全文获取类型
收费全文 | 8051篇 |
免费 | 218篇 |
国内免费 | 56篇 |
专业分类
化学 | 4796篇 |
晶体学 | 72篇 |
力学 | 168篇 |
数学 | 1498篇 |
物理学 | 1791篇 |
出版年
2023年 | 27篇 |
2022年 | 74篇 |
2021年 | 185篇 |
2020年 | 137篇 |
2019年 | 204篇 |
2018年 | 234篇 |
2017年 | 207篇 |
2016年 | 283篇 |
2015年 | 231篇 |
2014年 | 244篇 |
2013年 | 522篇 |
2012年 | 476篇 |
2011年 | 580篇 |
2010年 | 424篇 |
2009年 | 356篇 |
2008年 | 493篇 |
2007年 | 453篇 |
2006年 | 424篇 |
2005年 | 399篇 |
2004年 | 346篇 |
2003年 | 287篇 |
2002年 | 234篇 |
2001年 | 124篇 |
2000年 | 108篇 |
1999年 | 123篇 |
1998年 | 101篇 |
1997年 | 74篇 |
1996年 | 98篇 |
1995年 | 60篇 |
1994年 | 58篇 |
1993年 | 65篇 |
1992年 | 63篇 |
1991年 | 49篇 |
1990年 | 24篇 |
1989年 | 29篇 |
1988年 | 22篇 |
1987年 | 29篇 |
1986年 | 33篇 |
1985年 | 25篇 |
1984年 | 30篇 |
1983年 | 32篇 |
1982年 | 22篇 |
1981年 | 30篇 |
1978年 | 22篇 |
1977年 | 32篇 |
1975年 | 21篇 |
1974年 | 31篇 |
1973年 | 22篇 |
1972年 | 21篇 |
1971年 | 18篇 |
排序方式: 共有8325条查询结果,搜索用时 312 毫秒
21.
On a Definitizable Analog of the Trigonometric Moment Problem Generating an Indefinite Toeplitz Form
We prove the existence of an integro-polynomial representation for a sequence of numbers such that there exists a difference operator mapping this sequence to a sequence that generates the solvable trigonometric moment problem. A similar result related to the power moment problem was given in [12]. 相似文献
22.
For any chain Γ the ring NT(Γ,K) of all finitary Γ-matrices ‖a ij ‖ i,jεΓ over an associative ring K with zeros on and above the main diagonal is locally nilpotent and hence radical. If R′=NT(Γ′,K′),R=NT(Γ,K) and either |Γ|<∞ or K is a ring with no zero-divisors, then isomorphisms between rings R and R′, their adjoint groups and associated Lie rings are described. 相似文献
23.
The large N phase transition point is investigated in the heat kernel on the U(N) group with respect to arbitrary boundary conditions. A simple functional relation is found relating the density of eigenvalues of the boundary field to the saddle point shape of the typical Young tableaux in the large N limit of the character expansion of the heat kernel. Both strong coupling and weak coupling phases are investigated for some particular cases of the boundary holonomy. 相似文献
24.
Velislava A Ignatova Sven Van Den Berghe Steven Van Dyck Vladimir N Popok 《Microscopy and microanalysis》2006,12(5):432-437
The oxide scales of AISI 304 formed in boric acid solutions at 300 degrees C and pH = 4.5 have been studied using X-ray photoelectron spectroscopy (XPS) depth profiling. The present focus is depth profile quantification both in depth and chemical composition on a molecular level. The roughness of the samples is studied by atomic force microscopy before and after sputtering, and the erosion rate is determined by measuring the crater depth with a surface profilometer and vertical scanning interferometry. The resulting roughness (20-30 nm), being an order of magnitude lower than the crater depth (0.2-0.5 microm), allows layer-by-layer profiling, although the ion-induced effects result in an uncertainty of the depth calibration of a factor of 2. The XPS spectrum deconvolution and data evaluation applying target factor analysis allows chemical speciation on a molecular level. The elemental distribution as a function of the sputtering time is obtained, and the formation of two layers is observed-one hydroxide (mainly iron-nickel based) on top and a second one deeper, mainly consisting of iron-chromium oxides. 相似文献
25.
The coherent inelastic processes of the type a → b, which may take place in the interaction of hadrons and γ quanta with nuclei at very high energies (the nucleus remains the same), are theoretically investigated. Analytical formulas for the effective cross-section σcoh(a→b) are obtained. 相似文献
26.
Kuibyshev State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 2, pp. 242–245, February, 1989. 相似文献
27.
Vladimir Kozlov 《Journal of Functional Analysis》2004,217(2):448-488
We develop an asymptotic theory of nonlinear operator differential equations of an arbitrary order in Banach spaces. The nonlinear part of the equation is written in a divergent form. It is shown that the main term in an asymptotic representation of solutions at infinity satisfies a finite-dimensional dynamical system perturbed by a small nonlocal operator. 相似文献
28.
Harper equations are derived for a px, py electronic system. Analysis is carried out for extreme points of the quasi-continuous spectrum in the cases when the number of magnetic flux quanta through a unit cell is a rational number and calculations are made for square and triangular lattices as well as for a honeycomb lattice with two nonequivalent atoms. The possibility of application of the results for explaining the fractional Hall effect is considered. 相似文献
29.
30.