全文获取类型
收费全文 | 2151篇 |
免费 | 243篇 |
国内免费 | 189篇 |
专业分类
电工技术 | 99篇 |
综合类 | 223篇 |
化学工业 | 35篇 |
金属工艺 | 49篇 |
机械仪表 | 139篇 |
建筑科学 | 127篇 |
矿业工程 | 33篇 |
能源动力 | 23篇 |
轻工业 | 16篇 |
水利工程 | 25篇 |
石油天然气 | 16篇 |
武器工业 | 14篇 |
无线电 | 296篇 |
一般工业技术 | 154篇 |
冶金工业 | 86篇 |
原子能技术 | 9篇 |
自动化技术 | 1239篇 |
出版年
2024年 | 2篇 |
2023年 | 21篇 |
2022年 | 30篇 |
2021年 | 27篇 |
2020年 | 43篇 |
2019年 | 44篇 |
2018年 | 33篇 |
2017年 | 47篇 |
2016年 | 66篇 |
2015年 | 72篇 |
2014年 | 136篇 |
2013年 | 112篇 |
2012年 | 121篇 |
2011年 | 155篇 |
2010年 | 137篇 |
2009年 | 143篇 |
2008年 | 161篇 |
2007年 | 181篇 |
2006年 | 176篇 |
2005年 | 145篇 |
2004年 | 106篇 |
2003年 | 113篇 |
2002年 | 91篇 |
2001年 | 73篇 |
2000年 | 70篇 |
1999年 | 35篇 |
1998年 | 41篇 |
1997年 | 28篇 |
1996年 | 36篇 |
1995年 | 32篇 |
1994年 | 23篇 |
1993年 | 22篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1981年 | 3篇 |
1977年 | 2篇 |
1962年 | 1篇 |
1961年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有2583条查询结果,搜索用时 31 毫秒
1.
AbstractIndustry 4.0 aims at providing a digital representation of a production landscape, but the challenges in building, maintaining, optimizing, and evolving digital models in inter-organizational production chains have not been identified yet in a systematic manner. In this paper, various Industry 4.0 research and technical challenges are addressed, and their present scenario is discussed. Moreover, in this article, the novel concept of developing experience-based virtual models of engineering entities, process, and the factory is presented. These models of production units, processes, and procedures are accomplished by virtual engineering object (VEO), virtual engineering process (VEP), and virtual engineering factory (VEF), using the knowledge representation technique of Decisional DNA. This blend of the virtual and physical domains permits monitoring of systems and analysis of data to foresee problems before they occur, develop new opportunities, prevent downtime, and even plan for the future by using simulations. Furthermore, the proposed virtual model concept not only has the capability of Query Processing and Data Integration for Industrial Data but also real-time visualization of data stream processing. 相似文献
2.
文章分析了网络安全等级保护2.0时期国家标准的新变化对等级测评结论可能产生的影响,并用实际案例和数据论述了以往描述的基于测评指标和基于测评对象的定量分析方法存在的局限性。根据网络安全等级保护国家标准结构和内容的新特点,结合新的等级测评结论表述方法,文章提出了调整和优化定量计算产生等级测评结论的思路,给出了缺陷扣分的原理和缺陷扣分的定量计算方法,并比较了各种定量计算方法在计算结果上的差异,提出了适合新标准的测评结论定量计算公式。 相似文献
3.
An optoelectronic method is considered for noncontacting reconstruction of the surface profile of three-dimensional objects of large dimensions. The optimal conditions for performing measurements are identified. It is shown that the proposed method, in contrast to the already known methods, does not require fine tuning of the equipment. A numerical method is given for compensating distortions caused by aberrations. A method is described for reconstructing the surface profile cell by cell which increases the accuracy of measurements. 相似文献
4.
论文在对现有一类典型图像混沌加密算法的分析基础上,提出了一种改进的图像混沌加密算法。该算法引入小波变换,可以有效地克服一些混沌加密算法不能抵御已知/选择明文攻击的缺陷。 相似文献
5.
In this paper,a sequential algorithm computing the aww vertex pair distance matrix D and the path matrix Pis given.On a PRAM EREW model with p,1≤p≤n^2,processors,a parallel version of the sequential algorithm is shown.This method can also be used to get a parallel algorithm to compute transitive closure array A^* of an undirected graph.The time complexity of the parallel algorithm is O(n^3/p).If D,P and A^* are known,it is shown that the problems to find all connected components,to compute the diameter of an undirected graph,to determine the center of a directed graph and to search for a directed cycle with the minimum(maximum)length in a directed graph can all be solved in O(n^2/p logp)time. 相似文献
6.
The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management. 相似文献
7.
Georgios D. Styliaras Georgios K. Tsolis Chris M. Papaterpos 《International Journal on Digital Libraries》2007,8(1):61-78
In this paper, AssetCollector is presented, which is a system for managing collections of cultural assets. AssetCollector
covers the needs of collection curators towards defining, populating and searching a collection in a flexible way, while supporting
them in generating reports based on the collection’s assets and reusing them in order to build web sites and CD-ROMs. In order
to support the above functionality, the system provides the content structuring subsystem, the content input subsystem, the
search subsystem and the report subsystem. The use of the subsystems is straightforward and requires no technical skills from
the curators. AssetCollector has been successfully applied for organizing various collections of cultural assets in Greece,
such as archaeological sites, museums and published books. In the future, an evaluation procedure is planned in order to further
refine the use of the system according to the targeted users’ needs. Furthermore, more import and export facilities will be
provided, which will make the system compliant with widely accepted standards. 相似文献
8.
9.
Boundary objects are a critical, but understudied, theoretical construct in CSCW. Through a field study of aircraft technical
support, we examined the role of boundary objects in the practical achievement of safety by service engineers. Their resolution
of repair requests was preserved in the organization’s memory via three compound boundary objects. These crystallizations
did not manifest a static interpretation, but instead were continually reinterpreted in light of meta-negotiations. This suggests
design implications for organizational memory systems which can more fluidly represent the meta-negotiations surrounding boundary
objects. 相似文献
10.
一种探测二维电磁目标的新方法 总被引:2,自引:0,他引:2
电磁目标的探测对通信而言有着十分重要的意义。本文描述一种收敛迅速、结果准确、抗强随机噪声的探测二维电磁目标的新方法。首先从体等效原理出发得到一个积分方程组,此方程组可求解散射问题。随后,对此方程组求变分,变形后得到散射场变化与介电参数变化之间关系的矩阵方程,即反演方程。文中列举了几个例子,通过数值实验结果证明本法收敛速度快、反演精度高、适应复杂目标的能力强,能抗强随机噪声干扰 相似文献