全文获取类型
收费全文 | 13208篇 |
免费 | 826篇 |
国内免费 | 788篇 |
专业分类
化学 | 6357篇 |
晶体学 | 84篇 |
力学 | 747篇 |
综合类 | 146篇 |
数学 | 3100篇 |
物理学 | 4388篇 |
出版年
2023年 | 118篇 |
2022年 | 204篇 |
2021年 | 325篇 |
2020年 | 285篇 |
2019年 | 297篇 |
2018年 | 268篇 |
2017年 | 298篇 |
2016年 | 329篇 |
2015年 | 303篇 |
2014年 | 439篇 |
2013年 | 826篇 |
2012年 | 490篇 |
2011年 | 500篇 |
2010年 | 454篇 |
2009年 | 724篇 |
2008年 | 804篇 |
2007年 | 836篇 |
2006年 | 721篇 |
2005年 | 517篇 |
2004年 | 478篇 |
2003年 | 479篇 |
2002年 | 504篇 |
2001年 | 436篇 |
2000年 | 401篇 |
1999年 | 358篇 |
1998年 | 338篇 |
1997年 | 217篇 |
1996年 | 164篇 |
1995年 | 163篇 |
1994年 | 157篇 |
1993年 | 169篇 |
1992年 | 243篇 |
1991年 | 133篇 |
1990年 | 103篇 |
1989年 | 82篇 |
1988年 | 95篇 |
1987年 | 97篇 |
1986年 | 80篇 |
1985年 | 76篇 |
1984年 | 76篇 |
1983年 | 46篇 |
1982年 | 93篇 |
1981年 | 168篇 |
1980年 | 182篇 |
1979年 | 179篇 |
1978年 | 165篇 |
1977年 | 101篇 |
1976年 | 107篇 |
1973年 | 75篇 |
1972年 | 37篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
71.
Silvia Vogel 《Annals of Operations Research》2006,142(1):269-282
The paper considers upper semicontinuous behavior in distribution of sequences of random closed sets. Semiconvergence in distribution
will be described via convergence in distribution of random variables with values in a suitable topological space. Convergence
statements for suitable functions of random sets are proved and the results are employed to derive stability statements for
random optimization problems where the objective function and the constraint set are approximated simultaneously.
The author is grateful to two anonymous referees for helpful suggestions. 相似文献
72.
We prove equivalence of the definitions by the author and by Korevaar and Schoen of the Sobolev classes of mappings of a domain of an arithmetic n-dimensional space to a metric space. 相似文献
73.
74.
It is suggested that the question of existence of a jamming phase transition in a broad class of single-lane cellular-automaton traffic models may be studied using a correspondence to the asymmetric chipping model. In models where such correspondence is applicable, jamming phase transition does not take place. Rather, the system exhibits a smooth crossover between free-flow and jammed states, as the car density is increased. 相似文献
75.
Employing positive-definiteness arguments we analyse Boson field states, which combine classical and quantum mechanical features (signal and noise), in a constructive manner. Mathematically, they constitute Bauer simplexes within the convex, weak-*-compact state space of the C*-Weyl algebra, defined by a presymplectic test function space (smooth one-Boson wave functions) and are affinely homeomorphic to a state space of a classical field. The regular elements are expressed in terms of weak distributions (probability premeasures) on the dual test function space. The Bauer simplex arising from the bare vacuum is shown to generalize the quantum optical photon field states with positive P-functions. 相似文献
76.
G. Kocher-Oberlehner W. Jantsch L. Palmetshofer A. Ulyashin 《Physica E: Low-dimensional Systems and Nanostructures》2003,16(3-4):347
Erbium (Er)- and oxygen (O)-doped Cz–Si was additionally doped with hydrogen, using plasma enhanced chemical vapour deposition. Photoluminescence (PL) spectra show a large enhancement especially for samples treated with solid phase epitaxy before hydrogenation and annealing at 900°C later. Secondary ion mass spectroscopy measurements give evidence for an enhanced diffusion of O and Er at this temperature towards the surface. Etching shows that the PL does not stem from the heavily doped surface layer but from a deeper region with lower Er concentration. This conclusion is supported by the appearance of the so-called “cubic” centre with low solubility. Comparing the PL yield of the hydrogenated samples to that of samples with similar Er volume concentration but without hydrogenation still gives a large enhancement. We thus conclude that hydrogen can enhance the solubility of the cubic centre in Si:Er,O. 相似文献
77.
78.
未来的照明光源--白光LED技术及其发展 总被引:22,自引:0,他引:22
白光是黑白和彩色摄像机的照明光源,可以替代白炽灯、荧光灯和高压气体放电灯等传统光源。介绍了白光LED技术的原理、特点、发展方向。 相似文献
79.
In this paper, we exhibit a unified treatment of the mixed initial boundary value problem for second order (in time) parabolic linear differential equations in Banach spaces, whose boundary conditions are of a dynamical nature. Results regarding existence, uniqueness, continuous dependence (on initial data) and regularity of classical and strict solutions are established. Moreover, several examples are given as samples for possible applications.
80.
开放式微波消解与干灰化法消解测量食品中铅的方法比较 总被引:1,自引:0,他引:1
对开放式微波消解法与干灰化法消解测量食品中铅的方法进行了比较,试验表明,前者操作简易,试验周期短,在测量精度和加标回收率方面两种方法无显著性差别。 相似文献