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61.
Ki-Change Lee Mitchell A. Winnik Tze-Chi Jao 《Journal of polymer science. Part A, Polymer chemistry》1994,32(12):2333-2344
Submicron and micron sized particles containing a crosslinked core and a polar shell were prepared by 3-stage nonaqueous dispersion [NAD] polymerization in an aliphatic hydrocarbon medium. When a poly (12-hydroxystearic acid) [PHS] comb stabilizer was used in all three stages, the particles produced were spherical, submicron in size, and had a relatively broad size distribution. If the monomer mixture in the third stage contained relatively large amounts of butyl acrylate, stable dispersions of sponge-like aggregates, 3–5 μm in size, were obtained. When butyl rubber was employed as a stabilizer precursor in the seed formation step, the shape of the final particles depended upon whether a crosslinker was employed in the second stage polymerization. When a crosslinker was present, the second-stage particles and the subsequent third-stage particles had a shrunken, raisin-like appearance. When no crosslinker was present, spherical particles were obtained. In both cases, the resulting third-stage particles were easily dispersed in water containing a small amount of amine base, indicating that ? COOH and ? OH groups are located at the surface (or in a shell at the surface) in these NAD particles. © 1994 John Wiley & Sons, Inc. 相似文献
62.
Wang XS Wang H Coombs N Winnik MA Manners I 《Journal of the American Chemical Society》2005,127(25):8924-8925
A new approach to encapsulate silver nanoparticles inside block copolymer nanotubes is reported and involves an in situ redox reaction between a polyferrocenylsilane (PFS) inner wall and silver ions. Partial preoxidation of the PFS domains was found to be a key step for the efficient formation of one-dimensional arrays of silver nanoparticles confined within the nanotubes. 相似文献
63.
Xiao-Bai Li Mitchell A. Winnik James E. Guillet 《Journal of polymer science. Part A, Polymer chemistry》1983,21(5):1263-1271
The acetate ester of 2-(2H-benzotriazol-2-yl)-4-methyl phenol [Tinuvin P] upon irradiation, either in methylene chloride solution or in poly(methyl methacrylate) films, undergoes a photocleavage reaction to regenerate Tinuvin P. No photo-Fries rearrangement product can be detected. 相似文献
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The rate constant kir for quenching diaryl ketone triplet states by electron poor olefins in CCl4 at room temperature decreases with decreasing reduction potential of the olefin. Unlike in previous cases, our data here fit the Weller equation, which predicts that en kir ≈ 1/RT. 相似文献
66.
Frdric Tronc Mei Li Jianping Lu Mitchell A. Winnik Bansi Lal Kaul Jean‐Christophe Graciet 《Journal of polymer science. Part A, Polymer chemistry》2003,41(6):766-778
We describe the synthesis and characterization of latex particles labeled with a brightly fluorescent yellow dye (HY) based on the benzothioxanthene ring structure. Three dye derivatives were synthesized with different spacers connecting the HY nucleus to a methacrylate group. For one of the dyes (HY2CMA, rA), we show that the reactivity ratios with styrene (rA = 0.71, rB = 0.25) and butyl methacrylate (rA = 0.87, rB = 0.14) should lead to random dye incorporation if the amount of dye in the feed is small. Seeded emulsion polymerization fails to lead to significant dye incorporation unless large amounts of nonionic surfactant are present. In contrast, miniemulsion polymerization worked well to yield latex particles of polystyrene, poly(butyl methacrylate), and poly(methyl methacrylate) with high monomer conversion and essentially quantitative dye incorporation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 766–778, 2003 相似文献
67.
Solute exchange experiments for the pyrene-labeled triglyceride TG-Py solubilized in sodium dodecyl sulfate (SDS) micelles in the presence and absence of salt show that the "observed" rate constant k(obs) for solute exchange varies by over 6 orders of magnitude as the free sodium ion concentration [Na(+)](aq) is varied between 10 and 850 mM. There is a sharp break in the log-log plot of k(obs) versus [Na(+)](aq) in the range of [Na(+)](aq) = 200 mM, with the exchange rate showing a weaker dependence on [Na(+)](aq) above this concentration. Up to 100 mM added NaCl, this exchange takes place essentially exclusively by a micelle fission mechanism in which each submicelle carries off one of the solutes. At higher salt concentrations, a bimolecular process becomes increasingly important. This fusion process, which involves formation of a transient supermicelle followed by fission back to two normal micelles, becomes the dominant process at high salt concentrations. The fission rate appears to level off for salt concentrations above 300-400 mM. These fission and fusion processes are related in an intimate way to the changes in the size and shape of the SDS micelles with increasing salt concentration. 相似文献
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Summary: We describe the results of Monte Carlo simulations, based on the cooperative motion algorithm, of the lamellar structure generated at finite temperature by a symmetric diblock copolymer. The (70 × 70 × 70) simulation box in which the polymer chains were embedded for each simulation was rotated, based on the interface orientation, to bring the interfacial planes of the simulated structure into parallel. We found that the interface thickness, as defined by the distribution of the junction points, became narrower at lower temperature, and that the interface plane was characterized by a waviness with a maximum peak‐to‐valley distance of 20–30 lattice bonds. Compared with the isotropic state (T/N = ∞), chains at lower temperatures were stretched in the direction perpendicular to the interface; but only modestly compressed in the direction parallel to the interface. Individual block chains within the lamellar domains still behave like random coils. The block copolymer molecules exhibit only a modest tendency to orient themselves with their end‐to‐end vector perpendicular to the plane of the lamellar interface. Considered as an ensemble average, the results we obtained are similar to those reported from small angle neutron scattering measurements for the mean conformation of the PSd blocks of symmetrical PSd‐PVP diblock copolymers.
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