全文获取类型
收费全文 | 276篇 |
免费 | 6篇 |
专业分类
化学 | 169篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 20篇 |
物理学 | 84篇 |
出版年
2023年 | 2篇 |
2022年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2015年 | 4篇 |
2014年 | 6篇 |
2013年 | 14篇 |
2012年 | 18篇 |
2011年 | 12篇 |
2010年 | 12篇 |
2009年 | 6篇 |
2008年 | 16篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 7篇 |
2004年 | 13篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 14篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 11篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1937年 | 2篇 |
1931年 | 1篇 |
1928年 | 2篇 |
1903年 | 1篇 |
排序方式: 共有282条查询结果,搜索用时 15 毫秒
101.
David K. Wang David J. T. Hill Firas A. Rasoul Andrew K. Whittaker 《Journal of polymer science. Part A, Polymer chemistry》2012,50(6):1143-1157
A new biodegradable, water‐soluble macromonomer based on the commercial hyperbranched polyester Boltorn®H20 has been synthesized through the use of click chemistry. The macromonomer was developed with the aim of being injected with a comacromonomer, poly(ethylene glycol) (PEG) diacrylate, for in situ copolymerization to form biodegradable polymer hydrogels. Copolymer hydrogels were prepared from the macromonomer and PEG diacrylate (FW 700) by free radical copolymerization. A degree of phase separation of the hydrogels was observed during polymerization and with increasing incorporation of the Boltorn macromonomer an increasing tendency for the formation of macropores was observed. The swelling ratios of the gels in water and phosphate buffered saline solution, PBS, all increase with increasing Boltorn macromonomer concentration, as did the penetrant diffusion coefficients and the degradation rate in PBS. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
102.
Fredrik Nyström Alexander H. Soeriyadi Cyrille Boyer Per B. Zetterlund Michael R. Whittaker 《Journal of polymer science. Part A, Polymer chemistry》2011,49(24):5313-5321
Copper(0)‐mediated radical polymerization (single electron transfer‐living radical polymerization) is an efficient polymerization technique that allows control over the polymerization of acrylates, vinyl chloride and other monomers, yielding bromide terminated polymer. In this contribution, we investigate the evolution of the end‐group fidelity at very high conversion both in the presence and in the absence of initially added copper (II) bromide (CuBr2). High resolution electrospray‐ionization mass spectroscopy (ESI‐MS) allows determination of the precise chemical structure of the dead polymers formed during the polymerization to very high monomer conversion, including post polymerization conditions. Two different regimes can be identified via ESI‐MS analysis. During the polymerization, dead polymer results mainly from termination via disproportionation, whereas at very high conversion (or in the absence of monomer, that is, post‐polymerization), dead polymers are predominantly generated by chain transfer reactions (presumably to ligand). The addition of CuBr2 significantly reduces the extent of termination by both chain transfer and disproportionation, at very high monomer conversion and under post‐polymerization conditions, offering a convenient approach to maintaining high end‐group fidelity in Cu(0)‐mediated radical polymerization. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
103.
Predictions of hot, dense iron plasma opacity at 89 eV photon energy are compared with experimental determinations from the transmission of laser-heated iron to extreme ultra-violet (EUV) laser radiation. The EUV laser was pumped using six beams of an Nd-Yag laser in a refraction compensating geometry, while another beam irradiated a tamped solid iron target with an intensity of 1014 W cm−2. The Ehybrid hydrodynamic and atomic physics code was used to predict temperatures, densities and ionisation throughout the evolving iron plasma. The iron opacities were deduced taking into account free–free, bound–free and bound–bound absorption. Bound–bound absorption was considered using atomic data generated by the Opacity Project. Reasonable overall agreement between theory and experiment was obtained for the iron layer transmission. The simulations indicated the dominance of bound–bound absorption throughout most regions of the iron plasma, but also the potential importance of photoionisation from core levels where energetically possible. 相似文献
104.
