全文获取类型
收费全文 | 248篇 |
免费 | 11篇 |
国内免费 | 63篇 |
专业分类
化学 | 314篇 |
力学 | 5篇 |
物理学 | 3篇 |
出版年
2024年 | 2篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 17篇 |
2012年 | 11篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 19篇 |
2005年 | 14篇 |
2004年 | 25篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 22篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 8篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 14篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有322条查询结果,搜索用时 62 毫秒
91.
Tsuneyuki Sato Nobuyuki Sato Makiko Seno Tomohiro Hirano 《Journal of polymer science. Part A, Polymer chemistry》2003,41(19):3038-3047
The copolymerization of divinylbenzene (DVB) and ethylstyrene (EtSt) was carried out at 70 and 80 °C in benzene with dimethyl 2,2‐azobisisobutyrate (MAIB) at high concentrations as initiator in the presence of methyl benzyloxyiminoacetate (MBOIA), a glyoxylic oxime ether, as a retarder. The copolymerization system of DVB (0.25 mol/L), EtSt (0.25 mol/L), MBOIA (0.5 mol/L), and MAIB (0.5 mol/L) gave benzene‐soluble copolymers despite a considerably high concentration of DVB as an excellent crosslinker. The yield and molecular weight of the resulting copolymers increased with time both at 70 and 80 °C and then leveled off because of initiator consumption. The homogeneous polymerization system involved electron spin resonance (ESR), observable nitrogen‐centered polymer radicals (MBOIA·) under the actual polymerization conditions. The MBOIA· concentration increased with time despite a homogeneous polymerization system, suggesting the formation of rigid hyperbranched polymers. A benzene solution of isolated copolymer also showed an ESR signal. The copolymer was soluble in acetone, toluene, chloroform, ethyl acetate, tetrahydrofuran, and N,N‐dimethylformamide but insoluble in n‐hexane, methanol, and dimethyl sulfoxide. MAIB fragments as high as 30–40 mol % were incorporated into the copolymers through initiation and primary radical termination, on the basis of which this polymerization was named the initiator‐fragment incorporation radical polymerization. MBOIA (13–16 mol%) was also incorporated into the copolymers through an opening of the C?N bond. The intrinsic viscosity of the copolymers was very low (0.08 dL/g), and the reduced viscosity was almost independent of the polymer concentration, supporting a hyperbranched structure of them. Gel permeation chromatography and multi‐angle laser light scattering and transmission electron microscopy revealed that the copolymer was formed as a hyperbranched nanoparticle. The thermal behavior of the copolymer was examined by dynamic thermogravimetry and differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3038–3047, 2003 相似文献
92.
Chen-yu Su Guang-li Zhang Hong-zhi Zhang Department of Polymer Science Engineering College of Chemistry Molecular Engineering Peking University Beijing China 《高分子科学》2001,(4):371-376
Polyurethane elastomers derived from 4,4'-methylene bis(phenyl isocyanate), butylene glycol and the lowoxyethylene moiety content copolyether of tetrahydrofuran and ethylene oxide, obtained by copolymerization usingheteropolyacid-ethylene oxide initiator system, were prepared. The polyurethanes exhibited an increased water absorptionand much better low temperature resilience, which remained high even at a temperature of -3℃, while that of polyurethanebased upon poly(tetramethylene ether) glycol of the same molecular weight, i.e. being 2000, and molecular weightdistribution, i.e. in the range of 1.4-1.5, starts to decrease dramatically at 5℃. 相似文献
93.
Zorica M. Bugarčić Biljana Mojsilović Ljiljana Marjanović Stanimir Konstantinović 《Monatshefte für Chemie / Chemical Monthly》2000,131(10):1091-1096
Summary. The reaction of some alkenols with tetrachloromethane in the presence of a radical initiator was investigated. Regarding
the effects of structural features of the starting alkenol (number and position of methyl substituents at the double bond
and at the carbinol carbon atom, constitutional relationship between the double bond and the hydroxyl group) there are two
possible competing reactions: addition and cyclization. In the case of the simplest alkenols (without substituents and with
a more remote double bond) addition occurs; mono- and disubstituted secondary and tertiary Δ4- and Δ5-alkenols cyclize in high yields to give the corresponding cyclic ethers.
Received March 17, 2000. Accepted (revised) May 31, 2000 相似文献
94.
Peroxide‐initiated chemical modification of poly(isobutylene‐co‐isoprene): H‐atom transfer yields and regioselectivity
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Christopher Twigg Elena Mueller Brian M. Molloy J. Scott Parent 《Journal of polymer science. Part A, Polymer chemistry》2016,54(19):3102-3109
The yield and regioselectivity of H‐atom abstraction by cumyloxy radicals from poly(isobutylene‐co‐isoprene) (IIR) are quantified and discussed in the context of cross‐linking/degradation outcomes and vinyltriethoxysilane (VTEOS) graft yields. Studies of IIR materials with different isoprene contents show that H‐atom abstraction from the allylic functionality provided by isoprene mers is responsible for the heightened H‐atom transfer reactivity of IIR relative to poly(isobutylene). Differences in the reactivity of allylic and alkyl macroradical intermediates makes high isoprene IIR materials less prone to peroxide‐initiated chain scission, but less responsive to VTEOS grafting formulations. Improved knowledge of H‐atom transfer reactivity is extended to a new approach for IIR cross‐linking involving acrylate‐functionalized nitroxyl chemistry. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3102–3109 相似文献
95.
