全文获取类型
收费全文 | 13753篇 |
免费 | 1497篇 |
国内免费 | 397篇 |
专业分类
化学 | 1320篇 |
晶体学 | 31篇 |
力学 | 1102篇 |
综合类 | 152篇 |
数学 | 6821篇 |
物理学 | 1522篇 |
无线电 | 4699篇 |
出版年
2024年 | 62篇 |
2023年 | 234篇 |
2022年 | 427篇 |
2021年 | 482篇 |
2020年 | 404篇 |
2019年 | 391篇 |
2018年 | 387篇 |
2017年 | 517篇 |
2016年 | 556篇 |
2015年 | 489篇 |
2014年 | 842篇 |
2013年 | 848篇 |
2012年 | 977篇 |
2011年 | 826篇 |
2010年 | 641篇 |
2009年 | 755篇 |
2008年 | 782篇 |
2007年 | 807篇 |
2006年 | 665篇 |
2005年 | 596篇 |
2004年 | 442篇 |
2003年 | 422篇 |
2002年 | 368篇 |
2001年 | 339篇 |
2000年 | 309篇 |
1999年 | 233篇 |
1998年 | 254篇 |
1997年 | 215篇 |
1996年 | 157篇 |
1995年 | 175篇 |
1994年 | 143篇 |
1993年 | 128篇 |
1992年 | 110篇 |
1991年 | 90篇 |
1990年 | 78篇 |
1989年 | 64篇 |
1988年 | 51篇 |
1987年 | 43篇 |
1986年 | 39篇 |
1985年 | 57篇 |
1984年 | 50篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 31篇 |
1978年 | 20篇 |
1977年 | 29篇 |
1976年 | 18篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
我国的军工科研所成立于上世纪,它以军工项目的科研、预研为主,为我国的国防军工提供研发产品。伴随着我国经济实力的增强和科技军事力量的增长,军工科研院所也转变了原有的工业专属性质,走上了军民两用、寓军于民的道路,并在时代的进步中成为了我国先进装备制造业的重要科研力量和科技创新支柱。凸现军事工业“高、精、尖”的特点,以项目管理的优化为具体策略进行军工科研开发工作。 相似文献
3.
在介绍宽带无线移动发展趋势所采用的新技术的基础上,论述了宽带无线移动通信网络优化及相关发展策略的一些问题。 相似文献
4.
Ying Tan 《The Journal of VLSI Signal Processing》2002,32(1-2):45-54
In this paper, we propose a new approach for signal detection in wireless digital communications based on the neural network with transient chaos and time-varying gain (NNTCTG), and give a concrete model of the signal detector after appropriate transformations and mappings. It is well known that the problem of the maximum likelihood signal detection can be described as a complex optimization problem that has so many local optima that conventional Hopfield-type neural networks fail to solve. By refraining from the serious local optima problem of Hopfield-type neural networks, the NNTCTG makes use of the time-varying parameters of the recurrent neural network to control the evolving behavior of the network so that the network undergoes the transition from chaotic behavior to gradient convergence. It has richer and more flexible dynamics rather than conventional neural networks only with point attractors, so that it can be expected to have much ability to search for globally optimal or near-optimal solutions. After going through a transiently inverse-bifurcation process, the NNTCTG can approach the global optimum or the neighborhood of global optimum of our problem. Simulation experiments have been performed to show the effectiveness and validation of the proposed neural network based method for the signal detection in digital communications. 相似文献
5.
6.
Mikhail Andramonov 《Journal of Global Optimization》2002,24(2):115-132
We consider applications of disjunctive programming to global optimization and problems with equilibrium constraints. We propose a modification of the algorithm of F. Beaumont for disjunctive programming problems and show its numerical efficiency. 相似文献
7.
8.
Y. Wardi 《Journal of Optimization Theory and Applications》1989,61(3):473-485
A stochastic algorithm for finding stationary points of real-valued functions defined on a Euclidean space is analyzed. It is based on the Robbins-Monro stochastic approximation procedure. Gradient evaluations are done by means of Monte Carlo simulations. At each iteratex
i
, one sample point is drawn from an underlying probability space, based on which the gradient is approximated. The descent direction is against the approximation of the gradient, and the stepsize is 1/i. It is shown that, under broad conditions, w.p.1 if the sequence of iteratesx
1,x
2,...generated by the algorithm is bounded, then all of its accumulation points are stationary. 相似文献
9.
We consider the problem of maximizing a linear fractional function on the Pareto efficient frontier of two other linear fractional functions. We present a finite pivoting-type algorithm that solves the maximization problem while computing simultaneously the efficient frontier. Application to multistage efficiency analysis is discussed. An example demonstrating the computational procedure is included. 相似文献
10.
We describe a new algorithm which uses the trajectories of a discrete dynamical system to sample the domain of an unconstrained objective function in search of global minima. The algorithm is unusually adept at avoiding nonoptimal local minima and successfully converging to a global minimum. Trajectories generated by the algorithm for objective functions with many local minima exhibit chaotic behavior, in the sense that they are extremely sensitive to changes in initial conditions and system parameters. In this context, chaos seems to have a beneficial effect: failure to converge to a global minimum from a given initial point can often be rectified by making arbitrarily small changes in the system parameters. 相似文献