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971.
Magrone P Cavallo F Panzeri W Passarella D Riva S 《Organic & biomolecular chemistry》2010,8(24):5583-5590
Polyhydroxylated hybrid molecules have been synthesized using a protocol based on the regioselective acylation of the target compounds with activated dicarboxylic acids catalyzed by Novozym-435. The procedure implies that the mixed ester derivatives prepared and isolated from the first esterification step act as acylating agents in the second esterification step. 相似文献
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973.
Adriana Valore Dr. Elena Cariati Prof. Dr. Claudia Dragonetti Dr. Stefania Righetto Dr. Dominique Roberto Prof. Dr. Renato Ugo Prof. Dr. Filippo De Angelis Dr. Simona Fantacci Dr. Antonio Sgamellotti Prof. Dr. Alceo Macchioni Prof. Dr. Daniele Zuccaccia Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(16):4814-4825
Cyclometalated cationic IrIII complexes with substituted 1,10‐phenanthrolines (1,10‐phen), such as [Ir(ppy)2(5‐R‐1,10‐phen)]Y (ppy=cyclometalated 2‐phenylpyridine; R=NO2, H, Me, NMe2; Y?=PF6?, C12H25SO3?, I?) and [Ir(ppy)2(4‐R,7‐R‐1,10‐phen)]Y (R=Me, Ph) are characterized by a significant second‐order optical non linearity (measured by the electrical field induced second harmonic generation (EFISH) technique). This nonlinearity is controlled by MLCT processes from the cyclometalated IrIII, acting as a donor push system, to π* orbitals of the phenanthroline, acting as an acceptor pull system. Substitution of cyclometalated 2‐phenylpyridine by the more π delocalized 2‐phenylquinoline (pq) or benzo[h]quinoline (bzq) or by the sulfur‐containing 4,5‐diphenyl‐2‐methyl‐thiazole (dpmf) does not significantly affect the μβ absolute value, which instead is affected by the nature of the R substituents on the phenanthroline, the higher value being associated with the electron‐withdrawing NO2 group. By using a combined experimental (the EFISH technique and 1H and 19F PGSE NMR spectroscopy) and theoretical (DFT, time‐dependent‐DFT (TDDFT), sum over states (SOS) approach) investigation, evidence is obtained that ion pairing, which is controlled by the nature of the counterion and by the concentration, may significantly affect the μβ values of these cationic NLO chromophores. In CH2Cl2, concentration‐dependent high absolute values of μβ are obtained for [Ir(ppy)2(5‐NO2‐1,10‐phen)]Y if Y is a weakly interacting anion, such as PF6?, whereas with a counterion, such as C12H25SO3? or I?, which form tight ion‐pairs, the absolute value of μβ is lower and quite independent of the concentration. This μβ trend is partially due to the perturbation of the counterion on the LUMO π* levels of the phenanthroline. The correlation between the μβ value and dilution shows that the effect of concentration is a factor that must be taken into careful consideration. 相似文献
974.
Anna Esposito Concetta di Giovanni Dr. Maria De Fenza Prof. Giovanni Talarico Dr. Marco Chino Prof. Giovanni Palumbo Dr. Annalisa Guaragna Dr. Daniele D'Alonzo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(12):2597-2601
A highly regio- and stereoselective route to d - and l -cyclohexenyl nucleosides has been devised, using the Tsuji–Trost reaction as the key step. Contrarily to the widely accepted mechanism (involving a net retention of configuration), the reaction proceeded in a highly stereoconvergent manner, providing cis nucleosides regardless of the relative configuration of the starting materials. DFT calculations confirmed the experimental data while suggesting the origin of the stereochemical reaction outcome. 相似文献
975.
Dr. Stefano Turchini Dr. Daniele Catone Dr. Nicola Zema Dr. Giorgio Contini Dr. Tommaso Prosperi Prof. Piero Decleva Prof. Mauro Stener Dr. Flaminia Rondino Dr. Susanna Piccirillo Dr. Kevin C. Prince Prof. Maurizio Speranza 《Chemphyschem》2013,14(8):1723-1732
A study of (R)‐3‐methylcyclopentanone [(R)‐3‐MCP] by photoelectron spectroscopy and photoelectron circular dichroism (PECD) is presented. The synchrotron radiation gas‐phase photoelectron spectra of (R)‐3‐MCP were measured and are discussed on the basis of different theoretical methodologies. The experimental dichroism of (R)‐3‐MCP for selected deconvoluted valence states and for the carbonyl carbon 1s core state are reported and reproduced well by calculated dispersions generated by considering the contributions of two different conformers. The theoretical dichroic parameters are calculated by employing a multicentre basis set of B‐spline functions and a Kohn–Sham Hamiltonian. Temperature‐dependent PECD studies of the HOMO state and the carbonyl carbon 1s core level allowed the separation of the contributions of each conformer by photoelectron dichroism. This new approach clearly shows how the PECD methodology is sensitive to conformational and structural changes of unoriented (R)‐3‐MCP in the gas phase, opening up new perspectives in the characterisation of chiral molecular systems. 相似文献
976.
“Green polyethylene” and curauá cellulose nanocrystal based nanocomposites: Effect of vegetable oils as coupling agent and processing technique
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Daniele Oliveira de Castro Elisabete Frollini Adhemar Ruvolo‐Filho Alain Dufresne 《Journal of Polymer Science.Polymer Physics》2015,53(14):1010-1019
Cellulose nanocrystals (CNC) were prepared from curauá fibers via acid hydrolysis, and used as reinforcing phase for high‐density biopolyethylene (HDBPE) or green polyethylene. Castor oil (CO), epoxidized soybean oil (ESO) and epoxidized linseed oil (ELO) were chosen as compatibilizers for this study. Nanocomposites reinforced with CNC (3, 6, and 9 wt %) were processed by extrusion, using CO (3, 6, and 9 wt %) to evaluate its action as CNC dispersing agent in the HDBPE matrix. From the results obtained for these films, the CNC and oil contents were set at 3 wt%. In addition to CO, ELO, and ESO were also used, and besides processing by extrusion, extrusion/hot‐pressing process was also considered, in order to compare the two processing techniques. The nanocomposites were characterized by microscopic, thermal, mechanical, and rheological analyses. The presence of oil leads to less opaque films and improved dispersion. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1010–1019 相似文献
977.
Carmela Napolitano Manuela Borriello Francesca Cardullo Daniele Donati Alfredo Paio 《合成通讯》2013,43(14):2031-2035
A rapid and efficient synthesis of 1-benzyl-2-difluoromethyl-piperazine is herein described. The new pathway has the advantage of avoiding orthogonal protection at the two piperazine nitrogen atoms; therefore it is suitable for access to several 1-benzyl 2-substituted piperazines starting from the simple commercially available N,N′-dibenzylethylendiamine. 相似文献
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