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191.
Several N‐heterocyclic carbene precursors are synthesized and used in the α‐alkylations of ketones with primary alcohols. With the assistance of a base, these N‐heterocyclic carbenes can catalyze the reaction smoothly to furnish dialkylated ketones in good‐to‐excellent yields. 相似文献
192.
Ramazan Koçak Giuseppe Borsato Ottorino De Lucchi Arif Daştan 《Helvetica chimica acta》2014,97(4):537-545
New optically active polycyclic ketones 6a – 6d , amenable to a large variety of synthetic applications, have been prepared from readily available 2,3‐dibromonorbornene and analogs (Scheme 2) via desymmetrization with (?)‐ephedrine, followed by hydrolysis under mild acidic conditions. At variance with substrates 4a – 4d , the sterically hindered norbornene derivative 4e reacts with the solvent N‐methylpyrrolidin‐2‐one (NMP) leading to the formation of the unusual cyclopropanoid products 8a and 8b . 相似文献
193.
An efficient one-pot synthesis of fused pyrazoles has been developed. The procedure involved three components reaction of o-alkynylaldehydes 1a–s with ketones 2a–m and hydrazine under mild, metal-free reaction conditions. The desired products were obtained in one-step up to 85% yield. The molecular structure was confirmed by the X-ray crystallographic analysis. 相似文献
194.
Chemoselectivity in the Mannich reaction for three different types of bifunctional substrates has been investigated. 1-Hydroxy-2-naphthalenylethanone affords either phenolic Mannich bases at high pH (free amines), or ketonic Mannich bases at low pH (amine hydrochlorides), whereas the use of N,N-dimethylmethyleneiminium chloride as a preformed dimethylaminomethylation reagent gave the phenolic Mannich base. 1-Aryl-3-(1H-pyrazol-1-yl)-1-propanones undergo aminomethylation at position 4 of the pyrazole ring, and not at the methylene group α to the carbonyl function, regardless of the reaction conditions. 4-(2,5-Dimethyl-1H-pyrrol-1-yl)phenol is aminomethylated chemoselectively on the pyrrole ring under mild reaction conditions. 相似文献
195.
Xiaolei Hu 《Tetrahedron letters》2009,50(30):4378-1707
Enantioselective trifluoromethylation of aromatic ketones promoted by the cinchona alkaloid-derived ammonium bromide and sodium hydride was described. A series of trifluoromethyl-substituted aryl alcohols could be obtained in up to 82% ee with 98% yield under mild conditions. A possible catalytic cycle was also presented. 相似文献
196.
Structurally diverse aldehydes are successfully converted into 1,1‐diacetates with acetic anhydride using cyanuric chloride as a mild, convenient and inexpensive catalyst under solvent‐free conditions. The noteworthy features of the present system are shorter reaction times, and mild and solvent‐free conditions. Furthermore, it offers chemoselective protection of aldehydes. 相似文献
197.
The reaction conditions employed directed the site of functionalisation of ketones with NBS: under solvent-free conditions α-bromination was the exclusive process, while in water, ring functionalisation occurred in the case of methoxy substituted aromatic ketones. 相似文献
198.
An efficient method is reported to reduce aromatic ketones selectively into arylmethylenes or alcohols with hypophosphites and Pd/C, depending on the selected conditions. This study could represent a promising alternative to the classical uses of standard hydrides or molecular hydrogen involved in reduction and deoxygenation procedures. 相似文献
199.
A convenient, two-step synthesis of substituted furans from readily available aryl alkynes and ketones is reported. The furan-forming oxidative cyclization is mediated by the combination of cerium(IV) ammonium nitrate and potassium bromide and can be carried out in an open flask. 相似文献
200.
A new class of hemilabile unsymmetrical 2-(1-arylimino)-6-(pyzazol-1-yl)pyridine ligands and their ruthenium(II) and nickel(II) NNN complexes were synthesized. The Ru(II) complex catalysts have been fully characterized and exhibited good to excellent catalytic activity in the transfer hydrogenation (TH) of ketones in refluxing 2-propanol. These results have demonstrated rare examples of active ruthenium(II) NNN complex catalysts that do not feature a N-H functionality for TH of ketones. 相似文献