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101.
Appleby I Boulton LT Cobley CJ Hill C Hughes ML de Koning PD Lennon IC Praquin C Ramsden JA Samuel HJ Willis N 《Organic letters》2005,7(10):1931-1934
Two methods to produce (2S)-5-amino-2-(1-n-propyl-1H-imidazol-4-ylmethyl)-pentanoic acid were investigated. Diastereoisomeric salt resolution, using the quinidine salt, gave the desired intermediate in 98% ee and 33% yield. Asymmetric hydrogenation of various substrates gave high conversions, with up to 83% ee. Integration of these two approaches via asymmetric hydrogenation of a quinidine salt substrate followed by crystallization provided the desired intermediate in 94% ee and 76% yield. 相似文献
102.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Katherine Flynn Amy N. Addante Julio C. Argueta 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(3):197-201
Novel copolymers of trisubstituted ethylene monomers, alkyl ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC6H4CH = C(CN)2 (where R is 2-methyl, 3-methyl, 4-methyl, 4-ethyl, 4-i-propyl, 4-butyl, 4-i-butyl, and 4-t-butyl) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r 1) for the monomers is 4-ethyl (42.6) > 4-butyl (29.4) > 4-t-butyl (26.7) > 4-i-butyl (1.6) > 4-i-propyl (1.29) > 3-methyl (1.26) > 2-methyl (0.8) > 4-methyl (0.4). High T g of the copolymers, in comparison with that of poly(4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in 183–500°C range with residue (5–30% wt.), which then decomposed in the 500–800°C range. 相似文献
103.
104.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Salima Atlas Mustapha Raihane 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(7):650-655
Copolymerization of 2-phenyl-1,1-dicyanoethylene (PDE) with 4-fluorostyrene and pentafluorostyrene in solution with radical initiation (ABCN) at 70°C yielded random copolymers with PDE alternating units. The composition of the copolymers was calculated from nitrogen analysis and the structure was analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r1) and the tendency toward alternation of monomer units in the copolymer for these two monomers, is 4-fluorostyrene (1.96) > pentafluorostyrene (0.51). Higher glass transition temperature of the copolymers in comparison with that of homopolymers indicates a decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. 相似文献
105.
Gregory B. Kharas Emi Hanawa Benjamin L. Hill Katherine T. Flynn Libby Lapson Amanda Mueller 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1055-1058
Novel copolymers of trisubstituted ethylene monomers, ring-substituted 2-phenyl-1,1-dicyanoethylenes, RC6H4CH=C(CN)2 (where R is 4-dimethylamino, 4-diethylamino, 3-phenoxy, 3-benzyloxy, 4-benzyloxy, 4-acetoxy, 2-cyano, 3-cyano, and 4-cyano) and 4-fluorostyrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator (ABCN) at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, 1H and 13C-NMR. The order of relative reactivity (1/r 1) for the monomers is 3-benzyloxy (2.9) > 4-cyano (2.7) > 3-phenoxy (1.9) > 4-acetoxy (1.8) > 3-cyano (1.7) > 2-cyano (1.6) > 4-benzyloxy (0.6) > 4-dimethylamino (0.4) = 4-diethylamino (0.4). High T g of the copolymers, in comparison with that of poly (4-fluorostyrene) indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 290–400°C range with residue, which then decomposition in 400–800°C range. 相似文献
106.
Dr. J. Grant Hill Xiaojun Hu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3620-3628
Benchmark quality geometries and interaction energies for the prereactive halogen‐bonded complexes of dihalogens and ammonia, including hypothetical astatine containing dihalogens, have been produced via explicitly correlated coupled cluster methods. The application of local electron correlation partitioning reveals dispersion, electrostatics and ionic substitutions all contribute significantly to the interaction energy, with a linear relationship between the ionic substitutions and the degree of charge transfer. Potential energy curves for H3N???ClF show that as the relative orientations of the two subunits are manipulated appreciable interactions can be found at considerably angular displaced geometries, signifying lower directionality in halogen bonding than previously supposed. 相似文献
107.
J. Grant Hill 《International journal of quantum chemistry》2013,113(1):21-34
The choice of basis set in quantum chemical calculations can have a huge impact on the quality of the results, especially for correlated ab initio methods. This article provides an overview of the development of Gaussian basis sets for molecular calculations, with a focus on four popular families of modern atom‐centered, energy‐optimized bases: atomic natural orbital, correlation consistent, polarization consistent, and def2. The terminology used for describing basis sets is briefly covered, along with an overview of the auxiliary basis sets used in a number of integral approximation techniques and an outlook on possible future directions of basis set design. © 2012 Wiley Periodicals, Inc. 相似文献
108.
Dr. Paul Smart Dr. Charles A. Mason Jason R. Loader Dr. Anthony J. H. M. Meijer Prof. Alastair J. Florence Dr. Kenneth Shankland Dr. Ashleigh J. Fletcher Dr. Stephen P. Thompson Dr. Michela Brunelli Dr. Adrian H. Hill Prof. Lee Brammer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(11):3552-3557
109.
G. K. Chuah S. Jaenicke K. S. Chan S. T. Khor J. O. Hill 《Journal of Thermal Analysis and Calorimetry》1993,40(3):1157-1164
Thermal decomposition of metal-organic precursors for the mixed oxide BaBiO3 was studied using TG and EGA. Precursors produced by polyesterification of bifunctional acids with ethylene glycol (Pechini process) decomposed about 100°C higher than those without the diol. BaCO3 was identified by IR and XRD as a reaction intermediate. EGA proved that the amount of BaCO3 was below 10% of the total barium, and that the barium exists mainly as a nitro-compound up to 650°C. Phase-pure BaBiO3 with a moderately high surface area (1.4 m2/g) could be synthesised from a citrate precursor by the Pechini process at around 850°C. 相似文献
110.
Cano Sierra J Hüerländer D Hill M Kehr G Erker G Fröhlich R 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(15):3618-3622
The titanium complex [(C(5)H(4)bond;allyl)TiCl(3)] (2) undergoes olefin metathesis coupling when treated with 3 mol % of [Cl(2)(L(1))(L(2))Ru=CHPh] (L(1)=L(2)=PCy(3), 4 a; L(1)=PCy(3), L(2)=(H(2)IMes), 4 b) to yield the dimetallic complex [Cl(3)Ti(C(5)H(4))-CH(2)CH=CHCH(2)-(C(5)H(4))TiCl(3)] (5). The allyl-substituted titanocene complex [Cp(C(5)H(4)bond;allyl)TiCl(2)] (3) analogously yields the dimetallic system 6 when treated with 4. The ansa-zirconocene complex [Me(2)Si(C(5)H(4))(C(5)H(3)bond;allyl)ZrCl(2)] (7) cleanly yields the analogous dimetallic coupling product 8 (>95 % isomerically pure), when treated with catalytic amounts of 4 b in toluene. Complex 8 gives an active homogeneous ethene or propene polymerization catalyst, especially at elevated temperatures, when treated with excess methylalumoxane. 相似文献