全文获取类型
收费全文 | 175篇 |
免费 | 2篇 |
专业分类
化学 | 106篇 |
力学 | 1篇 |
数学 | 19篇 |
物理学 | 51篇 |
出版年
2019年 | 1篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 3篇 |
2012年 | 9篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 1篇 |
2008年 | 11篇 |
2007年 | 5篇 |
2006年 | 16篇 |
2005年 | 9篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有177条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
Zhao Y Shirai Y Slepkov AD Cheng L Alemany LB Sasaki T Hegmann FA Tour JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(12):3643-3658
A series of multiple [60]fullerene terminated oligo(p-phenylene ethynylene) (OPE) hybrid compounds has been synthesized through a newly developed in situ ethynylation method. Structural and magnetic shielding properties of the highly unsaturated carbon-rich C(60) and OPE scaffolds were characterized by 1D and 2D NMR spectroscopic analyses. Electronic interactions between the [60]fullerenes and the OPE backbones were investigated by UV/Vis spectroscopic and cyclic voltammetry (CV) experiments. Our studies clearly show that although the multiple [60]fullerene groups are connected via pi-conjugated OPE frameworks, they present diminutive electronic interactions in the ground state, and the electronic behavior of the [60]fullerene cages are only affected by the OPE backbones through modest inductive effects. Interestingly, sizable third-order nonlinear optical (NLO) responses (gamma) and enhanced two-photon absorption (TPA) cross-sections (sigma((2))) were determined for the multifullerene-OPE hybrid 31 relative to its OPE precursor from differential optical Kerr effect (DOKE) experiments. Such enhanced NLO performance is presumably due to the occurrence of periconjugation and/or charge transfer effects in the excited state. In addition, comparatively strong excited-state absorption was observed and characterized for OPE pentamer 12. Thus, the use of such fullerene-derivatized conjugated oligomers aids the quest for molecules with large third-order NLO and TPA properties. 相似文献
55.
Hadjiev VG Mitchell CA Arepalli S Bahr JL Tour JM Krishnamoorti R 《The Journal of chemical physics》2005,122(12):124708
We present an unusual temperature dependence of thermal strains in 4-(10-hydroxy)decyl benzoate (HDB) modified SWNTPS (SWNT-single wall carbon nanotube, PS-polystyrene) nanocomposites. The strain transfer from the matrix to nanotubes in these nanocomposites, inferred from the frequency change of the Raman active tangential modes of the nanotubes, is enhanced strongly below 300 K, whereas it is vanishingly small at higher temperatures. The increased strain transfer is suggestive of reinforcement of the HDB-SWNTPS nanocomposites at low temperatures. On the other hand, the pristine SWNTs couple weakly to the PS matrix over the entire temperature range of 4.5-410 K. We argue that the strain transfer in HDB-SWNTPS is determined by the thermomechanical properties of the interface region composed of polystyrene plasticized by the tethered alkanelike modifier. 相似文献
56.
In this paper we prove that any Riemannian surface, with no restriction of curvature at all, can be decomposed into blocks belonging just to some of these types: generalized Y-pieces, generalized funnels and halfplanes. 相似文献
57.
The combinatorial synthesis of oligo(phenylene ethynylene) tetramers, both in solution and on solid support, is described. These products are of interest for molecular electronics applications. An iterative sequence, coupling of aryl halides to alkynes under Sonogashira conditions, was used. Five monomers functionalized with electron-donating or electron-withdrawing groups were synthesized, and used to generate a library of 25 trimers in a solution-phase based process. A library of 24 tetramers was prepared by subsequent protodesilylation and coupling with the alligator clip 4-iodo-1-thioacetylbenzene. The solution-phase based sequence was successfully adapted to a higher yielding directed split-and-pool solid-phase process, with average yields of 78–86% for each step over seven steps. A triazene linker group was used to attach the starting monomer to the polymer beads. At the completion of the solid-phase-based process, traceless cleavage of trimers from the resin was achieved by sonication of the resin in 10% HCl/THF solution. The released products were then poised for the final step in the sequence, attachment of the alligator clip. 相似文献
58.
Joseph Q. Pham Cynthia A. Mitchell Jeffrey L. Bahr James M. Tour Ramanan Krishanamoorti Peter F. Green 《Journal of polymer science. Part A, Polymer chemistry》2003,41(24):3339-3345
The glass-transition temperatures (Tg's) of nanocomposites of polystyrene (PS) and single-walled carbon nanotubes were measured in the bulk and in thin films with differential scanning calorimetry and spectroscopic ellipsometry, respectively. The bulk Tg of the nanocomposites increased by approximately 3 °C and became much broader than that of PS. For the nanocomposite films thinner than 45 nm, Tg decreased with decreasing film thickness [i.e., ΔTg(nano) < 0]. This phenomenon also occurred in thin PS films, the magnitude of the depression in PS [ΔTg(PS)] being somewhat larger. The film thickness dependence and the differences in the magnitude of ΔTg in the two systems were examined in light of current theory, and a quantitative comparison was made. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 3339–3345, 2003 相似文献
59.
Alvarez NT Kittrell C Schmidt HK Hauge RH Engel PS Tour JM 《Journal of the American Chemical Society》2008,130(43):14227-14233
Ultraviolet (UV) irradiation of single wall carbon nanotubes (SWCNTs) individually dispersed in surfactants leads to diameter and type-selective photohydroxylation of the nanotubes. Photohydroxylation of first semiconductor and then small diameter metallic SWCNTs was confirmed after 254 nm UV irradiation in acidic, neutral, and basic aqueous solutions at ambient and elevated temperatures. The increased oxygen content of the SWCNTs after UV irradiation, as detected by X-ray photoelectron spectroscopy, suggests that SWCNTs were hydroxylated by reaction with water. Attenuated total reflectance Fourier transform infrared analysis provides evidence of hydroxyl functional groups on their surface. This photochemical reaction is impeded by molecular oxygen and appears to involve a reactive intermediate generated in the vicinity of semiconducting SWCNTs. This represents a noncontaminating selective reaction in the liquid phase that uses an intrinsic property of the tubes. 相似文献
60.
A nanovehicle with a new photoactive moiety has been synthesized. The incorporation of the azobenzene chassis allows for potential wormlike movement accompanying the rolling behavior of the wheels. Two versions, the fullerene-wheeled and carborane-wheeled nanoworms, were synthesized to examine the solution-based photoisomerization yields of the chassis. 相似文献