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331.
Dayse N. Moreira Clarissa P. Frizzo Kelvis Longhi Nilo Zanatta Helio G. Bonacorso Marcos A. P. Martins 《Monatshefte für Chemie / Chemical Monthly》2008,37(6):1049-1054
The synthesis of eleven 1-cyanoacetyl-5-hydroxy-5-halomethyl-4,5-dihydro-1H-pyrazoles from the reaction of 4-alkoxy-3-alken-2-ones f(R
3C(O)C(R
2) = C(R
1)OR, where R
3 = CF3, CCl3, CHCl2, CO2
Et; R
2/R
1 = H/H, H/Me, H/Et, -(CH2)4-, Me/H, H/Pr, and R = Me, Et) with cyanoacetohydrazide is reported. The reaction was carried out in the ionic liquid ([bmim][BF4]) and molecular solvents. The results showed that when the ionic liquid was used as reaction medium, the reaction time was
drastically decreased and the yield was improved. 相似文献
332.
Marcos A. P. Martins Emerson A. Guarda Clarissa P. Frizzo Mara R. B. Marzari Dayse N. Moreira Nilo Zanatta Helio G. Bonacorso 《Monatshefte für Chemie / Chemical Monthly》2008,139(11):1321-1327
A series of twenty halomethylated β-enaminones [RC(O)CH=C(R
1)NR
3
R
4, where R = CF3,CCl3, CHCl2; R
1 = H, Me, Ph; R
3 = H, Me, Bu, Et; R
4 = Me, Et, Bu, allyl, tert-amyl, CH2CH2OH, Bn, Ph] were synthesized using the ionic liquid [bmim]BF4 at room temperature. It is demonstrated that this ionic liquid is a reaction medium suitable for the amination of β-alkoxyvinyl
halomethyl ketones. The advantages of this method are the absence of solvents, short reaction times, and good yields.
Correspondence: Marcos A. P. Martins, Núcleo de Química de Heterociclos – NUQUIMHE, Universidade Federal de Santa Maria, Santa
Maria, RS, Brazil. 相似文献
333.
Ten alpha-cyclodextrin [2]-rotaxanes have been prepared with alkane-, stilbene- and azobenzene-based axles, capped through nucleophilic substitution of either 2-chloro-4,6-dimethoxy-1,3,5-triazine or 2,4-dichloro-6-methoxy-1,3,5-triazine in aqueous solution, followed by further substitution of the remaining triazinyl chlorine in some cases when the latter capping reagent was used. In one case the rotaxane is a [c(2)]-daisy chain obtained by double-capping the corresponding hermaphroditic cyclic dimer. One of the rotaxane azobenzene derivatives was shown to undergo photochemically-induced reversible interconversion between its trans- and cis-isomers, causing the cyclodextrin to move back and forth along the axle, and therefore behave as a molecular shuttle. The methodology is therefore shown to constitute a general and versatile approach for the construction of supramolecular species as the basis of photochemical molecular devices. 相似文献
334.
Aquines O Li Z Lopez A Mendez H Ramirez J Huang GS Miller DH Pavlunin V Sanghi B Shipsey IP Xin B Adams GS Anderson M Cummings JP Danko I Napolitano J He Q Insler J Muramatsu H Park CS Thorndike EH Coan TE Gao YS Liu F Stroynowski R Artuso M Blusk S Butt J Li J Menaa N Mountain R Nisar S Randrianarivony K Redjimi R Sia R Skwarnicki T Stone S Wang JC Zhang K Csorna SE Bonvicini G Cinabro D Dubrovin M Lincoln A Asner DM Edwards KW Briere RA Brock I Chen J Ferguson T Tatishvili G Vogel H 《Physical review letters》2006,96(15):152001
Using 420 pb(-1) of data collected on the upsilon(5S) resonance with the CLEO III detector, we reconstruct B mesons in 25 exclusive decay channels to measure or set upper limits on the decay rate of upsilon(5S) into B meson final states. We measure the inclusive B cross section to be sigma(upsilon(5S) --> BB(X)) = (0.177 +/- 0.030 +/- 0.016) nb and make the first measurements of the production rates of sigma(upsilon(5S) --> B*B*) = (0.131 +/- 0.025 +/- 0.014) nb and sigma(upsilon(5S) --> BB*) = (0.043 +/- 0.016 +/- 0.006) nb, respectively. We set 90% confidence level limits of sigma(upsilon(5S) -->BB) < 0.038 nb, sigma(upsilon(5S) --> B(*)B(*)pi) < 0.055 nb and sigma(upsilon(5S) --> BBpipi) < 0.024 nb. We also extract the most precise value of the B(s)* mass to date, M(B(s)*) = (5411.7 +/- 1.6 +/- 0.6) MeV/c2. 相似文献
335.
