全文获取类型
收费全文 | 6000篇 |
免费 | 606篇 |
国内免费 | 344篇 |
专业分类
化学 | 357篇 |
晶体学 | 9篇 |
力学 | 744篇 |
综合类 | 91篇 |
数学 | 4281篇 |
物理学 | 1468篇 |
出版年
2024年 | 7篇 |
2023年 | 49篇 |
2022年 | 84篇 |
2021年 | 84篇 |
2020年 | 166篇 |
2019年 | 159篇 |
2018年 | 151篇 |
2017年 | 176篇 |
2016年 | 185篇 |
2015年 | 131篇 |
2014年 | 289篇 |
2013年 | 723篇 |
2012年 | 246篇 |
2011年 | 323篇 |
2010年 | 272篇 |
2009年 | 355篇 |
2008年 | 361篇 |
2007年 | 405篇 |
2006年 | 320篇 |
2005年 | 294篇 |
2004年 | 265篇 |
2003年 | 258篇 |
2002年 | 219篇 |
2001年 | 192篇 |
2000年 | 202篇 |
1999年 | 185篇 |
1998年 | 154篇 |
1997年 | 98篇 |
1996年 | 108篇 |
1995年 | 64篇 |
1994年 | 67篇 |
1993年 | 44篇 |
1992年 | 55篇 |
1991年 | 53篇 |
1990年 | 29篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 20篇 |
1984年 | 24篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有6950条查询结果,搜索用时 15 毫秒
191.
In this paper, by employing linear algebra methods we obtain the following main results:
- (i) Let and be two disjoint subsets of such that Suppose that is a family of subsets of such that for every pair and for every i. Then Furthermore, we extend this theorem to k‐wise L‐intersecting and obtain the corresponding result on two cross L‐intersecting families. These results show that Snevily's conjectures proposed by Snevily (2003) are true under some restricted conditions. This result also gets an improvement of a theorem of Liu and Hwang (2013).
- (ii) Let p be a prime and let and be two subsets of such that or and Suppose that is a family of subsets of [n] such that (1) for every pair (2) for every i. Then This result improves the existing upper bound substantially.
192.
193.
讨论了光纤光栅传感系统中常用的复用技术及其限制,阐述了利用CDMA技术实现光纤布拉格光栅阵列波长解调的复用方式,对系统的原理和性能进行了理论分析。在此基础上通过MATLAB做了基于CDMA的光纤光栅传感仿真分析,仿真结果表明该方法能区分反射波长重叠的光栅,从而提高FBG网络复用的频带利用率。 相似文献
194.
On the global asymptotic stability and oscillation of solutions in a stochastic business cycle model
Guifeng Deng Guoting Chen Lili Qian 《Journal of Difference Equations and Applications》2016,22(11):1609-1620
We discuss a second order nonlinear stochastic difference equation which is constructed of a business cycle model with organized labor considered. A global asymptotic mean square stability criterion is obtained by Lyapunov function method. We also prove a theorem on the almost sure oscillation of the solutions for the difference equation with state-independent stochastic perturbations. 相似文献
195.
Tian Xiang Svetlin Georgiev Georgiev 《Mathematical Methods in the Applied Sciences》2016,39(4):833-863
In this paper, we first establish some user‐friendly versions of fixed‐point theorems for the sum of two operators in the setting that the involved operators are not necessarily compact and continuous. These fixed‐point results generalize, encompass, and complement a number of previously known generalizations of the Krasnoselskii fixed‐point theorem. Next, with these obtained fixed‐point results, we study the existence of solutions for a class of transport equations, the existence of global solutions for a class of Darboux problems on the first quadrant, the existence and/or uniqueness of periodic solutions for a class of difference equations, and the existence and/or uniqueness of solutions for some kind of perturbed Volterra‐type integral equations. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
196.
Mansur I. Ismailov Bülent Oğur 《Numerical Methods for Partial Differential Equations》2016,32(2):564-590
This article considers the inverse problem of identification of a time‐dependent thermal diffusivity together with the temperature in an one‐dimensional heat equation with nonlocal boundary and integral overdetermination conditions when a heat exchange takes place across boundary of the material. The well‐posedness of the problem is studied under some regularity, and consistency conditions on the data of the problem together with the nonnegativity condition on the Fourier coefficients of the initial data and source term. The inverse problem is also studied numerically by using the Crank–Nicolson finite difference scheme combined with predictor‐corrector technique. The numerical examples are presented and discussed. © 2015 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 32: 564–590, 2016 相似文献
197.
一类非线性二阶差分方程解的振动性 总被引:7,自引:0,他引:7
本文建立了非线性二阶差分方程的若干振动准则,所得结果改进了文[5]中相应的定理. 相似文献
198.
In this paper, we aim to investigate the difference equation
\begin{align*}
\Delta^{2}y(t-1)+|y(t)|=0, \ \ \ \ \ t\in[1,T]_{\mathbb{Z}}
\end{align*}
with different boundary conditions $y(0)=0$ or $\Delta y(0)=0$ and $y(T+1)=B$ or $\Delta y(T)=B$,\ where\ $T\geq 1$ is an integer and $B\in\mathbb{R}$. We will show that how the values of $T$ and $B$ influence the existence and uniqueness of the solutions to the about problem. In details, for the different problems, the $TB$-plane explicitly divided into different parts according to the number of the solutions to the above problems. These parts of $TB$-plane for the value of $T$ and $B$ guarantee the uniqueness, the existence and the nonexistence of solutions respectively. 相似文献
199.
本文结合差分方法与边界积分方程方法,提出并研究了一类新的求解发展型方程初边值问题的高阶差分与边界积分方程耦合数值方法.对于有界区域问题与无界区域问题给出了数值计算格式及其误差的先验估计. 相似文献
200.
本文研究了混合序列部分和的若干收敛性质.利用Serfling不等式推广情形,证明了一类随机变量序列部分和的一个收敛性结果,获得了混合序列部分和的收敛性,并进一步得到了混合序列加权和的强收敛性和完全收敛性,推广并改进了文[2]中有关结果. 相似文献