全文获取类型
收费全文 | 9535篇 |
免费 | 721篇 |
国内免费 | 221篇 |
专业分类
系统科学 | 1260篇 |
丛书文集 | 101篇 |
教育与普及 | 59篇 |
理论与方法论 | 292篇 |
现状及发展 | 886篇 |
研究方法 | 15篇 |
综合类 | 7863篇 |
自然研究 | 1篇 |
出版年
2024年 | 15篇 |
2023年 | 46篇 |
2022年 | 86篇 |
2021年 | 94篇 |
2020年 | 46篇 |
2019年 | 18篇 |
2018年 | 757篇 |
2017年 | 767篇 |
2016年 | 473篇 |
2015年 | 124篇 |
2014年 | 129篇 |
2013年 | 143篇 |
2012年 | 377篇 |
2011年 | 1106篇 |
2010年 | 942篇 |
2009年 | 628篇 |
2008年 | 679篇 |
2007年 | 935篇 |
2006年 | 168篇 |
2005年 | 202篇 |
2004年 | 221篇 |
2003年 | 272篇 |
2002年 | 193篇 |
2001年 | 152篇 |
2000年 | 139篇 |
1999年 | 219篇 |
1998年 | 173篇 |
1997年 | 187篇 |
1996年 | 164篇 |
1995年 | 160篇 |
1994年 | 166篇 |
1993年 | 139篇 |
1992年 | 124篇 |
1991年 | 125篇 |
1990年 | 86篇 |
1989年 | 91篇 |
1988年 | 57篇 |
1987年 | 41篇 |
1986年 | 20篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1973年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
991.
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
992.
Frank Stowell 《Systemic Practice and Action Research》2007,20(5):413-427
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
993.
LIANG Yan ZUO JianRu YANG WeiCai 《科学通报(英文版)》2007,52(13):1729-1733
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
994.
LU Zhengding WEN Zhumu TANG Zhuo LI Ruixuan 《武汉大学学报:自然科学英文版》2007,12(5):955-960
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
995.
本文作者用电阻法对渐开线圆柱直齿轮,渐开线圆柱斜齿轮、单圆弧圆柱齿轮、双圆弧圆柱齿轮等轮齿油膜承载能力进行了测试,利用单位面积电阻的概念,使电阻法测量对各种齿轮润滑副的油膜厚度有了共同比较的基础,得出了若干有用的结论。 相似文献
996.
隐马尔可夫模型在被动声信号分类中的应用 总被引:2,自引:0,他引:2
为了提高被动声目标识别率,该文研究了隐马尔可夫模型在被动声信号分类中的应用问题,然后,又提出了2种混合分类器:特征矢量混合的HMM分类器和HMM/MLPNN(多层感知机神经网络)混合模型分类器。结果表明,这2种混合分类器在性能上都优于单个特定的分类器,它们在被动声信号分类中具有良好的应用前景。 相似文献
997.
研究被孢霉生产γ-亚麻酸的方法,并通过诱变获得了GLA大幅度提高的高产菌株。 相似文献
998.
以特征函数为传递参数的CF-GERT及其矩阵法求解 总被引:1,自引:0,他引:1
本文构建了以特征函数和传递概率为传递函数的CF-GERT(characteristic function based GERT)模型,利用特征函数的性质,证明了CF-GERT网络串联结构、并联结构、自环结构的传递关系与信号流图等价传递参数计算完全相同,故可借鉴信号流图理论求解CF-GERT模型.考虑以梅森公式为基础的经典GERT解析算法需要分析复杂的网络拓扑结构,提出了CF-GERT网络的矩阵式表征方法,进而设计了CF-GERT的矩阵式求解算法,推导了期望、方差、等价特征函数的计算公式.若等价特征函数绝对可积,则利用傅里叶逆变换推导概率密度函数;否则,运用Fang等提出的COS方法推导.最后用两个案例说明了所提方法的有效性. 相似文献
999.
The composite membranes with cellulose acetate (CA) as the separating layer material and polyacrylonitrile (PAN) as the supporting
layer material were prepared for separating caprolactam (CPL) from CPL/water mixtures by pervaporation technique. The swelling
experiments were carried out to investigate the effects of swelling time and CPL concentration on the degree of swelling.
The results showed that the CA membrane reached swelling equilibrium within 24 h, and the degree of swelling first slightly
decreased then increased with the increase of CPL concentration in the feed under the experimental conditions. Respectively
comparing flux with permeance, and separation factor with selectivity, we found out that the separation performance of the
CA/PAN composite membrane is more strongly dependent on its hydrophilic/hydrophobic nature as well as on the effects of operating
parameters, such as feed composition concentration and feed temperature. 相似文献
1000.
<正> This paper considers the problem of actuator failure compensation for a class of nonlinearsystems in the form of output-feedback.MT-filters are exploited to estimate the unmeasured states.The backsteppping technique is used to construct the controller recursively.The proposed compensationscheme can grantee the boundedness of all the closed-loop signals and asymptotic output tracking.Thetheoretical results are illustrated by a simulation example. 相似文献