全文获取类型
收费全文 | 64290篇 |
免费 | 280篇 |
国内免费 | 588篇 |
专业分类
系统科学 | 1259篇 |
丛书文集 | 568篇 |
教育与普及 | 285篇 |
理论与方法论 | 539篇 |
现状及发展 | 35014篇 |
研究方法 | 1281篇 |
综合类 | 24021篇 |
自然研究 | 2191篇 |
出版年
2013年 | 822篇 |
2012年 | 732篇 |
2011年 | 2825篇 |
2009年 | 620篇 |
2008年 | 971篇 |
2007年 | 1103篇 |
2006年 | 1162篇 |
2005年 | 1310篇 |
2004年 | 2430篇 |
2003年 | 2040篇 |
2002年 | 1745篇 |
2001年 | 1756篇 |
2000年 | 1246篇 |
1999年 | 1189篇 |
1998年 | 651篇 |
1997年 | 775篇 |
1996年 | 540篇 |
1994年 | 684篇 |
1993年 | 690篇 |
1992年 | 1122篇 |
1991年 | 902篇 |
1990年 | 1022篇 |
1989年 | 858篇 |
1988年 | 800篇 |
1987年 | 877篇 |
1986年 | 878篇 |
1985年 | 1060篇 |
1984年 | 908篇 |
1983年 | 734篇 |
1982年 | 857篇 |
1981年 | 897篇 |
1980年 | 1021篇 |
1979年 | 1651篇 |
1978年 | 1481篇 |
1977年 | 1481篇 |
1976年 | 1261篇 |
1975年 | 1275篇 |
1974年 | 1286篇 |
1973年 | 1450篇 |
1972年 | 1538篇 |
1971年 | 1562篇 |
1970年 | 1762篇 |
1969年 | 1513篇 |
1968年 | 1477篇 |
1967年 | 1346篇 |
1966年 | 1128篇 |
1965年 | 873篇 |
1964年 | 516篇 |
1958年 | 709篇 |
1957年 | 563篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
901.
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
902.
903.
Ayyar RAHMAN 《系统科学与复杂性》2006,(2)
We study a single-server queueing system with state-dependent arrivals and general service-distribution.or simply M(n)/G/1/K.where the server follows an N policy and takes multiple vacationswhen the system is empty.We provide a recursive algorithm using the supplementary variable tech-nique to munerically compute the stationary queue length distribution of the system.The only inputrequirements are the Laplace-Stieltjes transforms of the service time distribution and the vacation timedistribution.and the state-dependent arrival rate.The computational complexity of the algorithm isO(K~3). 相似文献
904.
基于相对论性激光-等离子体动力学理论和PIC方法建立了激光入射等离子弧柱的模型,该模型描述了激光入射等离子弧后粒子的运动,并模拟了弧柱形态的变化。通过改变激光的平均功率、脉冲宽度以及重复频率,模拟等离子弧柱形态变化,得到的激光参数对等离子弧柱形态的影响规律。通过控制弧柱的直径可以提高材料的熔积性能。计算结果表明增大激光平均功率、脉冲宽度,可以更深地压缩等离子弧;但是,重复频率的影响则会出现波动现象。激光等离子复合加工更适合于精细加工。 相似文献
905.
1 .INTRODUCTIONπ/4 DQPSKmodemhasbeenchosenasthemodemschemeinmanymobilecommunicationsystems[1 ] .Inπ/4 DQPSKmodem ,theinformationbitsaremappedintophasetransitionsratherthanabsolutephasevalues.Thisencodingofinformationinthetransitionsovercomesthephaseambiguityproblemsresultingfromtheestimationofcarrierphaseinnon differentialPSKsystems.Soπ/4 DQPSKallowsforsimplebasebanddifferentialdemodulation .Further,inπ/4 DQPSK ,themaximumphaseshiftisrestrict edto± 1 35°(ascomparedto± 1 80… 相似文献
906.
Zhou XianminShanghai Research & Development Centre Guil in Road Shanghai P.R.China 《系统工程与电子技术(英文版)》1993,(4)
Computer simulation models may by used to gain further information about missile performance variability. Model validation is an important aspect of the test program for a missile system. Validation provides a basis for confidence in the model's results and is a necessary step if the model is to be used to draw inference about the behavior of the real missile. This paper is a review of methods useful for validation of computer simulation models of missile systems and provides a new method with high degree of confidence for validation of computer simulation models of missile systems. Some examples of the use of the new method in validating computer simulation models are given. 相似文献
907.
本文针对分布式系统提出一种多程序并行-协同求解问题的方法;叙述求解环境的实现和运行机理,以及相关协议问题。 相似文献
908.
Ozgur M ARAZ 《系统科学与系统工程学报(英文版)》2013,22(3):319-339
Recent developments in computational sciences and computer modeling have allowed emergency preparedness exercises to include simulation models as supporting tools.These simulation models are generally built for predicting temporal and geographic patterns of disease spread.However sole use of simulation models in exercise design falls short in terms of incorporating policy decision makers’ preferences into decision-making processes.In this paper,a general framework for exercising public health preparedness plans with a decision support system is presented to integrate estimation of key epidemiological parameters with a system dynamics model of an outbreak.A multi-criteria decision making framework,an Analytical Hierarchy Process model,is then developed and integrated with the simulation model to help public health policy makers prioritize their response goals and evaluate mitigation strategies in a table-top exercise environment. 相似文献
909.
910.
Application of Method-of-Lines to Charging-Up Process in Pipelines with Entrapped Air 总被引:1,自引:0,他引:1
Introduction The initial charging-up process is an important opera-tion in an intermittent,undulating pipeline system.Re-cently,the charging-up process has received attention with the aim of predicting the effective duration of supply in different regions… 相似文献