全文获取类型
收费全文 | 12752篇 |
免费 | 558篇 |
国内免费 | 89篇 |
专业分类
化学 | 8715篇 |
晶体学 | 106篇 |
力学 | 339篇 |
综合类 | 1篇 |
数学 | 1968篇 |
物理学 | 2270篇 |
出版年
2023年 | 103篇 |
2022年 | 135篇 |
2021年 | 224篇 |
2020年 | 245篇 |
2019年 | 267篇 |
2018年 | 173篇 |
2017年 | 193篇 |
2016年 | 452篇 |
2015年 | 354篇 |
2014年 | 380篇 |
2013年 | 694篇 |
2012年 | 731篇 |
2011年 | 813篇 |
2010年 | 522篇 |
2009年 | 472篇 |
2008年 | 715篇 |
2007年 | 757篇 |
2006年 | 600篇 |
2005年 | 653篇 |
2004年 | 518篇 |
2003年 | 430篇 |
2002年 | 411篇 |
2001年 | 211篇 |
2000年 | 182篇 |
1999年 | 117篇 |
1998年 | 123篇 |
1997年 | 128篇 |
1996年 | 134篇 |
1995年 | 117篇 |
1994年 | 108篇 |
1993年 | 133篇 |
1992年 | 105篇 |
1991年 | 103篇 |
1990年 | 97篇 |
1989年 | 83篇 |
1988年 | 69篇 |
1987年 | 75篇 |
1986年 | 86篇 |
1985年 | 128篇 |
1984年 | 122篇 |
1983年 | 95篇 |
1982年 | 93篇 |
1981年 | 95篇 |
1980年 | 91篇 |
1979年 | 81篇 |
1978年 | 94篇 |
1977年 | 60篇 |
1976年 | 62篇 |
1975年 | 56篇 |
1974年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Il Bong Jung Alan Lambert Jan Stochel 《Proceedings of the American Mathematical Society》2004,132(8):2291-2302
The concept of backward extension for subnormal weighted shifts is generalized to arbitrary subnormal operators. Several differences and similarities in these contexts are explored, with emphasis on the structure of the underlying measures.
23.
We perform three tests on our proposal to implement diffeomorphism invariance in the non-abelian D0-brane DBI action as a base-point independence constraint between matrix Riemann normal coordinate systems. First, we show that T-duality along an isometry correctly interchanges the potential and kinetic terms in the action. Second, we show that the method to impose base-point independence using an auxiliary dN2-dimensional nonlinear sigma model also works for metrics which are curved along the brane, provided a physical gauge choice is made at the end. Third, we show that without alteration this method is applicable to higher order in velocities. Testing specifically to order 4, we elucidate the range of validity of the symmetrized trace approximation to the non-abelian DBI action. 相似文献
24.
25.
26.
For a dynamical system (X, B, T, μ) we investigate the connections between metric invariants, the rankr(T) and the covering numberF
*(T) and a spectral property for having a simple spectrum. Given a positive integerr≥2, a real numberb, 0<b<1 such thatr·b≥1, we construct examples of systems withr(T)=r, F
*(T)=b and having a simple spectrum. 相似文献
27.
Jan J. Slawianowski 《International Journal of Theoretical Physics》1998,37(1):411-420
We formulated some criticisms of the Diracequation and its Clifford-algebraic philosophy; inparticular, we show that, within a general-relativisticcontext, they seem to contain hidden action-at-distance concepts. We suggest a new model based on thefour-component Klein-Gordon equation locally invariantunder the U(2,2) gauge group. The usual Dirac equationis then obtained as a certain approximation. The geometrodynamical sector shows reasonablecorrespondence with general relativity. 相似文献
28.
Paul Van Der Meeren Jan Vanderdeelen Leon Baert 《Particle & Particle Systems Characterization》1994,11(4):320-326
Using a monodisperse PMMA dispersion, it was shown that light reflection at the sample cuvette walls may greatly influence the results of both static (SLS) and dynamic (DLS) light scattering experiments. Considering SLS, this reflection phenomenon mostly causes an overestimation of the scattered intensity at high scattering angles, which may give rise to the emergence of an additional, artificial peak in the lower region of the particle size distribution. On the other hand, the influcence of reflection on DLS measurements was shown to be particularly important in the upper region of the particle size distribution. The experimentally observed phenomena were explained from the basic principles of both particle sizing methods. Finally, it was shown that the disturbing effect of reflection could be avoided by modifying either the hardware or the software of the static and dynamic light scattering technique. 相似文献
29.
30.
W. Brüggemann K. Fischer H. Jahnke 《Journal of Mathematical Modelling and Algorithms》2003,2(2):153-169
In Part I of this study, we suggest to identify an operations research (OR) problem with the equivalence class of models describing the problem and enhance the standard computer-science theory of computational complexity to be applicable to this situation of an often model-based OR context. The Discrete Lot-sizing and Scheduling Problem (DLSP) is analysed here in detail to demonstrate the difficulties which can arise if these aspects are neglected and to illustrate the new theoretical concept. In addition, a new minimal model is introduced for the DLSP which makes this problem eventually amenable to a rigorous analysis of its computational complexity. 相似文献