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31.
S. Pandey K. A. Fletcher W. E. Acree Jr C. Fetzer 《Fresenius' Journal of Analytical Chemistry》1998,360(6):669-674
Applicability of the nitromethane selective quenching rule for discriminating between alternant versus nonalternant polycyclic
aromatic hydrocarbons (PAHs) is examined for 20 representative PAH solutes dissolved in micellar sodium dodecylsulfate (SDS)
+ cetyltrimethylammonium bromide (CTAB), SDS + dodecyltrimethylammonium bromide (DTAB), SDS + Brij-35, and SDS + sodium octanoate
(SO) mixed surfactant solvent media. Experimental results show that nitromethane quenched fluorescence of all 8 alternant
PAHs studied in the four different solvent systems. Unexpected quenching behavior was observed, however, in the case of nonalternant
PAHs. Nitromethane quenched fluorescence emission of nonalternant PAHs dissolved in the SDS + SO solvent media, which is contrary
to the selective quenching rule. In the case of the mixed anionic + cationic surfactant solvent media, nitromethane quenching
selectivity was restored at concentration ratios of approximately 4 : 1 (anionic:cationic) or less.
Received: 22 May 1997 / Revised: 29 September 1997 / Accepted: 3 October 1997 相似文献
32.
33.
Various new structural entities related to x-azatricyclo[m.n.0. 0(a)()(,)(b)()]alkanes are constructed by the intramolecular [3 + 2] dipolar cycloaddition of nonstabilized cyclic azomethine ylides. The ylide is generated by the sequential double desilylation of N-alkyl alpha,alpha'-bis(trimethylsilyl)cyclic amines using Ag(I)F as a one-electron oxidant. 相似文献
34.
35.
Densities,ρ, ultrasonic speeds, u, viscosities,η, and refractive indices, n, of pure benzene, benzyl alcohol (BA), benzonitrile (BN), benzoyl chloride (BC), chlorobenzene (CB) and their thirty six binary mixtures, with benzene as common component, were measured at 303.15 K over the entire mole fraction range. From these experimental data the values of deviations in ultrasonic speed, △u, isentropic compressibility, △ks,excess acoustic impedance, ZE, deviation in viscosity, Dh, and excess Gibbs free energy of activation of viscous flow, G*E, and partial molar isentropic compressibility, Kφ,20 of BA, BN, BC and CB in benzene were computed. The variation of these derived functions with composition of the mixtures suggested the increased cohesion
(molecular order) in the solution and that interaction (A-B)>(A-A) or (B-B).Moreover, theoretical prediction of ultrasonic speed, viscosity and refractive index of all the four binary mixtures was made on the basis of empirical and semi-empirical relations by using the experimental values of the pure components. Comparison of theoretical results with the experimental values was made in order to assess the suitability of these relations in reproducing the
experimental values of u, η and n. Also, molecular radii of pure liquids and the average molecular radii of binary mixtures were evaluated using the corresponding refractive indices of pure liquids and binary mixtures. The average molecular radii of binary mixtures were found to be additive with respect to mole fraction of the pure component. 相似文献
36.
Sengupta Soumitra K. Pandey Om P. Srivastava Bimal K. Sharma Vinod K. 《Transition Metal Chemistry》1998,23(4):349-353
The reactions of bis(cyclopentadienyl)titanium(IV)/zirconium(IV) dichloride with a new class of organometallic thiosemicarbazones (LH), derived by condensing acetylferrocene with substituted thiosemicarbazides, have been studied and two types of bimetallic products, viz. [Cp2M(L)Cl] (M = Ti or Zr) and [CpZr(L)3], have been isolated. On the basis of various physicochemical and spectral studies, five- and seven-coordinate structures have been assigned to these derivatives, respectively. Attempts have been made to establish a correlation between biological activity and the structures of the products. 相似文献
37.
Summary FeIII complexes of a tetradentate ligand with pendant benzimidazolyl groups have been synthesized and characterized. Room temperature Mössbauer spectra depict a quadruple split doublet in the case of NO
inf3
p–
as co-ligand, while a nearly symmetrical one line spectrum is obtained for complexes with Cl–as co-ligand. The isomer shift values are towards the lower end of the range found for other high spin FeIII complexes. 1H-n.m.r. spectra of the complexes reveal relatively broad linewidths with large isotropic shifts. Paramagnetically shifted resonances are observed in the range of –10.0–+70.0 p.p.m.Author to whom all correspondence should be directed. 相似文献
38.
The core structure of the complex pentacyclic 5,11-methanomorphanthridine alkaloids is constructed stereospecifically in one step employing an intramolecular [3 + 2]-cycloaddition of nonstabilized azomethine ylide as the key step. The strategy is demonstrated by accomplishing the formal total synthesis of (+/-)-pancracine. [reaction: see text] 相似文献
39.
40.
J.C. Joshi B.C. Joshi N.C. Pandey R. Belwal Janardan Joshi 《Journal of solid state chemistry》1977,22(4):439-443
Energy transfer studies have been made in a terbium-erbium coactivated calibo-glass system at room temperature and at liquid-air temperature. A study of the emission and decay of 5D4 level of Tb3+ has been made by varying the acceptor (Er3+) concentration. Probabilities and efficiencies of energy transfer as well as donor-acceptor distances have been calculated. At low acceptor concentration the decay of the donor (Tb3+) emission has been found to be diffusion limited. At high acceptor concentration the mechanism governing the transfer is found to be dipole-dipole. 相似文献