全文获取类型
收费全文 | 724728篇 |
免费 | 5740篇 |
国内免费 | 2132篇 |
专业分类
化学 | 354213篇 |
晶体学 | 10268篇 |
力学 | 38505篇 |
综合类 | 22篇 |
数学 | 114906篇 |
物理学 | 214686篇 |
出版年
2021年 | 5835篇 |
2020年 | 6361篇 |
2019年 | 7197篇 |
2018年 | 19141篇 |
2017年 | 18966篇 |
2016年 | 19071篇 |
2015年 | 8335篇 |
2014年 | 12681篇 |
2013年 | 29465篇 |
2012年 | 25958篇 |
2011年 | 36395篇 |
2010年 | 24879篇 |
2009年 | 25083篇 |
2008年 | 31211篇 |
2007年 | 33068篇 |
2006年 | 23355篇 |
2005年 | 21899篇 |
2004年 | 20770篇 |
2003年 | 19254篇 |
2002年 | 18107篇 |
2001年 | 18653篇 |
2000年 | 14606篇 |
1999年 | 11237篇 |
1998年 | 9647篇 |
1997年 | 9472篇 |
1996年 | 8944篇 |
1995年 | 8084篇 |
1994年 | 7924篇 |
1993年 | 7675篇 |
1992年 | 8200篇 |
1991年 | 8629篇 |
1990年 | 8272篇 |
1989年 | 8062篇 |
1988年 | 7966篇 |
1987年 | 7770篇 |
1986年 | 7391篇 |
1985年 | 9409篇 |
1984年 | 10001篇 |
1983年 | 8359篇 |
1982年 | 8752篇 |
1981年 | 8346篇 |
1980年 | 7920篇 |
1979年 | 8386篇 |
1978年 | 8728篇 |
1977年 | 8572篇 |
1976年 | 8597篇 |
1975年 | 8162篇 |
1974年 | 7988篇 |
1973年 | 8394篇 |
1972年 | 5978篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
This note introduces a refinement to a previously proposed tabu search algorithm for vehicle routing problems with time windows. This refinement yields new best known solutions on a set of benchmark instances of the multi-depot, the periodic and the site-dependent vehicle routing problems with time windows. 相似文献
963.
Let SB(X,Y) be the set of the bounded sublinear operators from a Banach space X into a Banach lattice Y. Consider π2(X,Y) the set of 2-summing sublinear operators. We study in this paper a variation of Grothendieck's theorem in the sublinear operators case. We prove under some conditions that every operator in SB(C(K),H) is in π2(C(K),H) for any compact K and any Hilbert H. In the noncommutative case the problem is still open. 相似文献
964.
Ledzewicz U. Nowakowski A. Schättler H. 《Journal of Optimization Theory and Applications》2004,122(2):345-370
It is shown that, if a parametrized fämily of extremals F can be stratified in a way compatible with the flow map generated by F, then those trajectories of the family which realize the minimal values of the cost in F are indeed optimal in comparison with all trajectories which lie in the region R covered by the trajectories of F. It is not assumed that F is a field covering the state space injectively. As illustration, an optimal synthesis is constructed for a system where the flow of extremals exhibits a simple cusp singularity. 相似文献
965.
966.
A method is developed for a stress analysis in an infinite elastic body containing two neighboring periodically cophasaly curved fibers located along two parallel lines. The stress distribution is studied when the body is loaded at infinity by uniformly distributed normal forces in the fiber direction. The investigation is carried out within the framework of a piecewise homogeneous body model with the use of exact three-dimensional equations of elasticity theory. Numerical results related to the stress distribution considered and the influence of interaction between the fibers on this distribution are given. 相似文献
967.
CuPc molecules adsorbed on Au(1 1 0)-(1 × 2): growth morphology and evolution of valence band states
Fabrizio Evangelista A. RuoccoValdis Corradini M.P. DonzelloCarlo Mariani Maria Grazia Betti 《Surface science》2003,531(2):123-130
We present the growth morphology, the long-range ordering, and the evolution of the valence band electronic states of ultrathin films of copper phthalocyanine (CuPc) deposited on the Au(1 1 0)-(1 × 2) reconstructed surface, as a function of the organic molecule coverage. The low energy electron diffraction patterns present a (5 × 3) reconstruction from the early adsorption stages. High-resolution UV photoelectron spectroscopy data show the disappearance of the Au surface states related to the (1 × 2) reconstruction, and the presence of new electronic features related to the molecule-substrate interaction and to the CuPc molecular states. The CuPc highest occupied molecular orbital gradually emerges in the valence band, while the interface electronic states are quenched, upon increasing the coverage. 相似文献
968.
A. Budhiraja 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2003,39(6):2318-941
In this work we study connections between various asymptotic properties of the nonlinear filter. It is assumed that the signal has a unique invariant probability measure. The key property of interest is expressed in terms of a relationship between the observation σ field and the tail σ field of the signal, in the stationary filtering problem. This property can be viewed as the permissibility of the interchange of the order of the operations of maximum and countable intersection for certain σ-fields. Under suitable conditions, it is shown that the above property is equivalent to various desirable properties of the filter such as
- (a) uniqueness of invariant measure for the signal,
- (b) uniqueness of invariant measure for the pair (signal, filter),
- (c) a finite memory property of the filter,
- (d) a property of finite time dependence between the signal and observation σ fields and
- (e) asymptotic stability of the filter.
969.
970.
C.J. MeiningH.A. Nickel A.B. Dzyubenko A. PetrouM. Furis D.R. Yakovlev B.D. McCombe 《Solid State Communications》2003,127(12):821-827
Many body effects contribute significantly to the energy states of electron-hole pairs confined in quantum wells in the presence of excess electrons. We present results of optically detected resonance spectroscopy of the internal transitions of photo-excited electron-hole pairs in the presence of excess electrons for GaAs QWs and CdTe QWs. Compared to the case of isolated negatively charged excitons, excess electrons produce a large blue shift of the internal transitions in modulation-doped GaAs quantum wells (QWs) for filling factor <2, and similar effects are found in CdTe QWs. For filling factor >2 no internal transitions are observed. These measurements demonstrate the strong effects of electron-electron correlations on the internal transitions of charged excitons in these quasi-2D systems and the importance of magnetic translation invariance. In the presence of excess electrons, the observed internal transitions are those of a magnetoplasmon bound to a mobile valence band hole. 相似文献