全文获取类型
收费全文 | 79篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 52篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 20篇 |
出版年
2021年 | 1篇 |
2020年 | 4篇 |
2019年 | 1篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 7篇 |
2011年 | 3篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 1篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2001年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1976年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1909年 | 1篇 |
排序方式: 共有84条查询结果,搜索用时 343 毫秒
21.
Ilknur Yildirim Sarah Crotty Claas H. Loh Grit Festag Christine Weber Pier‐Francesco Caponi Michael Gottschaldt Matthias Westerhausen Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2016,54(3):437-448
A simple and convenient method for the synthesis of end functionalized polylactides (PLAs) under mild conditions by ring opening polymerization (ROP) in the absence of potentially toxic catalysts is described. Various alcohols were used as initiators in combination with Ca[N(SiMe3)2]2(THF)2 as the precatalyst in THF at room temperature. Tailored end functionalities were obtained in a controlled fashion. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐ToF‐MS) and electrospray ionization quadrupole time of flight mass spectrometry (ESI‐Q‐ToF‐MS) analysis were performed to investigate the end groups. The results confirmed that the end group fidelity was maintained in the isolated PLAs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 437–448 相似文献
22.
23.
H. M. H. Hurks C. Out-Luiting B. J. Vermeer F. H. J. Claas A. M. Mommaas 《Photochemistry and photobiology》1995,62(3):485-489
The mixed epidermal cell lymphocyte reaction (MECLR) is a commonly used method to study the effects of ultraviolet B (UVB) radiation on the skin immune system. In UVB experiments dosimetry is very important. The influence of irradiance on the MECLR was studied in vitro using Philips FS40 lamps with variable UV intensities. Irradiation of isolated epidermal cells with high irradiance impaired the alloactivating capacity more than irradiation with low irradiance. In vivo, the influence of long-term UVB exposure on the MECLR was studied by treating normal healthy volunteers with suberythemagenic doses of UVB thrice weekly during 4 weeks. The first set of experiments, using low irradiance Sylvania UV-21 F75/85 W lamps, resulted in a decrease of MECLR responses of 83.1%. In the second set of experiments performed a year later, employing an identical protocol except for the use of high irradiance Waldmann UV-21 F85/100 W lamps, an increase of MECLR responses of 99.7% was observed. Volunteers of both sets of experiments received equal doses of UVB. In conclusion, this study shows that in vitro UVB-induced suppression of the MECLR is critically dependent on irradiance and therefore might explain contradictory results described in the literature. The in vivo data suggest that, comparable to the in vitro experiments, irradiance may influence the effects of UVB irradiation in vivo. Further experiments should prove whether this is indeed the case. 相似文献
24.
Claas Vortmann 《PAMM》2004,4(1):500-501
With regard to future calculations of the combustion inside a packed bed of wooden particles, the drying process of a single wet particle is simulated in the present study. Essentially, conservation equations in spherical coordinates are solved by a finite volume approach for the interior of the single wooden particle. It is shown that a thin transition zone between the wet and the dry area exists during evaporation. The fundamental reasons are pointed out. Furthermore, the high velocity values in the transition zone are explained physically. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
25.
Villar A Hövelmann CH Nieger M Muñiz K 《Chemical communications (Cambridge, England)》2005,(26):3304-3306
Conditions for a first oxidative conversion of alkenes into 2-amino ketones are described, which yield racemic products within a direct oxidation pathway and 2-amino ketones with up to 99% enantiomeric excess from the corresponding enantiopure amino alcohols. 相似文献
26.
Streuff J Hövelmann CH Nieger M Muñiz K 《Journal of the American Chemical Society》2005,127(42):14586-14587
Intramolecular diamination reactions are described which yield cyclic ureas as direct products of an oxidative alkene transformation in the presence of palladium acetate and iodosobenzene diacetate as terminal oxidant. The reaction is truly catalytic in metal catalyst and represents the proof of principle for this elusive type of alkene oxidation. 相似文献
27.
Simone Steig Frauke Cornelius Andreas Heise Rutger J. I. Knoop Gijs J. M. Habraken Cor E. Koning Henning Menzel 《Macromolecular Symposia》2007,248(1):199-206
A double-headed initiator was synthesized yielding two functional groups for the initiation of the nickel mediated ring-opening polymerization of γ-benzyl-L -glutamate-N-carboxyanhydride and controlled radical polymerization of vinyl monomers via ATRP or NMP. Well-defined block copolymers combining polypeptides and synthetic polymers were obtained. 相似文献
28.
Rutger J. I. Knoop Willem Vogelzang Jacco van Haveren Daan S. van Es 《Journal of polymer science. Part A, Polymer chemistry》2013,51(19):4191-4199
Furan‐2,5‐dicarboxylic acid (FDCA) is a widely advocated renewable substitute for terephthalic acid (TA). Preparation of high molecular weight FDCA based polyesters by an industrially common combination of melt polymerization and subsequent solid state post condensation is described. Ultimately, poly(ethylene 2,5‐furanoate) (PEF) with absolute Mn = 83,000 g mol?1 is obtained, determined by triple detection Size Exclusion Chromatography. The bulk polymer properties of FDCA based polyesters, necessary to evaluate their industrial potential were determined the Young's modulus of PEF is determined to be 2450 ± 220 MPa and the maximum stress 35 ± 8 MPa. The influence of crystallinity on the mechanical properties as function of temperature was determined by dynamic mechanical thermal analysis. A detailed differential scanning calorimetry study on the crystallization behavior of high molecular weight PEF allowed to calculate the equilibrium melting temperature (Tm0) of 239.3 and 239.7 °C for the first and second melting peak, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4191–4199 相似文献
29.
30.
Ariana Torres‐Knoop Prof. Dr. Rajamani Krishna Dr. David Dubbeldam 《Angewandte Chemie (International ed. in English)》2014,53(30):7774-7778
The development of energy‐efficient processes for selective separation of p‐xylene from mixtures with its isomers is of vital importance in the petrochemical industries. Current industrial practice uses BaX zeolite that has high adsorption selectivity for p‐xylene. Finding para‐selective structures is challenging. With state‐of‐the‐art simulation methodologies we systematically screened a wide variety of zeolites and metal–organic frameworks (MOFs). Our investigations highlight the crucial importance of the channel dimension on the separation. MAF‐X8 is particularly noteworthy because the channel dimensions and geometry allow “commensurate stacking” which we exploit as a separation mechanism at saturation conditions. Due to a significantly improved capacity compared to BaX, the cycle times for p‐xylene with MAF‐X8 are found to be about a factor of 4.5 longer. This is expected to result in significant process improvements. 相似文献