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   10539篇
  免费   823篇
  国内免费   271篇
系统科学   1260篇
丛书文集   161篇
教育与普及   121篇
理论与方法论   290篇
现状及发展   882篇
研究方法   12篇
综合类   8905篇
自然研究   2篇
  2024年   23篇
  2023年   56篇
  2022年   93篇
  2021年   94篇
  2020年   57篇
  2019年   21篇
  2018年   753篇
  2017年   780篇
  2016年   475篇
  2015年   148篇
  2014年   135篇
  2013年   121篇
  2012年   403篇
  2011年   1134篇
  2010年   953篇
  2009年   639篇
  2008年   733篇
  2007年   986篇
  2006年   186篇
  2005年   264篇
  2004年   264篇
  2003年   288篇
  2002年   189篇
  2001年   168篇
  2000年   144篇
  1999年   294篇
  1998年   308篇
  1997年   316篇
  1996年   263篇
  1995年   230篇
  1994年   206篇
  1993年   178篇
  1992年   155篇
  1991年   146篇
  1990年   121篇
  1989年   106篇
  1988年   86篇
  1987年   69篇
  1986年   24篇
  1985年   16篇
  1984年   3篇
  1983年   2篇
  1981年   2篇
  1967年   1篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
船体高谐调振动固有频率的估算   总被引:1,自引:1,他引:0  
本文提出三谐调至五谐调主船体垂向和水平方向振动的固有频率估算的几个新公 式.这些公式是以实船激振试验时获得的固有频率为基础,采用线性回归的方法推导 出来的。这些公式特别适用于船舶设计的初始阶段。它不仅可用于普通强度钢材料建 造的船舶.而且也适用于中部区域内的主要构件采用高强度钢材料建造的船舶.  相似文献   
992.
993.
Soft Systems Methodology is especially useful in diagnosing and addressing organizational problems and designing new systems in cultures that are characterised by pluralistic views and values. This paper demonstrates how SSM workshops in a large government agency resulted in a high level of creativity. SSM is then proposed as a methodology that could enhance group creativity in organizational design contexts.  相似文献   
994.
Increasingly knowledge has become a determining factor in achieving life’s potential and is the currency of the age. Without access to Information an individuals’ knowledge base cannot be enriched and without knowledge the individual becomes increasingly powerless. Advances in technology have provided opportunities for some to add to their stock of knowledge but access to sources of information is uneven and can lead to social unrest. The availability of information is an important factor in managing change and empowering citizens. The question about information and power then becomes one of ownership or sovereignty of the information. If we are to create an open society then we need to ensure that there is open access to knowledge through flexible and intelligent information systems that are available for all. In this paper we consider if we are truly entering the knowledge age or the age of ignorance.  相似文献   
995.
Arabidopsis thaliana, a model plant species, has a number of advantages over other plant species as an experimental organism due to many of its genetic and genomic features. The Chinese Arabidopsis community has made significant contributions to plant biology research in recent years[1,2]. In 2006, studies of plant biology in China received more attention than ever before, especially those pertaining to Arabidopsis research. Here we briefly summarize recent advances in Arabidopsis re-search in China.  相似文献   
996.
This paper proposes a method to formalize the interoperation in multi-domain environment. Through employing the algebra method, we conclude four types of the conflicts for the interoperation, and analyzes the cause of the policy conflicts. For each type of conflicts, we formalize it and proposes the method of detection and resolution. Finally, the method is illuminated be effective through comparing our work with others.  相似文献   
997.
研究试验的滴灌自控系统,用于农田、果园、塑料大棚、温室及草坪绿地灌水,根据果树物候期的生长需要,可实现果园科学自动给水。本系统采用真空表张力计和光导纤维传感器,可做为普及推广滴灌和喷灌的配套设备。  相似文献   
998.
本文考虑Banach空间中带约束的极值问题(P),通过引入容许集合的高阶逼近,首次建立了无限维空间上优化问题(P)的高于三阶的最优性充分条件,并概括了〔1,3,5,6,7〕中的极值问题最优性充分条件的二阶结果。  相似文献   
999.
Electrophysiological studies have utilized event-related brain potentials (ERPs) to investigate neural processes related to the evaluation of the outcome of behavioral performance or to the evaluation of external feedback. The feedback-related negativity (FRN) in brain potentials has been shown to be sensitive to information indicating monetary loss or negative feedback. Since monetary loss usually indicates both the consequence of previous performance and the reward value of stimuli, it is controversial whether the FRN reflects the cognitive process of error detection per se and/or the motivational/affective process related to the subjective evaluation of the error. This study manipulated the motivational/affective significance of negative feedback by penalizing errors in a context-dependent way in a line judgment task. Participants could lose more money in the loss incentive condition or win less money in the win incentive condition if their subsequent judgment of line segments was less accurate, whereas they could receive performance feedback but without monetary incentive in the neutral condition. Results showed that the size of the FRN effect as well as the size of the P300 effect, as assessed by comparing brain responses to the error trials with the responses to the correct trials, increased linearly over the loss, neutral, and win conditions, suggesting that the FRN is sensitive to the motivational/affective evaluation of the performance outcome.  相似文献   
1000.
重点介绍科技日语中被动句的种类,并通过例句分析各种被动句的特点以及翻译技巧。同时,还剖析了科技日语中形态相似的自发句与被动句的区别。  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