全文获取类型
收费全文 | 5519篇 |
免费 | 11篇 |
国内免费 | 40篇 |
专业分类
系统科学 | 641篇 |
丛书文集 | 562篇 |
教育与普及 | 166篇 |
理论与方法论 | 10篇 |
现状及发展 | 431篇 |
研究方法 | 679篇 |
综合类 | 3079篇 |
自然研究 | 2篇 |
出版年
2015年 | 8篇 |
2014年 | 16篇 |
2013年 | 10篇 |
2012年 | 290篇 |
2011年 | 357篇 |
2010年 | 91篇 |
2009年 | 21篇 |
2008年 | 304篇 |
2007年 | 327篇 |
2006年 | 469篇 |
2005年 | 522篇 |
2004年 | 379篇 |
2003年 | 339篇 |
2002年 | 299篇 |
2001年 | 248篇 |
2000年 | 399篇 |
1999年 | 113篇 |
1998年 | 49篇 |
1997年 | 19篇 |
1996年 | 13篇 |
1995年 | 28篇 |
1994年 | 37篇 |
1993年 | 52篇 |
1992年 | 39篇 |
1991年 | 30篇 |
1990年 | 23篇 |
1989年 | 25篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 28篇 |
1985年 | 19篇 |
1984年 | 13篇 |
1983年 | 23篇 |
1982年 | 20篇 |
1981年 | 15篇 |
1980年 | 12篇 |
1979年 | 10篇 |
1971年 | 9篇 |
1970年 | 19篇 |
1959年 | 90篇 |
1958年 | 124篇 |
1957年 | 101篇 |
1956年 | 99篇 |
1955年 | 75篇 |
1954年 | 78篇 |
1953年 | 60篇 |
1952年 | 76篇 |
1951年 | 57篇 |
1950年 | 8篇 |
1948年 | 16篇 |
排序方式: 共有5570条查询结果,搜索用时 0 毫秒
31.
Chen Jingxiong Xie Lianggui Beijing Institute of Radio Measurement P.O. Box Beijing China 《系统工程与电子技术(英文版)》1993,(3)
This paper presents the principle of electromagnetic missile from the mathematical point of view, and verifies rigorously that the radiating power over whole space is limited. 相似文献
32.
LQ YingzhongInst. for Techno-Economics Energy System Analysis. P.O. Box Beijing China 《系统工程与电子技术(英文版)》1991,(1)
The long-term energy demand in China and the-Chinese share in global CO2 emission are forecasted on the basis of scenarios of population growth and economy development up to 2050 proposed in view of the interaction of energy, economy, environment and social development. The total energy demand in 2050 will reach 4.4~ 5.4 billion tce. It is shown in energy supply analysis that coal is China's major energy in primary energy supply. The share of CO2 emission in the future Chinese energy system will be out of proportion to its energy consumption share because of the high persentage of coal to be consumed. It will reach about 27%. The nuclear option which would replace 30.7% of coal in the total primary energy supply will reduce the share by 9.8%. So the policy considerations on the future Chinese energy system is of great importance to the global CO2 issues. 相似文献
33.
Wang FuhengBeijing Institute of Environment Features P.O.Box - Beijing China 《系统工程与电子技术(英文版)》1991,(1)
A systematic elaboration is given on atomic and molecular theory problems encountered in dealing with space science and engineering. Three sections are presented in the paper on calculations for gas thermodynamic and transfer properties, characteristics of the optical radiation from the reentry' bodies, and the interaction between surfaces of man-made satellites and incident particles. Researches on them are much related to the fundamental problems regarding the atomic and molecular theory. 相似文献
34.
Hu Yi He DehuanBeijing Institute of Remote Sensing Equipment P. O. Box Beijing China 《系统工程与电子技术(英文版)》1991,(1)
A new type of vocoder system based upon formant analysis is presented in this paper. The LMS adaptive algorithm is used for tracking formants of speech signals. The results of computer simulation show that the new vocoder has better synthesized speech quality. 相似文献
35.
Qiangfu Zhao Zhong Wang Youan KeDept. of Electronic Eng. Beijing Institute of Technology P.O.Box Beijing China 《系统工程与电子技术(英文版)》1991,(2)
It has long been realized that the problem of radar imaging is a special case of image reconstruction in which the data are incomplete and noisy. In other fields, iterative reconstruction algorithms have been used successfully to improve the image quality. This paper studies the application of iterative algorithms in radar imaging. A discrete model is first derived, and the iterative algorithms are then adapted to radar imaging. Although such algorithms are usually time consuming, this paper shows that, if the algorithms are appropriately simplified, it is possible to realize them even in real time. The efficiency of iterative algorithms is shown through computer simulations. 相似文献
36.
Luo Xueshan Liu PeilinDepartment of System Engineering & Math National University of Defense Technology Changsha Hunan .P.R.CHINA 《系统工程与电子技术(英文版)》1992,(2)
In this paper a model of military command process under the combat situation is presented. The model is based on the Lanchester Equations and Fuzzy Decision Theory. The decision of a military commander is usually a process from precise to fuzzy and then from fuzzy to precise,and the model fitted this process well. The model was used in a Warfare Simulation System whose object is to evaluate the effectiveness of the military C3I systems. 相似文献
37.
Li LayuanWuhan University of Water Transportation Engineering Wuhan P.R.China 《系统工程与电子技术(英文版)》1992,(4)
A dist ributed optimal local double loop (DOLDL) network is presented. Emphasis is laid on the topology and distributed routing algorithms for the DOLDL. On the basis of building an abstract model, a set of definitions and theorems are described and proved. An algorithm which can optimize the double loop networks is presented. The optimal values of the topologic parameters for the DOLDL have been obtained by the algorithm, and these numerical results are analyzed. The study shows that the bounds of the optimal diameter d and average hop distance a for this class of networks are [3N- 2]≤d≤[3N ] and (5N/9 (N-1))-(3N -1.8)相似文献
38.
39.
1.INTaODUCTIONThemultilayerfeedforwardneuralnetworks(MFNN)hasbeenwidelyappliedinmanyfieldssuchaspatternrecognition,nonlinearoptimization,systemidentificationandcontrol.Thesimpleback-propagation(BP)learningalgorithmisusuallyadoptedtoupdateitsweights.TheBPalgorithm,however,suffersdrawbacksofslowconvergenceandunpredictablesolutionsduringlearning.Althoughmailyapproachessuchasvariablestepsize,conjugategradient,pseudo-Newtonmethods[4]andothermethods[3,10],havebeendevelopedtoovercometheproble… 相似文献
40.
1.INTRODUCTION2-statesystemreliabilityoftenassumesthatthesystemisrepresentedbyaprobabilisticgraphG=(V,E),withasetV~{yi,v2,'',}ofvenicesandasetE~{el,e2,'',}ofedges(orlinks,branches)containedinit.Thesystemisfunctioningifthereexistsapathfromtheinputnodetotheoutputnode.Thusthereliabilityisconsideredwithamatterofconnectivityonlyandthereliabilityanalysishasbeenprimarilyconcernedwiththeenumerationofpathesorcutsinthereferences[1-4].Butinmanyphysicalsystemsuchaspowertransmissionsystems,oilorwat… 相似文献