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61.
62.
Thermal Decomposition Kinetics of Dicyclopentadiene‐1,8‐dione: The Reaction Path through Quantum Chemical Calculation 下载免费PDF全文
Luis V. Amaiz Loriett Cartaya Edgar Marquez Jackson J. Alcázar Alexis Maldonado José R. Mora Tania Cordova Gabriel Chuchani 《国际化学动力学杂志》2016,48(12):812-821
Thermal decomposition kinetics of dicyclopentadiene‐1,8‐dione 7 implied an intramolecular competition between α,β‐ and β,γ‐double bond to assist the CO elimination. Experimental thermolysis of 7 in dioxane gave 3a,7a‐dihydro‐1H‐inden‐1‐one (cis‐bicyclo[4.3.0]nona‐2,4,7‐triene‐9‐one), CO gas, and a very small amount of indanone. This result suggested β,γ‐double bond favored the extrusion of CO gas. Calculations of several density functional theory (DFT) levels of theory and CBS‐QB3 method were employed. Two mechanisms were considered: a one‐step concerted pathway and a stepwise mechanism involving [1,3] and [1,5] hydrogen sigmatropic migrations. The CAM‐B3LYP/6‐31G(d,p) calculation reasonably agrees with the experimental kinetic parameters. The mechanism appears to be unimolecular in one step concerted through a five‐membered cyclic transition state. Isomerization of product cis‐bicyclo[4.3.0]nona‐2,4,7‐triene‐9‐one yielding 1‐indanone is presented and described. Calculation from substrate 7 may explain in a similar way the mechanism of decomposition of compounds 1‐6 . The present work may well promote to the possibility of carrying out experimental research works on the thermal decarbonylation kinetics in a liquid solution and in the gas phase of β,γ‐unsaturated aliphatic ketones. 相似文献
63.
Carla Zanella Guidini Líbia Diniz Santos Marquez Helisângela de Almeida Silva Miriam Maria de Resende Vicelma Luiz Cardoso Eloízio Júlio Ribeiro 《Applied biochemistry and biotechnology》2014,172(3):1623-1638
Studies have been conducted on selecting yeast strains for use in fermentation for ethanol production to improve the performance of industrial plants and decrease production costs. In this paper, we study alcoholic fermentation in a fed-batch process using a Saccharomyces cerevisiae yeast strain with flocculant characteristics. Central composite design (CCD) was used to determine the optimal combination of the variables involved, with the sucrose concentration of 170 g/L, a cellular concentration in the inoculum of 40 % (v/v), and a filling time of 6 h, which resulted in a 92.20 % yield relative to the theoretical maximum yield, a productivity of 6.01 g/L h and a residual sucrose concentration of 44.33 g/L. With some changes in the process such as recirculation of medium during the fermentation process and increase in cellular concentration in the inoculum after use of the CCD was possible to reduce the residual sucrose concentration to 2.8 g/L in 9 h of fermentation and increase yield and productivity for 92.75 % and 9.26 g/L h, respectively. A model was developed to describe the inhibition of alcoholic fermentation kinetics by the substrate and the product. The maximum specific growth rate was 0.103 h?1, with K I and K s values of 109.86 and 30.24 g/L, respectively. The experimental results from the fed-batch reactor show a good fit with the proposed model, resulting in a maximum growth rate of 0.080 h?1. 相似文献
64.
The glass transition temperature, Tg, and the coordination peak of the radial distribution function, obtained from electron diffraction experiments, are studied for amorphous thin films of the Se100−xBix system (x ≤ 8) prepared by vacuum evaporation. The controversial problem of the coordination of Bi in these alloys is raised. The Tg data versus composition are analyzed by means of a simple analytic model. All results can be interpreted by assuming that the average coordination of Bi for the more dilute portions of the system is four, as opposed to the expected value of three, and three when x is greater than 5. 相似文献
65.
The synthesis of a new Schiff base containing 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-aminobenzenethiol subunits is
described. The reaction of 1,10-phenanthroline-2,9-dicarboxaldehyde with 2-aminobenzenethiol leads to the isolation of 2,9-bis(2-benzothiazolinyl)-1,10-phenanthroline
(I) which undergoes rearrangement when reacted with cobalt, nickel, copper or zinc ions to produce complexes of the tautomeric
Schiff base 2,9-bis[2-(2-mercaptophenyl)-2-azaethene]-1,10-phenanthroline (L). The [Cu(L)ClO4][ClO4] and [M(L)X2] complexes (where M = Co(II), Ni(II) and Zn(II) and X = Br) were characterized by physical and spectroscopic measurements
which indicated that the ligand is acting probably as a tetradentate N4 chelating agent. 相似文献
66.
Gong T Shen J Hu Z Marquez M Cheng Z 《Langmuir : the ACS journal of surfaces and colloids》2007,23(6):2919-2923
An emulsion crystallization method has been demonstrated to measure the nucleation rate of a thermoresponsive colloidal poly-N-isopropylacrylamide (PNIPAM) system. The colloidal PNIPAM suspension was injected into a microfluidic flow-focusing device to generate monodispersed droplets in oil. The temperature was controlled to fine tune the volume fraction of the PNIPAM particles, and the microfluidic flow rate was varied to change the droplet sizes, thus altering the nucleation volume. Using independent droplets, we can isolate the nucleation events to eliminate the interactions among crystallites that existed in bulk or large droplet systems. Therefore, we were able to carry out accurate nucleation rate measurements of colloidal crystals. This emulsion crystallization method is promising for bridging the gap among theories, simulations, and experiments for nucleation kinetics studies. 相似文献
67.
Lawrence DB Cai T Hu Z Marquez M Dinsmore AD 《Langmuir : the ACS journal of surfaces and colloids》2007,23(2):395-398
We present semipermeable, hollow capsules (colloidosomes) that expand and contract upon heating and cooling. The capsules are composed of micrometer-sized poly(N-isopropylacrylamide)-co-acrylic acid microgel particles, which exhibit a reversible size transition near 34 degrees C. The microgel particles assemble on the surfaces of water droplets in oil. Addition of the diblock copolymer poly(butadiene-b-N-methyl 4-vinyl pyridinium iodide) to the oil results in soft, elastic membranes of microgel particles that remain intact after the droplet interfaces are dissolved. Under heating, the capsules contract reversibly by 13% or irreversibly by 40% in radius. These stimulus-responsive colloidosomes might be useful for controlled release or as microscopic actuators. 相似文献
68.
Monodisperse microgels of P(MEO2MA-co-OEGMA) have been synthesized by using free radical polymerization. Microgels with a variety of particle radii ranging from 82 to 412 nm have been obtained with different surfactant concentrations. The particle size distribution is extremely narrow and even better than that for PNIPAM microgels. Pure MEO2MA microgels have an LCST of about 22 degrees C. The LCSTs corresponding to the molar ratio of OEGMA to MEO2MA at 10 and 20% are 31 and 37 degrees C, respectively. Microgels in water self-assemble into various phases, including a crystalline phase with iridescent colors, which are the result of Bragg diffraction from differently oriented crystalline planes. Considering that PEG is nontoxic and anti-immunogenic as proven by the FDA, thermoresponsive P(MEO2MA-co-OEGMA) microgels may have many exciting biomedical applications. 相似文献
69.
70.
[reaction: see text] A fast, flexible, and efficient approach for the stereocontrolled synthesis of enamides has been developed starting from lactams and amides through the use of imides. This new approach provides access to enamide systems not easily or currently accessible through other approaches. 相似文献