全文获取类型
收费全文 | 152705篇 |
免费 | 1349篇 |
国内免费 | 384篇 |
专业分类
化学 | 81973篇 |
晶体学 | 2028篇 |
力学 | 6657篇 |
综合类 | 7篇 |
数学 | 15279篇 |
物理学 | 48494篇 |
出版年
2020年 | 1113篇 |
2019年 | 1171篇 |
2018年 | 1475篇 |
2017年 | 1451篇 |
2016年 | 2467篇 |
2015年 | 1545篇 |
2014年 | 2422篇 |
2013年 | 6315篇 |
2012年 | 4927篇 |
2011年 | 6257篇 |
2010年 | 4277篇 |
2009年 | 4290篇 |
2008年 | 5691篇 |
2007年 | 5767篇 |
2006年 | 5405篇 |
2005年 | 4992篇 |
2004年 | 4409篇 |
2003年 | 3852篇 |
2002年 | 3882篇 |
2001年 | 4333篇 |
2000年 | 3316篇 |
1999年 | 2572篇 |
1998年 | 2241篇 |
1997年 | 2184篇 |
1996年 | 1981篇 |
1995年 | 1897篇 |
1994年 | 1886篇 |
1993年 | 1726篇 |
1992年 | 1991篇 |
1991年 | 2119篇 |
1990年 | 1917篇 |
1989年 | 1916篇 |
1988年 | 1856篇 |
1987年 | 1755篇 |
1986年 | 1692篇 |
1985年 | 2193篇 |
1984年 | 2324篇 |
1983年 | 1897篇 |
1982年 | 2080篇 |
1981年 | 1964篇 |
1980年 | 1888篇 |
1979年 | 2029篇 |
1978年 | 2197篇 |
1977年 | 2067篇 |
1976年 | 2112篇 |
1975年 | 2019篇 |
1974年 | 2072篇 |
1973年 | 2060篇 |
1972年 | 1354篇 |
1971年 | 1210篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
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
212.
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
213.
We analyse some identifiers which can univocally identify hyperbolic components and Misiurewicz points of one-dimensional quadratic maps. After seeing the equivalence among the different identifiers and how to go from one to another, we show which are the best for some specific tasks. Likewise, we present the analytic expressions, some of them shown for the first time in this paper, to calculate these identifiers. Some experimental considerations are taken into account. 相似文献
214.
215.
A ring R has right SIP (SSP) if the intersection (sum) of two direct summands of R is also a direct summand. We show that the right SIP (SSP) is the Morita invariant property. We also prove that the trivial extension of R by M has SIP if and only if R has SIP and (1 – e)Me = 0 for every idempotent e in R. Moreover, we give necessary and sufficient conditions for the generalized upper triangular matrix rings to have SIP. 相似文献
216.
217.
M. A. Sakhbetdinov P. F. Kartsev 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(8):1115-1117
Schemes and calculated characteristics of effective logic elements with two inputs for classical ground-state computations are reported. These elements have a high threshold (0.48) and perform a desired logical operation in a wide range of input signals. 相似文献
218.
Hyperfine Interactions - The YFe4Al8 and ErFe4Al8 intermetallics were studied by57Fe Mössbauer spectroscopy between 2 K and room temperature. The spectra are consistent with iron occupying 8f... 相似文献
219.
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
220.
C. Bréchignac Ph. Cahuzac F. Carlier C. Colliex M. de Frutos N. Kébaïli J. Le Roux A. Masson B. Yoon 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):265-268
We studied shape relaxation of nano-fractal islands,
during annealing, after their growth from antimony cluster
deposition on graphite surface. Annealing at
180°C shows evidence of an increase
of the fractal branch width with time followed by branch
fragmentation, without changing the fractal dimension. The time
evolution of the width of the arm suggests the surface
self-diffusion mechanism as the main relaxation process. With
Monte Carlo simulations, we confirmed the observed behavior.
Comparison is done with our previous results on fragmentation of
nano-fractal silver islands when impurity added to the incident
cluster promotes rapid fragmentation by surface self-diffusion
enhancement [1]. 相似文献