全文获取类型
收费全文 | 42939篇 |
免费 | 3752篇 |
国内免费 | 3029篇 |
专业分类
化学 | 30623篇 |
晶体学 | 585篇 |
力学 | 1569篇 |
综合类 | 262篇 |
数学 | 4646篇 |
物理学 | 12035篇 |
出版年
2024年 | 45篇 |
2023年 | 426篇 |
2022年 | 1024篇 |
2021年 | 1170篇 |
2020年 | 1132篇 |
2019年 | 1163篇 |
2018年 | 960篇 |
2017年 | 996篇 |
2016年 | 1571篇 |
2015年 | 1502篇 |
2014年 | 2011篇 |
2013年 | 2879篇 |
2012年 | 3435篇 |
2011年 | 3663篇 |
2010年 | 2574篇 |
2009年 | 2333篇 |
2008年 | 3051篇 |
2007年 | 2626篇 |
2006年 | 2556篇 |
2005年 | 2143篇 |
2004年 | 1890篇 |
2003年 | 1585篇 |
2002年 | 1615篇 |
2001年 | 1119篇 |
2000年 | 877篇 |
1999年 | 727篇 |
1998年 | 493篇 |
1997年 | 408篇 |
1996年 | 492篇 |
1995年 | 350篇 |
1994年 | 353篇 |
1993年 | 347篇 |
1992年 | 274篇 |
1991年 | 263篇 |
1990年 | 203篇 |
1989年 | 186篇 |
1988年 | 115篇 |
1987年 | 128篇 |
1986年 | 99篇 |
1985年 | 127篇 |
1984年 | 73篇 |
1983年 | 57篇 |
1982年 | 76篇 |
1981年 | 76篇 |
1980年 | 43篇 |
1979年 | 55篇 |
1978年 | 55篇 |
1977年 | 43篇 |
1976年 | 50篇 |
1975年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
61.
文章简要地叙述了法国著名物理学家路易·奈尔的成长历程与生平业绩,其中包括他在磁学领域的诸多重大贡献、成功地创立和领导了一个富有成就的科学研究团体以及他堪称为一位出色的科技开发企业家的风范. 相似文献
62.
Burn‐in is a widely used method to improve the quality of products or systems after they have been produced. In this paper, we consider the problem of determining the optimal burn‐in time and optimal work size maximizing the long‐run average amount of work saved per time unit in the computer applications. Assuming that the underlying lifetime distribution of the computer has an initially decreasing or/and eventually increasing failure rate function, an upper bound for the optimal burn‐in time is derived for each fixed work size and a uniform (with respect to the burn‐in time) upper bound for the optimal work size is also obtained. Furthermore, it is shown that a non‐trivial lower bound for the optimal burn‐in time can be derived if the underlying lifetime distribution has a large initial failure rate. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
63.
Jiří Herec 《Czechoslovak Journal of Physics》2004,54(12):1473-1481
In this paper the quantum-statistical properties of light beams propagating in a directional nonlinear coupler are investigated.
This device is composed of a pair of linearly coupled nonlinear waveguides operating by means of degenerate parametric downconversion.
The possibility of generation of nonclassical states of light in single and compound modes, using the short-length approximation,
is discussed. Influence of linear and nonlinear mismatches for generation of nonclassical light is taken into account.
This work was supported by Project LN00A015, Research Project No. CEZ: J14/98 and the COST project OC P11.003 of the Czech
Ministry of Education. 相似文献
64.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and
first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
65.
66.
The Mannich-type reaction of imines with (1-methoxy-2-methylpropenyloxy)trimethylsilane and aza-Diels-Alder reaction of imines with Danishefsky's diene can be carried out in scCO2 in the presence of lithium heptadecafluorooctanesulfonate which offer a way to synthesize β-amino carbonyl compounds and nitrogen-containing six-membered ring compounds under environmentally benign conditions. 相似文献
67.
A parallel DSMC method based on a cell‐based data structure is developed for the efficient simulation of rarefied gas flows on PC‐clusters. Parallel computation is made by decomposing the computational domain into several subdomains. Dynamic load balancing between processors is achieved based on the number of simulation particles and the number of cells allocated in each subdomain. Adjustment of cell size is also made through mesh adaptation for the improvement of solution accuracy and the efficient usage of meshes. Applications were made for a two‐dimensional supersonic leading‐edge flow, the axi‐symmetric Rothe's nozzle, and the open hollow cylinder flare flow for validation. It was found that the present method is an efficient tool for the simulation of rarefied gas flows on PC‐based parallel machines. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
68.
The glow curve structures for LiF:Mg,Cu,Na,Si TL detectors with various dopant concentrations and sintering temperatures were investigated for the improvement of the glow curve structure and sensitivity of the TL detector. The dopant concentrations were varied over the following ranges: Mg (0–0.25 mol%), Cu (0–0.07 mol%), Na and Si (0–1.5 mol%). With increasing Cu concentration, the intensity of the main peak was intensified and reached a maximum at a concentration of 0.05 mol%. The high-temperature peak was reduced. The dependency of the main peak intensity on the Mg concentration exhibits a sharp maximum at 0.2 mol%. The intensity of the high-temperature peak tends to rise slightly with increasing Mg concentration. It was found that the optimum concentrations of the dopants in the LiF:Mg,Cu,Na,Si TL material are Mg: 0.2 mol%, Cu: 0.05 mol%, Na and Si: 0.9 mol%. The dependency of the main peak intensity on sintering temperature exhibits a very sharp maximum at 830°C. The high-temperature peak was rapidly reduced after 825°C. 相似文献
69.
P. D. Kim I. A. Turpanov S. V. Stolyar R. S. Iskhakov V. I. Yushkov A. Ya. Beten’kova L. A. Li E. V. Bondareva T. N. Isaeva M. M. Karpenko 《Technical Physics》2004,49(4):431-434
The crystal structure and hysteretic magnetic properties of equiatomic single-crystal CoPt films applied on MgO substrates
by magnetron sputtering, as well as modification of these properties by thermal annealing, are studied. Heat-treated films
of thickness in the range 2<d≤16 nm exhibit perpendicular magnetic anisotropy. A correlation between the crystalline anisotropy constant of the CoPt films
and the order parameter of the LI0 superstructure in these alloys is found. The effect of a single-crystalline MgO substrate on the structure and magnetic properties
of equiatomic CoPt films is revealed. 相似文献
70.
Russian Physics Journal - 相似文献