全文获取类型
收费全文 | 128810篇 |
免费 | 2008篇 |
国内免费 | 982篇 |
专业分类
化学 | 71011篇 |
晶体学 | 2099篇 |
力学 | 5212篇 |
综合类 | 28篇 |
数学 | 12679篇 |
物理学 | 40771篇 |
出版年
2016年 | 1449篇 |
2015年 | 1167篇 |
2014年 | 1541篇 |
2013年 | 5068篇 |
2012年 | 3709篇 |
2011年 | 4732篇 |
2010年 | 2954篇 |
2009年 | 2769篇 |
2008年 | 4174篇 |
2007年 | 4194篇 |
2006年 | 4285篇 |
2005年 | 4140篇 |
2004年 | 3566篇 |
2003年 | 3248篇 |
2002年 | 3152篇 |
2001年 | 3652篇 |
2000年 | 2745篇 |
1999年 | 2270篇 |
1998年 | 1949篇 |
1997年 | 1921篇 |
1996年 | 1863篇 |
1995年 | 1810篇 |
1994年 | 1584篇 |
1993年 | 1564篇 |
1992年 | 1779篇 |
1991年 | 1775篇 |
1990年 | 1703篇 |
1989年 | 1695篇 |
1988年 | 1692篇 |
1987年 | 1686篇 |
1986年 | 1593篇 |
1985年 | 2139篇 |
1984年 | 2264篇 |
1983年 | 1893篇 |
1982年 | 2216篇 |
1981年 | 2032篇 |
1980年 | 2076篇 |
1979年 | 2058篇 |
1978年 | 2186篇 |
1977年 | 2093篇 |
1976年 | 2116篇 |
1975年 | 2053篇 |
1974年 | 1896篇 |
1973年 | 2104篇 |
1972年 | 1282篇 |
1971年 | 976篇 |
1970年 | 913篇 |
1969年 | 923篇 |
1968年 | 1050篇 |
1967年 | 1101篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
F. W. Nijhoff 《Letters in Mathematical Physics》1994,30(4):327-336
We present aq-analog of the discrete Painlevé I equation, and a special realization of it in terms ofq-orthogonal polynomials. 相似文献
102.
R. W. Lourie 《Zeitschrift fur Physik C Particles and Fields》1991,50(2):345-351
We calculate the recoil polarization observables for neutral pion electroproduction on the proton. In particular, for theN(938)→N *(1440) transition, we study these observables for several quark models of the resonant amplitudes. We find that the polarization response functions, unlike the unpolarized cross section, have encouragingly large sensitivity to the presence of the Roper. Furthermore, these observables can clearly reveal the presence of a longitudinal coupling. 相似文献
103.
The temperature dependence of the principal values of the refractive index in Sr1−x
CaxTiO3 (x=0.014) has been measured in the 17–275 K range under various conditions of sample illumination with 1.96 eV photons. The
spontaneous photorefractive contribution δn
ph to the temperature-induced variation of the refractive index of Sr1−x
CaxTiO3, which appears after illumination of the sample in the ferrophase (transition temperature T
c=32 K) and persists in the paraphase under heating up to 150 K, has been separated. The photoinduced polarization has been
estimated.
Fiz. Tverd. Tela (St. Petersburg) 39, 711–713 (April 1997) 相似文献
104.
W. Brüggemann K. Fischer H. Jahnke 《Journal of Mathematical Modelling and Algorithms》2003,2(2):153-169
In Part I of this study, we suggest to identify an operations research (OR) problem with the equivalence class of models describing the problem and enhance the standard computer-science theory of computational complexity to be applicable to this situation of an often model-based OR context. The Discrete Lot-sizing and Scheduling Problem (DLSP) is analysed here in detail to demonstrate the difficulties which can arise if these aspects are neglected and to illustrate the new theoretical concept. In addition, a new minimal model is introduced for the DLSP which makes this problem eventually amenable to a rigorous analysis of its computational complexity. 相似文献
105.
