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101.
Baba Y Hirukawa N Tanohira N Sodeoka M 《Journal of the American Chemical Society》2003,125(32):9740-9749
Protein serine/threonine phosphatases (PP1, PP2A and PP2B) play important roles in intracellular signal transductions. The immunosuppressant drugs FK506 and cyclosporin A (CsA) bind to immunophilins, and these complexes selectively inhibit PP2B (calcineurin), leading to the suppression of T-cell proliferation. Both FK506 and CsA must, however, form complexes with immunophilins to exert their inhibitory action on PP2B. Thus, it is of interest to find a direct and selective inhibitor of PP2B that does not involve the immunophilins as a biological tool for studies of PP2B and also as a candidate therapeutic agent. We selected the simple natural product cantharidin, a known PP2A-selective inhibitor, as a lead compound for this project. Primary SAR indicated that norcantharidin (7-oxabicyclo[2.2.1]heptane-2,3-dicarboxylic anhydride) inhibits not only PP1 and PP2A but also PP2B, and a binding model of norcantharidin carboxylate to the PP2B catalytic site was computationally constructed. Based on this binding model, we designed and synthesized several cantharidin derivatives. Among these compounds, 1,5-dibenzoyloxymethyl-substituted norcantharidin was found to inhibit PP2B without inhibiting PP1 or PP2A. To our knowledge, this is the first highly selective catalytic site-directed inhibitor of PP2B. 相似文献
102.
6-Chloro-2-pyridyl esters (OPyCl) of N alpha-benzyloxycarbonyl and tert-butyloxycarbonylamino acids were synthesized by the N,N'-dicyclohexylcarbodiimide (DCC) method from the acids and 6-chloro-2-hydroxypyridine in dimethylformamide (DMF). The reactivity of the 6-chloro-2-pyridylester with amino group is much higher than that of the corresponding 2-pyridyl ester (OPy) and p-nitrophenyl esters (ONp) in dioxane and DMF, and a peptide bond is formed without acylation at the side chain hydroxyl group of amino acids. Z-Asp(OBzl)-OPyCl reacted with amino acid methyl esters in dioxane to give the corresponding dipeptide without any detectable aspartimide formation. 相似文献
103.
Kamata J Okada T Kotake Y Niijima J Nakamura K Uenaka T Yamaguchi A Tsukahara K Nagasu T Koyanagi N Kitoh K Yoshimatsu K Yoshino H Sugumi H 《Chemical & pharmaceutical bulletin》2004,52(9):1071-1081
As part of a series of studies to discover new topoisomerase II inhibitors, novel pyrimidoacridones, pyrimidophenoxadines, and pyrimidocarbazoles were synthesized, and in vitro and in vivo antitumor activities and DNA-protein and/or DNA-topoisomerase II cross-linking activity as an indicator of topoisomerase II-DNA cleavable complex formation were evaluated. The pyrimidocarbazoles possessed high in vitro and in vivo potencies. Compound 26 (ER-37326), 8-acetyl-2-[2-(dimethylamino)ethyl]-1H-pyrimido[5,6,1-jk]carbazole-1,3(2H)-dione, showed in vitro growth inhibitory activity with respective IC(50) values of 0.049 microM and 0.35 microM against mouse leukemia P388 and human oral cancer KB. In vivo, this compound inhibited the tumor growth of mouse sarcoma M5076 implanted into mice with T/C values of 42% and 13% at 3.13 and 6.25 mg/kg/d respectively without significantly affecting the body weight. In addition, compound 26 (ER-37326) increased the formation of DNA-topoisomerase II cross-linking in P388 cells. 相似文献
104.
MNDO, a semiempirical SCF-MO method, was applied to study the structure of the borate glass. The clusters, B(OH)3, H3B3O6, B3O63?, (HO)2BOB (OH)2, (HO)2B3O3OB3O3 (OH)2, BO3[B(OH)2]3 and BO3[B3O3(OH)2]3 were treated and their geometries, the heats of reactions, the π electron systems and electronic structures were discussed. The geometry and the electronic structures show a good correspondence with the experimental data. The resonance stabilization effect of the π electron system is not so large as to control the geometries and reactions. 相似文献
105.
Akito Tsuboi 《Mathematical Logic Quarterly》2001,47(1):45-50
Let T1 and T2 be two simple complete theories in disjoint languages. We prove that there is a simple complete theory which extends T1 ∪ T2 if T2 has a certain condition. 相似文献
106.
