全文获取类型
收费全文 | 3724篇 |
免费 | 104篇 |
国内免费 | 1篇 |
专业分类
化学 | 2008篇 |
晶体学 | 72篇 |
力学 | 134篇 |
综合类 | 5篇 |
数学 | 926篇 |
物理学 | 684篇 |
出版年
2023年 | 29篇 |
2022年 | 45篇 |
2021年 | 73篇 |
2020年 | 85篇 |
2019年 | 101篇 |
2018年 | 177篇 |
2017年 | 157篇 |
2016年 | 193篇 |
2015年 | 138篇 |
2014年 | 197篇 |
2013年 | 520篇 |
2012年 | 217篇 |
2011年 | 236篇 |
2010年 | 237篇 |
2009年 | 156篇 |
2008年 | 235篇 |
2007年 | 205篇 |
2006年 | 135篇 |
2005年 | 74篇 |
2004年 | 76篇 |
2003年 | 61篇 |
2002年 | 55篇 |
2001年 | 39篇 |
2000年 | 47篇 |
1999年 | 28篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 20篇 |
1995年 | 11篇 |
1994年 | 10篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 18篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 18篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1974年 | 12篇 |
1973年 | 9篇 |
1968年 | 9篇 |
排序方式: 共有3829条查询结果,搜索用时 31 毫秒
11.
We continue the studies on the so–called genuine Bernstein–Durrmeyer operators U
n
by establishing a recurrence formula for the moments and by investigating the semigroup T(t) approximated by U
n
. Moreover, for sufficiently smooth functions the degree of this convergence is estimated. We also determine the eigenstructure
of U
n
, compute the moments of T(t) and establish asymptotic formulas.
Received: January 26, 2007. 相似文献
12.
In this paper, it is shown that some of the results of torus actions on Poincaré duality spaces, Borel’s dimension formula
and topological splitting principle to local weights, hold if ‘torus’ is replaced by ‘pro-torus’. 相似文献
13.
We examine the nonlinear dynamical behavior of a spinor Bose-Einstein condensate in a double-well potential. Considering a condensate with large number of atoms, such that it can be described using the mean field theory, we separate the spinor dynamics from the spatial dynamics under the single-mode approximation. We limit ourselves to certain initial conditions under which the spatial mode is frozen so that we can focus on the spinor dynamics only. Identifying collective spin variables of our system, we derive the corresponding nonlinear equations of motion for them. Employing standard stability analysis, we find and characterize fixed points of the system. For a wide range of physical parameters such as tunneling strength and non-linear interactions, as well as for various initial preparations of the system, we identify qualitatively different dynamical regimes possible in the system. In particular, complete and incomplete oscillations of spin variables between quantum wells are found. We also show that by bringing some fixed points close to each other in the phase space of the system, it is possible to induce amplitude modulation to those otherwise regular tunneling oscillations. 相似文献
14.
We give a concise review and extension of S-procedure that is an instrumental tool in control theory and robust optimization analysis. We also discuss the approximate S-Lemma as well as its applications in robust optimization.The many suggestions and detailed corrections of an anonymous referee are gratefully acknowledged. 相似文献
15.
The spectral structure of two parameter unbounded operator pencils of waveguide type is studied. Theorems on discreteness
of the spectrum for a fixed parameter are proved. Variational principles for real eigenvalues in some parts of the root zones
are established. In the case of n = 1 (quadratic pencils) domains containing the spectrum are described (see Fig. 1–3). Conditions in the definition of the
pencils of waveguide type arise naturally from physical problems and each of them has a physical meaning. In particular a
connection between the energetic stability condition and a perturbation problem for the coefficients is given. 相似文献
16.
Adsorption of the copper ions from aqueous solutions, benzene, and water on the active carbon obtained by chemical activation
from walnut shells was studied. The active carbon was additionally oxidized with hydrogen peroxide and then impregnated with
nitrogen-containing compounds. As a result of impregnation with melamine, a secondary porosity is formed within the oxidized
active carbon, leading to an increase in the specific surface of the sorbent. A modified carbon surface is heterogeneous,
and the carbons themselves exhibit catalytic activity in the oxidation of luminol and decomposition of hydrogen peroxide. 相似文献
17.
18.
We discuss role of partially gravitating scalar fields, scalar fields whose energy–momentum tensors vanish for a subset of dimensions, in dynamical compactification of a given set of dimensions. We show that the resulting spacetime exhibits a factorizable geometry consisting of usual four-dimensional spacetime with full Poincaré invariance times a manifold of extra dimensions whose size and shape are determined by the scalar field dynamics. Depending on the strength of its coupling to the curvature scalar, the vacuum expectation value (VEV) of the scalar field may or may not vanish. When its VEV is zero the higher-dimensional spacetime is completely flat and there is no compactification effect at all. On the other hand, when its VEV is nonzero the extra dimensions get spontaneously compactified. The compactification process is such that a bulk cosmological constant is utilized for curving the extra dimensions. 相似文献
19.
20.
Two polynuclear complexes, a dimer and a tetramer, involving sulfate and hydroxo bridges and ligating ascorbate were isolated from aqueous solutions. Structural formulae are proposed on the basis of microanalytical and thermal analysis results, i.r., 13C-n.m.r., mass spectral data and magnetic measurements. 相似文献