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141.
C. S. Barnes R. J. Goldsack Ravindra Pratap Rao 《Journal of mass spectrometry : JMS》1971,5(3):317-324
The low resolution mass spectra of a number of homologous 5-alkylthio-1,3,4-thiadiazolyl-2-amines have been determined. With the methylthio compound the only significant loss from the molecular ion is the sulphydryl radical. As the homologous series is ascended this reaction becomes less important and is insignificant with the butylthio isomers. The ethylthio compound suffers extensive loss of ethylene and when the alkyl group contains three or more carbon atoms the main reaction is always loss of the olefin coresponding to the alkyl group.All of the n-alkylthio compounds showed in addition loss of methylthio radical from the molecular ion. A mechanism is proposed and comparisons made with alkyl phenyl thioethers and alkylthio substituted heterocycles. 相似文献
142.
Ruthenium(III) has been precipitated gravimetrically in the pH range 7.0-8.5 with morpholine-4-carbodithioate and determined by weighing as a black complex (C5H6ONS2)3 Ru after drying at l00–110°C. The interference of the various metal ions has been avoided by using an ammonical mixture of EDTA and tartrate (1:1 molar ratio). The complex is thermally stable up to l60°C. 相似文献
143.
Ravindra Singh B. V. Sukhatme 《Annals of the Institute of Statistical Mathematics》1973,25(1):627-633
Summary The paper considers the problem of optimum stratification on an auxiliary variablex when the information on the auxiliary variablex is also used to estimate the population mean
using ratio or regression methods of estimation. Assuming the form of the regression of the estimation variabley on the auxiliary variablex as also the form of the conditional variance function V(y/x), the problem of determining optimum strata boundaries (OSB) is shown to be a particular case of optimum stratification on
the auxiliary variable for stratified simple random sampling estimate. A numerical investigation has also been made to study
the amount of gain in efficiency that can be brough about by stratifying the population. 相似文献
144.
Theoretical studies of charge transport in deoxyribonucleic acid (DNA) and peptide nucleic acid (PNA) indicate that structure and dynamics modulate the charge transfer rates, and that different members of a structural ensemble support different charge transport mechanisms. Here, we review the influences of nucleobase geometry, electronic structure, solvent environment, and thermal conformational fluctuations on the charge transfer mechanism. We describe an emerging framework for understanding the diversity of charge transport mechanisms seen in nucleic acids. 相似文献
145.
Umesh B. Kosurkar Tulshiram L. Dadmal K. Appalanaidu Y. Khageswara Rao Jagadeesh B. Nanubolu Ravindra M. Kumbhare 《Tetrahedron letters》2014
A highly, efficient synthetic protocol for the synthesis of 2-aminooxazolo[4,5-b]pyridine derivatives is established via intramolecular C–O bond coupling using copper iodide as a catalyst and water as solvent. A variety of functionalized substrates were found to react under this reaction conditions to provide products in good to excellent yields. 相似文献
146.
Noy B. Nechmad Ravindra Phatake Elisa Ivry Albert Poater N. Gabriel Lemcoff 《Angewandte Chemie (International ed. in English)》2020,59(9):3539-3543
The development of selective olefin metathesis catalysts is crucial to achieving new synthetic pathways. Herein, we show that cis‐diiodo/sulfur‐chelated ruthenium benzylidenes do not react with strained cycloalkenes and internal olefins, but can effectively catalyze metathesis reactions of terminal dienes. Surprisingly, internal olefins may partake in olefin metathesis reactions once the ruthenium methylidene intermediate has been generated. This unexpected behavior allows the facile formation of strained cis‐cyclooctene by the RCM reaction of 1,9‐undecadiene. Moreover, cis‐1,4‐polybutadiene may be transformed into small cyclic molecules, including its smallest precursor, 1,5‐cyclooctadiene, by the use of this novel sequence. Norbornenes, including the reactive dicyclopentadiene (DCPD), remain unscathed even in the presence of terminal olefin substrates as they are too bulky to approach the diiodo ruthenium methylidene. The experimental results are accompanied by thorough DFT calculations. 相似文献
147.
