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71.
Investigation of n-hexane dehydrocyclization over supported Pt catalyst modified by adsorbed rhenium
G. A. Nesterov V. M. Mastikhin O. B. Lapina V. A. Zakharov 《Reaction Kinetics and Catalysis Letters》1982,18(1-2):175-179
A -Al2O3 supported Re–Pt bimetallic catalyst prepared by electrochemical adsorption has been studied in n-hexane dehydrocyclization, using the slug-pulse method. The activity of the Re–Pt/Al2O3 catalyst treated only in hydrogen was low, but markedly increased by a calcination step before hydrogen treatment. The modified catalyst showed higher activity and increased selectivities for benzene and iso-hexanes than the base Pt/Al2O3 catalyst.
Pd/Pt, -Al2O3, -. Pd–Pt/Al2O3, , , . Pd–Pt/Al2O3 , Pt/Al2O3.相似文献
72.
Smith AB Pitram SM Gaunt MJ Kozmin SA 《Journal of the American Chemical Society》2002,124(49):14516-14517
High chemoselectivity can be achieved in the addition of lithium dithiane anions to vinyl epoxides exploiting the steric nature of the dithiane substituent. Unencumbered dithiane anions afford SN2 adducts, whereas sterically encumbered anions lead primarily to SN2' adducts. Furthermore, the SN2' addition occurs syn to the vinyl epoxide. 相似文献
73.
Morozova OB Korchak SE Sagdeev RZ Yurkovskaya AV 《The journal of physical chemistry. A》2005,109(45):10459-10466
Using time-resolved chemically induced dynamic nuclear polarization (CIDNP) techniques, we have studied the mechanism of the photoreactions of triplet excited 4-carboxybenzophenone (CBP) with l-methionine (Met) and 3-(methylthio)propylamine (MTPA) in aqueous solution and the details of the formation of CIDNP at pH from 6.7 to 13.6. At a pH below the pKa of the nitrogen atom of Met, the CIDNP is strongly affected by degenerate electron exchange between the S-S cationic radical dimer and the zwitterionic form of Met with the rate constant kex = 3.4 x 10(8) s(-1) providing an exhaustive explanation of the pH dependence of steady-state CIDNP that was previously interpreted as a manifestation of fast interconversion among three different methionine radical species (Goez, M.; Rozwadowski, J. J. Phys. Chem. A 1998, 102, 7945-7953). By analyzing the polarization of different protons formed in geminate recombination as a function of the pH, we obtained the branching ratio between two reaction pathways for oxidative quenching of (T)CBP via electron transfer from the sulfur and nitrogen atoms of Met and MTPA. Nuclear spin-lattice relaxation times were determined in the dimeric cation radical of Met (T1,S = 8.5 micros). In the cyclic radical cation of MTPA with a three-electron two-center S-N bond, the estimated paramagnetic relaxation is comparatively slow for all protons. Fast deprotonation of the primary aminium radical cation of MTPA and Met in strongly basic solution takes place on the submicrosecond time scale leading to efficient formation of CIDNP in the neutral aminyl radical. 相似文献
74.
V. V. Zagoskin E. A. Zamotrinskaya T. G. Mikhailova V. M. Nesterov 《Russian Physics Journal》1978,21(9):1142-1147
A method of measuring the complex dielectric constant of a mixture composed of a disperse substance and water by insertion of dielectric spacers between the electrodes and the investigated substance is discussed. This system exhibits relaxation of the Maxwell-Wagner type in the conductivity range 10–8–10–2 –1·m–1. By constructing and analyzing Cole-Cole diagrams it is possible to determine the complex dielectric constant of mixtures with a water content of 1–100 wt.% in the frequency range 102–107 Hz.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 40–46, September, 1978. 相似文献
75.
Victoria V. Lipson Irina V. Ignatenko Sergey M. Desenko Svetlana V. Shishkina Oleg V. Shishkin Sergey A. Komykhov Natalya V. Logvinenko Valery D. Orlov Herbert Meier 《Journal of heterocyclic chemistry》2003,40(6):1081-1086
The reaction of 5,7‐diphenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 1 ) with α,β‐unsaturated carbonyl compounds 2a‐f led to the formation of the alkylated heterocycles 3a‐f (Figure 1). However, the reaction of 5‐methyl‐7‐phenyl‐4,7‐dihydro‐1,2,4‐triazolo[1,5‐a]pyrimidine ( 5 ) with 2a‐c yielded under the same conditions the triazolo[5,1‐b]quinazolines 6a‐c (Figure 3). In this case, the alkylation is followed by a cyclocondensation. The structure elucidation of the products is based on ir, ms, 1H and 13C nmr measurements and on an X‐ray diffraction study. 相似文献
76.