Hema Malani Huifeng Zhong Hideyuki Tsuboi Nozomu Hatakeyama Hiromitsu Takaba Carlos A. Del Carpio 《Applied Surface Science》2008,254(23):7608-7611
The ethylene/1-butene copolymerization using constrained geometry catalyst CpSiH2-NH-TiCl2 (CGC) was investigated by the density functional theory and molecular dynamics. Structures and energetics of reactants, π-complexes, transition states, and products during insertion of ethylene and 1-butene monomers into the catalytic reactive site of the CGC were investigated by the density functional theory (DFT) using the software Dmol3, while dynamics of atoms during copolymerization process was investigated by classical molecular dynamics (MD) using the New-Ryudo-CR program. The calculated results were compared with the available experimental and theoretical ones. It was found that the ethylene insertion into Ti-Me active species is energetically more favorable than the butene one and the 2,1-butene insertion is more favorable than 1,2-butene one. Once the initial ethylene insertion has taken place, the further ethylene insertion occurring with a less energy barrier, in good agreement with experimental findings. 相似文献
107.
Masamichi Tsuboi Yoshiaki Hamada Lucien Henry Jean Chazelas Alain Valentin 《Journal of Molecular Spectroscopy》1984,108(2):328-342
The infrared absorption spectrum of NH2NH2 vapor has been observed in the region 899–1077 cm?1, where the antisymmetric wagging band (va = 1 ← 0) appears, by the use of a Fourier transform spectrometer with a practical resolution of 0.003 cm?1. In the region 925.0–925.6 cm?1, the spectrum was also observed with a tunable diode laser, and a component, β, of the pQ2 cluster has been further resolved. Most of the absorption lines assignable to β-pP2(J″), γ-pP2(J″), β-pQ2(J″), γ-rQ0(J″), β-rR0(J″), and γ-rR0(J″), where J″ = 2 ~ 15, have been identified. From these observed transition frequencies, in combination with the ground state energy levels given by microwave spectroscopy, the energy level structure of the K′ = 1 rotational states was determined. From this, the following molecular parameters for the va = 1 state were determined: molecular asymmetry, B′-C″ = 0.00017 cm?1; a parameter q5 describing an umbrella motion Coriolis interaction (q5K) about the a axis, q5 = ?0.0030 cm?1; its J(J + 1) variation, q5j = 0.00014 cm?1; and a parameter describing an umbrella-motion K-type doubling g5J(J + 1), g5 = 0.000021 cm?1. 相似文献
108.
We investigate stationarity of types over models in simple theories. In particular, we show that in simple theories with finite SU‐rank, any complete type over a model having Cantor‐Bendixson rank is stationary. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
109.
Yutaka Wada Yoshio Seike Nobuyuki Tsuboi Katsuya Hasegawa Kiyokazu Kobayashi Makihito Nishioka Keiichi Hori 《Proceedings of the Combustion Institute》2009,32(2):2005-2012
Tetra-ol glycidyl azide polymer (GAP) is one of the best candidates for the solid fuel of gas hybrid rocket system because of self-combustibility, better mechanical property and high heat of formation, and comprehensive understanding of combustion phenomena is indispensable for such an application. Combustion model of GAP, which is one-dimensional three-phase mode combustion model, was developed by Beckstead et al. and they applied it to tri-ol GAP successfully. We have applied this model to tetra-ol GAP as an initial attempt, and numerical simulation showed that maximum temperatures in the gas phase exceeded those of experimental results significantly, and calculated burning rates were much higher than strand burner data, thus, modification of the model taking account of combustion incompleteness was found to be necessary. Combustion residues of GAP were investigated, and those were found to be composed of soot (black color), and high viscosity residue (HVR), and yellow powder which was only observed at high pressures. These residues were analyzed by means of SEM and FTIR, and mass balance was also measured. Modifications of combustion model were made taking the residue analysis results into account as Blow Off Mechanism. Simulated final temperature in the gas phase and burning rate are lowered effectively and coincide well with experimental data adjusting kinetic parameters. 相似文献
110.
Seven new monoterpene glycoside esters related to paeoniflorin were isolated from Paeoniae Radix, together with polymeric proanthocyanidins, polygalloylglucoses and 48 known compounds (a benzoylsucrose, seven aromatic acids, adenosine, nine monoterpene glycosides, eight flavan-3-ols, a catechin dimer formed by oxidation, seven proanthocyanidins, three galloylsucroses, five galloylglucoses, and six ellagitannins). The structures of the new compounds were determined by spectral investigation including two-dimensional NMR techniques. In addition, increased water solubility of polymeric proanthocyanidin in the presence of paeoniflorin was examined by n-octanol-water partition and 1H-NMR spectral experiments. 相似文献