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111.
In this work, we have studied the substituent effect of several alkyl groups in the rate-determining step of the catalyzed Baeyer-Villiger (BV) reaction of phenyl alkyl ketones with performic (PFA) and trifluoroperacetic (TFPAA) acids, using quantum chemistry methods. Our results reveal that the substituent effect is more pronounced in the migration step barriers than in the corresponding addition step; that could change the rate-determining step (RDS) of the reaction, as observed in the oxidation of phenyl tert-butyl ketone with both peracids. In addition, the effect of the acid/peracid pairs used is also analyzed. We have demonstrated that the addition step is less susceptible to the acid/peracid nature since the acid strength and the nucleophilicity of the peracid have opposite effects. The effect of the acid/peracid pair is much more pronounced in the migration step because it only depends on the leaving ability of the acid, which in turn depends on its strength. These observations are relevant for understanding the effects of the substrate, the peracid, and the catalyst on the switching of the RDS in the BV reaction. 相似文献
112.
Fernández M Vicario JL Reyes E Carrillo L Badía D 《Chemical communications (Cambridge, England)》2012,48(15):2092-2094
We have developed an efficient procedure for the easy and straightforward preparation of functionalized dihydropyridazines as highly enantiopure materials by reaction of pyruvaldehyde 2-tosyl hydrazone with a variety of α,β-unsaturated aldehydes using a chiral secondary amine as catalyst. The overall process consists of a cascade reaction involving an initial aza-Michael reaction, in which the stereocentre is installed, followed by an intramolecular aldol reaction/dehydration step. 相似文献
113.
Silvia Reboredo Prof. Efraím Reyes Prof. Jose L. Vicario Prof. Dr. Dolores Badía Prof. Luisa Carrillo Dr. Abel de Cózar Prof. Dr. Fernando P. Cossío 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(23):7179-7188
The catalytic enantioselective [3+2] cycloaddition between azomethine ylides and α,β‐unsaturated aldehydes catalyzed by α,α‐diphenylprolinol has been studied in detail. In particular, the reaction has been extended to the use of 2‐alkenylidene aminomalonates generated in situ as azomethine ylide precursors. These reactions lead to the formation of pyrrolidines containing a 5‐alkenyl side chain with potential for chemical manipulation. Moreover, a detailed and concise computational study has been carried out to understand the exact nature of the mechanism of this reaction and especially the consequences derived from the incorporation of the chiral secondary amine catalyst on the reaction pathway. 相似文献
114.
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116.
Ricardo R. Contreras Bernardo Fontal Marisela Reyes Trino Surez Fernndo Bellandi All Bahsas 《Journal of heterocyclic chemistry》2001,38(5):1223-1225
The new compound Methyl‐2,4‐bis(cyclohexane)dispiro‐1,2,3,4,4a,5,6,7‐octahydro‐(1H,3H)‐quinazo‐line‐8‐carbodithioate has been synthesized from cyclohexanone and carbon disulfide. It has been characterized by uv‐visible, FTTR , mass spectra and a complete structure proposed based on 1H and 13C NMR spectroscopy. 相似文献
117.
Turra Christian Fernandes Elisabete A. De Nadai Bacchi Márcio Arruda Sarriés Gabriel Adrián Reyes Andrés Enrique Lai 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(1):219-224
Journal of Radioanalytical and Nuclear Chemistry - The objective of this study was to evaluate temporal variability of rare earth elements (REE) in soils of citrus agroecosystems. Instrumental... 相似文献
118.
Dr. Francisco Javier Ortiz-López M. Sc. Daniel Carretero-Molina Dr. Marina Sánchez-Hidalgo M. Sc. Jesús Martín Dr. Ignacio González M. Sc. Fernando Román-Hurtado Dr. Mercedes de la Cruz Dr. Sergio García-Fernández Dr. Fernando Reyes M. Sc. Julia Patricia Deisinger Dr. Anna Müller Dr. Tanja Schneider Dr. Olga Genilloud 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(31):12754-12758
Lantibiotics are ribosomally synthesized and post-translationally modified peptides (RiPPs) characterized by the presence of lanthionine or methyllanthionine rings and their antimicrobial activity. Cacaoidin, a novel glycosylated lantibiotic, was isolated from a Streptomyces cacaoi strain and fully characterized by NMR, mass spectrometry, chemical derivatization approaches and genome analysis. The new molecule combines outstanding structural features, such as a high number of d -amino acids, an uncommon glycosylated tyrosine residue and an unprecedented N,N-dimethyl lanthionine. This latter feature places cacaoidin within a new RiPP family located between lanthipeptides and linaridins, here termed lanthidins. Cacaoidin displayed potent antibacterial activity against Gram-positive pathogens including Clostridium difficile. The biosynthetic gene cluster showed low homology with those of other known lanthipeptides or linaridins, suggesting a new RiPP biosynthetic pathway. 相似文献
119.
C. Bentabol A. Reyes J. A. Narvaez M. Morell J. J. Laserna F. Garcia Sanchez 《Microchemical Journal》1985,32(3):317-323
A method for the kinetic determination of tonin activity in rat submaxillary gland extracts is described. The method is based on the fluorogenic reaction of o-phthalaldehyde with the dipeptide histidyl-leucine generated in the enzymatic hydrolysis of angiotensin I. The reaction is monitored by fluorescence at 440 nm. At pH 7.5, the method allows the determination of 2–15 nmol/ml histidyl-leucine with relative standard deviation of 6%. 相似文献
120.