全文获取类型
收费全文 | 10206篇 |
免费 | 1003篇 |
国内免费 | 742篇 |
专业分类
化学 | 2101篇 |
晶体学 | 27篇 |
力学 | 798篇 |
综合类 | 225篇 |
数学 | 6177篇 |
物理学 | 2623篇 |
出版年
2024年 | 21篇 |
2023年 | 106篇 |
2022年 | 162篇 |
2021年 | 219篇 |
2020年 | 272篇 |
2019年 | 282篇 |
2018年 | 254篇 |
2017年 | 307篇 |
2016年 | 399篇 |
2015年 | 259篇 |
2014年 | 489篇 |
2013年 | 897篇 |
2012年 | 442篇 |
2011年 | 607篇 |
2010年 | 554篇 |
2009年 | 608篇 |
2008年 | 624篇 |
2007年 | 661篇 |
2006年 | 573篇 |
2005年 | 536篇 |
2004年 | 462篇 |
2003年 | 453篇 |
2002年 | 416篇 |
2001年 | 332篇 |
2000年 | 307篇 |
1999年 | 257篇 |
1998年 | 239篇 |
1997年 | 189篇 |
1996年 | 174篇 |
1995年 | 140篇 |
1994年 | 99篇 |
1993年 | 92篇 |
1992年 | 81篇 |
1991年 | 79篇 |
1990年 | 40篇 |
1989年 | 45篇 |
1988年 | 34篇 |
1987年 | 22篇 |
1986年 | 30篇 |
1985年 | 29篇 |
1984年 | 25篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 18篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 7篇 |
1973年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Z. M. Topilova S. B. Meshkova V. P. Dotsenko A. V. Kiriyak V. P. Antonovich 《Journal of Applied Spectroscopy》2004,71(2):253-256
The conditions of sensitization of the luminescence of Eu(III) by Tb(III) ions in complexes with inorganic (Na2WO4) and organic (nalidixic acid) ligands in sorbates on solid matrices (zeolite CaX and crystalline zirconium phosphate (ZrP)) and in coprecipitation with CaWO4 have been investigated. It has been established that the maximum sensitization of the europium luminescence is attained in the case where Eu and Tb are present in a 1:0.5 ratio. In this case, the integral intensity of luminescence of Eu(III) (the band with max = 612 nm) in the sorbate of its complex with nalidixic acid on ZrP accounts for more than 60% of the luminescence intensity of the industrial photoluminophor Y2O3:Eu (FL-612) possessing red luminescence, and the intensity of Tb(III) luminescence (the band with max = 545 nm) accounts for about 40% of the luminescence intensity of the photoluminophor Gd2O2S:Tb possessing green luminescence. 相似文献
993.
We develop a dynamical formulation of one-dimensional scattering theory where the reflection and transmission amplitudes for a general, possibly complex and energy-dependent, scattering potential are given as solutions of a set of dynamical equations. By decoupling and partially integrating these equations, we reduce the scattering problem to a second order linear differential equation with universal initial conditions that is equivalent to an initial-value time-independent Schrödinger equation. We give explicit formulas for the reflection and transmission amplitudes in terms of the solution of either of these equations and employ them to outline an inverse-scattering method for constructing finite-range potentials with desirable scattering properties at any prescribed wavelength. In particular, we construct optical potentials displaying threshold lasing, antilasing, and unidirectional invisibility. 相似文献
994.
非负矩阵与有向图的谱半径 总被引:2,自引:0,他引:2
本文给出非负矩阵的谱半径的上界、下界,由此给出有向图的谱半径的界. 相似文献
995.
Suthep Suantai 《Southeast Asian Bulletin of Mathematics》2000,24(2):297-303
In this paper, we give necessary and sufficient conditions for infinite matrices mapping from the Nakano vector-valued sequence space (X, p) into any BK-space, and by using this result, we obtain the matrix characterizations from (X, p) into the sequence spaces (Y), c0(Y, q), c(Y), s(Y), Er(Y), and Fr(Y), where p = (pk) and q = (qk) are bounded sequences of positive real numbers such that pk 1 for all k N, r 0, and s 1.AMS Subject Classification (2000): 46A45 相似文献
996.
令n是一个正整数,[n]={1,2,…,n}.利用集合[叫上的s-子集族((ns))构作了二元(p,r,d)-叠加码,研究了它的容错和析取性质并介绍了它在非适应性群测(Nonadaptive Group Testing)方面的应用. 相似文献
997.
本文给出了一个关联图为圈的非负、半正定矩阵A为完全正的一个充要条件.我们还证明了这样的矩阵A(当A为完全正时)的分解指数即为A的阶数. 相似文献
998.
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
999.
Ammonia molecules interact with U atoms, and the resulting U:NH3 complex rearranges upon visible irradiation to form the H2N--UH and HN==UH2 molecules in excess argon. These products are identified by functional group frequencies, 15NH3 and ND3 isotopic shifts, and comparison to frequencies calculated by using density functional theory. The N==U pi bond in HN==UH2 is enhanced by partial triple-bond character through N(2p) to U(5f) conjugation, which is comparable to that found in the analogous HN==ThH2 molecule. These products also form complexes with additional ammonia molecules in the matrix. The interesting higher-energy N[triple chemical bond]UH3 complex is not formed. 相似文献
1000.
This paper develops a gradient based and a least squares based iterative algorithms for solving matrix equation AXB + CXTD = F. The basic idea is to decompose the matrix equation (system) under consideration into two subsystems by applying the hierarchical identification principle and to derive the iterative algorithms by extending the iterative methods for solving Ax = b and AXB = F. The analysis shows that when the matrix equation has a unique solution (under the sense of least squares), the iterative solution converges to the exact solution for any initial values. A numerical example verifies the proposed theorems. 相似文献