全文获取类型
收费全文 | 482294篇 |
免费 | 3041篇 |
国内免费 | 719篇 |
专业分类
化学 | 222096篇 |
晶体学 | 6915篇 |
力学 | 27615篇 |
综合类 | 9篇 |
数学 | 73894篇 |
物理学 | 155525篇 |
出版年
2020年 | 4257篇 |
2019年 | 5052篇 |
2018年 | 12382篇 |
2017年 | 12790篇 |
2016年 | 12277篇 |
2015年 | 5152篇 |
2014年 | 8738篇 |
2013年 | 17504篇 |
2012年 | 16889篇 |
2011年 | 24649篇 |
2010年 | 17667篇 |
2009年 | 17998篇 |
2008年 | 22670篇 |
2007年 | 24855篇 |
2006年 | 14483篇 |
2005年 | 16142篇 |
2004年 | 13642篇 |
2003年 | 13050篇 |
2002年 | 12087篇 |
2001年 | 11265篇 |
2000年 | 9055篇 |
1999年 | 6670篇 |
1998年 | 6125篇 |
1997年 | 5915篇 |
1996年 | 5523篇 |
1995年 | 5008篇 |
1994年 | 5035篇 |
1993年 | 4916篇 |
1992年 | 5122篇 |
1991年 | 5629篇 |
1990年 | 5406篇 |
1989年 | 5409篇 |
1988年 | 5158篇 |
1987年 | 5153篇 |
1986年 | 4774篇 |
1985年 | 5796篇 |
1984年 | 6139篇 |
1983年 | 5198篇 |
1982年 | 5528篇 |
1981年 | 5122篇 |
1980年 | 4829篇 |
1979年 | 5404篇 |
1978年 | 5646篇 |
1977年 | 5568篇 |
1976年 | 5719篇 |
1975年 | 5344篇 |
1974年 | 5260篇 |
1973年 | 5459篇 |
1972年 | 4275篇 |
1971年 | 3855篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
231.
232.
We use the eikonal approximation to develop a general formula for the cross sections of inelastic collisions of multicharged
fast ions (including relativistic ions) with atoms that is applicable within a broad range of collision energies, has the
standard nonrelativistic limit, and becomes, in the ultrarelativistic case, the well-known result that follows from the exact
solution of the Dirac equation. As an example we study the excitation and ionization of a hydrogenlike atom, the single and
double excitation and ionization of a heliumlike atom, and multiple (up to the eighth order) ionization of the neon atom and
(up to eighteenth order) ionization of the argon atom. We derive simple analytical expressions for the inelastic cross sections
and establish recurrence relations linking the cross sections of ionization of different orders. Finally, we compare our results
with the experimental data.
Zh. éksp. Teor. Fiz. 114, 1646–1660 (November 1998) 相似文献
233.
234.
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
235.
236.
Stephen C. Littlechild 《The Journal of the Operational Research Society》1996,47(5):601-611
In this Blackett Lecture, Professor Littlechild, Director General of Electricity Supply in the UK's Office of Electricity Regulation, renews acquaintance with some models he has developed over the years, introduces some models he has recently met, and discusses models that it would seem to be worthwhile developing. He concludes that for all concerned in the electricity industry, success depends on ever improving decision-making, in which OR has a vital role. 相似文献
237.
Highly sensitive optical reflectivity measurements are used to investigate the layer-by-layer transition in extremely thin
and thick N-(4-n-hexyloxybenzylidene)-4-n-hexylaniline (6O.6) films. The simple power-law form, N=N
0
t
−1/3, for the penetration of the crystal-B order is found to describe the transitions only near the surface. A deviation from
the power law is observed for the interior layers.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 4, 266–269 (25 February 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
238.
Open circuit voltage (OCV) measurements in H2O/air concentration cells at T<580 K using Yb-doped SrCeO3 electrolyte indicate that under these conditions, protons are transported through the electrolyte as -ve ions, possibly as
hydroxyl (OH−) ions. The H+ ionic transport, which is generally reported, becomes the dominant mode for H2O/air concentration cells at temperatures greater than 750 K or when H2O/air electrodes are replaced by H2/Ar, and the anomalous OCV sign disappears. The combination of low temperature and the presence of hydrogen and oxygen as
provided by the H2O/air system appears to be necessary for the postulated hydroxyl ion electrode reactions to take place.
In addition to OCV measurements, results from impedance spectroscopy are used to provide evidence in support of the suggested
hydroxyl ion mode of protonic transport under the specified conditions. These findings are directly relevant in the development
of novel humidity sensors in the temperature range 450–580K and is reported in a separate paper in this conference.
Paper presented at the 3rd Euroconference on Solid State Ionics, Teulada, Sardinia, Italy, Sept. 15–22, 1996 相似文献
239.
NaY zeolite samples loaded with sodium metal by vapor phase deposition have been investigated using129Xe NMR spectroscopy. At low sodium concentration, the129Xe NMR spectrum showed three resonance lines which clearly indicate the existence of distinct domains in the zeolite sample. Such an observation suggests that the diffusion of the xenon atoms into each domain only occurs with respect to the NMR time scale (2.9 ms). As the sodium concentration increases, observation of a single broad line indicate a macroscopic homogenization of the system. The shift of this line is explained in part due to a paramagnetic interaction between the xenon atoms and the unpaired electrons of particles containing an odd number of sodium atoms. The linewidth is due to the distribution of the local magnetic fields partially averaged by the rapid motion of the xenon atoms and to the statistical distribution of the sodium particles in the supercage cavities. The paramagnetic interaction vanishes with the oxidation of the sample leading to a narrowing and a shift of the line to higher magnetic fields. 相似文献
240.
V. I. Verkhoturov O. S. Grafodatskii V. I. Simanchuk A. V. Kargapol'tsev 《Russian Physics Journal》1993,36(9):865-869
Experimental results are presented on acoustic probing of electric fields in solid insulators. An experimental apparatus and methods are described for acoustic measurements of the bulk space charge density and electric field strength in solid insulators. The sensitivity and spatial resolution of the acoustic probe technique are determined.Institute of Introscopy Research, Polytechnical University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 62–67, September, 1993. 相似文献