全文获取类型
收费全文 | 51628篇 |
免费 | 7764篇 |
国内免费 | 5839篇 |
专业分类
化学 | 36572篇 |
晶体学 | 582篇 |
力学 | 2707篇 |
综合类 | 377篇 |
数学 | 6888篇 |
物理学 | 18105篇 |
出版年
2024年 | 114篇 |
2023年 | 930篇 |
2022年 | 1308篇 |
2021年 | 1575篇 |
2020年 | 1885篇 |
2019年 | 1786篇 |
2018年 | 1585篇 |
2017年 | 1494篇 |
2016年 | 2262篇 |
2015年 | 2175篇 |
2014年 | 2600篇 |
2013年 | 3593篇 |
2012年 | 4271篇 |
2011年 | 4645篇 |
2010年 | 3209篇 |
2009年 | 3057篇 |
2008年 | 3401篇 |
2007年 | 3101篇 |
2006年 | 2789篇 |
2005年 | 2467篇 |
2004年 | 1948篇 |
2003年 | 1633篇 |
2002年 | 1699篇 |
2001年 | 1389篇 |
2000年 | 1151篇 |
1999年 | 1136篇 |
1998年 | 951篇 |
1997年 | 836篇 |
1996年 | 886篇 |
1995年 | 736篇 |
1994年 | 645篇 |
1993年 | 549篇 |
1992年 | 522篇 |
1991年 | 488篇 |
1990年 | 383篇 |
1989年 | 305篇 |
1988年 | 239篇 |
1987年 | 200篇 |
1986年 | 228篇 |
1985年 | 215篇 |
1984年 | 137篇 |
1983年 | 94篇 |
1982年 | 90篇 |
1981年 | 68篇 |
1980年 | 57篇 |
1979年 | 61篇 |
1978年 | 44篇 |
1976年 | 39篇 |
1974年 | 41篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
91.
The crystal structure, magnetic and magnetotransport properties of the variation of B′-site transition metal in Sr2FeMO6 (M=Mo, W) with double perovskites structure have been investigated systematically. Measurements of magnetization vs. temperature at H=5 T show that Sr2FeMoO6 is a ferromagnet and Sr2FeWO6 is an antiferromagnet with TN∼35 K. Additionally, the large magnetoresistance ratio (MR) of ∼22% (H=3 T) at room temperature (RT) was observed in the Sr2FeWO6 compound. However, the Sr2FeMoO6 compound did not show any significant MR even at high fields and RT (MR∼1%; H=3 T and 300 K). The implications of these findings are supported by band structure calculations to explain the interaction between the 4d(Mo) and 5d(W) orbitals of transition metal ions and oxygen ions. 相似文献
92.
Kunyu Guo 《Journal of Functional Analysis》2004,213(2):380-411
This paper mainly concerns defect operators and defect functions of Hardy submodules, Bergman submodules over the unit ball, and Hardy submodules over the polydisk. The defect operator (function) carries key information about operator theory (function theory) and structure of analytic submodules. The problem when a submodule has finite defect is attacked for both Hardy submodules and Bergman submodules. Our interest will be in submodules generated by polynomials. The reason for choosing such submodules is to understand the interaction of operator theory, function theory and algebraic geometry. 相似文献
93.
Yang Mujie Zhao Jian Li Aibing Shen Zhiquan Zhang Mingjian Lin Senhao 《Journal of polymer science. Part A, Polymer chemistry》1989,27(11):3829-3835
This paper reports that 60Co γ-ray irradiation can convert cis-polyphenylacetylene (cis-PPA) films prepared with rare-earth coordination catalysts to highly photosensitive materials. The dependence of the photosensitivity on irradiation dose, preparation methods, and microstructure of the PPA films has been investigated by means of a potential discharge technique. The photosensitivity was enhanced with increasing irradiation dose. The critical dose to produce a light response was 5 × 103 Gy. The maximum surface potential discharge rate was 618 V/s, and the dark decay was approximately 2 V/s for cis-PPA films irradiated with 60Co γ-ray (dose: 2 × 105 Gy). The cis-transoidal-PPA and an electrophotographic photoreceptor device incorporating cis-PPA showed a higher irradiation effect. The structure and properties of 60Co γ-ray irradiated rare-earth PPA films are similar to the unirradiated films. 相似文献
94.
95.
96.
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
97.
Ching‐Yuan Cheng Kuan‐Jiuh Lin 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(8):m363-m365
In the title compound, catena‐poly[lithium‐μ3‐ethylenediphosphonato], [Li(C2H7O6P2)]n, the supramolecular monoclinic (C2/c) structure consists of one‐dimensional lithium chains [Li⋯Li = 2.7036 (8) Å] that are embedded within ethylenediphosphonate anions linked by strong symmetric hydrogen bonds [O⋯O = 2.473 (3) Å]. The Li atoms and the H atom in the symmetric hydrogen bond reside on twofold rotation axes and there is an inversion center at the mid‐point of the C—C bond of the ethylenediphosphonate ligand. 相似文献
98.
线性泛函方程解的振动性的新结果 总被引:1,自引:0,他引:1
本文研究高阶泛函方程x(g(t))=P(t)x(t)+Q1(t)x(g2(t))+…+Qk(t)x(gk+1(t))解的振动性,得到了一些新的振动条件.改进和推广了已有结果. 相似文献
99.
100.