenomena, namely, the inhomogeneity of rate constants and the concentration dependence of diffusion coefficients, on overall rates are discussed. 相似文献
18.
Ko C Levine B Toniolo A Manohar L Olsen S Werner HJ Martínez TJ 《Journal of the American Chemical Society》2003,125(42):12710-12711
The photoisomerization mechanism of the neutral form of the photoactive yellow protein (PYP) chromophore is investigated using ab initio quantum chemistry and first-principles nonadiabatic molecular dynamics (ab initio multiple spawning or AIMS). We identify the nature of the two lowest-lying excited states, characterize the short-time behavior of molecules excited directly to S2, and explain the origin of the experimentally observed wavelength-dependent photoisomerization quantum yield. 相似文献
19.
For the determination of flouride, chloride and bromide, a suitable metal ion is added in a modified graphite tube atomizer. After drying and ashing, the substances are vaporized and diatomic molecules between the metal and nonmetal are formed. These molecules are excited by a pulsed dye laser and the resulting fluorescence is measured. At constant metal concentration, the fluorescence is proportional to the halide concentration. The diatomic molecules used are MgF, InCl and AlBr. The detection limits are 11 pg of fluoride, 15 pg of chloride and 70 pg of bromide in the 10-μl injections, corresponding to 6 x 10?8 mol l?1 fluoride, 4 x 10?8 mol l?1 chloride and 9 x 10?8 mol l?1 bromides. 相似文献
20.
Winfried Mientus Hans-Georg Bartel Werner Haberditzl Hans-Joachim Spitzer 《Monatshefte für Chemie / Chemical Monthly》1980,111(3):597-606
A normalization of the wave functions by means of the theoretical exact Multiple-Scattering-(MS)-formalism is discussed within the framework of the SCF-X-SW-method. For the atomic and extramolecular regions the integrals of normalization can be easily determined and the results can be described by the corresponding electronic charges. The calculation of the integral of the interatomic region is problematic. The needful volume integration is only necessary to theGreen's functions of the wave functions and can be solved by means of the residual theory. The further analytical calculation of the surface integrals leads to a complicated formalism which can be numerically evaluated. 相似文献