首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3446篇
  免费   225篇
  国内免费   156篇
化学   283篇
晶体学   4篇
力学   139篇
综合类   6篇
数学   1496篇
物理学   823篇
无线电   1076篇
  2024年   11篇
  2023年   31篇
  2022年   48篇
  2021年   58篇
  2020年   61篇
  2019年   60篇
  2018年   65篇
  2017年   85篇
  2016年   91篇
  2015年   96篇
  2014年   203篇
  2013年   277篇
  2012年   180篇
  2011年   202篇
  2010年   216篇
  2009年   253篇
  2008年   258篇
  2007年   229篇
  2006年   186篇
  2005年   162篇
  2004年   127篇
  2003年   105篇
  2002年   116篇
  2001年   108篇
  2000年   88篇
  1999年   69篇
  1998年   56篇
  1997年   64篇
  1996年   36篇
  1995年   45篇
  1994年   38篇
  1993年   28篇
  1992年   36篇
  1991年   26篇
  1990年   14篇
  1989年   16篇
  1988年   15篇
  1987年   13篇
  1986年   8篇
  1985年   8篇
  1984年   4篇
  1983年   6篇
  1982年   11篇
  1981年   2篇
  1980年   2篇
  1979年   3篇
  1978年   4篇
  1977年   3篇
  1973年   1篇
  1972年   1篇
排序方式: 共有3827条查询结果,搜索用时 8 毫秒
1.
文章介绍了新一代IP骨干网上的IP QoS实现技术,论述了集成业务(IntServ)与差分业务(DiffServ)解决方案的特点,详细介绍了相关的队列管理与排队机制。并结合多协议标签交换(MPLS)技术的最新发展,阐述了综合多协议标签交换流量工程与DiffServ技术体系端到端IP QoS的实现。  相似文献   
2.
小波变换在金融数据分析中的应用   总被引:11,自引:0,他引:11  
市场上的数据,从本质上讲都是一种时间序列。它和小波分析中的信号具有相同的特性。因此,完全可以将这些经济时间序列看成信号,应用小波变换进行分析和预测。  相似文献   
3.
Space time-index plots for probing dynamical nonstationarity   总被引:3,自引:0,他引:3  
We propose a simple method to efficiently probe dynamical nonstationarity in observed time series. In a space time-index plot, the density distributions as a function of normalized time-index are V-shaped due to nonstationarity. We show that this method is workable for short data sets and typical examples are illustrated.  相似文献   
4.
Mathematical models with stage structures are proposed to describe the process of awareness, evaluation and decision-making. First, a system of ordinary differential equations is presented that incorporates the awareness stage and the decision-making stage. If the adoption rate is bilinear and imitations are dominant, we find a threshold above which innovation diffusion is successful. Further, if the adoption rate has a higher nonlinearity, it is shown that there exist bistable equilibria and a region such that an innovation diffusion is successful inside and is unsuccessful outside. Secondly, a model with a time delay is proposed that includes an evaluation stage of a product. It is proved that the system exhibits stability switches. The bifurcation direction of equilibria is also discussed.  相似文献   
5.
We consider queuing systems where customers are not allowed to queue, instead of that they make repeated attempts, or retrials, in order to enter service after some time. We obtain the distribution of the number of retrials produced by a tagged customer, until he finds an available server.  相似文献   
6.
In this paper, by means of a new twin fixed-point theorem in a cone, the existence of at least two positive solutions of m-point boundary value problem for second order dynamic equations on time scales is considered.  相似文献   
7.
We consider a delayed predator-prey system with Beddington-DeAngelis functional response. The stability of the interior equilibrium will be studied by analyzing the associated characteristic transcendental equation. By choosing the delay τ as a bifurcation parameter, we show that Hopf bifurcation can occur as the delay τ crosses some critical values. The direction and stability of the Hopf bifurcation are investigated by following the procedure of deriving normal form given by Faria and Magalhães. An example is given and numerical simulations are performed to illustrate the obtained results.  相似文献   
8.
Imaging of latent fingerprints using time-resolved (TR) method offers a broader platform to eliminate the unwanted background emission. In this paper, a novel TR imaging technique is demonstrated and implemented, which facilitates the detection of latent fingerprints with nanosecond resolution. Simulated experiments were carried out with two overlapping fingerprints treated with two fluorescent powders having different lifetimes in nanosecond range. The dependence of the fluorescence emission intensity in nanosecond resolution of TR imaging is also revealed.  相似文献   
9.
The aim of this paper is to propose an algorithm based on the philosophy of the Variable Neighborhood Search (VNS) to solve Multi Depot Vehicle Routing Problems with Time Windows. The paper has two main contributions. First, from a technical point of view, it presents the first application of a VNS for this problem and several design issues of VNS algorithms are discussed. Second, from a problem oriented point of view the computational results show that the approach is competitive with an existing Tabu Search algorithm with respect to both solution quality and computation times.  相似文献   
10.
教学质量的时齐马尔可夫链评估法   总被引:1,自引:0,他引:1  
本文研究了教学质量评估中的一种定量分析方法──时齐马尔可夫链评估法.阐明了这种方法的理论依据及其实施程序、并指出它较之其他教学质量评估法更显合理.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号