A new 2,3-methylated 3*-monoacetylated 6-O-tert-butyldimethylsilylated beta-CD derivative was synthesized and chemically bonded onto aminopropyl derivatized monolithic silica HPLC columns. In this CD derivative, only one of seven methyl groups in 3-position was substituted by an acetyl group. Its applicability as a chiral stationary phase for HPLC was tested and compared with exclusively 2,3-methylated 6-O-tert-butyldimethylsilylated beta-CD immobilized onto aminopropyl-modified monoliths. Thirty-two chiral compounds from different chemical classes and different functionalities were tested under RP conditions. Fourteen compounds were resolved into their enantiomers by methylated 6-O-tert-butyldimethylsilylated beta-CD. By use of methylated/acetylated 6-O-tert-butyldimethylsilylated beta-CD as the chiral stationary phase 7 analytes were successfully stereodifferentiated. 相似文献
336.
Harnessing the energy of molecular recognition in a nanomachine having a photochemical on/off switch
Coulston RJ Onagi H Lincoln SF Easton CJ 《Journal of the American Chemical Society》2006,128(46):14750-14751
6A-Deoxy-6A-(N-methyl-3-phenylpropionamido)-beta-cyclodextrin operates as a molecular machine, where the amide group serves as a torsion bar to harness the work output resulting from extraction of 1-adamantanol and consequent complexation of the aryl substituent by the cyclodextrin, when the latter behave as the piston and cylinder, respectively, of a molecular pump. At 25 degrees C, the complexation changes the ratio of the amide (Z)- and (E)-isomers from 2.4:1 to 25:1, on which basis the work performed on the amide bond is calculated to be 1.4 kcal mol-1. trans-6A-Deoxy-6A-(N-methylcinnamido)-beta-cyclodextrin and the cis isomer function as a more advanced version of the machine, with the alkene moiety serving as a photochemical on/off switch. Irradiation at 300 nm converts the trans cinnamide to the cis isomer, while the reverse process occurs at 254 nm. With the cis isomer there is little interaction of the phenyl group with the cyclodextrin cavity, so in that mode the machine is turned off. By contrast, complexation of the aryl substituent by the cyclodextrin occurs with the trans cinnamide and changes the ratio of the amide (Z)- and (E)-isomers from 2.6:1 to 100:1. Consequently, in this mode the machine is turned on, and the work harnessed by the amide bond is 2.1 kcal mol-1. 相似文献
337.
The syntheses of three new diamide-linked γ-cyclodextrin dimers joined by substitution at either a glucopyranose C6A or C3A carbon are reported. The syntheses involve the reaction of either C6A or C3A amino-substituted γ-cyclodextrin with bis(4-nitrophenyl)succinate to form succinamide linked γ-cyclodextrin dimers or reaction of C6A azide-substituted γ-cyclodextrin with carbon dioxide to form a urea linked γ-cyclodextrin dimer. 相似文献
338.
Julian Kund Jan-Hendrik Kruse Andreas Gruber Dr. Ivan Trentin Marcel Langer Dr. Clarissa Read Dr. Gregor Neusser Dominik Blaimer Dr. Ulrich Rupp Prof. Dr. Carsten Streb Prof. Dr. Kerstin Leopold Prof. Dr. Felix H. Schacher Prof. Dr. Christine Kranz 《Angewandte Chemie (International ed. in English)》2023,62(22):e202217196
Heterogeneous light-driven catalysis is a cornerstone of sustainable energy conversion. Most catalytic studies focus on bulk analyses of the hydrogen and oxygen evolved, which impede the correlation of matrix heterogeneities, molecular features, and bulk reactivity. Here, we report studies of a heterogenized catalyst/photosensitizer system using a polyoxometalate water oxidation catalyst and a model, molecular photosensitizer that were co-immobilized within a nanoporous block copolymer membrane. Via operando scanning electrochemical microscopy (SECM), light-induced oxygen evolution was determined using sodium peroxodisulfate (Na2S2O8) as sacrificial electron acceptor. Ex situ element analyses provided spatially resolved information on the local concentration and distribution of the molecular components. Infrared attenuated total reflection (IR-ATR) studies of the modified membranes showed no degradation of the water oxidation catalyst under the reported light-driven conditions. 相似文献
339.
Dr. Samuel E. Griffin Grant P. Domecus Clarissa E. Flores Dr. R. Eric Sikma Prof. Lauren Benz Prof. Seth M. Cohen 《Angewandte Chemie (International ed. in English)》2023,62(23):e202301611
Low-valent metal–organic frameworks (LVMOFs) and related materials have gained interest due to their potential applications in heterogeneous catalysis. However, of the few LVMOFs that have been reported, none have shown catalytic activity. Herein, a low-valent metal-organic material constructed from phosphine linkers and IrI nodes is reported. This material is effectively a crystalline, insoluble analogue of Vaska's complex. As such, the material reversibly binds O2 and catalyzes the reductive formation of enamines from amides. 相似文献