全文获取类型
收费全文 | 328篇 |
免费 | 13篇 |
国内免费 | 3篇 |
专业分类
化学 | 180篇 |
力学 | 4篇 |
数学 | 67篇 |
物理学 | 93篇 |
出版年
2023年 | 2篇 |
2021年 | 2篇 |
2019年 | 6篇 |
2018年 | 2篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 12篇 |
2014年 | 8篇 |
2013年 | 12篇 |
2012年 | 15篇 |
2011年 | 23篇 |
2010年 | 19篇 |
2009年 | 8篇 |
2008年 | 21篇 |
2007年 | 8篇 |
2006年 | 27篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 11篇 |
2002年 | 11篇 |
2001年 | 4篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 7篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 9篇 |
1972年 | 2篇 |
1970年 | 4篇 |
1966年 | 1篇 |
1941年 | 1篇 |
1920年 | 2篇 |
排序方式: 共有344条查询结果,搜索用时 15 毫秒
51.
A new formulation for the channel capacity problem is derived by using the duality theory of convex programming. The simple nature of this dual representation is suitable for computational purposes. The results are derived in a unified way by formulating the channel capacity problem as a special case of a general class of concave programming problems involving a generalized information measure recently introduced by Burbea and Rao [10].Research supported by National Science Foundation Grant No. ECS-8604354. 相似文献
52.
53.
54.
55.
The polar Kerr effect in the spin-triplet superconductor Sr2RuO4 was measured with high precision using a Sagnac interferometer with a zero-area Sagnac loop. We observed nonzero Kerr rotations as big as 65 nanorad appearing below Tc in large domains. Our results imply a broken time-reversal symmetry state in the superconducting state of Sr2RuO4, similar to 3He-A. 相似文献
56.
We show that in atomic gases cooperative effects like superradiance and subradiance lead to a potential between two atoms that decays like 1/r. In the case of superradiance, this potential is attractive for close enough atoms and can be interpreted as a coherent mesoscopic effect. The contribution of superradiant pairs to multiple scattering properties of a dilute gas, such as photon elastic mean free path and group velocity, is significantly different from that of independent atoms. We discuss the conditions under which these effects may be observed and compare our results to recent experiments on photon transport in cold atomic gases. 相似文献
57.
The stable adsorption sites for both Ga and N ions on the ideal and on the reconstructed LiNbO3 (0 0 0 1) surface are determined by means of first-principle total energy calculations. A single N layer is found to be more strongly bound to the substrate than a single Ga layer. The adsorption of a GaN monolayer on the polar substrate within different orientations is then modeled. On the basis of our results, we propose a microscopic model for the GaN/LiNbO3 interface. The GaN and LiNbO3 (0 0 0 1) planes are parallel, but rotated by 30° each other, with in-plane epitaxial relationship [1 0 0]GaN‖ [1 1 0]LiNbO3. In this way the (0 0 0 1) plane lattice mismatch between GaN and LiNbO3 is minimal and equal to 6.9% of the GaN lattice constant. The adsorbed GaN and the underlying LiNbO3 substrate have parallel c-axes. 相似文献
58.
We describe a general scheme for solving nonconvex optimization problems, where in each iteration the nonconvex feasible set
is approximated by an inner convex approximation. The latter is defined using an upper bound on the nonconvex constraint functions.
Under appropriate conditions, a monotone convergence to a KKT point is established. The scheme is applied to truss topology
design (TTD) problems, where the nonconvex constraints are associated with bounds on displacements and stresses. It is shown
that the approximate convex problem solved at each inner iteration can be cast as a conic quadratic programming problem, hence
large scale TTD problems can be efficiently solved by the proposed method. 相似文献
59.
60.
Charlotte Ashworth Christian Weller Gero Frisch 《Journal of separation science》2019,42(15):2517-2522
A methodology has been developed to chromatographically quantify indium in polymetallic (bio)hydrometallurgical processing solutions using the Dionex IonPac CS5A column and pyridine‐2,6‐dicarboxylic acid eluent. Cu(II) and In(III) could be separated by elevating the column temperature to 45°C. The comparatively low stability constant of the In‐eluent complex (log K2 = 3.8) required typical leaching samples to be diluted in the eluent rather than acid or water to overcome ligand competition between components of the sample solution and the eluent. The methodology was applied to leachates from (bio)hydrometallurgical processing of oxidic flue dust residues and sulfidic zinc ores, where both are promising candidates for the recovery of indium from low grade ores and metallurgical wastes. Indium, ferrous iron, ferric iron, copper, zinc, nickel, and manganese concentrations could be simultaneously quantified. The method was found suitable for samples containing at least 0.25 mg/L indium and an iron to indium ratio of up to 100:1. 相似文献