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   7683篇
  免费   641篇
  国内免费   118篇
系统科学   1160篇
丛书文集   86篇
教育与普及   167篇
理论与方法论   286篇
现状及发展   881篇
研究方法   7篇
综合类   5851篇
自然研究   4篇
  2024年   18篇
  2023年   35篇
  2022年   52篇
  2021年   56篇
  2020年   32篇
  2019年   4篇
  2018年   743篇
  2017年   758篇
  2016年   449篇
  2015年   76篇
  2014年   63篇
  2013年   61篇
  2012年   327篇
  2011年   1038篇
  2010年   904篇
  2009年   577篇
  2008年   633篇
  2007年   877篇
  2006年   75篇
  2005年   117篇
  2004年   168篇
  2003年   209篇
  2002年   119篇
  2001年   77篇
  2000年   77篇
  1999年   122篇
  1998年   87篇
  1997年   109篇
  1996年   99篇
  1995年   98篇
  1994年   99篇
  1993年   70篇
  1992年   39篇
  1991年   40篇
  1990年   53篇
  1989年   31篇
  1988年   29篇
  1987年   13篇
  1986年   5篇
  1985年   2篇
  1967年   1篇
排序方式: 共有8442条查询结果,搜索用时 15 毫秒
11.
By analyzing the observation data from Dongchuan Debris Flow Observation and Research Station and historical data from year 1965 to 1990 gotten from National Astronomical Ob-servatories/Yunnan Observatory,the responding of debris flow in Jiangjia Ravine to Solar Proton Flare is studied. The following conclusion can be drawn. Solar Proton Flare,as one of most im-portant astronomical factors,affects the activity of debris flow in Yunnan. Generally,from 1965 to1990,the more active Solar Pro-ton Flare is,the greater the probability of high frequency and large runoff of debris flow is. On the contrary,the less active Solar Pro-ton Flare is,the greater the probability of low frequency,small runoff,and low sediment transport of debris flow is.  相似文献   
12.
本文提出了一种轴结构设计的知识表示方法,实现了轴的结构设计,并绘制出轴的结构图  相似文献   
13.
本文是文[1]的继续,我们以Q-远域为工具,首先引入和研究了拓扑分子格的STi分离公理(i=-1,0,1,2,3,4)。其次我们引入了S-不定序同态和S-同胚序同态等概念,给出了它们的若干特征性质。最后我们得到了各种STi分离公理是S-同胚序同态下保持不变的性质。  相似文献   
14.
We consider a risk model with a premium rate which varies with the level of free reserves. In this model, the occurrence of claims is described by a Cox process with Markov intensity process, and the influence of stochastic factors is considered by adding a diffusion process. The integro-differential equation for the ruin probability is derived by a infinitesimal method.  相似文献   
15.
社会主义道德建设的系统辩证思考   总被引:1,自引:0,他引:1  
社会主义道德建设要用系统辩证的眼光来认识 ,要遵循系统辩证论的基本规律来推进和完善  相似文献   
16.
STABILITY CRITERIA FOR A CLASS OF UNCERTAINSYSTEMS WITH TIME—DELAY   总被引:1,自引:0,他引:1  
Some stability criteria are obtained for a class of uncertain systems with time-delay usingLyapunov functional and analytic techniques. It is easy to check the criteria by making use of theboundedness of the uncertainties.  相似文献   
17.
This paper investigates the impact of a secondary market, where retailers can buy and sell excessinventories, on the supply chain. We develop a two-period model with a single manufacturer and tworetailers. At the beginning of the first period the retailers order and receive products from themanufacturer, but at the beginning of the second period, they can trade surplus products betweenthemselves in the secondary market. We investigate the impact of the correlated dependence ofretailers' demand on both the quantity effect and the allocation effect under the secondary market.Lastly,we study potential strategies for the manufacturer to increase sales with the existence of thesecondary market.  相似文献   
18.
With time-based competition and rapid technology advancements, effective manufacturingscheduling and supply chain coordination are critical to quickly respond to changing marketconditions. These problems, however, are difficult in view of inherent complexity and variousuncertainties involved. Based on a series of results by the authors, decomposition and coordination byusing Lagrangian relaxation is identified in this paper as an effective way to control complexity anduncertainty.A manufacturing scheduling problem is first formulated within the job shop context withuncertain order arrivals, processing times, due dates, and part priorities as a separable optimizationproblem. A solution methodology that combines Lagrangian relaxation, stochastic dynamicprogramming, and heuristics is developed. Method improvements to effectively solve large problemsare also highlighted. To extend manufacturing scheduling within a factory to coordinate autonomicmembers across chains of suppliers, a decentralized supply chai  相似文献   
19.
We consider the stability of a random Riccati equation with a Markovian binary jump coefficient. More specifically, we are concerned with the boundedness of the solution of a random Riccati difference equation arising from Kalman filtering with measurement losses. A sufficient condition for the peak covariance stability is obtained which has a simpler form and is shown to be less conservative in some cases than a very recent result in existing literature. Furthermore, we show that a known sufficient condition is also necessary when the observability index equals one.  相似文献   
20.
In the present paper, we focus on constructive spherical codes. By employing algebraic geometry codes, we give an explicit construction of spherical code sequences. By making use of the idea involved in the proof of the Gilbert-Varshamov bound in coding theory, we construct a spherical code sequence in exponential time which meets the best-known asymptotic bound by Shamsiev and Wyner.  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