全文获取类型
收费全文 | 20227篇 |
免费 | 2048篇 |
国内免费 | 1870篇 |
专业分类
电工技术 | 1666篇 |
技术理论 | 2篇 |
综合类 | 2532篇 |
化学工业 | 1671篇 |
金属工艺 | 2338篇 |
机械仪表 | 1550篇 |
建筑科学 | 1441篇 |
矿业工程 | 1005篇 |
能源动力 | 463篇 |
轻工业 | 480篇 |
水利工程 | 398篇 |
石油天然气 | 448篇 |
武器工业 | 242篇 |
无线电 | 2027篇 |
一般工业技术 | 2339篇 |
冶金工业 | 1314篇 |
原子能技术 | 104篇 |
自动化技术 | 4125篇 |
出版年
2024年 | 67篇 |
2023年 | 279篇 |
2022年 | 500篇 |
2021年 | 630篇 |
2020年 | 643篇 |
2019年 | 518篇 |
2018年 | 464篇 |
2017年 | 598篇 |
2016年 | 649篇 |
2015年 | 821篇 |
2014年 | 1382篇 |
2013年 | 1240篇 |
2012年 | 1525篇 |
2011年 | 1618篇 |
2010年 | 1232篇 |
2009年 | 1225篇 |
2008年 | 1099篇 |
2007年 | 1398篇 |
2006年 | 1253篇 |
2005年 | 1050篇 |
2004年 | 850篇 |
2003年 | 762篇 |
2002年 | 648篇 |
2001年 | 541篇 |
2000年 | 510篇 |
1999年 | 390篇 |
1998年 | 346篇 |
1997年 | 336篇 |
1996年 | 270篇 |
1995年 | 241篇 |
1994年 | 251篇 |
1993年 | 142篇 |
1992年 | 143篇 |
1991年 | 119篇 |
1990年 | 110篇 |
1989年 | 100篇 |
1988年 | 63篇 |
1987年 | 28篇 |
1986年 | 17篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1956年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
142.
143.
点模式匹配是计算机视觉和模式识别领域中的一个重要问题 .通过研究 ,在假定待匹配的两个点模式中已知有三对点整体对应的前提下 ,基于射影坐标以及对投影变换和排序变换同时保持不变的 p2 -不变量等理论 ,通过定义一种广义距离 ,给出了一种求解透视变换下 ,点数不等的两个平面点模式匹配问题的新算法 .理论分析和仿真实验表明 ,该算法是快速、有效的 相似文献
144.
LIN Peng-fei 《数字社区&智能家居》2008,(35)
作为一名信息技术教师不仅要有扎实的专业知识,还要能灵活运用教学语言来调动学生的学习积极性,在新课程改革过程中,不仅要保持原有的用词准确规范、表达简明扼要外,还要注意语言表达的几种转变:由命令式转变为商讨式、由评判式转变成建议鼓励式、由灌输式转变为引导式、由统一的语言转变为开放的语言、由单一的评价转变为评价的多元化,使得我们的教学语言更符合新课程标准,更加有效地提高课堂教学效果。 相似文献
145.
Esther Guerra Juan de Lara Paloma Díaz 《Journal of Visual Languages and Computing》2008,19(3):399-425
Ensuring model quality is a key success factor in many computer science areas, and becomes crucial in recent software engineering paradigms like the one proposed by model-driven software development. Tool support for measurements and redesigns becomes essential to help developers improve the quality of their models. However, developing such helper tools for the wide variety of (frequently domain specific) visual notations used by software engineers is a hard and repetitive task that does not take advantage from previous developments, thus being frequently forgotten.In this paper we present our approach for the visual specification of measurements and redesigns for Domain Specific Visual Languages (DSVLs). With this purpose, we introduce a novel DSVL called SLAMMER that contains generalisations of some of the more used types of internal product measurements and redesigns. The goal is to facilitate the task of defining measurements and redesigns for any DSVL, as well as the generation of tools from such specification reducing or eliminating the necessity of coding. We rely on the use of visual patterns for the specification of the relevant elements for each measurement and redesign type. In addition, SLAMMER allows the specification of redesigns either procedurally or by means of graph transformation rules. These redesigns can be triggered when the measurements reach a certain threshold.These concepts have been implemented in the meta-modelling tool AToM3. In this way, when a DSVL is designed, it is possible to specify measurements and redesigns that will become available in the final modelling environment generated for the language. As an example, we show a case study in the web modelling domain. 相似文献
146.