Ya. S. Kayukov P. M. Lukin O. E. Nasakin V. N. Khrustalev V. N. Nesterov M. Yu. Antipin V. V. Sheverdov 《Chemistry of Heterocyclic Compounds》1997,33(4):423-425
It has been established by x-ray structural analysis that on reacting 4-oxoalkane-1,1,2,2-tetracarbonitriles with aldehydes
6-imino-2,7-dioxabicyclo[3.2.1]octane-4,4,5-tricarbonitriles are formed and not 3-imino-2,6-dioxabicyclo[2,2,2] octane-4,8,8-tricarbonitriles
as has been proposed.
Chuvash State University, Cheboksary 428015. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 497–499,
April, 1997. 相似文献
77.
Ivachtchenko AV Tkachenko SE Sandulenko YB Vvedensky VY Khvat AV 《Journal of combinatorial chemistry》2004,6(5):828-834
The parallel solution-phase synthesis of a series of building blocks and combinatorial libraries based on natural bispidine scaffold has been accomplished. Key reactions include catalytic hydrogenation of the (-)-cytisine heterocyclic system, followed by alkali-mediated ring cleavage. Using this approach, a series of new bispidine core building blocks for combinatorial synthesis with three points of diversity were effectively synthesized. The libraries from libraries were then obtained in good yields and purities using solution-phase acylation reactions. Obtained combinatorial libraries of 3,4,7-trisubstituted bispidines are potentially useful in the discovery of novel physiologically active compounds. 相似文献
78.
V. L. Ivanov V. A. Artemov L. A. Rodinovskaya A. M. Shestopalov V. N. Nesterov Yu. T. Struchkov V. P. Litvinov 《Chemistry of Heterocyclic Compounds》1996,32(1):105-111
Substituted pyrido,[3',2':4,5]thieno[3,2-b]pyndines were obtained by the reaction of 3-amino-2-benzoylthieno [2,3-b]pyridines with malononitrile and the reaction of 3-cyanopyridine-2(IH)-thiones with 2-aryl-3-bromo-I,I-dicyanopropene. 2-Amino-4-(4-bromophenyl)-7, 9-dimethyl-3-cyanopyrido [3',2':4,5]thieno[3, 2-b]-pyridine was used for the synthesis of a derivative of pyrido[3",2":4', 5']thieno[2',3':5,6]pyrido[2,3-d]-pyrimidine. The structure of these compounds was confirmed by spectral data and x-ray diffraction structural analysis.Deceased. 相似文献
79.
Sergey?P.?BabailovEmail author Dmitry?A.?Mainichev Lubov?D.?Nikulina Svetlana?S.?Petrova 《Journal of inclusion phenomena and macrocyclic chemistry》2005,51(1-2):73-78
Earlier the intramolecular inversion of the 18-crown-6 molecules was found in the complex ion pairs [Ln(ptfa)2 (18-crown-6)]+ [Ln(ptfa)4]− (H2O)4 where Ln = La(1), Ce (2), Pr (3), Nd (4), and ptfa is 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione. In this work the peculiarities of the molecular structure and dynamics were studied for [Eu(ptfa)2 (18-crown-6)]+ [Eu(ptfa)4]− (H2O)4 (5) by NMR spectroscopy techniques. Through VT-NMR spectra analysis the temperature dependence was obtained for the rate constant. The free energy ΔG‡(320) of 18-crown-6 ring inversion activation was found to be 65 ± 5 kJ mol−1 for 5 in CDCl3. This result is comparable with the earlier data [S.P. Babailov and D.A. Mainichev: J. Inclusion Phenom. Macrocyclic Chem. 43, 187–193 (2002)] for complexes 2, 3, 4 in deuterated toluene (ΔG‡(320)=65 ± 9, 64 ± 9, 64 ± 9 kJ mol−1 respectively). It was found by relaxation NMR spectroscopy that the effective distance between Ln and protons of the crown molecule is 4.5 ± 0.2 Å. The analysis of structural parameters testifies that the crown ether and chelated anions are in the first coordination sphere of a Ln cation. Obtained geometrical parameters show that the complex cations of Eu, Ce and Pr have similar spatial structures.This revised version was published online in July 2005 with a corrected issue number. 相似文献
80.
Eugene A. Komissarov Yuri I. Baukov Eugeniya P. Kramarova Sergey Yu. Bylikin Vadim V. Negrebetsky Alexander A. Korlyukov 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):m144-m146
In the title compound, [Ge(C8H14NO)2Cl]CF3SO3, which is the first complex containing an eight‐membered lactam (enantholactam) as ligand, the coordination polyhedron of the GeIV atom is intermediate between trigonal–bipyramidal and square‐pyramidal. Quantum chemical calculations of the crystal structure indicate the absence of additional coordination bonding between the GeIV atom and the trifluoromethanesulfonate anion. 相似文献