全文获取类型
收费全文 | 33692篇 |
免费 | 5880篇 |
国内免费 | 4224篇 |
专业分类
化学 | 25405篇 |
晶体学 | 412篇 |
力学 | 1933篇 |
综合类 | 348篇 |
数学 | 3645篇 |
物理学 | 12053篇 |
出版年
2024年 | 71篇 |
2023年 | 728篇 |
2022年 | 937篇 |
2021年 | 1129篇 |
2020年 | 1404篇 |
2019年 | 1447篇 |
2018年 | 1113篇 |
2017年 | 1016篇 |
2016年 | 1667篇 |
2015年 | 1631篇 |
2014年 | 1880篇 |
2013年 | 2365篇 |
2012年 | 3016篇 |
2011年 | 3116篇 |
2010年 | 2130篇 |
2009年 | 1918篇 |
2008年 | 2205篇 |
2007年 | 2093篇 |
2006年 | 1827篇 |
2005年 | 1656篇 |
2004年 | 1284篇 |
2003年 | 1168篇 |
2002年 | 1229篇 |
2001年 | 1034篇 |
2000年 | 781篇 |
1999年 | 785篇 |
1998年 | 544篇 |
1997年 | 534篇 |
1996年 | 448篇 |
1995年 | 425篇 |
1994年 | 384篇 |
1993年 | 318篇 |
1992年 | 277篇 |
1991年 | 285篇 |
1990年 | 252篇 |
1989年 | 152篇 |
1988年 | 120篇 |
1987年 | 109篇 |
1986年 | 84篇 |
1985年 | 67篇 |
1984年 | 61篇 |
1983年 | 32篇 |
1982年 | 27篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 2篇 |
1975年 | 2篇 |
1959年 | 1篇 |
1957年 | 4篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 984 毫秒
61.
Let T be a bounded linear operator on Hilbert space H, M an invariant subspace of T. If there exists another invariant subspace N of T such that H = M + N and M ∩ N = 0, then M is said to be a completely reduced subspace of T. If T has a nontrivial completely reduced subspace, then T is said to be completely reducible; otherwise T is said to be completely irreducible. In the present paper we briefly sum up works on completely irreducible operators that
have been done by the Functional Analysis Seminar of Jilin University in the past ten years and more.
The paper contains four sections. In section 1 the background of completely irreducible operators is given in detail. Section
2 shows which operator in some well-known classes of operators, for example, weighted shifts, Toeplitz operators, etc., is
completely irreducible. In section 3 it is proved that every bounded linear operator on the Hilbert space can be approximated
by the finite direct sum of completely irreducible operators. It is clear that a completely irreducible operator is a rather
suitable analogue of Jordan blocks in L(H), the set of all bounded linear operators on Hilbert space H. In section 4 several questions concerning completely irreducible operators are discussed and it is shown that some properties
of completely irreducible operators are different from properties of unicellular operators.
__________
Translated from Acta Sci. Nat. Univ. Jilin, 1992, (4): 20–29 相似文献
62.
Propagation of the Hermite–Gaussian beams through misaligned optical system with a circular aperture
By means of expanding a hard-edged aperture into a finite sum of complex Gaussian functions, the approximate analytical formula of one kind of higher-order Gaussian beams called the Hermite–Gaussian beams (HGBs) passing through circular apertured and misaligned optical system is obtained in this paper. The result provides more convenience for studying its propagation than the usual way by using diffraction integral directly. Some numerical simulations are also given for illustrating the propagation properties of the HGBs through the circular apertured optical systems. 相似文献
63.
64.
65.
根据Co P非晶态合金结构的短程有序和结构中可能存在P -P相互作用的实验事实 ,选择了单磷原子簇模型ConP(n =1~ 5 )和双磷原子簇模型ConP2 (n =1~ 4 ) ,用密度泛函理论方法对其进行计算 .结果表明 ,在单磷Co2 P( 2 ) 、Co3 P( 1) 及Co4P( 2 ) 模型体系中 ,Co原子供给P原子电子 ,与电负性规则一致 ,同时Co和P之间具较强化学作用 ,可以形成稳定的原子簇 ;而在双磷和单磷原子簇Co5P( 1) 模型体系中 ,形成的原子簇不稳定 ,采用单磷Co2 P( 2 ) 、Co3 P( 1) 及Co4P( 2 ) 模型能较好地反映Co P非晶态合金的结构特点 . 相似文献
66.
67.
GAO Xiaoyan CAI Xiao CAO Zeng CUI Chenghe 《核工业西南物理研究院年报(英文版)》2004,(1):54-56
HL-2A is the first divertor tokamak in China. The vacuum system is one of the important parts of the HL-2A tokamak, which has to be work well during the physics campaign in 2004. As the tokamak machine is separated from the operation staff during discharges, to guarantee the safe and reliable operation of the vacuum system, it is necessary to watch the vacuum system outside the machine hall with an automatic monitoring system. The paper describes the design and manufacture of the monitoring system. 相似文献
68.
The vacuum system of today's tokamak devices is designed to meet the operational requirements of the experiments. The operation can be divided into five modes, (1) pumping down and leak detecting of the vacuum vessel, (2) baking, (3) plasma-facing component (PFC) conditioning, (4)evacuating and controlling of the particles at plasma edge, (5) plasma discharge experiments. 相似文献
69.
70.