图像校正技术的研究及应用 总被引:2,自引:2,他引:0
基于单应性矩阵方法研究了图像校正技术,该方法的关键问题在于边缘检测及寻找边缘的交点。针对车牌图像的校正,提出了一种自动化的边缘提取方法。该方法通过对霍夫变换得到的直线进行合并、分类、排序等方法来自动获取图像边缘并计算相应的交点。对校正后的图像因为长宽比例不同而产生的问题,作了分析和相应处理。该方法保留了单应性矩阵恢复算法的方便性,同时速度更快,取得的效果也比较好。 相似文献
147.
A comparison of finite elements for nonlinear beams: the absolute nodal coordinate and geometrically exact formulations 总被引:2,自引:2,他引:0
Ignacio Romero 《Multibody System Dynamics》2008,20(1):51-68
Two of the most popular finite element formulations for solving nonlinear beams are the absolute nodal coordinate and the
geometrically exact approaches. Both can be applied to problems with very large deformations and strains, but they differ
substantially at the continuous and the discrete levels. In addition, implementation and run-time computational costs also
vary significantly. In the current work, we summarize the main features of the two formulations, highlighting their differences
and similarities, and perform numerical benchmarks to assess their accuracy and robustness. The article concludes with recommendations
for the choice of one formulation over the other. 相似文献
148.
In this study, the effect of the centrifugal forces on the eigenvalue solution obtained using two different nonlinear finite
element formulations is examined. Both formulations can correctly describe arbitrary rigid body displacements and can be used
in the large deformation analysis. The first formulation is based on the geometrically exact beam theory, which assumes that the cross section does not deform in its own plane and remains plane after deformation. The second formulation,
the absolute nodal coordinate formulation (ANCF), relaxes this assumption and introduces modes that couple the deformation of the cross section and the axial and bending
deformations. In the absolute nodal coordinate formulation, four different models are developed; a beam model based on a general
continuum mechanics approach, a beam model based on an elastic line approach, a beam model based on an elastic line approach
combined with the Hellinger–Reissner principle, and a plate model based on a general continuum mechanics approach. The use
of the general continuum mechanics approach leads to a model that includes the ANCF coupled deformation modes. Because of these modes, the continuum mechanics model differs from the models based on the elastic line approach. In both
the geometrically exact beam and the absolute nodal coordinate formulations, the centrifugal forces are formulated in terms
of the element nodal coordinates. The effect of the centrifugal forces on the flap and lag modes of the rotating beam is examined, and the results obtained using the two formulations are compared for different values of
the beam angular velocity. The numerical comparative study presented in this investigation shows that when the effect of some
ANCF coupled deformation modes is neglected, the eigenvalue solutions obtained using the geometrically exact beam and the
absolute nodal coordinate formulations are in a good agreement. The results also show that as the effect of the centrifugal
forces, which tend to increase the beam stiffness, increases, the effect of the ANCF coupled deformation modes on the computed
eigenvalues becomes less significant. It is shown in this paper that when the effect of the Poisson ration is neglected, the
eigenvalue solution obtained using the absolute nodal coordinate formulation based on a general continuum mechanics approach
is in a good agreement with the solution obtained using the geometrically exact beam model. 相似文献
149.
Enterprise applications may be classified into management applications used by managerial staffs for making decisions on business
operations, and engineering applications used by engineers for solving multidisciplinary design problems. In the literature,
enterprise application integration is extensively addressed in the context of management applications, but insufficiently
discussed in the engineering disciplines. Practitioners in manufacturing industries have for a long time feel the increasing
need of integrating engineering applications, in order to accelerate product development paces and improve design qualities.
Integrating engineering applications used in the multiple engineering disciplines has to cope with a number of challenges.
This paper focuses on one of the critical issues: parameter mapping and data transformation, which is of pivotal importance
to integrating engineering applications. Design parameter mapping provides a consistent approach to data extraction, storage,
display and manipulation among different data sources. Data transformation describes the operational logic of parsing input/output
files, extracting and transforming data, and maintaining consistency among multiple data sources.
相似文献
Chengen WangEmail: |
150.
Ordered binary decision diagrams are the state-of-the-art representation of switching functions. In order to keep the sizes of OBDDs tractable, heuristics and dynamic reordering algorithms are applied to optimize the underlying variable order. When finite state machines are represented by OBDDs the state encoding can be used as an additional optimization parameter. In this paper, we analyze local encoding transformations which can be applied dynamically. First, we investigate the potential of re-encoding techniques. We then propose the use of an XOR-transformation and show why this transformation is most suitable among the set of all encoding transformations. The presented theoretical framework establishes a new optimization technique for OBDDs. 相似文献