首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   152篇
  免费   1篇
化学   140篇
物理学   13篇
  2023年   2篇
  2022年   2篇
  2021年   3篇
  2020年   3篇
  2019年   4篇
  2018年   1篇
  2017年   1篇
  2016年   1篇
  2013年   9篇
  2012年   10篇
  2011年   7篇
  2010年   8篇
  2009年   10篇
  2008年   6篇
  2007年   7篇
  2006年   16篇
  2005年   14篇
  2004年   11篇
  2003年   6篇
  2002年   6篇
  2001年   2篇
  1996年   5篇
  1995年   1篇
  1994年   1篇
  1992年   3篇
  1990年   3篇
  1989年   1篇
  1985年   1篇
  1982年   1篇
  1981年   1篇
  1978年   1篇
  1977年   1篇
  1975年   2篇
  1973年   2篇
  1969年   1篇
排序方式: 共有153条查询结果,搜索用时 31 毫秒
61.
A microbial cellulose film (pellicle), prepared by Acetorbactor xylinum, is a supramolecule system, absorbing a huge amount of water (99% by weight). To elucidate the affinity to water, we investigated the hierarchical structure in a pellicle by using ultra-small-angle and small-angle neutron scattering, observing a wide range of length scales from nm to µm. We successfully determined mass fractal dimensions for the amorphous structure, which hierarchically varies local concentration fluctuations, bundle and network, appeared as the length scale increases. On a basis of these findings, we discuss to address a question what factors determine the hierarchy in the microbial cellulose. This is a new topic of soft matter science, regarded as reaction-induced self-assembly in a non-equilibrium open system, therein soft matter physics, biochemistry and cell biology crucially interplay.  相似文献   
62.
We focussed on the following two topics on block copolymers; (i) the Brazovskii effects, effects of thermal fluctuations on phase transition of systems having a short characteristic length L, and (ii) nanofabrication and nanohybrids based on block copolymer nanostructures. We highlight the following two aspects: Block copolymers provide good model systems for studies of basic physical science and are useful for advanced functional materials and devices.  相似文献   
63.
Structure factors of dispersible units of carbon black filler in rubbers   总被引:1,自引:0,他引:1  
We report the structures of dispersible units, a most fundamental but minimal dispersible structural unit of a carbon black (CB) filler that is formed in two kinds of rubber (polyisoprene and styrene-butadiene random copolymer) matrices under a given processing condition. The results obtained from various small-angle scattering techniques showed that the CB aggregates, as observed after the sonification of a CB/toluene solution, were a spherical shape composed of approximately nine primary CB particles fused together. In the rubber matrices, the aggregates clustered into higher order structures defined in this work as the dispersible units, which are the fundamental structural elements (or the "lower cutoff structures") that build up a higher order mass-fractal structure. Furthermore, we found that the morphology of the dispersible units strongly depended on the rubber matrix, although the mass-fractal dimensions remained unchanged.  相似文献   
64.
Nonspherical polystyrene (PS)/poly(methyl methacrylate) (PMMA) composite particles having a dent were prepared by releasing toluene from PS/PMMA/toluene droplets dispersed in a poly(vinyl alcohol) aqueous medium. An ex-centered PS-core/PMMA-shell morphology, in which a part of the PS core contacted with the aqueous medium and toluene partitioned more in the PS core than in the PMMA shell, was formed in the polymers/toluene droplet in the process of phase separation therein with releasing toluene. The volume of the dent became bigger with an increase in the PS content and in the toluene content partitioned in the PS core.Part CCLXI of the series Studies on Suspension and Emulsion.  相似文献   
65.
66.
We have demonstrated the features of curve-structured phenalenyl chemistry, for the first time. A phenalenyl-fused corannulene anion has been designed by the annelation of a six-memberd ring across peri-positions of corannulene and generated as a stable species in a degassed solution. The 1H and 13C NMR spectra have shown the highly symmetrical structure and high-field shifts of protons and carbons at the asterisked positions in the chemical structure, indicating the occurrence of large negative charge densities at these positions. These results well agree with the HOMO picture and the electrostatic potential surface, demonstrating the phenalenyl anion-type electronic structure is retained in the curved-surface pi-system. The calculated bowl-inversion barrier of the anion (11.3 kcal/mol) is larger than that of corannulene (9.2 kcal/mol) because of peri-annelation of the corannulene skeleton. The calculations of the barriers of the neutral radical (12.6 kcal/mol), radical dianion (8.1 kcal/mol), and trianion (5.4 kcal/mol) of the phenalenyl-fused corannulene have exhibited a stepwise flattening of the curvature with increase in negative charge. Therefore, we have revealed that the bowl-inversion barrier of the anion is governed by the setoff of the peri-annelation and negative charge effects.  相似文献   
67.
68.
We investigated the self-assembling structure of the 1,3:2,4-bis-O-(p-methylbenzylidene)-D-sorbitol (PDTS)/n-dibutylphthalate (DBP) system in the parameter space of temperature T and solute concentration Phi(PDTS). Optical microscopic studies revealed that the phase diagram can be divided into four regions. In region I at high T the system is a homogeneous solution. In region II at lower T and low Phi(PDTS), the system still has fluidity but has microgels having spherulitic texture of PDTS crystallites. Regions III and IV at even lower T but higher Phi(PDTS) are in a gel state. In region III, the PDTS forms volume-filling spherulites due to the solid-liquid phase transition of the saturated PDTS solutions. In region IV at the lowest T, both the liquid-liquid phase-separation process and the solid-liquid transition of the PDTS are involved in the self-assembling processes. In this region a bicontinuous phase-separated structure is first formed by liquid-liquid phase separation via spinodal decomposition (SD). The subsequent solid-liquid transition of the PDTS in the PDTS-rich region forms percolating crystalline fibrils rather than spherulites. The formation of the crystalline fibrils pins further growth of the bicontinuous structure via SD.  相似文献   
69.
The synthesis and the solid state magnetic properties of (nitronyl nitroxide)‐substituted trioxytriphenylamine radical cation tetrachlorogallate, NNTOT+·GaCl4? , are reported. In the temperature region between 300 and 3 K, the magnetic behavior is characterized by the strong intramolecular ferromagnetic interaction (J/kB=+400 K) between the radical ( NN ) and the radical cation ( TOT +) and the weak intermolecular antiferromagnetic interaction (J/kB=?1.9 K) between NNTOT+ ions. Below 3 K, a 3D‐type long‐range magnetic ordering into a weak ferromagnet was observed (TN=2.65 K). The magnetic entropy (Smag=8.97 J K?1 mol?1) obtained by the heat capacity measurement is in good agreement with the theoretical value of R ln3=9.13 J K?1 mol?1 based on the S=1 state.  相似文献   
70.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号