全文获取类型
收费全文 | 203篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 64篇 |
晶体学 | 1篇 |
力学 | 3篇 |
数学 | 115篇 |
物理学 | 25篇 |
出版年
2023年 | 2篇 |
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 2篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 5篇 |
2013年 | 17篇 |
2012年 | 15篇 |
2011年 | 14篇 |
2010年 | 5篇 |
2009年 | 8篇 |
2008年 | 7篇 |
2007年 | 11篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 3篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
1972年 | 2篇 |
1971年 | 3篇 |
排序方式: 共有208条查询结果,搜索用时 15 毫秒
51.
S,S-dialkyl dithiocarbonates such as S,S-dimethyl dithiocarbonate and S,S-diethyl dithiocarbonate were tested as solvents
for rechargeable lithium ion batteries. Graphite electrodes can be successfully cycled at high reversible capacities in an
S,S-dimethyl dithiocarbonate solution containing 1 M LiAsF6, while lithium ions cannot intercalate into graphite in S,S-diethyl dithiocarbonate solutions. Fourier transform infrared
spectroscopy, cyclic voltammetry and chronopotentiometric methods were used in order to monitor the reaction mechanism.
Received: 23 April 1997 / Accepted: 5 June 1997 相似文献
52.
An infinite cardinal λ is Magidor if and only if . It is known that if λ is Magidor then for some , and the first such α is denoted by . In this paper we try to understand some of the properties of . We prove that can be the successor of a supercompact cardinal, when λ is a Magidor cardinal. From this result we obtain the consistency of being a successor of a singular cardinal with uncountable cofinality. 相似文献
53.
An active flow control experiment was conducted on a cropped NACA 0018 airfoil to study 3D effects and maneuverability aspects
made possible by a segmented actuation system installed in the airfoil. The 14 piezo-fluidic actuators were installed at the
corner of the cropped region, inclined at 30° to the local surface, facing downstream. Operating all actuators at unison significantly
increased lift and generated a pitch-down moment. Operating all actuators at the same magnitude but varying the phase along
the span generated larger lift-increment, with respect to the uniform phase excitation. Significant rolling moment can be
generated when only half-span of the wing is actuated. The latter effect, as indicated by the 3D pressure distribution, persists
to the leading edge even though the excitation was introduced close to the trailing edge. When a pair, out of the possible
fourteen actuators is not operating, very little of the control authority is lost. This is an important finding when issues like fault tolerance and robustness
of fluidic-piezo actuators are considered. 相似文献
54.
Lev M. Bregman Yair Censor Simeon Reich Yael Zepkowitz-Malachi 《Journal of Approximation Theory》2003,124(2):194-218
We present a modification of Dykstra's algorithm which allows us to avoid projections onto general convex sets. Instead, we calculate projections onto either a half-space or onto the intersection of two half-spaces. Convergence of the algorithm is established and special choices of the half-spaces are proposed.The option to project onto half-spaces instead of general convex sets makes the algorithm more practical. The fact that the half-spaces are quite general enables us to apply the algorithm in a variety of cases and to generalize a number of known projection algorithms.The problem of projecting a point onto the intersection of closed convex sets receives considerable attention in many areas of mathematics and physics as well as in other fields of science and engineering such as image reconstruction from projections.In this work we propose a new class of algorithms which allow projection onto certain super half-spaces, i.e., half-spaces which contain the convex sets. Each one of the algorithms that we present gives the user freedom to choose the specific super half-space from a family of such half-spaces. Since projecting a point onto a half-space is an easy task to perform, the new algorithms may be more useful in practical situations in which the construction of the super half-spaces themselves is not too difficult. 相似文献
55.
Garti Shimon Hayut Yair Horowitz Haim Magidor Menachem 《Periodica Mathematica Hungarica》2022,84(2):250-258
Periodica Mathematica Hungarica - We study the Galvin property. We show that various square principles imply that the cofinality of the Galvin number is uncountable (or even greater than $$\aleph... 相似文献
56.
We construct an innite family of (q + 1)-regular Ramanujan graphs
X
n
of girth 1. We also give
covering maps X
n+1
X
n
such that the minimal
common covering of all the X
n
s is the universal
covering tree. 相似文献
57.
Pareto optimality in multiobjective problems 总被引:2,自引:0,他引:2
Yair Censor 《Applied Mathematics and Optimization》1977,4(1):41-59
In this study, the optimization theory of Dubovitskii and Milyutin is extended to multiobjective optimization problems, producing new necessary conditions for local Pareto optima. Cones of directions of decrease, cones of feasible directions and a cone of tangent directions, as well as, a new cone of directions of nonincrease play an important role here. The dual cones to the cones of direction of decrease and to the cones of directions of nonincrease are characterized for convex functionals without differentiability, with the aid of their subdifferential, making the optimality theorems applicable. The theory is applied to vector mathematical programming, giving a generalized Fritz John theorem, and other applications are mentioned. It turns out that, under suitable convexity and regularity assumptions, the necessary conditions for local Pareto optima are also necessary and sufficient for global Pareto optimum. With the aid of the theory presented here, a result is obtained for the, so-called, scalarization problem of multiobjective optimization.The author's work in this area is now supported by NIH grants HL 18968 and HL 4664 and NCI contract NO1-CB-5386. 相似文献
58.
59.
A closed-form solution is provided for the problem of finding the closest reflection-symmetric object, and its relation to the problems of finding the closest achiral object, the closest inversion-symmetric object, and the closest projection plane is discussed. The key to the solution is reducing this problem to the problem of finding the best (least squares) c2 rotation between two sets of points, in addition to solving the problem of finding the closest C2-symmetric object. The solution is derived using the quaternion representation of rotation. It is shown that calculation of the best c2 rotation can be reduced to the diagonalization of the outer product matrix of the pair (between the two sets). ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 772–780, 1999 相似文献
60.
Yair Caro 《Journal of Graph Theory》1997,25(1):85-94
A graph is well-covered if every maximal independent set is maximum. This concept, introduced by Plummer in 1970 (J. Combin. Theory 8 (1970)), is the focal point of much interest and current research. We consider well-covered 2-degenerate graphs and supply a structural (and polynomial time algorithm) characterization of the class called 3-separable graphs. Also we consider parity graphs studied by Finbow and Hartnell and answer the question posed by them (Ars. Combin. 40 (1995)) by proving, among other results, that the decision problem: “given a graph G which is a parity graph, is G also well-covered graph?” is in the class CO-NPC. In addition we supply some complexity results that answer some problems due to Plummer (Quaestiones Math. 16 (1993)) and Finbow, Hartnell, and Whitehead (Discrete Math. 125 (1994)). © 1997 John Wiley & Sons, Inc. J Graph Theory 25: 85–94, 1997 相似文献