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641.
Samson Afewerki Prof. Dr. Ismail Ibrahem Jonas Rydfjord Palle Breistein Prof. Dr. Armando Córdova 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(10):2972-2977
The first direct intermolecular regiospecific and highly enantioselective α‐allylic alkylation of linear aldehydes by a combination of achiral bench‐stable Pd0 complexes and simple chiral amines as co‐catalysts is disclosed. The co‐catalytic asymmetric chemoselective and regiospecific α‐allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2‐alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2‐alkyl substituted hemiacetals, 2‐alkyl‐butane‐1,4‐diols, and amines. The concise co‐catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed. 相似文献
642.
Kopylovich MN Karabach YY da Silva MF Figiel PJ Lasri J Pombeiro AJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(3):899-914
Template combination of copper acetate (Cu(AcO)2?H2O) with sodium dicyanamide (NaN(C≡N)2, 2 equiv) or cyanoguanidine (N≡CNHC(=NH)NH2, 2 equiv) and an alcohol ROH (used also as solvent) leads to the neutral copper(II)–(2,4‐alkoxy‐1,3,5‐triazapentadienato) complexes [Cu{NH?C(OR)NC(OR)?NH}2] (R=Me ( 1 ), Et ( 2 ), nPr ( 3 ), iPr ( 4 ), CH2CH2OCH3 ( 5 )) or cationic copper(II)–(2‐alkoxy‐4‐amino‐1,3,5‐triazapentadiene) complexes [Cu{NH?C(OR)NHC(NH2)?NH}2](AcO)2 (R=Me ( 6 ), Et ( 7 ), nPr ( 8 ), nBu ( 9 ), CH2CH2OCH3 ( 10 )), respectively. Several intermediates of this reaction were isolated and a pathway was proposed. The deprotonation of 6 – 10 with NaOH allows their transformation to the corresponding neutral triazapentadienates [Cu{NH?C(OR)NC(NH2)?NH}2] 11 – 15 . Reaction of 11 , 12 or 15 with acetyl acetone (MeC(?O)CH2C(?O)Me) leads to liberation of the corresponding pyrimidines NC(Me)CHC(Me)NC NHC(?NH)OR, whereas the same treatment of the cationic complexes 6 , 7 or 10 allows the corresponding metal‐free triazapentadiene salts {NH2C(OR)?NC(NH2)?NH2}(OAc) to be isolated. The alkoxy‐1,3,5‐triazapentadiene/ato copper(II) complexes have been applied as efficient catalysts for the TEMPO radical‐mediated mild aerobic oxidation of alcohols to the corresponding aldehydes (molar yields of aldehydes of up to 100 % with >99 % selectivity) and for the solvent‐free microwave‐assisted synthesis of ketones from secondary alcohols with tert‐butylhydroperoxide as oxidant (yields of up to 97 %, turnover numbers of up to 485 and turnover frequencies of up to 1170 h?1). 相似文献
643.
Electrostatic assembly of Ag nanoparticles onto nanofibrillated cellulose for antibacterial paper products 总被引:1,自引:0,他引:1
Natércia C. T. Martins Carmen S. R. Freire Ricardo J. B. Pinto Susana C. M. Fernandes Carlos Pascoal Neto Armando J. D. Silvestre Jessica Causio Giovanni Baldi Patrizia Sadocco Tito Trindade 《Cellulose (London, England)》2012,19(4):1425-1436
Nanofibrillated cellulose offers new technological solutions for the development of paper products. Here, composites of nanofibrillated cellulose (NFC) and Ag nanoparticles (NP) were prepared for the first time via the electrostatic assembly of Ag NP (aqueous colloids) onto NFC. Distinct polyelectrolytes have been investigated as macromolecular linkers in order to evaluate their effects on the building-up of Ag modified NFC and also on the final properties of the NFC/Ag composite materials. The NFC/Ag nanocomposites were first investigated for their antibacterial properties towards S. aureus and K. pneumoniae microorganisms as compared to NFC modified by polyelectrolytes linkers without Ag. Subsequently, the antibacterial NFC/Ag nanocomposites were used as fillers in starch based coating formulations for Eucalyptus globulus-based paper sheets. The potential of this approach to produce antimicrobial paper products will be discussed on the basis of complementary optical, air barrier and mechanical data. 相似文献
644.
Di Fabio G Malgieri G Isernia C D'Onofrio J Gaglione M Messere A Zarrelli A De Napoli L 《Chemical communications (Cambridge, England)》2012,48(32):3875-3877
A first solid phase approach to obtain monosubstituted CD conjugates to different labels has been developed. A new solid support has been designed to get a variety of C-6 monofunctionalized CDs (α, β, MeβCD and HPβCD) covalently linked through a phosphodiester bridge to different labels, in highly pure form and under very mild detachment conditions. 相似文献
645.
