全文获取类型
收费全文 | 9911篇 |
免费 | 351篇 |
国内免费 | 489篇 |
专业分类
系统科学 | 415篇 |
丛书文集 | 307篇 |
教育与普及 | 234篇 |
理论与方法论 | 37篇 |
现状及发展 | 43篇 |
研究方法 | 35篇 |
综合类 | 9680篇 |
出版年
2024年 | 83篇 |
2023年 | 109篇 |
2022年 | 208篇 |
2021年 | 229篇 |
2020年 | 145篇 |
2019年 | 57篇 |
2018年 | 103篇 |
2017年 | 83篇 |
2016年 | 130篇 |
2015年 | 224篇 |
2014年 | 344篇 |
2013年 | 282篇 |
2012年 | 371篇 |
2011年 | 407篇 |
2010年 | 396篇 |
2009年 | 434篇 |
2008年 | 460篇 |
2007年 | 438篇 |
2006年 | 392篇 |
2005年 | 355篇 |
2004年 | 297篇 |
2003年 | 255篇 |
2002年 | 294篇 |
2001年 | 342篇 |
2000年 | 301篇 |
1999年 | 523篇 |
1998年 | 477篇 |
1997年 | 461篇 |
1996年 | 435篇 |
1995年 | 402篇 |
1994年 | 335篇 |
1993年 | 253篇 |
1992年 | 248篇 |
1991年 | 218篇 |
1990年 | 189篇 |
1989年 | 151篇 |
1988年 | 151篇 |
1987年 | 91篇 |
1986年 | 46篇 |
1985年 | 20篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1960年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
针对可重构视频阵列处理器的设计要求及传统测试方法测试视频编解码系统时速度慢、精度低和可观测性不强的问题。开发了基于Qt的用户界面,设计实现了以现场可编程门阵列(Field programmable gate-array,FPGA)为核心的软硬件协同测试平台。在PC端实现以软件仿真为基础的数据传输与图像重现,在FPGA端实现以可重构视频阵列处理器为基础的视频编解码算法并行映射。实验结果表明,在工作频率为100 MHz时,FPGA与PC之间可正确传输数据并满足算法测试时不同测试用例的更换需求,具有较好的可观测性。 相似文献
42.
43.
Yigal GERCHAK 《系统科学与系统工程学报(英文版)》2004,13(1):36-44
We consider tasks where in order to perform them it is sufficient that one member of a group will know how to do it. We are interested in the effect of task difficulty, and variability of that difficulty, on group performance, and in particular on the marginal contribution of an additional number to the performance of groups of different size. We explore the implications of various stochastic orders over task difficulty and variability. Some intuitive conjectures are shown to be false. 相似文献
44.
Aiming at the reference range selection for different antennas in interferometric inverse synthetic aperture radar (InISAR) systems, this paper proposes a respective focusing (RF) method. The reference ranges for echoes of different antennas are selected respectively for RF, which is different from the traditional uniform focusing (UF) with the same reference range applied to all the antennas. First, a comparison between UF and RF for InISAR signal model considering the ranging error is given. Compared with RF, UF has an advantage in overcoming the ranging error differences between different antennas. Then the influence of ranging error upon the interferometric imaging with RF is investigated particularly, and it is found that the ranging error differences between different antennas are far smaller than the wavelength, which is advantageous to imaging. By comparing the capabilities of interferometric imaging between RF and UF, it is concluded that RF is a better choice in conquering problems such as image mismatching and phase ambiguity even with ranging errors. Simulations demonstrate the validity of the proposed method. 相似文献
45.
An efficient design method is proposed for the cooperative control problem of morphing wing systems with distributed structures and bounded control inputs. The multi-agent model of the distributed morphing wing system is established. The cooperative controllers with saturation constraints are presented. By introducing the concepts in consensus algorithms, the cooperative information links in the controllers are described by graphs, and the corresponding Laplacian matrix is defined. The design conditions of the cooperative controllers are proposed, in the form of linear matrix inequalities. For the case of undirected information links, the controller design conditions are simplified as algebraic inequalities, which highly reduce the computation cost. The designed controllers are implemented on a distributed morphing wing platform, and experiments are carried out. Simulation and experiment results show that the controllers can make all the actuating units in the morphing wing system cooperatively achieve the desired positions, which demonstrates the effectiveness of the proposed theory. 相似文献
46.
This paper studies variational discretization for the optimal control problem governed by parabolic equations with control constraints.First of all,the authors derive a priori error estimates where |||u-U(h|||L∞(J;L2(Ω))=O(h2+k).It is much better than a priori error estimates of standard finite element and backward Euler method where |||μ-Uh|||(L∞(J;L2(Ω))=O(h+ k).Secondly,the authors obtain a posteriori error estimates of residual type.Finally,the authors present some numerical algorithms for the optimal control problem and do some numerical experiments to illustrate their theoretical results. 相似文献
47.
In this paper, we analyze the pricing decision and the compensation strategy of a firm that relies on a heterogeneous sales force to sell its product in two periods. The sales agents’ selling abilities are their private information and will determine the effectiveness of the agents’ selling efforts. We introduce three compensation contract strategies, i.e. pooling, semi-separating and separating that the firm can adopt in period one and by applying principle-agent theory, derive the optimal compensation contracts and optimal price for the firm in two periods in each strategy. Comparing these three contract strategies, we found that the optimal strategy for the firm depends on the discount factor. We show that the firm will surely offer separating contracts in period one for some small discount factor, and for some large discount factor pooling contract is certain to be provided in period one. However, semi-separating contracts may be considered for some mediate discount factor, and also may not appear for all discount factors in period one. Our analysis also reveals that the optimal price decreases with the discount factor when pooling contract is offered in period one and increases with the discount factor when separating contracts is offered in period one. 相似文献
48.
应用闽东地区柳杉人工林样地材料,探讨了密度效应二次模型,并对其进行生产弹性分析和边际产量分析,测定了柳杉人工林林分密度的生产弹性值和边际产量。 相似文献
49.
技术转移谈判一直困扰着参与技术转移的双方,针对这一问题本文借鉴并发展了现有的协商谈判方法,提出了适用于技术转移的协商谈判的系统方法,以引导双方在谈判中达到“共同盈得”的协议. 相似文献
50.
提出了二次型多层前馈神经网络的卡尔曼滤波学习算法,并证明了该算法的收敛性。与文献[2,3]中的学习算法和经典的误差反向传播学习算法相比,新的学习算法具有更快的学习速度、良好的泛化能力,并且对学习率有很好的鲁棒性,不容易陷入局部极小点。仿真实验结果表明了新算法的有效性。 相似文献