全文获取类型
收费全文 | 174篇 |
免费 | 2篇 |
国内免费 | 1篇 |
专业分类
化学 | 110篇 |
力学 | 3篇 |
数学 | 25篇 |
物理学 | 39篇 |
出版年
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 4篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 3篇 |
2012年 | 11篇 |
2011年 | 21篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 6篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1958年 | 1篇 |
1947年 | 1篇 |
排序方式: 共有177条查询结果,搜索用时 31 毫秒
51.
In the late 1970s, in two celebrated papers, Aizenman and Higuchi independently established that all infinite-volume Gibbs measures of the two-dimensional ferromagnetic nearest-neighbor Ising model at inverse temperature ${\beta\geq 0}$ are of the form ${\alpha\mu^{+}_\beta + (1-\alpha)\mu^{-}_\beta}$ , where ${\mu^{+}_\beta}$ and ${\mu^{-}_\beta}$ are the two pure phases and ${0\leq\alpha\leq 1}$ . We present here a new approach to this result, with a number of advantages: (a) We obtain an optimal finite-volume, quantitative analogue (implying the classical claim); (b) the scheme of our proof seems more natural and provides a better picture of the underlying phenomenon; (c) this new approach might be applicable to systems for which the classical method fails. 相似文献
52.
53.
Eszter E. Najbauer Kumar Tekwani Movellan Dr. Tobias Schubeis Dr. Tom Schwarzer Prof. Dr. Kathrin Castiglione Karin Giller Prof. Dr. Guido Pintacuda Dr. Stefan Becker Dr. Loren B. Andreas 《Chemphyschem》2019,20(2):302-310
Determination of the environment surrounding a protein is often key to understanding its function and can also be used to infer the structural properties of the protein. By using proton-detected solid-state NMR, we show that reduced spin diffusion within the protein under conditions of fast magic-angle spinning, high magnetic field, and sample deuteration allows the efficient measurement of site-specific exposure to mobile water and lipids. We demonstrate this site specificity on two membrane proteins, the human voltage dependent anion channel, and the alkane transporter AlkL from Pseudomonas putida. Transfer from lipids is observed selectively in the membrane spanning region, and an average lipid-protein transfer rate of 6 s−1 was determined for residues protected from exchange. Transfer within the protein, as tracked in the 15N-1H 2D plane, was estimated from initial rates and found to be in a similar range of about 8 to 15 s−1 for several resolved residues, explaining the site specificity. 相似文献
54.
Alexander J. Myers Michael L. Tarlton Steven P. Kelley Wayne W. Lukens Justin R. Walensky 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(42):15033-15037
To extend organoactinide chemistry beyond uranium, reported here is the first structurally characterized transuranic hydrocarbyl complex, Np[η4‐Me2NC(H)C6H5]3 ( 1 ), from reaction of NpCl4(DME)2 with four equivalents of K[Me2NC(H)C6H5]. Unlike the UIII species, the neptunium analogue can be used to access other NpIII complexes. The reaction of 1 with three equivalents of HE2C(2,6‐Mes2‐C6H3) (E=O, S) yields [(2,6‐Mes2‐C6H3)CE2]3Np(THF)2, maintaining the trivalent oxidation state. 相似文献
55.
Tomas Orlando Rza Derviolu Marcel Levien Igor Tkach Thomas F. Prisner Loren B. Andreas Vasyl P. Denysenkov Marina Bennati 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(5):1416-1420
Nuclear magnetic resonance (NMR) techniques play an essential role in natural science and medicine. In spite of the tremendous utility associated with the small energies detected, the most severe limitation is the low signal‐to‐noise ratio. Dynamic nuclear polarization (DNP), a technique based on transfer of polarization from electron to nuclear spins, has emerged as a tool to enhance sensitivity of NMR. However, the approach in liquids still faces several challenges. Herein we report the observation of room‐temperature, liquid DNP 13C signal enhancements in organic small molecules as high as 600 at 9.4 Tesla and 800 at 1.2 Tesla. A mechanistic investigation of the 13C‐DNP field dependence shows that DNP efficiency is raised by proper choice of the polarizing agent (paramagnetic center) and by halogen atoms as mediators of scalar hyperfine interaction. Observation of sizable DNP of 13CH2 and 13CH3 groups in organic molecules at 9.4 T opens perspective for a broader application of this method. 相似文献
56.
Alexander B. Barnes Loren B. Andreas Matthias Huber Ramesh Ramachandran Patrick C.A. van der Wel Mikhail Veshtort Robert G. Griffin Manish A. Mehta 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(1):95-100
We present a de novo high-resolution structure of the peptide Alanyl-Prolyl-Glycine using a combination of sensitive solid-state NMR techniques that each yield precise structural constraints. High-quality 13C–13C distance constraints are extracted by fitting rotational resonance width (R2W) experiments using Multimode Multipole Floquet Theory and experimental chemical shift anisotropy (CSA) orientations. In this strategy, a structure is first calculated using DANTE-REDOR and torsion angle measurements and the resulting relative CSA orientations are used as an input parameter in the 13C–13C distance calculations. Finally, a refined structure is calculated using all the constraints. We investigate the effect of different structural constraints on structure quality, as determined by comparison to the crystal structure and also self-consistency of the calculated structures. Inclusion of all or subsets of these constraints into CNS calculations resulted in high-quality structures (0.02 Å backbone RMSD using all 11 constraints). 相似文献
57.
The ground state of the two-dimensional electron gas near nu=1 is investigated by inelastic light scattering measurements carried down to very low temperatures. Away from nu=1, the ferromagnetic spin wave collapses and a new low-energy spin wave emerges below the Zeeman gap. The emergent spin wave shows soft behavior as its energy increases with temperature and reaches the Zeeman energy for temperatures above 2 K. The observed softening indicates an instability of the two-dimensional electron gas towards a magnetic order that breaks spin rotational symmetry. We discuss our findings in light of the possible existence of a Skyrme crystal. 相似文献
58.
59.
60.
Masahiro Yoshita Yuhei Hayamizu Hidefumi Akiyama Loren N. Pfeiffer Ken W. West 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):230
A T-shaped single quantum-wire laser with high spatial uniformity has been fabricated by a cleaved-edge overgrowth method with molecular beam epitaxy and a growth-interrupt annealing technique. Using micro-photoluminescence imaging and spectroscopy, we confirmed the formation of a spatially uniform quantum wire over 20 μm long without hetero-interface roughness. By optical pumping, we achieved single-mode lasing from the ground state of the single quantum wire at a threshold excitation power as low as 5 mW at 5 K. 相似文献