全文获取类型
收费全文 | 252篇 |
免费 | 5篇 |
专业分类
化学 | 129篇 |
晶体学 | 6篇 |
力学 | 4篇 |
数学 | 19篇 |
物理学 | 99篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 6篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 17篇 |
2010年 | 11篇 |
2009年 | 10篇 |
2008年 | 19篇 |
2007年 | 16篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 14篇 |
2003年 | 15篇 |
2002年 | 13篇 |
2001年 | 11篇 |
2000年 | 3篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 2篇 |
1994年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有257条查询结果,搜索用时 78 毫秒
71.
Hideaki?FurukawaEmail author Tsuyoshi?Konishi Yoshinori?Oshita Wanji?Yu Kazuyoshi?Itoh Yoshiki?Ichioka 《Optical Review》2004,11(2):119-125
Optical header recognition is one key function that enables ultrafast optical routing in photonic packet-switched networks. Especially, optical header recognition based on optical correlation processing has attracted much attention. Header signals using optical codes are decoded using optical correlation processing. We improve the decoding method for Binary Phase Shift Keying (BPSK) header signals in order to suppress crosstalk caused by matched filtering in the header recognition unit. We design a header recognition filter using the technique of a multiple-object discriminant filter (MODF). Results of preliminary experiments show that the designed header recognition filter can suppress crosstalk. The intensity ratio of correlation signals of a target header signal to non-target ones is higher than 1.95 : 1 in case of 4-bits BPSK header signals. 相似文献
72.
The effects of anisotropic gap structures on a diamagnetic response are investigated in order to demonstrate that the field-angle-resolved magnetization [ML(chi)] measurement can be used as a spectroscopic method to detect gap structures. Our microscopic calculation based on the quasiclassical Eilenberger formalism reveals that ML(chi) in a superconductor with a fourfold gap displays a fourfold oscillation reflecting the gap and Fermi-surface anisotropies, and the sign of this oscillation changes at a field between Hc1 and Hc2. As a prototype of unconventional superconductors, magnetization data for borocarbides are also discussed. 相似文献
73.
It is proposed that the spatially modulated superfluid phase, or the Fulde-Ferrell-Larkin-Ovchinnikov state could be observed in resonant fermion atomic condensates which are realized recently. We examine optimal experimental setups to achieve it by solving the Bogoliubov-de Gennes equation for both idealized one-dimensional and realistic three-dimensional cases. The spontaneous modulation of this superfluid is shown to be directly imaged as the density profiles either by optical absorption or by Stern-Gerlach experiments. 相似文献
74.
Møller SP Csete A Ichioka T Knudsen H Uggerhøj UI Andersen HH 《Physical review letters》2002,88(19):193201
The stopping power for antiprotons in various solid targets has been measured in the low-energy range of 1-100 keV. In agreement with most models, in particular free-electron gas models, the stopping power is found to be proportional to the projectile velocity below the stopping-power maximum. Although a stopping power proportional to velocity has also been observed for protons, the interpretation of such measurements is difficult due to the presence of charge exchange processes. Hence, the present measurements constitute the first unambiguous support for a velocity-proportional stopping power due to target excitations by a pointlike projectile. 相似文献
75.
76.
Yusuke Ogura Jun Tanida Yoshiki Ichioka Yoshiaki Mokuno Katsunori Matsuoka 《Optical Review》2001,8(6):416-421
A diffractive phase element (DPE) capable of shrinking the main-lobe of the focal spot of an incident beam has been developed.
The DPE is expected to be used in laser beam lithography to improve the resolution. Special constraints, which force the focal
spot to be small while permitting increase of the side-lobes, are introduced in the design of the DPE using an iterative method
based on the Gerchberg-Saxton algorithm. Two kinds of DPEs are fabricated by a laser beam lithography system of our own composition
and their performances are experimentally measured. The minimum line width obtained by the system is improved from 1.2 μm
to 1.0 μm with the fabricated DPE. Focal depth of the focusing system is discussed. 相似文献
77.
