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   10561篇
  免费   245篇
  国内免费   534篇
系统科学   360篇
丛书文集   354篇
教育与普及   289篇
理论与方法论   32篇
现状及发展   72篇
研究方法   44篇
综合类   10185篇
自然研究   4篇
  2024年   83篇
  2023年   124篇
  2022年   193篇
  2021年   236篇
  2020年   106篇
  2019年   44篇
  2018年   92篇
  2017年   112篇
  2016年   109篇
  2015年   232篇
  2014年   345篇
  2013年   284篇
  2012年   319篇
  2011年   390篇
  2010年   362篇
  2009年   383篇
  2008年   467篇
  2007年   457篇
  2006年   371篇
  2005年   378篇
  2004年   303篇
  2003年   234篇
  2002年   266篇
  2001年   279篇
  2000年   304篇
  1999年   570篇
  1998年   565篇
  1997年   570篇
  1996年   518篇
  1995年   450篇
  1994年   401篇
  1993年   317篇
  1992年   311篇
  1991年   294篇
  1990年   219篇
  1989年   237篇
  1988年   183篇
  1987年   123篇
  1986年   65篇
  1985年   17篇
  1984年   6篇
  1979年   2篇
  1977年   2篇
  1976年   2篇
  1973年   2篇
  1972年   2篇
  1969年   4篇
  1967年   2篇
  1964年   1篇
  1957年   2篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
<正> In this paper,an equivalency condition of nonsingularity in nonlinear semidefinite programming,which can be viewed as a generalization of the equivalency condition of nonsingularity for linearsemidefinite programming,is established under certain conditions of convexity.  相似文献   
52.
Taking the institution design of controlling the pollution behavior of enterprises as an example, the symbol system specialized for the design and analysis of behavior management institution is put forward, which predigests the institution design greatly and make the process of institution design much like the engineering design. The measure combination method for improving the parameters of the institution, the arithmetic for calculating the validity of the institution and the arithmetic for calculating the behavior probability of the irrational managed are also put forward, which make the design and analysis technology of behavior management institution more practical.  相似文献   
53.
Model-set is utilized in state estimation for maneuvering target tracking.Two minimal symmetric model-subsets are designed and investigated by moment matching method,which include hypersphere-symmetric model-subset and axis-symmetric model-subset,if system mode is a random variable and obeys certain probability distribution.They can be used as the fundamental model-subset for multiple models estimation with fixed structure,variable structure and moving bank.The model-groups constructed by above designed subsets are given,which give the practical guidance for use of model-set in multiple models approach with a variable structure.Simulation results show that the performances of two minimal model-set significantly outperform the corresponding model-sets with fixed spacing.  相似文献   
54.
The coordinated Bayesian optimization algorithm (CBOA) is proposed according to the characteristics of the function independence, conformity and supplementary between the electronic countermeasure (ECM) and the firepower attack systems. The selection criteria are combinations of probabilities of individual fitness and coordinated degree and can select choiceness individual to construct Bayesian network that manifest population evolution by producing the new chromosome. Thus the CBOA cannot only guarantee the effective pattern coordinated decision-making mechanism between the populations, but also maintain the population multiplicity, and enhance the algorithm performance. The simulation result confirms the algorithm validity.  相似文献   
55.
Process capability analysis and estimation scheme for autocorrelated data   总被引:1,自引:0,他引:1  
<正>Autocorrelation is prevalent in continuous production processes,such as the processes in the chemical and pharmaceutical industries.With the development of measurement technology and data acquisition technology,sampling frequency is getting higher and the existence of autocorrelation cannot be ignored.This paper analyzes five estimation schemes of process capability for autocorrelated data.Comparisons among these schemes are discussed for small sample and large sample.In conclusion,this paper gives a procedure of process capability analysis for autocorrelated data.  相似文献   
56.
车辆组合导航定位技术   总被引:14,自引:1,他引:14  
介绍车辆导航定位及其组合导航定位技术.组合导航利用现代信息融合技术,实现对车辆组合导航的准确定位,具有全方位、全天候、自主式定位功能.着重研究了GPS/GLNOASS/MM和GPS/DR/MM三组合导航定位及跑车试验分析.跑车试验表明,车辆组合导航定位精度及可靠性比单独GPS导航定位有所提高,车辆运行效率和安全性大大改善,提高了通行能力,有效地缓解了交通拥挤状况,从而为实现交通管理"自动化"以及车辆行驶"智能化"提供了可靠的保证.  相似文献   
57.
Knowledge-based bridge detection from SAR images   总被引:2,自引:0,他引:2       下载免费PDF全文
Automatic bridge detection is an important application of SAR images. Differed from the classical CFAR method, a new knowledge-based bridge detection approach is proposed. The method not only uses the backscattering intensity difference between targets and background but also applies the contextual information and spatial relationship between objects. According to bridges’ special characteristics and scattering properties in SAR images, the new knowledge-based method includes three processes: river segmentation, potential bridge areas detection and bridge discrimination. The application to AIRSAR data shows that the new method is not sensitive to rivers’ shape. Moreover, this method can detect bridges successfully when river segmentation is not very exact and is more robust than the radius projection method.  相似文献   
58.
A newly proposed distributed dynamic state estimation algorithm based on the maximum a posteriori (MAP) technique is generalised and studied for power systems. The system model involves linear time-varying load dynamics and nonlinear measurements. The main contribution of this paper is to compare the performance and feasibility of this distributed algorithm with several existing distributed state estimation algorithms in the literature. Simulations are tested on the IEEE 39-bus and 118-bus systems under various operating conditions. The results show that this distributed algorithm performs better than distributed quasi-steady state estimation algorithms which do not use the load dynamic model. The results also show that the performance of this distributed method is very close to that by the centralized state estimation method. The merits of this algorithm over the centralized method lie in its low computational complexity and low communication load. Hence, the analysis supports the efficiency and benefits of the distributed algorithm in applications to large-scale power systems.  相似文献   
59.
Product diffusion refers to the phenomenon that the later demand is dependent on the early sales. To investigate how a firm’s advance selling strategy is affected by the effect of product diffusion, we consider a monopolist seller who sells a fashionable product in a market that comprises of myopic and strategic consumers over two periods (i.e., the advance selling season and the regular selling season). For a linear product diffusion effect we find that, when the effect of product diffusion is positive, the seller may set an extremely high advance selling price to induce the strategic consumers to purchase in the regular selling season, which is counter-intuitive. Moreover, the optimal procurement quantity for the seller may increase in the negative effect of product diffusion and decrease in the amount of strategic consumers. When we extend our model to consider a concave quadratic product diffusion effect, however, the optimal procurement quantity is concave in the amount of strategic consumers. Numerical studies are further presented to discuss the managerial insights.  相似文献   
60.
变点理论在极值分布阈值选取中的应用   总被引:3,自引:0,他引:3  
极值理论已经被广泛应用于解决金融、保险等领域的厚尾分布问题,而阚值的选取一直是极值理论实际应用的难点和重点。在已有研究成果基础上。本文尝试引入变点理论进行定量化的阈值选取。分析了变,最理论进行阚值选取的基本原理和方法,利用Burr分布产生的随机样本进行模拟,得到了较好的效果。并在此基础上运用S&P500和Danish火灾保险数据进行了实证分析。  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