全文获取类型
收费全文 | 1173篇 |
免费 | 74篇 |
国内免费 | 143篇 |
专业分类
化学 | 440篇 |
晶体学 | 27篇 |
力学 | 65篇 |
综合类 | 1篇 |
数学 | 420篇 |
物理学 | 437篇 |
出版年
2023年 | 16篇 |
2022年 | 34篇 |
2021年 | 16篇 |
2020年 | 34篇 |
2019年 | 34篇 |
2018年 | 32篇 |
2017年 | 23篇 |
2016年 | 13篇 |
2015年 | 28篇 |
2014年 | 36篇 |
2013年 | 83篇 |
2012年 | 54篇 |
2011年 | 107篇 |
2010年 | 65篇 |
2009年 | 119篇 |
2008年 | 99篇 |
2007年 | 93篇 |
2006年 | 98篇 |
2005年 | 53篇 |
2004年 | 50篇 |
2003年 | 38篇 |
2002年 | 41篇 |
2001年 | 30篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 23篇 |
1995年 | 15篇 |
1994年 | 6篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1981年 | 2篇 |
1979年 | 2篇 |
排序方式: 共有1390条查询结果,搜索用时 15 毫秒
1.
2.
《Discrete Mathematics》2019,342(2):339-343
A strong edge-coloring of a graph is a partition of its edge set into induced matchings. Let be a connected planar graph with girth and maximum degree . We show that either is isomorphic to a subgraph of a very special -regular graph with girth , or has a strong edge-coloring using at most colors. 相似文献
3.
In a previous paper (Ref. 1), an exact solution of the optimal planar interception with fixed end conditions was derived in closed form. The optimal control was expressed as an explicit function of the state variables and two fixed parameters, obtained by solving a set of nonlinear algebraic equations involving elliptic integrals. In order to facilitate the optimal control implementation, the present paper derives a highly accurate simplified solution assuming that the ratio of the pursuer turning radius to the initial range is small. An asymptotic expansion further reduces the computational workload. Construction of a near-optimal open-loop control, based on the approximations, completes the present paper. 相似文献
4.
Lubomir Spanhel 《Journal of Sol-Gel Science and Technology》2006,39(1):7-24
The past research work devoted to ZnO nanocolloidal sol-gel route is reviewed. It highlights the cluster chemistry of alcoholic
ZnAc2 solutions and the results of ZnO colloid growth investigations performed worldwide. Moreover, the role of doping and co-doping
in the processing of functional ZnO coatings is discussed. The possibilities of tuning the optical properties are also reported
with a particular attention to luminescence. The last part of this paper deals with electrical and photoelectrochemical properties
of ZnO nanocrystals and their aggregates.
This contribution is dedicated to the 80th birthday of Prof. Arnim Henglein from the Hahn-Meitner-Institut in Berlin and to
the memory of Prof. Jacques Mugnier from the Université Claude-Bernard Lyon 1 in France. 相似文献
5.
Proton conductivity of phosphoric acid derivative of fullerene 总被引:1,自引:0,他引:1
The proton conductive property of methano [60] fullerene diphosphoric acid has been investigated under various humidity conditions at the temperature range between 15 and 45 °C. It shows proton conductivity as high as 10−2 S cm−1 at 25 °C under relative humidity of 95%. Thermal analyses including TG–DTA and thermal desorption mass spectroscopy (TDS) confirm that the compound is thermally stable up to 200 °C. Proton conduction of the compound depends very much on humidity or water content. The logarithmic conductivity at 25 °C is increased linearly with increasing relative humidity. The activation energy (Ea) estimated from the slope of log(σT) vs. 1/T is decreased from 1.08 to 0.52 eV, as the relative humidity is increased from 40% to 75%. The humidity dependence of conductivity is discussed in the light of the observed hydration isotherm. 相似文献
6.
Could simple intraannular-arm macrocyclic systems exist in enantiopure stable forms? The effective synthesis of two representative compounds of such a class, their resolution into enantiomers, and experiments justifying their stability toward racemization are presented. 相似文献
7.
8.
在水热晶化合成一系列NASICON型化合物的基础上,应用固体高分辨31P和29Si MAS NMR,研究了几种NASICON化合物的结构,观察其骨架原子P和Si在结构中的状态及分布,并解释了由于在结构中发生取代作用而引起,Si或P的化学位移的变化. 相似文献
9.
In a graph, a cluster is a set of vertices, and two clusters are said to be non-intersecting if they are disjoint or one of them is contained in the other. A clustered graph C consists of a graph G and a set of non-intersecting clusters. In this paper, we assume that C has a compound planar drawing and each cluster induces a biconnected subgraph. Then we show that such a clustered graph admits a drawing in the plane such that (i) edges are drawn as straight-line segments with no edge crossing and (ii) the boundary of the biconnected subgraph induced by each cluster is a convex polygon. 相似文献
10.
We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design. 相似文献