全文获取类型
收费全文 | 178046篇 |
免费 | 18355篇 |
国内免费 | 10411篇 |
专业分类
化学 | 92913篇 |
晶体学 | 1924篇 |
力学 | 13039篇 |
综合类 | 533篇 |
数学 | 42765篇 |
物理学 | 55638篇 |
出版年
2024年 | 369篇 |
2023年 | 2133篇 |
2022年 | 3644篇 |
2021年 | 3946篇 |
2020年 | 4248篇 |
2019年 | 4138篇 |
2018年 | 13045篇 |
2017年 | 12645篇 |
2016年 | 10744篇 |
2015年 | 5716篇 |
2014年 | 6291篇 |
2013年 | 8062篇 |
2012年 | 12937篇 |
2011年 | 19591篇 |
2010年 | 11677篇 |
2009年 | 11785篇 |
2008年 | 12761篇 |
2007年 | 14288篇 |
2006年 | 5666篇 |
2005年 | 5839篇 |
2004年 | 4843篇 |
2003年 | 4530篇 |
2002年 | 3372篇 |
2001年 | 2211篇 |
2000年 | 2044篇 |
1999年 | 2219篇 |
1998年 | 2032篇 |
1997年 | 1856篇 |
1996年 | 2080篇 |
1995年 | 1614篇 |
1994年 | 1531篇 |
1993年 | 1257篇 |
1992年 | 1121篇 |
1991年 | 1045篇 |
1990年 | 840篇 |
1989年 | 621篇 |
1988年 | 522篇 |
1987年 | 439篇 |
1986年 | 431篇 |
1985年 | 364篇 |
1984年 | 283篇 |
1983年 | 190篇 |
1982年 | 183篇 |
1981年 | 144篇 |
1980年 | 122篇 |
1979年 | 88篇 |
1978年 | 68篇 |
1976年 | 52篇 |
1974年 | 56篇 |
1973年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
In this paper we obtain a number of Maharam-type slice integral representations, with respect to scalar measures, for positive
projections in Dedekind complete vector lattices and f-algebras.
AMS Classification: 47B65, 46A40, 06F25 相似文献
112.
The Iyengar Type Inequalities with Exact Estimations and the Chebyshev Central Algorithms of Integrals 总被引:3,自引:0,他引:3
Xing Hua WANG Shi Jun YANG 《数学学报(英文版)》2005,21(6):1361-1376
In this paper, both low order and high order extensions of the Iyengar type inequality are obtained. Such extensions are the best possible in the same sense as that of the Iyengar inequality. hzrthermore, the Chebyshev central algorithms of integrals for some function classes and some related problems are also considered and investigated. 相似文献
113.
Neodymium doped bismuth layer structure ferroelectrics (BLSFs) ceramics CaBi4−xNdxTi4O15 (x=0, 0.25, 0.50, 0.75) were prepared by solid-state reaction method. X-ray diffraction pattern showed that single phase was formed when x=0-0.75. The refined lattice parameters showed that a (b) axes decrease at x=0.25 and increase with more Nd3+ dopant. The effects of Nd3+ doping on the dielectric and ferroelectric properties of CaBi4Ti4O15 ceramics are studied. Nd3+ dopant decreased the Curie temperature linearly, and the dielectric loss, tan δ, as well. The remnant polarization of Nd3+ doped CaBi4Ti4O15 ceramics was increased by 80% at x=0.25, while more Nd3+ dopant decreased the remnant polarization. CaBi3.75Nd0.25Ti4O15 ceramics had the largest piezoelectric constant d33. The structure and properties of CaBi4−xNdxTi4O15 ceramics showed that Nd3+ may occupy different crystal locations when Nd3+ content x is less than 0.25 and more than 0.50. 相似文献
114.
In this paper, the transformation processes of two types of bis(8-hydroxyquinoline)zinc: Znq2 dihydrate and anhydrous (Znq2)4 were investigated by X-ray diffraction (XRD), infrared spectra (IR), scanning electron microscope (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG). The effects of crystal structure on optical properties of bis(8-hydroxyquinoiline)zinc were analyzed. Znq2 dihydrate can be transformed into anhydrous (Znq2)4 during heating under vacuum. Reversal transformation occurs by the interaction between chloroform and (Znq2)4. But (Znq2)4 was partially transformed into Znq2 dihydrate by the interaction between ethanol and (Znq2)4. The different molecular structure results in different crystal stacking and electronic structure, thereby affect its optical properties. 相似文献
115.
Gaston Casanova 《Advances in Applied Clifford Algebras》2004,14(2):249-252
We define analytic functions within Clifford Algebras CL, and study their trigonometric properties. We write the addition formulas when their arguments, A and B in CL, commute, this generalizes ordinary trigonometry. We examine in particular the case A2 = 1.
相似文献
116.
M. Lashkarizadeh Bami 《Semigroup Forum》2004,69(2):219-229
In the present paper it is shown that if S1 and S2 are two
Clifford topological semigroups satisfying certain conditions
and T is an isometric isomorphism of LUC(S1*) onto LUC(S2*), then T
maps S1 topologically isomorphically onto S2. Furthermore, T
maps M
l
n(S1) (M(S1), respectively) isometrically
isomorphically onto M
l
n(S2) (M(S2), respectively). Indeed,
we have obtained a generalization of a well-known result of
Ghahramani, Lau and Losert for locally compact groups to a more
general setting of Clifford topological semigroups. 相似文献
117.
Geng Sheng WANG 《数学学报(英文版)》2005,21(5):1005-1014
This work is concerned with Pontryagin's maximum principle of optimal control problems governed by some non-well-posed semilinear heat equations. A type of approach to the non-well-posed optimal control problem is given. 相似文献
118.
Andrew Barton 《The Journal of the Operational Research Society》1987,38(10):965-974
This paper describes some work carried out in the Scientific Research and Development Branch (SRDB) of the Home Office, intended to contribute to an overall aim of building up internal expertise in the field of expert systems. This was done by carrying out a number of pilot and demonstrator projects, two of which are described in some detail. The plan, which proved successful, was to build as far as possible on the relevant skills already possessed by an OR group in the branch. The lessons learned from these are summarized in the hope that they will be of use to other groups who wish to become involved in this important area. 相似文献
119.
120.
Song LI Guo Mao WANG Zhi Song LIU 《数学学报(英文版)》2005,21(6):1475-1486
The purpose of this paper is to investigate the mean size formula of wavelet packets in Lp for 0 〈 p ≤ ∞. We generalize a mean size formula of wavelet packets given in terms of the p-norm joint spectral radius and we also give some asymptotic formulas for the Lp-norm or quasi-norm on the subdivision trees. All results will be given in the general setting, 相似文献