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   44086篇
  免费   1129篇
  国内免费   1882篇
系统科学   1507篇
丛书文集   1548篇
教育与普及   1875篇
理论与方法论   171篇
现状及发展   197篇
研究方法   152篇
综合类   41636篇
自然研究   11篇
  2024年   271篇
  2023年   615篇
  2022年   844篇
  2021年   936篇
  2020年   577篇
  2019年   185篇
  2018年   340篇
  2017年   475篇
  2016年   470篇
  2015年   964篇
  2014年   1343篇
  2013年   1240篇
  2012年   1363篇
  2011年   1629篇
  2010年   1611篇
  2009年   1867篇
  2008年   2087篇
  2007年   2025篇
  2006年   1546篇
  2005年   1559篇
  2004年   1101篇
  2003年   968篇
  2002年   1022篇
  2001年   1104篇
  2000年   1319篇
  1999年   2391篇
  1998年   2245篇
  1997年   2281篇
  1996年   2112篇
  1995年   1893篇
  1994年   1642篇
  1993年   1404篇
  1992年   1251篇
  1991年   1122篇
  1990年   966篇
  1989年   850篇
  1988年   704篇
  1987年   443篇
  1986年   225篇
  1985年   84篇
  1984年   15篇
  1983年   6篇
  1982年   1篇
  1981年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
本文提出了一种“谐波组清除算法”来估计周期信号的参数。该算法不仅计算简单并可获得较高的频率分辨率,而且对信号模型具有较强的鲁棒性。最后,用数值仿真数据与实测直升机噪声数据对该算法进行了检验。  相似文献   
182.
军用分布式交互仿真(DIS)原型系统的实现研究   总被引:1,自引:0,他引:1  
讨论以军事训练为目的的分布式交互仿真技术,分析了DIS设计需考虑的若干主要问题、一致通信环境、仿真应用开发的客户服务器环境,并在此基础上给出一个DIS原型系统的网络结构、功能原理与性能分析。  相似文献   
183.
基于规则专家系统的广义随机Petri网仿真分析模型   总被引:2,自引:0,他引:2  
利用广义随机Petri网为基于规则的专家系统建模,将推理过程中规则的匹配—选择—执行循环的各阶段统一于其广义随机Petri网模型中,通过对该模型的计算机仿真分析,可对系统的可靠性及性能进行评价。  相似文献   
184.
冷连轧过程线性化动态模型的研究   总被引:2,自引:0,他引:2  
以多机架四辊冷连轧机为背景,研究了冷连忆过程的动态模型,建立了冷连轧过程的工作点线性化状态空间模型,实验仿真结果说明了这一动态模型的有效性。  相似文献   
185.
Considering the design problem of non-fragile decentralized H∞ controller with gain variations, the dynamic feedback controller by measurement feedback for uncertain linear systems is constructed and studied. The parameter uncertainties are considered to be unknown but norm bounded. The design procedures are investigated in terms of positive definite solutions to modify algebraic Riccati inequalities. Using information exchange among local controllers, the designed non-fragile decentralized H∞ controllers guarantee that the uncertain closed-loop linear systems are stable and with H∞ -norm bound on disturbance attenuation. A sufficient condition that there are such non-fragile H∞ controllers is obtained by algebraic Riccati inequalities. The approaches to solve modified algebraic Riccati inequalities are carried out preliminarily. Finally, a numerical example to show the validity of the proposed approach is given.  相似文献   
186.
Traditional Chinese medicine (TCM) has a rich knowledge about human health and disease by its special way evolved along a very long history. As modern medicine is achieving much progress, arguments and disputes toward TCM never end. To avoid losing precious knowledge of living TCM masters, endeavors have been engaged to systematic collection of those knowledge of TCM masters, such as their growth experiences, effective practical cases toward diseases and typical therapeutic principles and methods. Knowledge mining methods have been expected to explore some useful or hidden patterns to unveil some mysteries of the TCM system. In the paper, some computerized methods are applied toward those collected materials about some living TCM masters in China mainland to show a different way of exposing essential ideas of those TCM masters by correspondence visualization which aims to help people understand TCM holistic views toward disease and body, and facilitate tacit knowledge transfer and sense-making of the essence of TCM. The work is one kind of qualitative meta-synthesis of TCM masters' knowledge.  相似文献   
187.
The authors consider the problem of on-line scheduling of unit execution time jobs on uniform machines with rejection penalty. The jobs arrive one by one and can be either accepted and scheduled, or be rejected. The objective is to minimize the total completion time of the accepted jobs and the total penalty of the rejection jobs. The authors propose an on-line algorithm and prove that the competitive ratio is 1/2 (2 W √3) ≈ 1.86602.  相似文献   
188.
Target modeling and scattering function calculating are important prerequisites and groundwork for the synthetic aperture radar (SAR) imaging simulation. According to the difficult problems that normal methods cannot calculate the scattering function of electrically large object under the condition to wideband, an effective method of improved equivalent edge currents is presented and applied to SAR imaging simulation for the first time. This method improves calculating velocity and has relatively high precision. The concrete steps of applying the method are given. By way of the simulation experiment, the effectiveness of the method is verified.  相似文献   
189.
In this paper, the joint production and recycling problem is investigated for a hybrid manufacturing and remanufacturing system where brand-new products are produced in the manufacturing plant and recycled products are remanufactured into as-new products in the remanufacturing facility. Both the brand-new products and remanufactured products are used to satisfy customer demands. Returns of used products that are recycled from customers are assumed to be stochastic and nonlinearly price-dependent. A mathematical model is proposed to maximize the overall profit of the system through simultaneously optimizing the production and recycling decisions, subject to two capacity constraints — the manufacturing capacity and the remanufacturing capacity. Based on Lagrangian relaxation method, subgradient algorithm and heuristic algorithm, a solution approach is developed to solve the problem. A representative example is presented to illustrate the system, and managerial analysis indicates that the uncertainties in demand and return have much influence on the production and recycling policy. In addition, twenty randomly produced examples are solved, and computational results show that the solution approach can obtain very good solutions for all examples in reasonable time.  相似文献   
190.
Most inventory researches assume that production level can fluctuate arbitrarily. However, large fluctuation of the production level in many firms may be much costly. This paper addresses the coordinating pricing and inventory control problem in a bounded production system with uncertain yield, in which the production level is constrained between a maximum and minimum level in each period and the price can be adjusted dynamically. We show that the optimal policy is the interval base-stock-list-price policy. Also, we study the impact of the production bounds and uncertainty of the yield on the production system. Numerical experiments are also performed to study the impact of parameters on the system.  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