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171.
ABSTRACT

1, 6-Anhydro-β-lactose (3) was prepared as its peracetate (2) from lactose monohydrate via its pentachlorophenyl β-lactoside derivative in 49% overall yield. Treatment of the 4′, 6′ 0-benzylidene derivative of 3 with 1.2 mol. equiv. of 1, 3-dichloro-1, 1, 3, 3-tetraisopropyldisiloxane gave two cyclic silyl ethers, the 2′, 3′-0-silyl and the 2, 3:2′, 3′-di-0-sllyl ethers, in the ratio of ca. 2:1. Cyclohexylidenation of 3 at 50°C with excess of 1, 1-dimethoxycyclohexane and trace of protic acid gave the 2′, 3′:4′, 6′- and the 2, 2′:3′, 4′-di-0-cyclohexylidene derivatives, whereas a similar reaction at 90-110 °C resulted in the 3, 2′:3′, 4′-di-0-cyclohexylidene derivative.  相似文献   
172.
Three new pyrazine-bridged dimers of oxoacetatotriruthenium with an NO ligand are synthesized. These complexes show two types of stable mixed-valence states. The ν(NO) stretches for five oxidation states were obtained, and the intramolecular electron-transfer rate within the mixed-valence state is evaluated from the IR spectral line-shape simulation based on Bloch-type analysis, which is the first application of this method to a spectator ligand of NO.  相似文献   
173.
A new μ(4)-bpym-bridged dimer of an oxoacetao-triruthenium complex with carbonyl, [{Ru(3)O(CH(3)COO)(5)(CO)(py)}(2)(μ(4)-bpym)], was synthesized. The complex possesses two stable mixed-valence states associated with Ru(3)(III,III,II)/Ru(3)(III,II,II) and Ru(3)(III,III,III)/Ru(3)(III,III,II). The IR-spectroelectrochemistry reveals ν(CO) spectra in five oxidation states, Ru(3)(III,III,III)-Ru(3)(III,III,III) to Ru(3)(III,II,II)-Ru(3)(III,II,II) and both the mixed-valence states show a spectrum indicating medium interaction between the Ru(3) units.  相似文献   
174.
Takamura H  Wada H  Lu N  Kadota I 《Organic letters》2011,13(14):3644-3647
Stereoselective synthesis of two possible diastereomers of (-)-gummiferol was accomplished by the stepwise epoxidation and Cadiot-Chodkiewicz reaction as the key transformations. Detailed comparison of their (1)H and (13)C NMR data and specific rotation with those of the natural product led to the absolute structural elucidation of (-)-gummiferol.  相似文献   
175.
In order to ensure long-term stability of structures in a rock mass, the study of time-dependent fracturing is essential. The influences of the surrounding environmental conditions and rock fabric on subcritical crack growth in sedimentary rocks in air are yet to be clarified, while the nature of subcritical crack growth in igneous rocks has been studied well. In this study, the influences of temperature and relative humidity on subcritical crack growth in Berea sandstone, Shirahama sandstone and Kushiro sandstone were investigated in air. The load relaxation method of Double Torsion (DT) testing method was used to measure both crack velocity and stress intensity factor under a controlled temperature and relative humidity.Results show that the change of the crack velocity at a given stress intensity factor was unclear when the temperature increased under a constant relative humidity in air. On the other hand, we show that the crack velocity increased by several orders of magnitude when the relative humidity increased threefold or fourfold under a constant temperature at a given stress intensity factor. This increase is much larger than that expected from the conventional concept based on the theory of stress corrosion. It is therefore necessary to consider the additional mechanisms for subcritical crack growth in sandstone. The increase of the crack velocity was larger for sandstone which contained larger amount of clays. We conclude that subcritical crack growth in sandstone in air is affected remarkably by the relative humidity and the amount of clays in rock.  相似文献   
176.
177.
We prepared novel proton‐conductivity membranes based on blends of sulfonated polyimides. The blend membranes were prepared from a sulfonated homopolyimide and a sulfonated copolyimide with a solvent‐casting method. The proton conductivities of the blend membranes were measured as functions of the temperature with four‐point‐probe electrochemical impedance spectroscopy. The conductivity of the membranes strongly depended on the sulfonated homopolyimide content and increased with an increase in the content. The proton conductivity of all the blended membranes indicated a higher value than that determined in Nafion at 80 °C, and this may mean that the proton transfer in the blend membranes is responsible for the ionic channels induced by the hydrophobic and hydrophilic domains. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1325–1332, 2007  相似文献   
178.
In this article, we have reported the influence of alcohol as a casting solution on the structure and the gas permeability of asymmetric polyimide membranes made by dry–wet phase inversion. The apparent skin layer thickness of the asymmetric membrane decreased with an increase in molecular weight of the alcohol, and the thicknesses of the membranes made from methanol, ethanol, propanol, and butanol were 250, 120, 61, and 31 nm, respectively. We found that χ12 as an interaction parameter of solvent–nonsolvent had a significant influence on the phase inversion occurring in the coagulant medium. On the other hand, the gas permeance and the gas selectivity in the asymmetric membranes increased with the increasing molecular weight of the alcohol. We believe that a more packed structure formed in the asymmetric polyimide membrane with a thinner surface skin layer is also responsible for the thickness‐dependence of the gas selectivity obtained in this study. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2739–2746, 2007  相似文献   
179.
In this article the novel design of an anticancer drug delivery system is reported based on a pH‐sensitive liposome retaining the Fe‐porphyrin as a superoxide dismutase(SOD) mimic. The liposomes contained cationic/anionic lipid combinations and were composed of Fe‐porphyrin, L ‐α‐phosphatidylcholine (DMPC), dimethylditetradecylammonium bromide (DTDAB), sodispdum oleate (OANa), and Tween‐80. The size of the liposome was approximately 30 nm. The EC50 value (the effective concentration of compound required to produce a 50% lethal dose against cells) of the liposome was found to be significantly smaller than that of cisplatin as the control drug, suggesting that the liposome showed a high cytotoxicity toward the cancer cells. This is due to the fact that the pH‐sensitive liposome rapidly corresponds to the acidic environments of the endosomes and is unstable, and the Fe‐porphyrin is delivered into the cytosol. This result suggests that O may be useful as a target molecule to induce the selective death of cancer cells and that a pH‐sensitive liposome retaining Fe‐porphyrin as an SOD mimic is a new class of anticancer agent. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
180.
The chemical structure of methylated poly(1‐vinylimidazole) (PVIm‐Me) has been tuned for gene carrier properties, which are cell viability, the stability of its DNA polyion complexes, and gene expression. The resulting PVIm‐Me with lower methylation degree (6 and 20 mol%) exhibited no significant cytotoxicity, as compared with 40 mol% PVIm‐Me, in spite of the same concentration and chemical structure of positive charges. The DNA complex with 20 mol% PVIm‐Me stably retained the DNA, as compared with 6 or 40 mol% PVIm‐Me, which was examined by competitive exchange with dextran sulfate. As a result, the DNA complex with 20 mol% PVIm‐Me mediated most efficient gene delivery, where the resulting transfection activity was higher than that mediated by a positive control, poly(ethylenimine). These results suggest that the optimization of the balance of the methylimidazolium and the imidazole groups of PVIm‐Me is essential for gene carrier design. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
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