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排序方式: 共有174条查询结果,搜索用时 15 毫秒
141.
Håvard Granlund Erik Andreassen Eirik Torbjørn Bakken Skjønsfjell Kristin Høydalsvik Ana Diaz Dag Werner Breiby 《Journal of Polymer Science.Polymer Physics》2014,52(17):1157-1167
Injection molded polymer parts are known to exhibit structural gradients of crystallinity, crystallite phases and crystallite orientations. The structural variations depend on the geometry, the material properties, and the processing conditions, and affect the mechanical properties of the molded part. We explore the use of raster‐scanning small‐ and wide‐angle X‐ray scattering (SAXS, WAXS) for mapping the microstructure in dogbone specimens of an isotactic polypropylene (PP) homopolymer and a talc‐reinforced isotactic PP compound. The specimens were injection molded with different mold temperatures and injection speeds, and the mapping approach revealed systematic structural heterogeneities and asymmetries. Accompanying numerical simulations of the injection molding process yielded predictions of the flow pattern, including the shear rate distribution and the resulting orientation of the flake‐shaped talc particles. We found a clear correspondence between the experimentally observed data and the simulations, in particular regarding the asymmetry of the orientation distributions relative to the center of the dogbone cross section, caused by asymmetric flow through the entrance of the mold. Furthermore, the shear rate distribution correlated with the occurrence of α‐ and β‐phases. Subtle differences in the crystallized structures along the long axis of the dogbones suggest an explanation to the observation that the specimens studied always tended to break at the same position in tensile tests. The results clearly demonstrate the potential of mapping experiments which combine lateral resolution on macroscopic length scales with the molecular‐scale resolution from scattering. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1157–1167 相似文献
142.
Ufuk Saim Gunay Hakan Durmaz Eda Gungor Aydan Dag Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2012,50(4):729-735
Well‐defined linear furan‐protected maleimide‐terminated poly(ethylene glycol) (PEG‐MI), tetramethylpiperidine‐1‐oxyl‐terminated poly(ε‐caprolactone) (PCL‐TEMPO), and azide‐terminated polystyrene (PS‐N3) or ‐poly(N‐butyl oxanorbornene imide) (PONB‐N3) were ligated to an orthogonally functionalized core ( 1 ) in a two‐step reaction mode through triple click reactions. In a first step, Diels–Alder click reaction of PEG‐MI with 1 was performed in toluene at 110 °C for 24 h to afford α‐alkyne‐α‐bromide‐terminated PEG (PEG‐alkyne/Br). As a second step, this precursor was subsequently ligated with the PCL‐TEMPO and PS‐N3 or PONB‐N3 in N,N‐dimethylformamide at room temperature for 12 h catalyzed by Cu(0)/Cu(I) through copper‐catalyzed azide‐alkyne cycloaddition and nitroxide radical coupling click reactions, yield resulting ABC miktoarm star polymers in a one‐pot mode. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
143.
Nese Cerit Nese Cakir Aydan Dag Okan Sirkecioglu Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2011,49(13):2850-2858
A 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐terminated poly(ethylene glycol) (PEG) or ‐poly(ε‐caprolactone) (PCL) (PEG11‐TEMPO or PCL23‐TEMPO) is grafted as a side chain onto a ROMP‐generated polyoxanorbornene (PONB) main backbone with bromide pendant groups (PONB20‐Br) using the NRC click reaction to yield related the brush copolymers, PONB20‐g‐PEG11 or PONB20‐g‐PCL23 catalyzed by Cu(I), Cu(0), and N,N,N′,N″,N″‐pentamethyldiethylenetriamine in N,N‐dimethylformamide at room temperature. Additionally, a ROMP‐generated brush copolymer PONB9‐g‐poly(methyl methacrylate)24 (PMMA)24‐Cl was reacted with a PEG11‐TEMPO or a PCL23‐TEMPO precursor via the NRC click reaction to yield a corresponding brush terpolymer, PONB9‐g‐(PMMA24‐b‐PEG11) or PONB9‐g‐(PMMA24‐b‐PCL23) under a similar reaction condition described above. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
144.
Aydan Dag Yanyan Jiang Khairil Juhanni Abd Karim Gene Hart‐Smith Wei Scarano Martina H. Stenzel 《Macromolecular rapid communications》2015,36(10):890-897
The delivery of macromolecular platinum drugs into cancerous cells is enhanced by conjugating the polymer to albumin. The monomers N‐(2‐hydroxypropyl)methacrylamide (HPMA) and Boc protected 1,3‐diaminopropan‐2‐yl acrylate (Ac‐DAP‐Boc) are copolymerized in the presence of a furan protected maleimide functionalized reversible addition‐fragmentation chain transfer (RAFT) agent. The resulting polymer with a composition of P(HPMA14‐co‐(Ac‐DAP‐Boc)9) and a molecular weight of Mn = 7600 g mol−1 (Đ = 1.24) is used as a macromolecular ligand for the conjugation to the platinum drug. Thermogravimetric analysis reveals full conjugation. After deprotection of the maleimide functionality of the polymer, the reactive polymer is conjugated to albumin using the Cys34 functionality. The conjugation is monitored using size exclusion chromatography, MALDI–TOF (matrix assisted laser desorption ionization time‐of‐flight), and SDS Page (sodium dodecyl sulphate polyacrylamide gel electrophoresis). The polymer–albumin conjugates self‐assemble in water into nanoparticles of sizes of around 80 nm thanks to the hydrophobic nature of the platinum drugs. The albumin coated nanoparticles are readily taken up by ovarian cancer cell lines and they show superior toxicity compared to a control sample without protein coating.