Afewerki S Ibrahem I Rydfjord J Breistein P Córdova A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(10):2972-2977
The first direct intermolecular regiospecific and highly enantioselective α-allylic alkylation of linear aldehydes by a combination of achiral bench-stable Pd(0) complexes and simple chiral amines as co-catalysts is disclosed. The co-catalytic asymmetric chemoselective and regiospecific α-allylic alkylation reaction is linked in tandem with in situ reduction to give the corresponding 2-alkyl alcohols with high enantiomeric ratios (up to 98:2 e.r.; e.r.=enantiomeric ratio). It is also an expeditious entry to valuable 2-alkyl substituted hemiacetals, 2-alkyl-butane-1,4-diols, and amines. The concise co-catalytic asymmetric total syntheses of biologically active natural products (e.g., Arundic acid) are disclosed. 相似文献
646.
Mijangos MV González-Marrero J Miranda LD Vincent-Ruz P Lujan-Montelongo A Olivera-Díaz D Bautista E Ortega A de la Luz Campos-González M Gamez-Montaño R 《Organic & biomolecular chemistry》2012,10(15):2946-2949
Flavones were directly alkylated at the C-3 position in moderate yields using a xanthate-based oxidative radical addition procedure. This methodology is a suitable synthetic tool for the direct substitution of the vinylic and unactivated C-H bond of the C ring of the flavone by an alkyl functionality under neutral conditions. 相似文献
647.
Karabach YY Guedes da Silva MF Kopylovich MN Gil-Hernández B Sanchiz J Kirillov AM Pombeiro AJ 《Inorganic chemistry》2010,49(23):11096-11105
The new three-dimensional (3D) heterometallic Cu(II)/Fe(II) coordination polymers [Cu(6)(H(2)tea)(6)Fe(CN)(6)](n)(NO(3))(2n)·6nH(2)O (1) and [Cu(6)(Hmdea)(6)Fe(CN)(6)](n)(NO(3))(2n)·7nH(2)O (2) have been easily generated by aqueous-medium self-assembly reactions of copper(II) nitrate with triethanolamine or N-methyldiethanolamine (H(3)tea or H(2)mdea, respectively), in the presence of potassium ferricyanide and sodium hydroxide. They have been isolated as air-stable crystalline solids and fully characterized including by single-crystal X-ray diffraction analyses. The latter reveal the formation of 3D metal-organic frameworks that are constructed from the [Cu(2)(μ-H(2)tea)(2)](2+) or [Cu(2)(μ-Hmdea)(2)](2+) nodes and the octahedral [Fe(CN)(6)](4-) linkers, featuring regular (1) or distorted (2) octahedral net skeletons. Upon dehydration, both compounds show reversible escape and binding processes toward water or methanol molecules. Magnetic susceptibility measurements of 1 and 2 reveal strong antiferromagnetic [J = -199(1) cm(-1)] or strong ferromagnetic [J = +153(1) cm(-1)] couplings between the copper(II) ions through the μ-O-alkoxo atoms in 1 or 2, respectively. The differences in magnetic behavior are explained in terms of the dependence of the magnetic coupling constant on the Cu-O-Cu bridging angle. Compounds 1 and 2 also act as efficient catalyst precursors for the mild oxidation of cyclohexane by aqueous hydrogen peroxide to cyclohexanol and cyclohexanone (homogeneous catalytic system), leading to maximum total yields (based on cyclohexane) and turnover numbers (TONs) up to about 22% and 470, respectively. 相似文献
648.
Rafael Aez Armando Herize Aníbal Sierraalta Tania Cordova Gabriel Chuchani 《国际化学动力学杂志》2006,38(3):184-193
Theoretical studies on the gas phase elimination of 2‐substituted alkyl ethyl methylcarbonates were performed at the B3LYP/6‐31G* and B3LYP/6‐31+G** level of theory. The results of these calculations provide additional evidence that the mechanism of carbonates with a Cβ H bond proceeds through a concerted nonsynchronous six‐membered cyclic transition state to produce methylcarbonic acid and the corresponding olefin. The unstable intermediate, methylcarbonic acid, rapidly decomposes through a four‐membered cyclic transition state to methanol and carbon dioxide. The correlation of the logarithm of theoretical rate coefficients against Hancock's steric parameters E gave an approximate straight line (δ = 0.30, r = 0.996 at 400°C). An additional fact is that when experimental log kre.l is plotted against the theoretical log kre.l. for 2‐alkyl ethyl methylcarbonates an approximate straight line (r = 0.997 at 400°C) is obtained. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 184–193, 2006 相似文献
649.
Simple, highly modular primary amino acid derivatives catalyze the direct enantioselective addition of ketones to nitro-olefins with high stereocontrol and furnish the corresponding aldol products in high yield with up to >38 1 dr and up to 99% ee. 相似文献
650.
Nesterov DS Kokozay VN Dyakonenko VV Shishkin OV Jezierska J Ozarowski A Kirillov AM Kopylovich MN Pombeiro AJ 《Chemical communications (Cambridge, England)》2006,(44):4605-4607
An unprecedented hexanuclear heterotrimetallic Fe/Cu/Co complex bearing two Cu(mu-O)2Co(mu-O)2Fe cores is easily prepared by self-assembly and acts as a remarkable catalyst for the peroxidative oxidation of cycloalkanes under mild conditions. 相似文献