全文获取类型
收费全文 | 14620篇 |
免费 | 917篇 |
国内免费 | 657篇 |
专业分类
系统科学 | 1645篇 |
丛书文集 | 202篇 |
教育与普及 | 150篇 |
理论与方法论 | 318篇 |
现状及发展 | 922篇 |
研究方法 | 18篇 |
综合类 | 12937篇 |
自然研究 | 2篇 |
出版年
2024年 | 30篇 |
2023年 | 63篇 |
2022年 | 152篇 |
2021年 | 183篇 |
2020年 | 146篇 |
2019年 | 77篇 |
2018年 | 830篇 |
2017年 | 860篇 |
2016年 | 578篇 |
2015年 | 309篇 |
2014年 | 402篇 |
2013年 | 437篇 |
2012年 | 768篇 |
2011年 | 1538篇 |
2010年 | 1385篇 |
2009年 | 1035篇 |
2008年 | 1257篇 |
2007年 | 1468篇 |
2006年 | 638篇 |
2005年 | 585篇 |
2004年 | 551篇 |
2003年 | 526篇 |
2002年 | 509篇 |
2001年 | 385篇 |
2000年 | 268篇 |
1999年 | 250篇 |
1998年 | 145篇 |
1997年 | 141篇 |
1996年 | 132篇 |
1995年 | 96篇 |
1994年 | 90篇 |
1993年 | 77篇 |
1992年 | 63篇 |
1991年 | 61篇 |
1990年 | 52篇 |
1989年 | 41篇 |
1988年 | 34篇 |
1987年 | 17篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1967年 | 1篇 |
1964年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 359 毫秒
61.
62.
Shape skeletonization (i.e., medial axis extraction) is powerful in many visual computing applications, such as pattern recognition, object segmentation, registration, and animation. In this paper, the authors expand the use of diffusion equations combined with distance field information to approximate medial axes of arbitrary 3D differential properties. It offers an alternative solids represented by polygonal meshes based on their but natural way for medial axis extraction for commonly used 3D polygonal models. By solving the PDE along time axis, this system can not only quickly extract diffusion-based medial axes of input meshes, but also allow users to visualize the extraction process at each time step. In addition, the proposed model provides users a set of manipulation toolkits to sculpt extracted medial axes, then use diffusion-based techniques to recover corresponding deformed shapes according to the original input datasets. This skeleton-based shape manipulation offers a fast and easy way for animation and deformation of complicated mesh objects. 相似文献
63.
Systemic Intervention in a University Department: Reflections on Arrested Action Research 总被引:1,自引:1,他引:0
Don Houston 《Systemic Practice and Action Research》2008,21(2):133-152
This paper reflects on my experience as an insider researcher attempting to use critical systems ideas and practices to promote
quality improvement in a university engineering department. Reflection is a key part of learning. This paper is intended to
contribute to critically, self-reflective learning for the community of systems practitioners. These reflections on my questions
about participation, ethics, politics of process, and the choices and actions resulting from them may help others to formulate
their own. The complexity of systems practice places substantial demands on the researcher, particularly in the case of insider,
practitioner research. Nevertheless, the exploration of critical systems approaches to critique boundaries and structure ‘problems’
in the core aspects of higher education in locally meaningful ways should continue. While demanding, it still can work to
promote learning about authentic quality. 相似文献
64.
65.
并行双回转的爬行现象对高精度光纤定位是十分不利的.为了克服这种爬行现象,首先从动力学角度建立光纤爬行的动力学模型,论证了光纤爬行的实质是一种复杂的摩擦自激振动现象,然后结合实际跑合过程,从机械学的角度进一步分析获得传动齿轮安装偏斜、中心轴支撑同心不良、中心零定位弹簧片安装过紧和偏心消隙弹簧不能正常储能、释能是导致光纤爬行的根本原因,并对此提出了一些可行的解决措施,收到了良好的效果. 相似文献
66.
Li XIE Lihua XIE 《系统科学与复杂性》2007,20(2):262-272
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
67.
Lanju XU 《系统科学与复杂性》2007,20(1):30-40
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
68.
文章以HFC32XXXX1重型自卸车为分析对象,建立了三轴汽车的制动力学模型,对其在空载、满载和超载情况下的前、后制动力矩,制动力分配和制动效能进行理论分析和模拟计算;结合平板试验台的试验结果,根据有关标准和ECE法规要求,评价了其在不同载荷情况下的制动性。 相似文献
69.
70.
通过对铁路车站行车工作细则业务的系统分析和对铁路运输生产和组织管理的理论研究表明:铁路运输实践课为铁路运输专业学生提供了理论联系实际的平台,对培养学生独立分析和解决铁路行车方案问题的能力有着重要的意义。 相似文献