全文获取类型
收费全文 | 475篇 |
免费 | 19篇 |
国内免费 | 2篇 |
专业分类
化学 | 332篇 |
晶体学 | 7篇 |
力学 | 3篇 |
数学 | 19篇 |
物理学 | 100篇 |
无线电 | 35篇 |
出版年
2023年 | 6篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 18篇 |
2012年 | 30篇 |
2011年 | 27篇 |
2010年 | 14篇 |
2009年 | 17篇 |
2008年 | 30篇 |
2007年 | 25篇 |
2006年 | 27篇 |
2005年 | 34篇 |
2004年 | 29篇 |
2003年 | 28篇 |
2002年 | 20篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 15篇 |
1998年 | 9篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 8篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1976年 | 4篇 |
1973年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有496条查询结果,搜索用时 468 毫秒
101.
Tomoaki Hinoue Yuta Shigenoi Misa Sugino Dr. Yuji Mizobe Dr. Ichiro Hisaki Prof. Dr. Mikiji Miyata Dr. Norimitsu Tohnai 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(15):4634-4643
The construction and precise control of the face‐to‐face π‐stacked arrangements of anthracene fluorophores in the crystalline state led to a remarkable red shift in the fluorescence spectrum due to unprecedented excited oligomer formation. The arrangements were regulated by using organic salts including anthracene‐1,5‐disulfonic acid (1,5‐ADS) and a variety of aliphatic amines. Because of the smaller number of hydrogen atoms at the edge positions and the steric effect of the sulfonate groups, 1,5‐ADS should prefer face‐to‐face π‐stacked arrangements over the usual edge‐to‐face herringbone arrangement. Indeed, as the alkyl substituents were lengthened, the organic salts altered their anthracene arrangement to give two‐dimensional (2D) edge‐to‐face and end‐to‐face herringbone arrangements, one‐dimensional (1D) face‐to‐face zigzag and slipped stacking arrangements, a lateral 1D face‐to‐face arrangement like part of a brick wall, and a discrete monomer arrangement. The monomer arrangement behaved as a dilute solution even in the close‐packed solid state to emit deep blue light. The 1D face‐to‐face zigzag and slipped stacking of the anthracene fluorophores caused a red shift of 30–40 nm in the fluorescence emission with respect to the discrete arrangement, probably owing to ground‐state associations. On the other hand, the 2D end‐to‐face stacking induced a larger red shift of 60 nm, which is attributed to the excimer fluorescence. Surprisingly, the brick‐like lateral face‐to‐face arrangement afforded a remarkable red shift of 150 nm to give yellow fluorescence. This anomalous red shift is probably due to excited oligomer formation in such a lateral 1D arrangement according to the long fluorescence lifetime and little shift in the excitation spectrum. The regulation of the π‐stacked arrangement of anthracene fluorophores enabled the wide modulation of the fluorescence and a detailed investigation of the relationships between the photophysical properties and the arrangements. 相似文献
102.
103.
104.
CuIn(SxSe1−x)2 thin polycrystalline films were grown by the chemical spray pyrolysis method on the glass substrate at 280-400°C. The alloy composition in the film was studied with relation to that in the splay solution. Films were characterized by X-ray diffraction, optical absorption, Raman spectroscopy, resistivity and surface morphology. The CuInSe2-rich alloy films grown at high substrate temperature had chalcopyrite structure, while, the CuInS2-rich films grown at low substrate temperature exhibited sphalerite structure. Optical-gap energies were smaller than that of the bulk crystal by 0.1-0.2 eV for CuInS2-rich films. Raman spectra exhibited both CuInSe2-like and CuInS2-like A1 modes, and their relative changed systematically with alloy composition. 相似文献
105.
Yoichi Asada Keith Slevin Tomi Ohtsuki 《Physica E: Low-dimensional Systems and Nanostructures》2006,34(1-2):228
Electron transport phenomena in disordered electron systems with spin–orbit coupling in two dimensions and below are studied numerically. The scaling hypothesis is checked by analyzing the scaling of the quasi-1D localization length. A logarithmic increase of the mean conductance is also confirmed. These support the theoretical prediction that the two-dimensional metal in systems with spin–orbit coupling has a perfect conductivity. Transport through a Sierpinski carpet is also reported. 相似文献
106.
