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61.
62.
Hideo Maehata Xinzhi Liu Michael Cunningham Barkev Keoshkerian 《Macromolecular rapid communications》2008,29(6):479-484
While miniemulsion polymerization has proven to be well‐suited for conducting living/controlled radical polymerizations, emulsion polymerizations have proven to be far more challenging. Ab initio emulsion polymerizations, in which monomer droplets are present during polymerization, have thus far not been successful with TEMPO‐mediated polymerizations, as a result of colloidal instability and coagulum formation. By selectively inhibiting polymerization in the monomer droplets, it is demonstrated that droplet polymerization is responsible for the formation of large (>1 µm) particles that can lead to coagulum formation. Furthermore, we show that coagulum‐free latexes can be produced using a TEMPO‐mediated ab initio emulsion polymerization by suppressing droplet polymerization.
63.
64.
Mark A. Schaffer Kim B. McAuley E. Keith Marchildon Michael F. Cunningham 《大分子反应工程》2007,1(5):563-577
An experimental investigation of nonoxidative thermal degradation kinetics of nylon 66 melt under high temperature (280–300 °C) and low water content (0.02–0.14 wt.‐%) conditions is presented. Experimental data for the time evolution of polymer end‐group concentrations and degradation‐product generation rates were compared with the predictions of the only published kinetic model. The omitted influence of water content is a plausible partial explanation for the considerable discrepancy between model predictions and some data. Several previously unreported or unquantified degradation products were identified and measured. Potential additional reactions to account for these results in future kinetic models are proposed.
65.
Mariano Asteasuain Matheus Soares Marcelo K. Lenzi Michael Cunningham Claudia Sarmoria José Carlos Pinto Adriana Brandolin 《大分子反应工程》2007,1(6):622-634
This is the first of a series of works aiming at developing a tool for designing “living” free radical polymerization processes in tubular reactors, in order to achieve tailor‐made MWDs. A mathematical model of the nitroxide‐mediated controlled free radical polymerization is built and implemented to predict the complete MWD. It is shown that this objective may be achieved accurately and efficiently by means of the probability generating function (pgf) transformation. Comparison with experimental data is good. The potential of the resulting model for optimization activities involving the complete MWD is also shown.
66.
M.F. Cunningham K. Tortosa J.W. Ma K.B. McAuley B. Keoshkerian M.K. Georges 《Macromolecular Symposia》2002,182(1):273-282
The introduction of the aqueous phase into a living radical polymerization increases the complexity of the kinetics by creating the possibility of species partitioning between the aqueous and organic phases, and introducing aqueous phase reactions which could play a significant role particularly in chain initiation and/or particle nucleation. We have conducted a series of styrene miniemulsion polymerizations in which the solubility of initiator and nitroxide have been systematically varied. Experiments were run using either water-soluble (potassium persulphate) or oil-soluble (benzoyl peroxide) initiator, and either TEMPO or 4-hydroxy-TEMPO. These two nitroxides vary considerably in their water solubility. The effects of initiator and nitroxide solubility in water on conversion-time behaviour, molecular weight and initiator efficiency are presented. 相似文献
67.
Karine Tortosa Jodi‐Anne Smith MichaelF. Cunningham 《Macromolecular rapid communications》2001,22(12):957-961
Living free‐radical butyl acrylate polymerization in miniemulsion was initiated by polystyrene bearing a nitroxyl end group to yield polystyrene‐block‐poly(butyl acrylate) block copolymers. Polystyrene macroinitiator was obtained using different initiating systems (potassium persulfate or benzoyl peroxide) in the presence of 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) or the more water‐soluble 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐N‐oxyl (OH‐TEMPO). The nitroxide water‐solubility has an important influence in determining molecular weight distribution and controlling the growth of the second block. 相似文献
68.
69.
RichardN. Butler AnthonyG. Coyne WilliamJ. Cunningham EamonM. Moloney LukeA. Burke 《Helvetica chimica acta》2005,88(7):1611-1629
Synthetic and kinetic studies on the 1,3‐dipolar cycloaddition reactions of dicyano(phthalazin‐2‐ium‐2‐yl)methanide ( 1 ) with some substituted styrenes and ‘benzylidene acetones’ in MeCN and H2O containing 10 mol‐% of MeCN are reported. The kinetic data were supported by theoretical calculations. The major products from styrenes were exo‐2‐aryl‐1,2,3,10b‐tetrahydropyrrolo[2,1‐a]phthalazine‐3,3‐dicarbonitriles 3 , and, from ‘benzylidene acetones’, 1‐endo,2‐exo‐2‐acetyl‐1‐aryl‐1,2,3,10b‐tetrahydropyrrolo[2,1‐a]phthalazine‐3,3‐dicarbonitriles 7 . There was no indication that the cycloadditon transition states were more polar in the aqueous environment than in MeCN. 相似文献
70.
Po J Margolis DJ Cunningham CH Herfkens RJ Ikeda DM Daniel BL 《Magnetic resonance imaging》2006,24(10):1363-1367
OBJECTIVE: This study investigates the use of contrast-enhanced, T1-weighted, water-selective spectral-spatial 3D gradient echo magnetic resonance imaging (MRI) with magnetization transfer (3DSSMT) for detecting breast cancer in patients with intraparenchymal silicone. CONCLUSION: Water-selective 3DSSMT provides superior fat and silicone suppression in patients with free silicone as compared with conventional fat saturation. It enables direct, high-quality, high-spatial-resolution, T1-weighted breast MRI of contrast enhancement without the need for subtraction processing and aids diagnosis of cancer in the breast with free silicone. 相似文献