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11.
Kiyoshi Endo Hiroharu Nagahama Takayuki Otsu 《Journal of polymer science. Part A, Polymer chemistry》1979,17(11):3647-3653
A study of the monomer isomerization polymerization of 2-, 3-, and 4-octenes has been made with TiCl3–(C2H5)3Al catalyst at 80°C in comparison with the ordinary polymerization of 1-octene. It was found that all these octenes underwent monomer-isomerization polymerization to give high-molecular-weight homopolymer consisting exclusively of the 1-octene unit. The addition of an isomerization catalyst such as nickel acetylacetonate accelerated this polymerization. The rates of polymerization were found to decrease in the following order: 1-octene > 2-octene > 3-octene > 4-octene. These results indicate that the isomerization proceeded by a stepwise double-bond migration. It was also found that the monomer-isomerization copolymerization of 2-octene and 2-butene occurred under similar conditions and produced copolymers of both 1-olefin units. 相似文献
12.
13.
The solubility of NdPO4(c) was studied at 23±2 °C from both the over and undersaturation directions, with pH ranging from 0 to 9, P concentrations ranging from 0.0003 to 1.00M, and equilibration periods ranging from 6 to 57 days. Equilibrium was reached in <6 days. From the H+, Nd, and P concentrations in equilibrated solutions, the logarithm of the thermodynamic equilibrium constant for the reaction (NdPO4(c) Nd3++PO4
3-) was calculated to be -24.65±0.23 and the value of the Pitzer ion-interaction parameter (2)for Nd3+-H2PO4
- was determined to be -92.9. Predictions based on these thermodynamic quantities were in excellent agreement with the experimental data. 相似文献
14.
Control of thermoresponsivity of biocompatible poly(trimethylene carbonate) with direct introduction of oligo(ethylene glycol) under various circumstances
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Nalinthip Chanthaset Yoshikazu Takahashi Yoshiaki Haramiishi Mitsuru Akashi Hiroharu Ajiro 《Journal of polymer science. Part A, Polymer chemistry》2017,55(20):3466-3474
Poly(trimethylene carbonate) (PTMC) is a well‐known biodegradable polymer with good biocompatible properties which make it suitable for biomedical applications. Poly(5‐[2‐{2‐(2‐methoxyethoxy)ethyoxy}‐ethoxymethyl]‐5‐methyl‐1,3‐dioxa‐2‐one) (PTMC‐MOE3OM) and copolymers, bearing oligo ethylene glycol (OEG) at the side chain of PTMC backbone, were selected to investigate the cloud point behavior by solvents such as PBS, water, 10% ethanol solution and various ionic strengths. A pH‐responsive copolymer, poly(TMCM‐MOE3OM‐co‐(5‐methyl‐5‐carboxylic‐1,3‐dioxane‐2‐one)) as carboxylic acid carbonate showed a decreased critical temperature at pH 2. Photo‐responsive copolymer, poly(TMCM‐MOE3OM‐co‐coumarin derivatives) bearing 1% and 10% of photo‐induced molecules (7‐[(5‐(5‐methyl‐1,3‐dioxa‐2‐one)methoxy)]‐methoxy coumarin (TMCM‐coumarin)) exhibited a low cloud point because of the hydrophobic moieties. Meanwhile, alternative coumarin polymer including 2% of 4‐methyl‐7‐[(5‐(5‐methyl‐1,3‐dioxa‐2‐one)methoxy)butoxy)]‐methoxy coumarin (TMCM‐4‐methyl‐coumarin) has been successfully synthesized and copolymerized as a novel molecule. The various combinations of monomers were studied and the significant properties were determined via external triggers after copolymerization. This study showed basically synthetic progress toward designs and trivial rationalization of thermoresponsive copolymers close to body temperature. At present, various pendant groups as side part affect to the lower critical solution temperature (LCST) and biodegradable polymer in order to utilize the actual external stimuli application. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3466–3474 相似文献
15.
Takuya Uto Takashi Hosoya Sachio Hayashi Toshifumi Yui 《Cellulose (London, England)》2013,20(2):605-612
In hot-water molecular dynamics simulation at 370 K, four cellulose IIII crystal models, with different lattice planes and dimensions, exhibited partial crystalline transformations of (1 ?1 0) chain sheets, in which hydroxymethyl groups were irreversibly rotated from gt into tg conformations, accompanied by hydrogen-bond exchange from the original O3–O6 to cellulose-I-like O2–O6 bonds. The final hydrogen-bond exchange ratio was about 95 % for some of the crystal models after 50 ns simulation. The corrugated (1 ?1 0) chain sheet was converted to a cellulose-I-like flat chain sheet with a slightly right-handed twist. The 3D structures of the three types of isolated chain sheet models were optimized using density functional theory calculations to compare their stabilities without crystal packing forces. The cellulose Iβ (1 0 0) models were more stable than the cellulose IIII (1 ?1 0) models. The optimized structure of cellulose IIII (1 0 0) models deviated largely from the initial sheet form. It was proposed to the crystalline transformation from cellulose IIII to Iβ that conversion of the chain sheet structure first take place, followed by sliding of the chain sheet along the fiber axis. 相似文献
16.
Cellulose - Cellulose I crystals swell on exposure to ethylenediamine (EDA) molecules to form a cellulose I–EDA complex, and successive extraction of EDA molecules converts the complex... 相似文献
17.
Tajima Kenji Imai Tomoya Yui Toshifumi Yao Min Saxena Inder 《Cellulose (London, England)》2022,29(5):2755-2777
Cellulose - Cellulose is produced by all plants and a number of other organisms, including bacteria. The most representative cellulose-producing bacterial species is Gluconacetobacter xylinus, an... 相似文献
18.
We report the generation of a nano-scale tubular structure of cellulose molecules (CelNT), through density functional theory (DFT) calculations. When a cellulose IIII (1 0 0) chain sheet model is optimized by DFT calculations, the sheet models spontaneously roll into tubes. The oligomers arrange in a right-handed, four-fold helix with one-quarter chain staggering, oriented with parallel polarity similar to the original crystal structure. Based on a one-quarter chain staggering relationship, six large CelNT models, consisting of 16 cellulose chains with DP = 80, are constructed by combinations of two types of chain polarities and three types of symmetry operations to generate a circular arrangement of molecular chains. All six CelNT models are examined by molecular dynamics (MD) calculations in chloroform. While four CelNT models retain a tubular form throughout MD calculations, the remaining two deform. 3D-RISM theory model is used to estimate the solvation free energies of the four CelNT models. The results suggest that the CelNT model with a chain arrangement of parallel polarity and right-handed helical symmetry forms the most stable tube structure. 相似文献
19.
Tooru Ooya Hideharu Mori Minoru Terano Nobuhiko Yui 《Macromolecular rapid communications》1995,16(4):259-263
A novel design of a biodegradable carrier for drug delivery was established by constructing a supramolecular assembly of drugs and polymer backbones without any covalent bonds. A biodegradable polyrotaxane was synthesized in which α-cyclodextrins (α-CDs) as drug carriers were threaded onto poly(ethylene glycol) chains which then were capped at each chain end by L -phenylalanine via peptide linkages. The release of α-CDs was observed only when the terminal peptide linkages were degraded. 相似文献
20.