Takafumi Mori Tungalag Dong Kouji Yazawa Yoshio Inoue 《Macromolecular rapid communications》2007,28(21):2095-2099
Films of an α‐cyclodextrin/poly(ε‐caprolactone) inclusion complex have been successfully prepared and show high transparency and heat resistance in comparison to the pure polymer film. The physical properties, such as transparency, mechanical properties, and thermal stability, of the α‐CD‐PCL‐IC films are found to depend on the α‐cyclodextrin‐to‐polymer stoichiometry.
78.
Pressure‐based unified solver for gas‐liquid two‐phase flows where compressible and incompressible flows coexist 下载免费PDF全文
We propose a pressure‐based unified solver for gas‐liquid two‐phase flows where compressible and incompressible flows coexist. Unlike the original thermo–Cubic Interpolated Propagation Combined Unified Procedure (CIP‐CUP) method proposed by Himeno et al (Transactions of the Japan Society of Mechanical Engineers, Series B, 2003), we split the advection term of the governing equations into a conservation part and into the rest. The splitting of advection term has two advantages. One is the high degree of freedom in choosing discretization schemes such as central‐difference schemes, upwind schemes, and Total Variation Diminishing (TVD) schemes. The other is the ease of implementation on unstructured grids. The advantages enable the analyses of various flows such as turbulent and supersonic ones in actual complicated boundaries. Therefore, the solver is useful for practical analyses. The solver was validated on the following test cases: subsonic single‐phase flows, incompressible single‐phase turbulent flows, and incompressible gas‐liquid two‐phase flows. With unstructured grids, we obtained the equivalent results as the ones with structured grids. After the validations, subsonic jet impinging on a water pool was calculated and compared with experimental results. It was confirmed that the calculated results were consistent with the experimental ones. 相似文献
79.
Coupling Reaction of Enol Derivatives with Silyl Ketene Acetals Catalyzed by Gallium Trihalides 下载免费PDF全文
Dr. Yoshihiro Nishimoto Yuji Kita Hiroki Ueda Hiroto Imaoka Kouji Chiba Prof. Dr. Makoto Yasuda Prof. Dr. Akio Baba 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(33):11837-11845
A cross‐coupling reaction between enol derivatives and silyl ketene acetals catalyzed by GaBr3 took place to give the corresponding α‐alkenyl esters. GaBr3 showed the most effective catalytic ability, whereas other metal salts such as BF3?OEt2, AlCl3, PdCl2, and lanthanide triflates were not effective. Various types of enol ethers and vinyl carboxylates as enol derivatives are amenable to this coupling. The scope of the reaction with silyl ketene acetals was also broad. We successfully observed an alkylgallium intermediate by using NMR spectroscopy, suggesting a mechanism involving anti‐carbogallation among GaBr3, an enol derivative, and a silyl ketene acetal, followed by syn‐β‐alkoxy elimination from the alkylgallium. Based on kinetic studies, the turnover‐limiting step of the reaction using a vinyl ether and a vinyl carboxylate involved syn‐β‐alkoxy elimination and anti‐carbogallation, respectively. Therefore, the leaving group had a significant effect on the progress of the reaction. Theoretical calculations analysis suggest that the moderate Lewis acidity of gallium would contribute to a flexible conformational change of the alkylgallium intermediate and to the cleavage of the carbon?oxygen bond in the β‐alkoxy elimination process, which is the turnover‐limiting step in the reaction between a vinyl ether and a silyl ketene acetal. 相似文献
80.
Kouji Chiba Toshiyuki Hirano Fumitoshi Sato Masahiro Okamoto 《International journal of quantum chemistry》2013,113(21):2345-2354
This article reports the proton tautomerization effects of distal histidine residues in carbonmonoxy myoglobin according to the density functional calculations of the whole protein. The electron eigenstates and electrostatic potential (ESP) distributed around heme and its pocket vary significantly depending on the protonation positions of the distal histidine residues. To investigate the range over which the electronic structures are affected by the proton tautomerization, the quantum mechanics/molecular mechanics (QM/MM) method is applied to probe the QM size to reproduce the atomic partial charges and ESP around the active center. Consequently, we show that these properties converged for the 300 pm QM/MM system in this study. During the analysis, we also find that amino residues such as Phe43, Val68, and Phe138 interact strongly with heme through orbital mixing, indicating that the protein is a medium not only interacting with the reaction center, but also buffering on electrons. © 2013 Wiley Periodicals, Inc. 相似文献