Brandau C. Bartsch T. Böhm S. Böhme C. Hoffknecht A. Kieslich S. Knopp H. Schippers S. Shi W. Müller A. Grün N. Scheid W. Steih T. Bosch F. Franzke B. Kozhuharov C. Krämer A. Mokler P. H. Nolden F. Steck M. Stöhlker T. Stachura Z. 《Hyperfine Interactions》2003,146(1-4):41-45
Hyperfine Interactions - An overview of measurements of dielectronic recombination (DR) with the heaviest lithiumlike ions is presented. The experiments have been carried out at the heavy ion... 相似文献
106.
C. Ziegler F. Baudenbacher H. Karl H. Kinder W. Göpel 《Fresenius' Journal of Analytical Chemistry》1991,341(3-4):308-313
Summary The influence of different preparation conditions and substrate surface orientations on the superconducting properties of thin YBa2Cu3O7–x (YBCO) films on silicon was studied. Comparative electrical and surface spectroscopic measurements were performed. SAM and SIMS depth profile analysis show an enrichment of barium at the interface between the superconductor and silicon for samples with Tc<76 K. Comparison with XPS data obtained for thin silicon films on YBCO indicates the formation of barium and yttrium silicates at the interface under these conditions. 相似文献
107.
We demonstrate a simple passive technique, using phase shifted fibre Bragg gratings, for extraction of optical clock signals from RZ optical data signals . The generation of an optical clock signal at 12.5 GHz from a 12.5 Gbs RZ optical data stream is experimentally demonstrated with simulation of optical clock extraction at 10 GHz fro m 40 Gbs OTDM data streams . 相似文献
108.
W.G. Schmidt 《Applied Physics A: Materials Science & Processing》2002,75(1):89-99
There has been renewed interest in the structure of III-V compound semiconductor (001) surfaces caused by recent experimental
and theoretical findings, which indicate that geometries different from the seemingly well-established dimer models describe
the surface ground state for specific preparation conditions. I review briefly the structure information available on the
(001) surfaces of GaP, InP, GaAs and InAs. These data are complemented with first-principles total-energy calculations. The
calculated surface phase diagrams are used to explain the experimental data and reveal that the stability of specific surface
structures depends largely on the relative size of the surface constituents. Several structural models for the Ga-rich GaAs (001)(4×6)
surface are discussed, but dismissed on energetic grounds. I discuss in some detail the electronic properties of the recently
proposed cation-rich GaAs (001)ζ(4×2) geometry.
Received: 18 May 2001 / Revised version: 23 July 2001 / Published online: 3 April 2002 相似文献
109.
We demonstrate the surprising integrability of the classical Hamiltonian associated to a spin 1/2 system under periodic external fields. The one-qubit rotations generated by the dynamical evolution is, on the one hand, close to that of the rotating wave approximation (RWA), on the other hand to two different “average” systems, according to whether a certain parameter is small or large. Of particular independent interest is the fact that both the RWA and the averaging theorem are seen to hold well beyond their expected region of validity. Finally, we determine conditions for the realization of the quantum NOT operation by means of classical stroboscopic maps. 相似文献
110.
E. Casarejos P. Armbruster L. Audouin J. Benlliure M. Bernas A. Boudard R. Legrain S. Leray B. Mustapha S. Czajkowski T. Enqvist B. Fernandez J. Pereira M. Pravikoff F. Rejmund K. -H. Schmidt C. Stephan J. Taieb L. Tassan-Got C. Villagrasa C. Volant W. Wlazlo 《Physics of Atomic Nuclei》2003,66(8):1413-1420
The isotopic production cross sections of heavy residues in relativistic heavy-ion collisions have been investigated in inverse kinematics. The primary reaction products were fully identified in mass and atomic number prior to beta decay using the fragment separator FRS. The huge collection of data obtained helps in the understanding of the two main reaction mechanisms involved: fragmentation and fission. These data provide basic information for future radioactive ion beam facilities and for technical applications like intense neutron sources by means of spallation targets. 相似文献