全文获取类型
收费全文 | 2452篇 |
免费 | 39篇 |
国内免费 | 10篇 |
专业分类
化学 | 1568篇 |
晶体学 | 33篇 |
力学 | 31篇 |
数学 | 437篇 |
物理学 | 432篇 |
出版年
2020年 | 13篇 |
2019年 | 23篇 |
2018年 | 14篇 |
2017年 | 19篇 |
2016年 | 35篇 |
2015年 | 29篇 |
2014年 | 32篇 |
2013年 | 114篇 |
2012年 | 75篇 |
2011年 | 94篇 |
2010年 | 47篇 |
2009年 | 55篇 |
2008年 | 116篇 |
2007年 | 92篇 |
2006年 | 88篇 |
2005年 | 127篇 |
2004年 | 85篇 |
2003年 | 88篇 |
2002年 | 89篇 |
2001年 | 49篇 |
2000年 | 40篇 |
1999年 | 30篇 |
1998年 | 41篇 |
1997年 | 31篇 |
1996年 | 54篇 |
1995年 | 45篇 |
1994年 | 52篇 |
1993年 | 45篇 |
1992年 | 36篇 |
1991年 | 30篇 |
1990年 | 34篇 |
1989年 | 30篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 25篇 |
1985年 | 29篇 |
1984年 | 35篇 |
1983年 | 22篇 |
1982年 | 23篇 |
1981年 | 42篇 |
1980年 | 37篇 |
1979年 | 31篇 |
1978年 | 24篇 |
1977年 | 27篇 |
1976年 | 22篇 |
1975年 | 24篇 |
1974年 | 25篇 |
1973年 | 26篇 |
1969年 | 10篇 |
1912年 | 8篇 |
排序方式: 共有2501条查询结果,搜索用时 0 毫秒
1.
2.
An algorithm is introduced and shown to lead to a unique infinite product representation for a given formal power series A(z) with A(0) = 1. The infinite product is , where all bn ≠ 0, rn
, and rn+1 > rn. The degree of approximation by the polynomial (1 + b1zr1) · · · (1 + bnzrn) is also considered. 相似文献
3.
TiCx-PECVD-layers were characterized by TEM. EDX analysis and electron diffraction. TiCx-layers deposited using benzene showed a columnar structure, at which the column size decreases with rising excess carbon content. TiCx-layers deposited using n-heptane presented a lamellar structure, at which the lamellar thickness diminishes with an increasing excess carbon content. In dependence on the layer thickness a periodic progress of the element contents was observed, at which a maximum for Ti and Cl correlates with a minimum for C. It was found that the incorporated chlorine is bonded to titanium. The lattice parameter depends on the chlorine content. Using TiCl4/H2/Ar-gas mixtures without any hydrocarbon, layers containing TiH2 are formed. 相似文献
4.
Arnold Walfisz 《Mathematische Annalen》1926,95(1):69-83
Ohne Zusammenfassung
k
(s) = ((s))
k
, und ebenso in allen analogen Fällen. 相似文献
5.
Polarization dynamics are considered in the presence of an anisotropic Kerr non-linearity in the most common semiconductor waveguide geometry. The equations of motion are formulated in terms of Stokes polarization parameters and their Hamiltonian form is derived. Stationary solutions and their stability are found for plane-wave propagation. It is found that the non-integrable problem of mixed-polarization spatial soliton dynamics can be largely explained in terms of the equivalent plane-wave solutions. 相似文献
6.
Summary For the numerical solution of non-stiff semi-explicit differentialalgebraic equations (DAEs) of index 1 half-explicit Runge-Kutta methods (HERK) are considered that combine an explicit Runge-Kutta method for the differential part with a simplified Newton method for the (approximate) solution of the algebraic part of the DAE. Two principles for the choice of the initial guesses and the number of Newton steps at each stage are given that allow to construct HERK of the same order as the underlying explicit Runge-Kutta method. Numerical tests illustrate the efficiency of these methods. 相似文献
7.
8.
Randolf Arnold 《Monatshefte für Mathematik》1989,108(4):277-293
LetK andL be convex bodies of then-dimensional Euclidean spaceE
n
. The -distance ofK andL is defined by
, whereh
k
andh
L
denote the support functions ofK andL restricted to the unit sphereS
n–1
E
n
. We consider the problem of best approximation ofL by the images k ofK under proper rigid motions :E
n
E
n
. A motion that minimizes 2(K
L) is called optimal for (K, L) in the sense of the metric 2. The results in the general case (n2 arbitrary) base on the fact that the Steiner points of K andL coincide if is optimal for (K, L). Forn=2 we obtain a relationship between convex convolution bodies and the underlying approximation problem. 相似文献
9.
10.