145.
Hans Vigeland Lerum Niels Højmark Andersen Dag Øistein Eriksen Eddy Walther Hansen Dirk Petersen Grethe Wibetoe Jon Petter Omtvedt 《Journal of solution chemistry》2018,47(8):1395-1417
A large number of model solutions with high ionic strength were synthesised to mimic industrial conditions and were used as a first approach to study Cd extraction in the presence of chloride at high salinity, as experienced in real industrial solutions. The extractant used throughout in this work was Aliquat 336, a quaternary ammonium salt well known to the hydrometallurgical industry. The effects of some selected anions in addition to chloride (i.e., perchlorate, nitrate, and sulfate) were studied. The distribution of cadmium was measured using 109Cd as a tracer. Liquid-scintillation spectroscopy quantified the concentration of 109Cd in both phases. Raman and NMR spectroscopy were employed to gain further insight into the extraction chemistry. A careful analysis of all Cd extraction data showed that within specific windows of the reactant concentrations the chemical reactions could be represented by simplified equations, as discussed thoroughly in the text. Equilibrium constants for the extraction of \({\text{CdCl}}_{3}^{ - }\) from chloride and chloride/sulfate media were determined to be log10Kext?=?4.9?±?0.8 and log10Kext?=?5.7?±?0.5, respectively. For the nitrate environment, an exchange reaction involving a LiNO3 ion pair is proposed and agrees with the experimental data, but was not proven. 14N-NMR and Raman spectroscopy confirmed that the relative affinity of Aliquat 336 for the relevant anions followed the order: perchlorate?>?nitrate?>?chloride?>?sulfate. Finally, 14N-NMR enabled the equilibrium constant of the exchange reaction between nitrate and chloride for Aliquat 336 to be determined. 相似文献
146.
The title compound is prepared by high‐pressure solid state reaction of a 4:1:2 mixture of SrH2, Co, and Mg2CoH5 (autoclave, 60 bar H2, 873 K, 12 h). 相似文献
147.
We give a characterisation of an extension of the Kleene-Kreisel continuous functionals to objects of transfinite types using
limit spaces of transfinite types.
Received: 24 August 1999 / Published online: 12 July 2002 相似文献
148.
149.
Hakan Durmaz Aydan Dag Elif Erdogan A. Levent Demirel Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2010,48(1):99-108
The synthesis of multiarm star block (and mixed‐block) copolymers are efficiently prepared by using Cu(I) catalyzed azide‐alkyne click reaction and the arm‐first approach. α‐Silyl protected alkyne polystyrene (α‐silyl‐alkyne‐PS) was prepared by ATRP of styrene (St) and used as macroinitiator in a crosslinking reaction with divinyl benzene to successfully give multiarm star homopolymer with alkyne periphery. Linear azide end‐functionalized poly(ethylene glycol) (PEG‐N3) and poly (tert‐butyl acrylate) (PtBA‐N3) were simply clicked with the multiarm star polymer described earlier to form star block or mixed‐block copolymers in N,N‐dimethyl formamide at room temperature for 24 h. Obtained multiarm star block and mixed‐block copolymers were identified by using 1H NMR, GPC, triple detection‐GPC, atomic force microscopy, and dynamic light scattering measurements. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 99–108, 2010 相似文献
150.
Hakan Durmaz Aydan Dag Ceyda Onen Ozgul Gok Amitav Sanyal Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2010,48(21):4842-4846
Dendritic 2‐ and 4‐arm PMMA‐based star polymers with furan‐protected maleimide at their focal point, (PMMA)2n‐MI and (PMMA)4n‐MI were efficiently clicked with the peripheral anthracene functionalized multiarm star polymer, (α‐anthryl functionalized‐polystyrene)m‐poly(divinyl benzene) ((α‐anthryl‐PS)m‐polyDVB) through the Diels–Alder reaction resulting in corresponding multiarm star block copolymers: (PMMA)2n‐(PS)m‐polyDVB and (PMMA)4n‐(PS)m‐polyDVB, respectively. Molecular weights (Mw,TDGPC), hydrodynamic radius (Rh), and intrinsic viscosity (η) of the multiarm star polymers were determined using three‐detection GPC (TD‐GPC). The high efficiency of this methodology to obtain such sterically demanding macromolecular constructs was deduced using 1H‐NMR and UV–vis spectroscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 相似文献