96.
Shuai Zhang Li-Qun Zhang You-Ping Wu 《Journal of Macromolecular Science: Physics》2014,53(7):1270-1285
Four miktoarms star-shaped polybutadiene-Sn-poly(styrene-butadiene) rubber (MSS-PB-PSBR) with 1,1-diphenylhexyl at the ends of the arms were prepared by two different coupling techniques. One technique was a one-step technology, from which two miktoarms star styrene-butadiene rubbers, called AMSS-PB-PSBR, were obtained in which the four arm stars had varying ratios of PB:PSBR arms; another was a two-step technology, from which another two miktoarms star styrene-butadiene rubbers, called BMSS-PB-PSBR, were obtained in which all consisted of PB-Sn-(PSBR)3 stars. The molecular structure parameters and morphology-properties of the four MSS-PB-PSBR were determined and studied, and compared with that of a star-shaped styrene-butadiene rubber (S-SSBR)/poly butadiene rubber (PBR) blend. The results showed that the total coupling efficiency (the ratio of the total number of polymer chains (arms) coupled by SnCl4 to that of the total number of polymer chains) of the MSS-PB-PSBR was higher than 60%. However, the coupling efficiency of the polybutadiene arms of BMSS-PB-PSBR was obviously higher than that of the AMSS-PB-PSBR. Compared with the S-SSBR/PBR blend, MSS-PB-PSBR had a more uniform distribution of the PB phase and a smaller phase size of PB. It was found that MSS-PB-PSBR composites filled with carbon black (CB) had a lower Payne effect than the S-SSBR/PBR/CB composite, with the BMSS-PB-PSBR/CB composites being especially lower. The BMSS-PB-PSBR/CB composites had higher mechanical properties and lower rolling resistance than the AMSS-PB-PSBR/CB composites due to the high coupling efficiency of the polybutadiene arms; the results indicated that the two-step technology was better than the one-step technology for preparing the tread material of “green” tires. 相似文献
97.
98.
Hyun Uk Kang Young Chang Yu Sang Jin Shin Ji Ho Youk 《Journal of polymer science. Part A, Polymer chemistry》2013,51(4):774-779
A range of well‐defined block copolymers were synthesized using 4‐cyano‐4‐(dodecylsulfanylthiocarbonyl)sulfanylpentanol (CDP) as a dual initiator for reversible addition‐fragmentation chain transfer (RAFT) polymerization and ring‐opening polymerization (ROP) in a one‐step process. Styrene, (meth)acrylate, and acrylamide monomers were polymerized in a controlled manner for one block composed of vinyl monomers, and δ‐valerolactone (VL), ε‐caprolactone (CL), trimethylene carbonate (TMC), and L ‐lactide (LA) were used for the other block composed of cyclic monomers. Diphenyl phosphate was used as a catalyst for the ROP of VL, CL, and TMC, and 4‐dimethyamino pyridine for the ROP of LA. These catalysts did not interfere with RAFT polymerization and the synthesis of various block copolymers proceeded in a controlled manner. CDP was found to be a very useful dual initiator for a one‐step synthesis of various block copolymers by a combination of RAFT polymerization and ROP. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献
99.
Neelamegan Haridharan Venkatachalam Ramkumar Raghavachari Dhamodharan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):918-926
A novel initiator containing pyrene, a fluorescent moiety, was prepared by reacting 1-aminopyrene and 2-bromoisobutyl bromide. The structure elucidation of the new initiator was carried out using various spectroscopic tools, as well as through single crystal X-ray diffraction studies. Novel, fluorescent amphiphilic block copolymers with a pyrene end-group, poly(styrene-b-acrylic acid) [P(S-b-AA)], poly(methyl methacrylate-b-dimethylaminoethyl methacrylate) [P(MMA-b-DMAEMA)], poly(styrene-b-tert-butyl acrylate) [P(S-b?t-BA)], poly(styrene-b-dimethylaminoethyl methacrylate) [P(S-b-DMAEMA)] were successfully synthesized by the atom transfer radical polymerization (ATRP) method, using CuBr as the catalyst and N,N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA)/N,N,N′,N″,N″-hexamethyltriethylenetetramine (HMTETA) as the complexing agent. The polymers were characterized by GPC, 1H-NMR, IR and UV-Vis spectroscopies. It was observed that as the polymerization time increased, both the conversion and the molecular weight increased linearly with time. The fluorescence properties of the polymers prepared were recorded. The physical properties and especially the pH dependent swelling properties of the amphiphilic block copolymers have been investigated. The utility of the block copolymers in the formation of stable dispersion of cadmium sulphide nanoparticles was investigated as a model study. 相似文献
100.
Benzyl chloride and phenacyl chloride are reported to condense with sodium acetate or sodium benzoate, affording the corresponding esters [1–4]. This suggested that a dichloride monomer can poly condense with a sodium dioate, affording a polyester. Akhmedzade and Yasnopolskii reported one such polyester synthesis based on polycondensation of p-xylylene dihalide with sodium terephthalate [5]. As phenacyl chloride is more reactive than benzyl chloride is more reactive than benzyl chloride [4], 4,4′-dichloroacetyldiphenyl ether (DADE) should prove even more reactive than a dichloride of the Ar(CH2Cl)2 type. The work presented here comprises a study of the polycondensation of DADE with sodium adipate (ADP), sebacate (SEB), or terephthalate (TER). 相似文献