全文获取类型
收费全文 | 4609篇 |
免费 | 593篇 |
国内免费 | 165篇 |
专业分类
化学 | 499篇 |
晶体学 | 3篇 |
力学 | 391篇 |
综合类 | 103篇 |
数学 | 1107篇 |
物理学 | 884篇 |
无线电 | 2380篇 |
出版年
2024年 | 6篇 |
2023年 | 36篇 |
2022年 | 64篇 |
2021年 | 74篇 |
2020年 | 112篇 |
2019年 | 75篇 |
2018年 | 89篇 |
2017年 | 147篇 |
2016年 | 156篇 |
2015年 | 190篇 |
2014年 | 264篇 |
2013年 | 272篇 |
2012年 | 348篇 |
2011年 | 333篇 |
2010年 | 218篇 |
2009年 | 217篇 |
2008年 | 279篇 |
2007年 | 268篇 |
2006年 | 257篇 |
2005年 | 258篇 |
2004年 | 230篇 |
2003年 | 219篇 |
2002年 | 170篇 |
2001年 | 143篇 |
2000年 | 109篇 |
1999年 | 110篇 |
1998年 | 105篇 |
1997年 | 101篇 |
1996年 | 69篇 |
1995年 | 81篇 |
1994年 | 60篇 |
1993年 | 77篇 |
1992年 | 64篇 |
1991年 | 31篇 |
1990年 | 21篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有5367条查询结果,搜索用时 15 毫秒
31.
We consider the generalization of the classical P||Cmax problem (assign n jobs to m identical parallel processors by minimizing the makespan) arising when the number of jobs that can be assigned to each processor cannot exceed a given integer k. The problem is strongly NP-hard for any fixed k > 2. We briefly survey lower and upper bounds from the literature. We introduce greedy heuristics, local search and a scatter search approach. The effectiveness of these approaches is evaluated through extensive computational comparison with a depth-first branch-and-bound algorithm that includes new lower bounds and dominance criteria. 相似文献
32.
关于非平行板电容器电容计算的讨论 总被引:4,自引:3,他引:1
用串联方法计算非平行板电容器的电容,简便地得到与其他方法相同的结果。 相似文献
33.
Due to interference, path loss, multipath fading, background noise, and many other factors, wireless communication normally
cannot provide a wireless link with both a high data rate and a long transmission range. To address this problem, striping
network traffic in parallel over multiple lower-data-rate but longer-transmission-range wireless channels may be used. In
this paper, we propose a new striping method and evaluate its performances over multiple IEEE 802.11(b) channels under various
conditions. Our extensive simulation results show that this method is quite effective for such an application.
S.Y. Wang is an Associate Professor of the Department of Computer Science and Information Engineering at National Chiao Tung University,
Taiwan. He received his Master and Ph.D. degree in computer science from Harvard University in 1997 and 1999, respectively.
His research interests include wireless networks, Internet technologies, network simulations, and operating systems. He is
the author of the NCTUns 2.0 network simulator and emulator, which is being widely used by network and communication researchers.
More information about the tool is available at http://NSL.csie.nctu.edu.tw/nctuns.html.
C.H. Hwang received his master degree in computer science from NCTU in 2002 and currently is working for a network company.
C.L. Chou currently is a third-year Ph.D. student at the Department of Computer Science and Information Engineering, National Chiao
TungUniversity (NCTU), Taiwan. He received his master degree in computer science from NCTU in 2002. 相似文献
34.
自动检测系统广泛应用于各类产品的设计、生产、使用、维护等各个阶段,对提高产品性能及生产率、降低生产成本及整个生产周期成本起着重要作用。首先介绍了检测、检验以及自动检测系统的概念,其次通过自动检测系统的各个组成部分,详述了系统的工作原理,介绍了自动检测系统组建的概念、结构以及在组建中所使用的关键技术。对早期的自动检测系统和新一代自动检测系统进行了介绍,并详述自动检测系统的3个发展阶段。 相似文献
35.
36.
37.
可编程光学二值双轨逻辑门 总被引:1,自引:0,他引:1
基于双轨逻辑,本文提出一种可级联的并行二值逻辑门。所有十六种二值逻辑运算可以采用偏振半波相延编程来实现。也提出了用电光晶体实现实时编程的方法。本文中给出了实验结果。 相似文献
38.
In this paper, we consider a queueing system in which there are two exponential servers, each having his own queue, and arriving
customers will join the shorter queue. Based on the results given in Flatto and McKean, we rewrite the formula for the probability
that there are exactlyk customers in each queue, wherek = 0, 1,…. This enables us to present an algorithm for computing these probabilities and then to find the joint distribution
of the queue lengths in the system. A program and numerical examples are given. 相似文献
39.
A parallel inexact Newton method with a line search is proposed for two-stage quadratic stochastic programs with recourse. A lattice rule is used for the numerical evaluation of multi-dimensional integrals, and a parallel iterative method is used to solve the quadratic programming subproblems. Although the objective only has a locally Lipschitz gradient, global convergence and local superlinear convergence of the method are established. Furthermore, the method provides an error estimate which does not require much extra computation. The performance of the method is illustrated on a CM5 parallel computer.This work was supported by the Australian Research Council and the numerical experiments were done on the Sydney Regional Centre for Parallel Computing CM5. 相似文献
40.
Simulation at the gate level is computationally very expensive.Parallel processing is one technique to reduce simulation time.Possessing knowledge of the distribution of computational activity insimulation can aid in parallelizing it efficiently. We present a newcharacterization of the distribution of the computational workload infault simulation. An empirical analysis shows that the workloaddistribution is circuit specific, and is largely independent of thevector set being simulated. An inexpensive method to predict theworkload distribution is also discussed. 相似文献