全文获取类型
收费全文 | 6159篇 |
免费 | 157篇 |
国内免费 | 132篇 |
专业分类
化学 | 1044篇 |
晶体学 | 131篇 |
力学 | 59篇 |
综合类 | 11篇 |
数学 | 3943篇 |
物理学 | 1260篇 |
出版年
2023年 | 14篇 |
2022年 | 42篇 |
2021年 | 33篇 |
2020年 | 49篇 |
2019年 | 138篇 |
2018年 | 129篇 |
2017年 | 92篇 |
2016年 | 82篇 |
2015年 | 95篇 |
2014年 | 162篇 |
2013年 | 319篇 |
2012年 | 235篇 |
2011年 | 311篇 |
2010年 | 325篇 |
2009年 | 431篇 |
2008年 | 414篇 |
2007年 | 458篇 |
2006年 | 382篇 |
2005年 | 249篇 |
2004年 | 224篇 |
2003年 | 190篇 |
2002年 | 176篇 |
2001年 | 128篇 |
2000年 | 131篇 |
1999年 | 140篇 |
1998年 | 117篇 |
1997年 | 91篇 |
1996年 | 184篇 |
1995年 | 183篇 |
1994年 | 161篇 |
1993年 | 126篇 |
1992年 | 131篇 |
1991年 | 97篇 |
1990年 | 81篇 |
1989年 | 66篇 |
1988年 | 21篇 |
1987年 | 17篇 |
1986年 | 15篇 |
1985年 | 32篇 |
1984年 | 36篇 |
1983年 | 9篇 |
1982年 | 31篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 19篇 |
1977年 | 15篇 |
1976年 | 9篇 |
1974年 | 5篇 |
1973年 | 7篇 |
排序方式: 共有6448条查询结果,搜索用时 31 毫秒
1.
Roberto Aravire Ahmed Laghribi Manuel ORyan 《Journal of Pure and Applied Algebra》2019,223(1):439-457
Let F be a field of characteristic 2. In this paper we give a complete computation of the kernel of the homomorphism induced by scalar extension, where is a purely inseparable extension (of any degree), is the cokernel of the Artin–Schreier operator given by: , where is the space of absolute m-differential forms over F and d is the differential operator. Other related results are included. 相似文献
2.
The effect of Re addition on the microstructure and hardening behaviour of the dual two-phase Ni3Al (L12) and Ni3V (D022) intermetallic alloy was investigated by scanning electron microscopy, transmission electron microscopy and Vickers hardness test. The two-phase eutectoid microstructure accompanying the Re-rich precipitates were observed in the channel region of the alloys in which Re substituted for Ni but not in those in which Re substituted for Al and V. The concomitant addition of Nb (or Ta) with Re more stabilized the two-phase eutectoid microstructure and consequently more induced the fine precipitates in the channel region. The annealing at temperatures below the eutectoid temperature was necessary to induce the fine precipitates in the channel region and thereby result in the precipitation hardening. The fine precipitation in the channel region and related hardening was attributed to the alloying feature so that Re is soluble in the A1 (fcc) phase at high temperatures and becomes less soluble in the two intermetallic phases decomposed from the A1 phase at low temperatures. 相似文献
3.
Masaaki Sugihara 《Numerische Mathematik》1997,75(3):379-395
Summary. In the light of the functional analysis theory we establish the optimality of the double exponential formula. The argument
consists of the following three ingredients: (1) introduction of a number of spaces of functions analytic in a strip region
about the real axis, each space being characterized by the decay rate of their elements (functions) in the neighborhood of
the infinity; (2) proof of the (near-) optimality of the trapezoidal formula in each space introduced in (1) by showing the
(near-) equality between an upper estimate for the error norm of the trapezoidal formula and a lower estimate for the minimum
error norm of quadratures; (3) nonexistence theorem for the spaces, the characterizing decay rate of which is more rapid than
the double exponential.
Received September 15, 1995 / Accepted December 14, 1995 相似文献
4.
Summary In 1980 Dahmen-DeVore-Scherer introduced a modulus of continuity which turns out to reflect invariance properties of compound cubature rules effectively. Accordingly, sharp error bounds are derived, the existence of relevant counterexamples being a consequence of a quantitative resonance principle, established previously. 相似文献
5.
Saida Sultanic 《Integral Equations and Operator Theory》2006,55(4):573-595
The central question of this paper is the one of finding the right analogue of the Commutant Lifting Theorem for the Bergman
space La2. We also analyze the analogous problem for weighted Bergman spaces La,α2, − 1 < α < ∞. 相似文献
6.
J. Kalliongis 《Mathematische Zeitschrift》2002,241(4):801-828
For compact irreducible sufficiently large 3-manifolds containing 2-sided projective planes, we consider the following Realization
Problem: Given a finite subgroup of the outer automorphism group of the fundamental group, is there a finite group of homeomorphisms,
which induces this subgroup?
Received: 16 November 1999; in final form: 18 January 2001 / Published online: 8 November 2002 相似文献
7.
Using Brown's construction (J. Algebra 15 (1970) 103) of an exact 6-term sequence for a fibration of groupoids we show how an exact 9-term sequence can be associated to a fibration of bigroupoids. Applications to topology and algebra are given. 相似文献
8.
F. Balibrea 《Topology and its Applications》2006,153(12):2092-2095
Recently, Forti, Paganoni and Smítal constructed an example of a triangular map of the unite square, F(x,y)=(f(x),g(x,y)), possessing periodic orbits of all periods and such that no infinite ω-limit set of F contains a periodic point. In this note we show that the above quoted map F has a homoclinic orbit. As a consequence, we answer in the negative the problem presented by A.N. Sharkovsky in the eighties whether, for a triangular map of the square, existence of a homoclinic orbit implies the existence of an infinite ω-limit set containing a periodic point. It is well known that, for a continuous map of the interval, the answer is positive. 相似文献
9.
András Vasy 《Journal of Functional Analysis》2004,209(2):468-492
We show the exponential decay of eigenfunctions of second-order geometric many-body type Hamiltonians at non-threshold energies. Moreover, in the case of first-order and small second-order perturbations we show that there are no eigenfunctions with positive energy. 相似文献
10.
通过调整Mn的成分,系统地研究了Ni81Fe19/Ni100-xMnx双层膜的磁学性质,特别是交换偏置场(Hex)的变化.当Ni100-xMnx中Mn的原子百分比在534%到600%之间时,对于150nm的Ni81Fe19,得到了最大的交换偏置场175kA/m,同时由于Mn对Ni81Fe19层的扩散所造成的磁矩的降低小于20%;高角x射线衍射证明Ni100-xMnx的晶格常数随着Mn成分的改变而变化,Mn含量越多,其晶格常数越大;制备态Ni100-xMnx膜晶格常数与θ相NiMn膜晶格常数的接近程度与NiMn膜θ相形成的容易程度相对应.也研究了交换偏置场随着Ni100-xMnx厚度的变化,第一次得到了当Ni100-xMnx中Mn的原子百分比为706%时,Ni81Fe19(150nm)/Ni100-xMnx(90nm)双层膜在经过240℃,5h退火后,可以有80kA/m的交换偏置场,此时铁磁层磁矩的大小几乎不变.
关键词:
Ni81Fe19/Ni100-xMnx
交换偏置场 相似文献