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61.
(E)-α,β-Unsaturated ketones 1 or esters 2 can be obtained with complete stereoselectivity by reaction of different 2-chloro-3-hydroxy ketones 3 or esters 4 and CrCl2. A comparative study of the results of synthesis of ketones 1 with CrCl2 or samarium is performed. A mechanism to explain both β-elimination reactions has been proposed. 相似文献
62.
A new type of ionic liquid supported selenium reagents were synthesized and found to be an excellent catalyst in the oxidation of alcohols to aldehydes and ketones in the presence of 30%H2O2.The predictable solubility of ionic liquids allows an easy separation of the oxidation products from the reaction mixture.Furthermore,the oxidation reaction can be carried out using an ionic liquid as the solvent,and the ionic liquid-supported selenium reagents can be recycled and used for four times with a little decrease in catalytic performance. 相似文献
63.
The three-component direct Mannich reaction between aldehydes, p-toluenesulfonamide, and enolizable ketones was achieved for the first time with organic bases as the catalysts. The corresponding N-tosylated β-aminoketones were obtained in high yields and good to excellent diastereoselectivities using TMG as the catalyst. Through reduction of the ketone group, the reaction product may be converted into β-aminol with excellent diastereoselectivity. 相似文献
64.
A Ph3P‐catalyzed cyclization of α‐halogeno ketones 2 with dialkyl acetylenedicarboxylates (=dialkyl but‐2‐ynedioates) 3 produced halogenated α,β‐unsaturated γ‐butyrolactone derivatives 4 in good yields (Scheme 1, Table). The presence of electron‐withdrawing groups such as halogen atoms at the α‐position of the ketones was necessary in this reaction. Cyclization of α‐chloro ketones resulted in higher yields than that of the corresponding α‐bromo ketones. Dihalogeno ketones similarly afforded the expected γ‐butyrolactone derivatives in high yields. 相似文献
65.
66.
Microbial asymmetric reduction of ketones is a method widely used for the preparation of chiral alcohols. The present progress report deals with the basic concepts that govern enantioselectivity of enzymes and intact cells. Strategies to control the stereochemical course of microbial reductions of carbonyl compounds and the relationship of substrate structure to enantioselectivity are considered. 相似文献
67.
Chao Qin Chuan-Jin Hou Hongzhu Liu Yan-Jun Liu De-Zhi Huang Xiang-Ping Hu 《Tetrahedron letters》2018,59(8):719-722
The Ir-catalyzed asymmetric hydrogenation of simple aromatic ketones with chiral ferrocenyl P,N,N-ligands has been developed. Under the optimized conditions, a wide range of ketones were hydrogenated to afford the corresponding chiral alcohols in good to excellent enantioselectivities (up to 98%?ee). 相似文献
68.
Subcritical water (<374 °C and <221 bar) has unique characteristics such as dramatically decreased dielectric constant, surface tension, and viscosity with increasing temperature, allowing for dissolution and reaction of organics in high-temperature water to occur. Additionally, the dissociation constant of water at temperatures of 200-300 °C is three orders of magnitude greater than that of ambient water, which may also contribute to the reactivity of subcritical water with certain organic compounds. In this study, the degradation and oxidation of phenanthrene in subcritical water were investigated. Both deionized water and water with 3% hydrogen peroxide were used in the degradation and oxidation studies. The effect of temperature on degradation efficiency has been determined with a temperature range of 100-350 °C. When the temperature was increased from 150 to 350 °C, the amount of phenanthrene degraded varied from 6 to 243 μg in each milliliter of deionized water. However, these quantities were increased to 195 μg at 150 °C and 3680 μg at 350 °C in each milliliter of water with 3% hydrogen peroxide. Several degradation products including phenol, benzoic acid, and ketones were identified by using gas chromatography/mass spectrometry (GC/MS). 相似文献
69.
Ivan Damljanović Mirjana Vukićević Rastko D. Vukićević 《Monatshefte für Chemie / Chemical Monthly》2006,137(3):301-305
Summary. The conversion of alicyclic and aliphatic carbonyl compounds as well as aromatic aldehydes into the corresponding oximes (up
to quantitative yields) was achieved by simply grinding these reactants, hydroxylamine hydrochloride and sodium hydroxide
without solvent. However, this procedure was unsuccessful in the case of aromatic ketones. In this case it was necessary to
add silica gel as a catalyst. 相似文献
70.
Aderivaldo P. da Silva 《Tetrahedron letters》2005,46(18):3233-3235
The reduction of the 2-cyclohexen-1-one, mediated by some transition metal ions (Zn2+, Cu2+, Ni2+, Co2+ and Fe2+) and complexes ([NiII(bipy)]Br2 and [FeII(bipy)]Br2, where bipy = 2,2′-bipyridine), was carried out by using a homogeneous electromediated system: sacrificial anode, nickel cathode, (0.2 M) NaI as supporting electrolyte and undivided cell. A constant current of <100 mA was applied with a maximum cell potential of 2.0 V. Cyclohexanone was the principal product in major cases yielding 98%. Cyclohexanol was also detected in some cases. The selectivity of the process can be controlled by choosing Ni as mediator and Zn or Ni as sacrificial anode. A more reactive system can be reached when Fe sacrificial anode is used, giving cyclohexanol as major product (87%). 相似文献