全文获取类型
收费全文 | 666篇 |
免费 | 29篇 |
国内免费 | 1篇 |
专业分类
化学 | 431篇 |
晶体学 | 17篇 |
力学 | 4篇 |
数学 | 52篇 |
物理学 | 192篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 29篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 21篇 |
2012年 | 35篇 |
2011年 | 35篇 |
2010年 | 24篇 |
2009年 | 36篇 |
2008年 | 32篇 |
2007年 | 36篇 |
2006年 | 43篇 |
2005年 | 34篇 |
2004年 | 24篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 16篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 14篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 10篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1942年 | 3篇 |
1939年 | 2篇 |
1932年 | 2篇 |
排序方式: 共有696条查询结果,搜索用时 31 毫秒
91.
92.
Synthesis and characterization of double hydrophilic block copolymers containing semi-rigid and flexible segments
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)
Alice M. Savage Elizabeth Ullrich Stacey M. Chin Zachary Kiernan Caitlyn Kost S. Richard Turner 《Journal of polymer science. Part A, Polymer chemistry》2015,53(2):219-227
3-Methyl-(E)-stilbene (3MSti) and 4-(diethylamino)-(E)-stilbene (DEASti) monomers are synthesized and polymerized separately with maleic anhydride (MAn) in a strictly alternating fashion using reversible addition-fragmentation chain transfer (RAFT) polymerization techniques. The optimal RAFT chain transfer agents (CTAs) for each copolymerization affect the reaction kinetics and CTA compatibilities. Psuedo-first order polymerization kinetics are demonstrated for the synthesis of poly((3-methyl-(E)-stilbene)-alt-maleic anhydride) (3MSti-alt-MAn) with a thiocarbonylthio CTA (methyl 2-(dodecylthiocarbonothioylthio)−2-methylpropionate, TTCMe). In contrast, a dithioester CTA (cumyl dithiobenzoate, CDB) controls the synthesis of poly((4-(diethylamino)-(E)-stilbene)-alt-maleic anhydride) (DEASti-alt-MAn) with pseudo-first order polymerization kinetics. DEASti-alt-MAn is chain extended with 4-acryloylmorpholine (ACMO) to synthesize diblock copolymers and subsequently converted to a double hydrophilic polyampholyte block copolymers (poly((4-(diethylamino)-(E)-stilbene)-alt-maleic acid))-b-acryloylmorpholine) (DEASti-alt-MA)-b-ACMO) via acid hydrolysis. The isoelectric point and dissociation behavior of these maleic acid-containing copolymers are determined using ζ-potential and acid–base titrations, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 219–227 相似文献
93.
Prof. Dr. Holger Braunschweig Dr. Rian D. Dewhurst Dipl.‐Chem. Christian Hörl Dr. Ashwini K. Phukan Florian Pinzner Stefan Ullrich 《Angewandte Chemie (International ed. in English)》2014,53(12):3241-3244
Synthetic access to electron‐precise boron chains is hampered by the preferential formation of nonclassical structures. The few existing strategies for this involve either strongly reducing reagents or transition‐metal catalysts, both with distinct disadvantages. The synthesis of new furyl‐ and thienyl‐substituted diborenes is presented, along with their direct hydroboration with catecholborane (CatBH) to form a new electron‐precise B? B bond and a B3 chain. The reaction is diastereoselective and proceeds under mild conditions without the use of strong reducing agents or transition‐metal catalysts commonly used in B‐B coupling reactions. 相似文献
94.
95.
Pina J de Melo JS Burrows HD Galbrecht F Bilge A Kudla CJ Scherf U 《The journal of physical chemistry. B》2008,112(4):1104-1111
A comprehensive study has been undertaken of the electronic spectral and photophysical properties of two oligophenyl (BPH and BPHF) and one oligothienyl (BTF) swivel cruciforms involving measurements of absorption, fluorescence, and phosphorescence spectra, quantum yields of fluorescence (phiF), phosphorescence (phiPh) and triplet formation (phiT), lifetimes of fluorescence (tauF) and of the triplet state (tauT), and quantum yields of singlet oxygen production (phiDelta). From these, all radiative kF and radiationless rate constants, kIC and kISC, have been obtained in solution. The energies of the lowest lying singlet and triplet excited states were also determined at 293 K. Several of the above properties have also been obtained at low temperature and in the solid state (thin films). In general, for the phenyl oligophenyl (BPH) and for the oligothienyl (BTF) compounds, the radiationless decay channels (phiIC+phiISC) are the dominant pathway for the excited-state deactivation, whereas with the fluorene based oligophenyl BPHF the radiative route prevails. In contrast to the general rule found for related oligomers (and polymers) where radiative emission from T1 is absent, with the compounds studied, phosphorescence has been observed for all of the compounds, indicating that this type of functionalization can lead to emissive triplets. Time-resolved fluorescence decays with picosecond resolution revealed multiexponential (bi- and triexponential) decay laws compatible with the existence of more than one species or conformation in the excited state. These results are discussed on the basis of conformational flexibility in the excited state. 相似文献
96.
Allard S Forster M Souharce B Thiem H Scherf U 《Angewandte Chemie (International ed. in English)》2008,47(22):4070-4098
The cost-effective production of flexible electronic components will profit considerably from the development of solution-processable, organic semiconductor materials. Particular attention is focused on soluble semiconductors for organic field-effect transistors (OFETs). The hitherto differentiation between "small molecules" and polymeric materials no longer plays a role, rather more the ability to process materials from solution to homogeneous semiconducting films with optimal electronic properties (high charge-carrier mobility, low threshold voltage, high on/off ratio) is pivotal. Key classes of materials for this purpose are soluble oligoacenes, soluble oligo- and polythiophenes and their respective copolymers, and oligo- and polytriarylamines. In this context, micro- or nanocrystalline materials have the general advantage of somewhat higher charge-carrier mobilities, which, however, could be offset in the case of amorphous, glassy materials by simpler and more reproducible processing. 相似文献
97.
Polyunsaturated fatty acids (PUFAs) are important constituents in all organisms. They fulfil many functions, ranging from modulating the structure of membranes to acting as precursors of physiologically important molecules, such as the prostaglandins, which for a long time were the most prominent cyclic PUFA metabolites. However, since the beginning of the 1990s a large variety of cyclic metabolites have been discovered that form under autoxidative conditions in vivo to a much larger extent than do prostaglandins. These compounds--isoprostanes, neuroprostanes, phytoprostanes, and isofurans--proved subsequently to be ubiquitous in nature. They display a wide range of biological activities, and isoprostanes have become the currently most reliable indicators of oxidative stress in humans. In a relatively short time, the structural variety, properties, and applications of the autoxidatively formed cyclic PUFA derivatives have been uncovered. 相似文献
98.
99.
Programmed temperature retention indices (PTRIs) calculated according to the equations of Van den Dool and Kratz, Golovnya and Uraletz, and Erdey et al. (also referred to as Antoine's integrated equation) are used in this work. Precalculation of isotherm retention indices from the results of a linearly programmed temperature GC is also presented. Deviations between experimental and calculated isothermal retention indices are below 2 retention index units. A relative "volatility" retention index is defined, as a function of the "volatilities"of the solute and the bracket reference n-alkanes. The comparison of the "volatility" retention indices with the PTRIs obtained with the other above equations shows absolute deviations of up to 4 retention index units. Based on an earlier "equivalent" temperature concept and on Tekler's proviso, a novel way for the utilization of Sadtler's retention index database, which takes advantage of the 3 data supplied by the library, is proposed. 相似文献