全文获取类型
收费全文 | 3701篇 |
免费 | 259篇 |
国内免费 | 259篇 |
专业分类
化学 | 1453篇 |
晶体学 | 24篇 |
力学 | 182篇 |
综合类 | 37篇 |
数学 | 1496篇 |
物理学 | 1027篇 |
出版年
2024年 | 7篇 |
2023年 | 45篇 |
2022年 | 48篇 |
2021年 | 77篇 |
2020年 | 87篇 |
2019年 | 90篇 |
2018年 | 83篇 |
2017年 | 102篇 |
2016年 | 84篇 |
2015年 | 93篇 |
2014年 | 159篇 |
2013年 | 323篇 |
2012年 | 144篇 |
2011年 | 197篇 |
2010年 | 127篇 |
2009年 | 205篇 |
2008年 | 215篇 |
2007年 | 231篇 |
2006年 | 211篇 |
2005年 | 143篇 |
2004年 | 124篇 |
2003年 | 161篇 |
2002年 | 130篇 |
2001年 | 139篇 |
2000年 | 117篇 |
1999年 | 108篇 |
1998年 | 105篇 |
1997年 | 81篇 |
1996年 | 67篇 |
1995年 | 53篇 |
1994年 | 51篇 |
1993年 | 42篇 |
1992年 | 43篇 |
1991年 | 36篇 |
1990年 | 17篇 |
1989年 | 28篇 |
1988年 | 22篇 |
1987年 | 26篇 |
1986年 | 22篇 |
1985年 | 18篇 |
1984年 | 24篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 16篇 |
1980年 | 25篇 |
1979年 | 24篇 |
1978年 | 8篇 |
1977年 | 10篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有4219条查询结果,搜索用时 31 毫秒
1.
Marcus Carlsson 《Expositiones Mathematicae》2021,39(1):149-157
von Neumann’s inequality in matrix theory refers to the fact that the Frobenius scalar product of two matrices is less than or equal to the scalar product of the respective singular values. Moreover, equality can only happen if the two matrices share a joint set of singular vectors, and this latter part is hard to find in the literature. We extend these facts to the separable Hilbert space setting, and provide a self-contained proof of the “latter part”. 相似文献
2.
3.
Design and development of a two‐dimensional system based on hydrophilic and reversed‐phase liquid chromatography with on‐line sample treatment for the simultaneous separation of excreted xenobiotics and endogenous metabolites in urine 下载免费PDF全文
Diego García‐Gómez Encarnación Rodríguez‐Gonzalo Rita Carabias‐Martínez 《Biomedical chromatography : BMC》2015,29(8):1190-1196
In the present work we describe a two‐dimensional liquid chromatographic system (2D‐LC) with detection by mass spectrometry (MS) for the simultaneous separation of endogenous metabolites of clinical interest and excreted xenobiotics deriving from exposure to toxic compounds. The 2D‐LC system involves two orthogonal chromatographic modes, hydrophilic interaction liquid chromatography (HILIC) to separate polar endogenous metabolites and reversed‐phase (RP) chromatography to separate excreted xenobiotics of low and intermediate polarity. Additionally, the present proposal has the novelty of incorporating an on‐line sample treatment based on the use of restricted access materials (RAMs), which permits the direct injection of urine samples into the system. The work is focused on the instrumental coupling, studying all possible options and attempting to circumvent the problems of solvent incompatibility between the RAM device and the two chromatographic columns, HILIC and RP. The instrumental configuration developed, RAM‐HILIC‐RPLC‐MS/MS, allows the simultaneous assessment of urinary metabolites of clinical interest and excreted compounds derived from exposure to toxic agents with minimal sample manipulation. Thus, it may be of interest in areas such as occupational and environmental toxicology in order to explore the possible relationship between the two types of compounds. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
Zhong-Qing Wang 《Journal of Mathematical Analysis and Applications》2002,274(1):374-403
An orthogonal system of rational functions is discussed. Some inverse inequalities, imbedding inequalities and approximation results are obtained. Two model problems are considered. The stabilities and convergences of proposed rational spectral schemes and rational pseudospectral schemes are proved. The techniques used in this paper are also applicable to other problems on the whole line. Numerical results show the efficiency of this approach. 相似文献
5.
6.
用Java实现网上结构图实验仿真 总被引:2,自引:0,他引:2
基于线性系统仿真的连接矩阵方法,用Java语言开发面向结构图的实验仿真程序,以Applet小应用程序的形式插入网页中运行,实现了信号与系统网上实验教学中的结构图实验仿真。经试用,程序在浏览器中运行正常,可以完成一般线性系统仿真,与以MATLAB,LABView等程序开发的实验仿真程序相比,该程序运行环境简单,几乎所有常用的Web浏览器都支持Java运行,不需另行安装相应组件。对于线性系统结构图,实现了所见即所得的图形化编程环境,具有较好的人机交互性。 相似文献
7.
8.
Robert S. Strichartz 《Proceedings of the American Mathematical Society》2002,130(3):805-817
Harmonic mappings from the Sierpinski gasket to the circle are described explicitly in terms of boundary values and topological data. In particular, all such mappings minimize energy within a given homotopy class. Explicit formulas are also given for the energy of the mapping and its normal derivatives at boundary points.
9.
A FUNDAMENTAL SOLUTION FOR THE LAPLACE OPERATOR ON THE QUATERNIONIC HEISENBERG GROUP 总被引:2,自引:0,他引:2
朱理 《数学物理学报(B辑英文版)》2002,22(3)
In this paper, the author studies the Laplace operator on the quaternionic Heisenberg group, construct a fundamental solution for it and use this solution to prove the Lp-boundedness and the weak (1-1) boundedness of certain singular convolution operators on the quaternionic Heisenberg group. 相似文献
10.
We call a one-way infinite word w over a finite alphabet (ρ,l)-repetitive if all long enough prefixes of w contain as a suffix a ρth power (or more generally a repetition of order ρ) of a word of length at most l. We show that each (2,4)-repetitive word is ultimately periodic, as well as that there exist continuum many, and hence also nonultimately periodic, (2,5)-repetitive words. Further, we characterize nonultimately periodic (2,5)-repetitive words both structurally and algebraically. 相似文献