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271.
Paul C. Unangst David T. Connor S. Russell Stabler Robert J. Weikert 《Journal of heterocyclic chemistry》1987,24(3):811-815
Methods for the synthesis of novel 3-hydroxy, 3-alkoxy, and 3-alkyl indole-2-carboxylic acids and esters are described. Dieckmann cyclization of various 2-[(carboxymethyl)amino]benzoic acid diesters yielded 1-unsubstituted-, 1-methyl-, and 1-phenyl-3-hydroxy-1H-indole-2-carboxylic acid esters. An Ullmann reaction with bromobenzene converted 1H-indoles to 1-phenylindoles. 相似文献
272.
Rhodium-catalyzed asymmetric ring opening of oxabicyclic alkenes with sulfur nucleophiles 总被引:2,自引:0,他引:2
The synthesis of 2-sulfanyl-1,2-dihydro-naphthalen-1-ols is described. This methodology is based on rhodium catalysis and enables various thiols to undergo an asymmetric SN2' ring opening of oxabenzonorbornadiene. Under the reaction conditions ([Rh(COD)Cl](2) (2.5 mol %), (S)-(R)-PPF-P(t)Bu(2) (6 mol %), AgOTf (7 mol %), NH(4)I (1.7 equiv), galvinoxyl (5 mol %), THF, 85 degrees C), aryl- and alkyl-sulfide adducts are obtained in good to excellent yield and in high enantiomeric excess (>90% ee). 相似文献
273.
Ivo Ngeli Corine Baud GErald Bernardinelli Yvan Jacquier Mary Moraon Paul Müllet 《Helvetica chimica acta》1997,80(4):1087-1105
The [Rh2(OAc)4]-catalyzed decomposition of {[(4-nitrophenyl)sulfonyl]imino}phenyl-λ3-iodane (NsN?IPh) resulted in formal insertions into CH bonds, activated by phenyl or vinyl groups, or by O-substituents. Scope and limitations of the reaction were investigated. Yields of up to 84% were achieved in the most favorable cases. Yields were enhanced by electron-releasing substituents and decreased by steric hindrance. Aziridination competed with allylic insertion with olefinic substrates. The insertion reaction proceeded with retention of configuration. With chiral RhII catalysts, a modest asymmetric induction was observed. A mechanism involving direct insertion by a Rh-complexed nitrene into the CH bond is proposed. 相似文献
274.
[reaction: see text] The spiroketal unit of the HIV-integrase inhibitor integramycin has been prepared in an efficient and convergent manner. Key steps in this sequence include the use of ruthenium-mediated hydroesterification reactions of homoallylic alcohols and silyl ethers, and a C,O-dianionic addition into a lactone provides the spiroketal while minimizing protecting group manipulations. 相似文献
275.
Ronald C. Crouch Ann O. Davis Timothy D. Spitzer Gary E. Martin Maged M. H. Sharaf Paul L. Schiff Charles H. Phoebe Albert N. Tackie 《Journal of heterocyclic chemistry》1995,32(3):1077-1080
Elucidation of minor natural product structures has been significantly augmented by inverse-detection; further improvement has been afforded by the development of micro inverse-detection probes. We report here the elucidation of the structure of a new alkaloid, quindolinone (5H, 10H-indolo[3,2-b]quinolin-11-one), from the West African plant Cryptolepis sanguinolenta. All nmr data for this minor, preparative hplc-isolated alkaloid, including 1H-15N one? bond heteronuclear shift correlation (HMQC) data, were recorded on an 800 μg sample of the alkaloid dissolved in 140 μl of 100% d6-DMSO using a 400 MHz spectrometer. 相似文献
276.
Werner Fuss Wolfram E Schmid Sergei A Trushin Paul S Billone William J Leigh 《Chemphyschem》2007,8(4):592-598
Photochemical pericyclic reactions are believed to proceed via a so-called pericyclic minimum on the lowest excited potential surface (S(1)), which is common to both the forward and backward reactions. Such a common intermediate has never been directly detected. The photointerconversion of 1,3-butadiene and cyclobutene is the prevailing prototype for such reactions, yet only diene ring closure proceeds with the stereospecificity that the Woodward-Hoffmann rules predict. This contrast seems to exclude a common intermediate. Using ultrafast spectroscopy, we show that the excited states of two cyclobutene/diene isomeric pairs are linked by not one, but by two common minima, p* and ct*. Starting from the diene side (cyclohepta-1,3-diene and cycloocta-1,3-diene), electrocyclic ring closure passes via the pericyclic minimum p*, whereas ct* is mainly responsible for cis-trans isomerization. Starting from the corresponding cyclobutenes (bicyclo[3.2.0]heptene-6 and bicyclo[4.2.0]octene-7), the forbidden isomer is formed from ct*. The path branches at the first (S(2)/S(1)) conical intersection towards p* and ct*. The fact that the energetically unfavorable ct* path can compete is ascribed to a dynamic effect: the momentum in C=C twist direction, acquired--such as in other olefins--in the Franck-Condon region of the cyclobutenes. 相似文献
277.
Taylor P Lahti PM Carroll JB Rotello VM 《Chemical communications (Cambridge, England)》2005,(7):895-897
Stable radical 2-(6-uradinyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazole-1-oxyl (1) binds to hydrogen-bonding complement 2,6-di(propylamido)pyridine (DAP) in chloroform with Ka=220 M(-1) at 33 degrees C; ESI-MS shows not only 1:DAP complementary dyad formation, but also 1:(DAP)2 formation at higher concentrations of DAP. 相似文献
278.
279.
Paul F. Reigler Jeff Larson Lyle Bowman 《Journal of polymer science. Part A, Polymer chemistry》1981,19(12):3247-3255
The thermal and/or catalytic degradation of chloride-containing polymers causes dehydrohalogenation which produces hydrochloric acid. A nonaqueous method has been developed for the termination of hydrochloric acid. The sample is dissolved in tetrahydrofuran and titrated potentiometrically with a standard tetrabutylammonium hydroxide solution in a 7.5% (V/V) aqueous tetrahydrofuran solution with a combination glass-calomel electrode. The method has a relative precision of ±3.7% at the 95% confidence limit and a sensitivity of 25 ppm HCI. 相似文献
280.
Paul Binger Michael J Doyle John McMeeking Carl Krüger Yi-Hung Tsay 《Journal of organometallic chemistry》1977,135(3):405-414
Oxidative addition of 2 molecules of 3,3-dimethylcyclopropene (I) to α,α′-bipyridyl(1,5-cyclooctadiene)nickel(0) (III) gave the title compound (IV) in over 90% yield. Complex IV was characterized by mass, 1H NMR and 13C NMR spectroscopy. Its structure was determined by X-ray diffraction (a 13.7081(2), b 14.638(2), c 9.5139(1) Å, β 110.82(1)°, C2/c, R = 0.05 for 1614 reflections). 相似文献