Combination of Cyanine Behaviour and Giant Hyperpolarisability in Novel Merocyanine Dyes: Beyond the Bond Length Alternation (BLA) Paradigm 下载免费PDF全文
Dr. Venkatakrishnan Parthasarathy Dr. Ravindra Pandey Dr. Matthias Stolte Dr. Sampa Ghosh Dr. Frédéric Castet Prof. Dr. Frank Würthner Prof. Dr. Puspendu Kumar Das Dr. Mireille Blanchard‐Desce 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):14211-14217
Merocyanine dyes that exhibit antithetic cyanine‐like behaviour and giant first‐order hyperpolarisability (β) values have been designed. These cyanine‐type dyes open up an intriguing route towards molecular‐based electro‐optic materials as well as new second‐harmonic generation dyes for imaging. 相似文献
148.
Liu C Dobhal MP Ethirajan M Missert JR Pandey RK Balasubramanian S Sukumaran DK Zhang M Kadish KM Ohkubo K Fukuzumi S 《Journal of the American Chemical Society》2008,130(43):14311-14323
The oxidation of bacteriopyropheophorbide with ferric chloride hexahydrate or its anhydrous form produced the ring-D oxidized (ring-B reduced) chlorin in >95% yield. Replacing the five-member isocyclic ring in bacteriopyropheophorbide- a with a fused six-member N-butylimide ring system made no difference in regioselective oxidation, and the corresponding ring-B reduced chlorin was isolated in almost quantitative yield. When the oxidant was replaced by 2,3-dichloro-5,6-dicyano-p-benzoquinone, which is frequently used at the oxidizing stage of the porphyrin synthesis, the ring-B oxidized (ring-D reduced) chlorins were obtained. With both ring-B reduced and ring-D reduced chlorins in hand, their photophysical and electrochemical properties were examined and compared for the first time. The ring-B reduced chlorine 20, with a fused six-member N-butylimide ring, exhibits the most red-shifted absorption band (at lambda(max) = 746 nm), the lowest fluorescence quantum yield (4.5%), and the largest quantum yield of singlet oxygen formation (67%) among the reduced ring-B and ring-D chlorins investigated in this study. Measurements of the one-electron oxidation and reduction potentials show that compound 20 is also the easiest to oxidize among the examined compounds and the third easiest to reduce. In addition, the 1.62 eV HOMO-LUMO gap of 20 is the smallest of the examined compounds, and this agrees with values calculated using the DFT method. Spectroelectrochemical measurements afforded UV-visible absorption spectra for both the radical cations and radical anions of the examined chlorins. The ring-B reduced compound 20, with a fused six-member N-butylimide ring, is regarded as the most promising candidate in this study for photodynamic therapy because it has the longest wavelength absorption and the largest quantum yield of singlet oxygen formation among the compounds investigated. 相似文献
149.
Thiquynhxuan Le Wang Tian Ravindra A. V. Xuxiang Yuquan Ju Shaohua Zhang Libo 《Kinetics and Catalysis》2021,62(3):436-444
Kinetics and Catalysis - Submicron zeolite has become the focus of research because of its high thermal stability, high catalytic activity, and uniform size. A rapid method for synthesizing... 相似文献
150.
Hrdlicka PJ Babu BR Sørensen MD Wengel J 《Chemical communications (Cambridge, England)》2004,(13):1478-1479
Very efficient interstrand communication systems in nucleic acid duplexes, based on pyrene excimer formation between 2'-N-(pyren-1-yl)methyl-2'-amino-LNA monomers, demonstrate the versatility of functionalized 2'-amino-LNA monomers for Angstrom-scale chemical engineering. 相似文献