全文获取类型
收费全文 | 102402篇 |
免费 | 18205篇 |
国内免费 | 11692篇 |
专业分类
化学 | 71152篇 |
晶体学 | 1157篇 |
力学 | 6414篇 |
综合类 | 702篇 |
数学 | 11672篇 |
物理学 | 41202篇 |
出版年
2024年 | 364篇 |
2023年 | 2135篇 |
2022年 | 3608篇 |
2021年 | 3785篇 |
2020年 | 4264篇 |
2019年 | 3957篇 |
2018年 | 3569篇 |
2017年 | 3281篇 |
2016年 | 5077篇 |
2015年 | 4932篇 |
2014年 | 6039篇 |
2013年 | 7682篇 |
2012年 | 9270篇 |
2011年 | 9450篇 |
2010年 | 6392篇 |
2009年 | 6264篇 |
2008年 | 6724篇 |
2007年 | 5936篇 |
2006年 | 5551篇 |
2005年 | 4573篇 |
2004年 | 3612篇 |
2003年 | 2789篇 |
2002年 | 2700篇 |
2001年 | 2306篇 |
2000年 | 1955篇 |
1999年 | 2119篇 |
1998年 | 1807篇 |
1997年 | 1750篇 |
1996年 | 1716篇 |
1995年 | 1430篇 |
1994年 | 1264篇 |
1993年 | 1073篇 |
1992年 | 927篇 |
1991年 | 839篇 |
1990年 | 699篇 |
1989年 | 531篇 |
1988年 | 408篇 |
1987年 | 329篇 |
1986年 | 342篇 |
1985年 | 274篇 |
1984年 | 162篇 |
1983年 | 129篇 |
1982年 | 105篇 |
1981年 | 62篇 |
1980年 | 46篇 |
1979年 | 16篇 |
1977年 | 3篇 |
1957年 | 31篇 |
1936年 | 7篇 |
1909年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
本文主要研究的是相函数为齐次椭圆多项式的自由高阶Schrodinger方程.通过相函数等值面的几何性质,得到了解算子的Strichartz加权估计和极大算子加权估计. 相似文献
22.
On Dirichlet Characters of Polynomials 总被引:1,自引:0,他引:1
The main purpose of this paper is to use the properties of Gaussiansums and the analytic method to study the problem of calculatingone kind of character sums modulo q, and to give an interestingidentity. 2000 Mathematics Subject Classification 11L10, 11L40. 相似文献
23.
A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity. 相似文献
24.
Liyue Liu Yingge Yang Yafei Zhang 《Physica E: Low-dimensional Systems and Nanostructures》2004,24(3-4):343-348
The electrical conductivity was investigated for multi-walled carbon nanotubes (MWNTs) dissolved in chloroform and toluene, respectively. The electrical conductivity remarkably increased with increase in the content of MWNTs, which is in accordance with Archie's equation . Furthermore, a hypothesis of the electronic transport process was proposed to explain the difference between the solution and the solid compound. In addition, the temperature dependence of the electrical conductivity shows that log σ vs. 1/T exist in a good linear relationship. The activation energy of the electrical conductivity decreased with increase in concentration and an inflexion was observed at 60 °C in MWNT/toluene solution. 相似文献
25.
26.
27.
28.
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
29.
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
30.
The first α‐diimine nickel(I) complex having a chloro bridge is reported. The centrosymmetric dinuclear structure of {[ArN?C(Me)C(Me)?NAr]NiCl}2[Ar?2,6?C6H3(i‐Pr)2] features two chelating α‐diimine ligands and two bridged chlorine atoms, so that a distorted tetrahedral N2Cl2 coordination geometry for nickel results. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献