Measurement of evaporation residue cross-sections of the reaction 30Si + 238U at subbarrier energies
K. Nishio S. Hofmann F. P. Heßberger D. Ackermann S. Antalic V. F. Comas Z. Gan S. Heinz J. A. Heredia H. Ikezoe J. Khuyagbaatar B. Kindler I. Kojouharov P. Kuusiniemi B. Lommel R. Mann M. Mazzocco S. Mitsuoka Y. Nagame T. Ohtsuki A. G. Popeko S. Saro H. J. Schött B. Sulignano A. Svirikhin K. Tsukada K. Tsuruta A. V. Yeremin 《The European Physical Journal A - Hadrons and Nuclei》2006,29(3):281-287
The reaction 30Si + 238U → 268Sg* was studied at beam energies close to the Coulomb barrier. At a center-of-mass energy of E
c.m. = 144.0MeV for reactions at half thickness of the target we measured three decay chains of 263Sg produced by evaporation of five neutrons. The cross-section was ( 67+67
-37) pb. At E
c.m. = 133.0MeV we measured three spontaneously fissioning nuclei which we assigned to the isotope 264Sg. The production cross-section was ( 10+10
-6) pb and a half-life of ( 120+126
-44) ms was determined. This half-life is a factor of twenty shorter than theoretical predictions. At E
c.m. = 128.0MeV an upper cross-section limit of 15pb was measured. The cross-section data reveal a strong influence of the orientation
of the deformed target nucleus on the production yield. Compared to excitation functions measured for the lighter system 16O + 238U → 254Fm*, a reduction of the fusion probability was observed at low beam energies indicating increasing competition from quasifission
processes. 相似文献
107.
Komaki Shozo Tsukamoto Katsutoshi Okada Minoru Ishida Tomoaki 《Optical and Quantum Electronics》1998,30(11-12):1079-1088
Mobile communication systems such as cellular radio and PHS are rapidly penetrating into our real life, and have gained many subscriber numbers. User demands will be growing to higher data rates that support multimedia mobile computing demands, such as graphics and motion pictures. These demands require more band width and/or spectrum utilization efficiency enhancement, and optically fed communication systems are considered to be one of the most powerful solutions. In this paper, the roles, technologies and application examples of optically fed communication systems are described. In the final part, prospects for systems and requirements for photonic devices are mentioned. 相似文献
108.
109.
Kirill A. Kovnir Yury V. Kolen’ko Sugata Ray Tomoaki Watanabe Masahiro Yoshimura 《Journal of solid state chemistry》2006,179(12):3756-3762
An effective method of synthesis of tin phosphide Sn4P3 starting from metallic tin and amorphous red phosphorus by a low-temperature (200 °C) solvothermal reaction in ethylenediamine is offered. The key parameters of this process - duration, temperature, and the ratio of initial components (Sn/P) are studied. The structure, phase composition, and morphology of the products are investigated using powder X-ray diffraction and scanning electron microscopy. Different synthetic ways for tin phosphide are discussed and compared with the proposed one. The mechanism of solvothermal preparation of tin phosphide in ethylenediamine is discussed. It is shown that the proposed solvothermal method opens up the possibility of preparing other metal-rich phosphides. 相似文献
110.
Tetsuo Sasaki Tomoaki Sakamoto Makoto Otsuka 《Journal of Infrared, Millimeter and Terahertz Waves》2018,39(9):828-839
Middle molecular weight (MMW) pharmaceuticals (MW 400~4000) are attracting attention for their possible use in new medications. Sharp absorption peaks were observed in MMW pharmaceuticals at low temperatures by measuring with a high-resolution terahertz (THz) spectrometer. As examples, high-resolution THz spectra for amoxicillin trihydrate, atorvastatin calcium trihydrate, probucol, and α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin p-toluenesulfonate (TMPyP) were obtained at 10 K. Typically observed as peaks with full width at half-height (FWHM) values as low as 5.639 GHz at 0.96492 THz in amoxicillin trihydrate and 8.857 GHz at 1.07974 THz for probucol, many sharp peaks of MMW pharmaceuticals could be observed. Such narrow absorption peaks enable evaluation of the crystal quality of MMW pharmaceuticals and afford sensitive detection of impurities. 相似文献