全文获取类型
收费全文 | 4790篇 |
免费 | 801篇 |
国内免费 | 708篇 |
专业分类
电工技术 | 389篇 |
综合类 | 576篇 |
化学工业 | 89篇 |
金属工艺 | 98篇 |
机械仪表 | 600篇 |
建筑科学 | 174篇 |
矿业工程 | 55篇 |
能源动力 | 51篇 |
轻工业 | 23篇 |
水利工程 | 72篇 |
石油天然气 | 146篇 |
武器工业 | 105篇 |
无线电 | 490篇 |
一般工业技术 | 513篇 |
冶金工业 | 53篇 |
原子能技术 | 11篇 |
自动化技术 | 2854篇 |
出版年
2024年 | 40篇 |
2023年 | 112篇 |
2022年 | 155篇 |
2021年 | 164篇 |
2020年 | 230篇 |
2019年 | 197篇 |
2018年 | 200篇 |
2017年 | 191篇 |
2016年 | 254篇 |
2015年 | 250篇 |
2014年 | 306篇 |
2013年 | 325篇 |
2012年 | 333篇 |
2011年 | 361篇 |
2010年 | 266篇 |
2009年 | 276篇 |
2008年 | 304篇 |
2007年 | 326篇 |
2006年 | 281篇 |
2005年 | 269篇 |
2004年 | 255篇 |
2003年 | 181篇 |
2002年 | 181篇 |
2001年 | 131篇 |
2000年 | 150篇 |
1999年 | 102篇 |
1998年 | 93篇 |
1997年 | 91篇 |
1996年 | 59篇 |
1995年 | 50篇 |
1994年 | 40篇 |
1993年 | 24篇 |
1992年 | 20篇 |
1991年 | 20篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 4篇 |
排序方式: 共有6299条查询结果,搜索用时 15 毫秒
1.
实体造型中的几何约束 总被引:5,自引:0,他引:5
实体造型是一个基于约束的过程,完成从功能约束到几何约束、再到代数约束的转化而得到实体模型。本文讨论了几何约束的层次性及其表示,并且对几何约束同设计意图的关系进行了研究,提出了基于CSG/GCG/B-rep的模型表示。 相似文献
2.
In this paper the optimal H∞, general distance problem, for continuous-time systems, with a prescribed degree on the solution is studied. The approach is based on designing the Hankel singular values using an imbedding idea. The problem is first imbedded into another problem with desirable characteristics on the Hankel singular values, then the solution to the original problem is retracted via a compression. The result is applicable to both the one-block and the four-block problems. A special case is given for illustration. 相似文献
3.
4.
几何设计约束的表示与满足问题研究 总被引:3,自引:1,他引:2
对于智能CAD系统来说,具有解决几何设计约束的功能是重要的。本文提出了一种面向对象的几何设计约束表示方法,它可以通过两种方式来表达。文中给出了一个约束传播算法,用于解决约束满足问题。 相似文献
5.
6.
Evaluate the performance of a stochastic-flow network with cost attribute in terms of minimal cuts 总被引:2,自引:0,他引:2
This paper proposes a performance index to measure the quality level of a stochastic-flow network in which each node has a designated capacity, which will have different lower levels due to various partial and complete failures. The performance index is the probability that the maximum flow of the network equals the demand d without exceeding the budget b. A simple algorithm in terms of minimal cuts is first proposed to generate all upper boundary points for (d, b), and then the probability that the maximum flow is less than or equal to d can be calculated in terms of such points. The upper boundary point for (d, b) is a maximal vector representing the capacity of each arc such that the maximum flow of the network under the budget b is d. The performance index can be calculated by repeating the proposed algorithm to obtain all upper boundary point for (d−1, b). A benchmark example is shown to illustrate the solution procedure. 相似文献
7.
Rinkenauer Gerhard; Osman Allen; Ulrich Rolf; Müller-Gethmann Hiltraut; Mattes Stefan 《Canadian Metallurgical Quarterly》2004,133(2):261
Lateralized readiness potentials (LRPs) were used to determine the stage(s) of reaction time (RT) responsible for speed-accuracy trade-offs (SATs). Speeded decisions based on several types of information were examined in 3 experiments, involving, respectively, a line discrimination task, lexical decisions, and an Erikson flanker task. Three levels of SAT were obtained in each experiment by adjusting response deadlines with an adaptive tracking algorithm. Speed stress affected the duration of RT stages both before and after the start of the LRP in all experiments. The latter effect cannot be explained by guessing strategies, by variations in response force, or as an indirect consequence of the pre-LRP effect. Contrary to most models, it suggests that SAT can occur at a late postdecisional stage. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
This paper addresses the problem of bandwidth allocation under the weighted maximum rate constrained link sharing policy and proves a key theory in the condition of allocation termination. We propose several algorithms with various worst-case and average-case time complexities, and evaluate their computation elapse times. 相似文献
9.
传统的形状及位置表示模型通常是建立在低层次的无应用意义的几何拓扑元素之上,因而无法很好地支持计算机辅助设计(CAD)向实用化和智能化方向发展。本文提出了一种非数值化的基于约束的产品形位描述模型,并对该模型中存在的一些问题进行了深入的讨论。该模型符合设计人员实际设计思维与过程,同时也支持高层次产品设计信息以及产品的设计过程信息,因而为传统CAD系统向新一代实用化智能化CAD系统过渡提供了一个良好的产品形位表示模型。 相似文献
10.
P.-C. Chung Author Vitae C.-L. Huang Author Vitae E.-L. Chen Author Vitae 《Pattern recognition》2007,40(3):1066-1077
Motion vector plays one significant feature in moving object segmentation. However, the motion vector in this application is required to represent the actual motion displacement, rather than regions of visually significant similarity. In this paper, region-based selective optical flow back-projection (RSOFB) which back-projects optical flows in a region to restore the region's motion vector from gradient-based optical flows, is proposed to obtain genuine motion displacement. The back-projection is performed based on minimizing the projection mean square errors of the motion vector on gradient directions. As optical flows of various magnitudes and directions provide various degrees of reliability in the genuine motion restoration, the optical flows to be used in the RSOFB are optimally selected based on their sensitivity to noises and their tendency in causing motion estimation errors. In this paper a deterministic solution is also derived for performing the minimization and obtaining the genuine motion magnitude and motion direction. 相似文献