全文获取类型
收费全文 | 22262篇 |
免费 | 1933篇 |
国内免费 | 1824篇 |
专业分类
化学 | 5483篇 |
晶体学 | 79篇 |
力学 | 1568篇 |
综合类 | 539篇 |
数学 | 11560篇 |
物理学 | 6790篇 |
出版年
2023年 | 177篇 |
2022年 | 320篇 |
2021年 | 401篇 |
2020年 | 440篇 |
2019年 | 510篇 |
2018年 | 434篇 |
2017年 | 512篇 |
2016年 | 582篇 |
2015年 | 453篇 |
2014年 | 802篇 |
2013年 | 1413篇 |
2012年 | 895篇 |
2011年 | 1165篇 |
2010年 | 1125篇 |
2009年 | 1431篇 |
2008年 | 1428篇 |
2007年 | 1376篇 |
2006年 | 1367篇 |
2005年 | 1025篇 |
2004年 | 880篇 |
2003年 | 877篇 |
2002年 | 827篇 |
2001年 | 706篇 |
2000年 | 643篇 |
1999年 | 627篇 |
1998年 | 532篇 |
1997年 | 422篇 |
1996年 | 398篇 |
1995年 | 271篇 |
1994年 | 243篇 |
1993年 | 208篇 |
1992年 | 197篇 |
1991年 | 143篇 |
1990年 | 135篇 |
1989年 | 111篇 |
1988年 | 111篇 |
1987年 | 94篇 |
1985年 | 494篇 |
1984年 | 350篇 |
1983年 | 271篇 |
1982年 | 268篇 |
1981年 | 189篇 |
1980年 | 163篇 |
1979年 | 186篇 |
1978年 | 108篇 |
1977年 | 120篇 |
1976年 | 106篇 |
1975年 | 99篇 |
1974年 | 136篇 |
1973年 | 139篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
We give an account of the appearance and first developments of the statistical model of atoms proposed by Thomas and Fermi, focusing on the main results achieved by Fermi and his group in Rome. Particular attention is addressed to the unknown contribution to this subject by Majorana, anticipating some important results reached later by leading physicists. 相似文献
52.
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
53.
Marco Pretti 《Journal of statistical physics》2003,111(3-4):993-1015
In this article we deal with the variational approach to cactus trees (Husimi trees) and the more common recursive approach, that are in principle equivalent for finite systems. We discuss in detail the conditions under which the two methods are equivalent also in the analysis of infinite (self-similar) cactus trees, usually investigated to the purpose of approximating ordinary lattice systems. Such issue is hardly ever considered in the literature. We show (on significant test models) that the phase diagram and the thermodynamic quantities computed by the variational method, when they deviates from the exact bulk properties of the cactus system, generally provide a better approximation to the behavior of a corresponding ordinary system. Generalizing a property proved by Kikuchi, we also show that the numerical algorithm usually employed to perform the free energy minimization in the variational approach is always convergent. 相似文献
54.
Bogdan Nita 《General Relativity and Gravitation》2003,35(10):1865-1868
Algebraically special gravitational fields are described using algebraic and differential invariants of the Weyl tensor. A type III invariant is also given and calculated for Robinson-Trautman spaces. 相似文献
55.
Summary Our purpose is to extend results due to P. Chandra and L. Leindler concerning the order of approximation by means of Fourier series for functions belonging to generalized Lipschitz-classes. 相似文献
56.
D. Barrios Rolanía G. Lpez Lagomasino E. B. Saff 《Journal of Approximation Theory》2003,124(2):263-281
Using a convergence theorem for Fourier–Padé approximants constructed from orthogonal polynomials on the unit circle, we prove an analogue of Hadamard's theorem for determining the radius of m-meromorphy of a function analytic on the unit disk and apply this to the location of poles of the reciprocal of Szeg
functions. 相似文献
57.
M.K. Gupta Vijay Gupta Manoj Kumar 《Journal of Mathematical Analysis and Applications》2007,330(2):799-816
In the present paper we introduce a new family of linear positive operators and study some direct and inverse results in simultaneous approximation. 相似文献
58.
The use of liquid fuels such as kerosene is of interest for the pulse detonation engine (PDE). Within this context, the aim
of this work, which is a preliminary study, was to show the feasibility to initiate a detonation in air with liquid-fuel pyrolysis
products, using energies and dimensions of test facility similars to those of PDEs. Therefore, two liquids fuels have been
compared, JP10, which is a synthesis fuel generally used in the field of missile applications, and decane, which is one of
the major components of standard kerosenes (F-34, Jet A1, ...). The thermal degradation of these fuels was studied with two
pyrolysis processes, a batch reactor and a flow reactor. The temperatures varied from 600°C to 1,000°C and residence times
for the batch reactor and the flow reactor were, respectively, between 10–30 s and 0.1–2 s. Subsequently, the detonability
of synthetic gaseous mixtures, which was a schematisation of the decomposition state after the pyrolysis process, has been
studied. The detonability study, regarding nitrogen dilution and equivalence ratio, was investigated in a 50 mm-diameter,
2.5 m-long detonation tube. These dimensions are compatible with applications in the aircraft industry and, more particularly,
in PDEs. Therefore, JP10 and decane were compared to choose the best candidate for liquid-fuel PDE studies.
This paper was based on work that was presented at the 20th International Colloquium on the Dynamics of Explosions and Reactive
Systems, Montreal, Canada, July 31 – August 5, 2005. 相似文献
59.
60.
Jonathan M. Borwein 《Optimization Letters》2007,1(1):21-32
This paper is a companion to a lecture given at the Prague Spring School in Analysis in April 2006. It highlights four distinct variational methods of proving that a finite dimensional Chebyshev set is convex and hopes to inspire renewed work on the open question of whether every Chebyshev set in Hilbert space is convex. 相似文献