David J. T. Hill James H. O'donnell Paulw O'sullivan Peter J. Pomery Andrew K. Whittaker 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(4):403-414
Free radicals produced in styrene and maleic anhydride mixtures and in solutions in acetone and chloroform by UV photolysis at 90 K have been studied by electron spin resonance and changes observed on warming. A doublet spectrum observed in all systems containing maleic anhydride has been assigned to the radical formed by H addition to a carbonyl group in the monomer, and not to the corresponding radical on maleic anhydride units in the copolymer or to the maleic anhydride propagating radical. Interpretations of copolymerization mechanisms based on radicals produced in frozen comonomers in bulk or in solution by photolysis or radiolysis must therefore be viewed with caution. 相似文献
105.
The advent of the quantum cascade laser (QCL) with emission wavelengths available in the infrared range from 3 μm through
more than 100 μm opens up the possibility of exploiting infrared atmospheric transparency windows for free space optical communications.
In an effort to establish the efficacy of using directly modulated QCLs for free space communications we have conducted a
series of investigations that demonstrate the potential advantages of this technology. In these experiments we first establish
that the QCL has very high modulation bandwidth. We then implement a practical free space communications link that under
conditions of atmospheric fog, dust and other obscurants offers significant transparency advantage when compared with near
infrared wavelength sources presently used in commercial free space optical communications links. 相似文献
106.
107.
Raymond J. Abraham Collette M. Holden Philip Loftus David Whittaker 《Magnetic resonance in chemistry : MRC》1974,6(3):184-189
The 13C spectra of α-thujene ( 1 ), isothujone ( 2 ), (?)isothujol ( 3 ), (+)neoisothujol ( 4 ), sabinol ( 5 ), dihydroumbellulone ( 6 ) and umbellulone ( 7 ) and the alcohol acetates are recorded and assigned. The C-6 chemical shift may be used in conjunction with the steric shift mechanism as a conformational probe in these molecules. The results obtained indicate that isothujol, neoisothujol, isothujone and dihydroumbellulone adopt boat-like conformations whilst sabinol has a much flatter conformation. Conjugation of the isolated double bond of α-thujene and the carbonyl group of dihydroumbellulone with the cyclopropane ring has virtually no effect on the 13C shifts, but those of umbellulone itself are anomalous, indicating conjugation of the α,β unsaturated ketone system with the cyclopropyl ring. 相似文献
108.
Kresten L.C. Nielsen David J.T. Hill Kent A. Watson Shigetoshi Ikeda Andrew K. Whittaker 《Polymer Degradation and Stability》2008,93(1):169-175
The radiation degradation of a nanotube-polyimide nanocomposite was studied. Radiation chemistry was observed that was not present in the unmodified polymer or in the imbedded single-walled carbon nanotubes (SWNTs) themselves. The tensile properties were found to be improved by the addition of SWNTs in the unirradiated materials, and no deterioration in these properties with irradiation was observed. The SWNTs were found to have a detrimental effect on the optical properties however. The transparency of the composite was degraded significantly faster by electron-beam radiation than the neat polymer was. This may make the SWNT/polyimide composites unsuitable for some space applications. Electron Spin Resonance (ESR) measurements determined that the SWNTs interfere with the radical chemistry in the irradiated materials. This could be due to energy dissipation by the SWNT network, preventing the formation of radical species, or alternatively, preferential reaction or termination of radicals by the nanotubes. FT-Raman spectroscopy was found to be a very useful tool for examining SWNTs embedded at low concentrations. It revealed no signs of SWNT degradation up to 10 MGy. 相似文献
109.
Coldham I Patel JJ Raimbault S Whittaker DT Adams H Fang GY Aggarwal VK 《Organic letters》2008,10(1):141-143
Asymmetric lithiation of substituted benzylamines, N-Boc-pyrrolidine, or N-Boc-indoline using Beak's methodology was followed by electrophilic quench with trialkylboranes. The resulting borate intermediates rearrange with concomitant C-N bond breakage to give, after oxidation, chiral secondary alcohols with high enantioselectivity. 相似文献
110.
Boyer C Soeriyadi AH Roth PJ Whittaker MR Davis TP 《Chemical communications (Cambridge, England)》2011,47(4):1318-1320
In this communication, we report on a new route to the functionalization of ATRP polymers exploiting their halide end-groups, which were converted successfully into reactive disulfide end-groups, using sodium methanethiosulfonate. The resultant disulfide-terminated polymers could then be reacted with different functional thiols to yield functional polymers exploiting either thiol/disulfide exchange chemistry or thiol/ene "click" reactions. 相似文献