全文获取类型
收费全文 | 2074篇 |
免费 | 59篇 |
国内免费 | 7篇 |
专业分类
化学 | 1176篇 |
晶体学 | 7篇 |
力学 | 38篇 |
数学 | 380篇 |
物理学 | 539篇 |
出版年
2020年 | 17篇 |
2019年 | 32篇 |
2018年 | 15篇 |
2016年 | 45篇 |
2015年 | 42篇 |
2014年 | 24篇 |
2013年 | 72篇 |
2012年 | 100篇 |
2011年 | 91篇 |
2010年 | 67篇 |
2009年 | 71篇 |
2008年 | 83篇 |
2007年 | 86篇 |
2006年 | 82篇 |
2005年 | 65篇 |
2004年 | 63篇 |
2003年 | 50篇 |
2002年 | 48篇 |
2001年 | 51篇 |
2000年 | 42篇 |
1999年 | 21篇 |
1998年 | 37篇 |
1997年 | 25篇 |
1996年 | 28篇 |
1995年 | 20篇 |
1994年 | 26篇 |
1993年 | 42篇 |
1992年 | 32篇 |
1991年 | 27篇 |
1990年 | 27篇 |
1989年 | 19篇 |
1988年 | 21篇 |
1987年 | 23篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 27篇 |
1983年 | 26篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 31篇 |
1978年 | 32篇 |
1977年 | 25篇 |
1976年 | 17篇 |
1975年 | 30篇 |
1974年 | 14篇 |
1973年 | 19篇 |
1971年 | 19篇 |
1970年 | 16篇 |
1969年 | 19篇 |
排序方式: 共有2140条查询结果,搜索用时 32 毫秒
1.
P. Seelig A. Dax S. Faber M. Gerlach G. Huber T. Kühl D. Marx P. Merz W. Quint F. Schmitt H. Winter M. Würtz 《Hyperfine Interactions》1998,114(1-4):135-139
The investigation of the 1s HFS provides a good possibility for testing QED effects in a combination of a strong electric
and magnetic field. Here, we report about the laserspectroscopic measurements of the ground state hyperfine splitting in 207Pb81+. To handle this M1-transition in the infrared optical regime with its long lifetime, we developed a new detection technique
using a bunched ion beam. For the observation of fluorescence light, a new mirror system is adapted to the emission characteristics
from an ion beam at relativistic velocities.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
2.
Erwin Bolthausen Jean-Dominique Deuschel Uwe Schmock 《Probability Theory and Related Fields》1993,95(3):283-310
Summary We discuss the limiting path measures of Markov processes with either a mean field or a polaron type interaction of the paths. In the polaron type situation the strength is decaying at large distances on the time axis, and so the interaction is of short range in time. In contrast, in the mean field model, the interaction is weak, but of long range in time. Donsker and Varadhan proved that for the partition functions, there is a transition from the polaron type to the mean field interaction when passing to a limit by letting the strength tend to zero while increasing the range. The discussion of the path measures is more subtle. We treat the mean field case as an example of a differentiable interaction and discuss the transition from the polaron type to the mean field interaction for two instructive examples.Research supported by the Swiss National Foundation (21-29833.90)This article was processed by the authors using the Springer-Verlag TEX ProbTh macro package 1991. 相似文献
3.
T. Engel M. Würtz S. Borneis St. Becker I. Klaft A. Kohl T. Kühl F. Laeri D. Marx K. Meier R. Neumann F. Schmitt P. Seelig L. Völker 《Hyperfine Interactions》1997,108(1-3):251-258
Laser spectroscopy at storage rings often suffers from a limited resolution due to Doppler-broadened resonances. Broadening
is caused by the velocity spread of the ions stored in the beam. In the following, the present status of our work on laser
systems specialized on the specific needs of laser spectroscopy at storage rings is reported.
Two pulsed laser systems were developed. One is a dye laser whose spectral bandwidth can be switched by inserting different
Littrow-prisms into the resonator. An increase in bandwidth up to a factor of 45 was achieved. This laser was used for fast
qualitative scans and high resolution measurements. The other laser system is a Nd : YAG laser pumped optical parametric oscillator.
It is a tunable laser system covering the spectral range from 410 to 4000 nm. Furthermore, a continuous wave laser with a
frequency shifted feedback cavity is described. It shows broadband emission with an adjustable bandwidth of up to 4.5 GHz.
This laser can be advantageous for laser cooling of ion beams.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
4.
5.
The magnetic properties of a TbNi2Si2 single crystal have been investigated experimentally by specific heat, anisotropy of the susceptibility and magnetization, and inelastic neutron scattering, leading to the determination of its fundamental coupling parameters. The lowest crystalline electric field states are two singlets close to each other, that explains the different magnetic structures evidenced in TbNi2Si2: an amplitude modulated structure, close to T N , a simple antiferromagnetic one at low temperature and an antiphase one when an external magnetic field is applied along the c direction. 相似文献
6.
7.
8.
The synthesis of a specific isotopomer, C6D4H(ortho)-H(ortho)D4C6 of biphenyl is reported. The intramolecular dipolar coupling of the protons leads to a well-resolved single-crystal proton
nuclear magnetic resonance (NMR) spectrum and allows one to study the dynamics of the phenyl rings in a unique way. At room
temperature and above, the most conspicuous dynamical mode consists of 180° ring flips. The present data together with previous
measurements of the total flip rate allow us to conclude that the rings flip almost exclusively independently of each other.
Between the incommensurate (IC) phase transition of biphenyl at 38 K andT=250 K, the prominent namical mode consists of oscillatory twists ϕ(t) of the two rings. The data allow us to infer the mean square, (φ2), of these twists. (φ2) is found to grow linearly withT for 50<T<200 K. From the slope of (φ2) vs.T the frequency (the wave number[(v)\tilde]\tilde v) is derived. The result is[(v)\tilde] = 20\tilde v = 20 cm−1. ForT<38 K, the spectra give direct evidence of the IC phase transition and its nature (stripelike rather than quiltlike). The
temperature dependence of the magnitude of the order parameter of the IC phase is obtained. 相似文献
9.
Electronic speckle interferometry (ESPI) is used to determine the Young's modulus E and Poisson ratio ν of an isotropic material. Micron scale deformations of the surface of the block of polymethyl-methacrylate (PMMA) are induced by normal application of a known near-point force. These deformations are recorded in speckle interferometric fringe patterns. An iterative minimum error inversion technique is developed to obtain the elastic properties from the positions of fringe peaks and troughs observed in the fringe patterns. Sensitivity tests of the method on calculated fringe patterns using measured experimental uncertainties suggest the technique will provide measures of the elastic moduli to better than 5%. In an experimental test on a bloc of PMMA (acrylic) the technique gave values of E and ν that differed from corresponding measures obtained using more conventional strain-gauge methods by less than 4%. 相似文献