全文获取类型
收费全文 | 10082篇 |
免费 | 485篇 |
国内免费 | 319篇 |
专业分类
电工技术 | 326篇 |
技术理论 | 2篇 |
综合类 | 1121篇 |
化学工业 | 392篇 |
金属工艺 | 124篇 |
机械仪表 | 400篇 |
建筑科学 | 1494篇 |
矿业工程 | 298篇 |
能源动力 | 199篇 |
轻工业 | 241篇 |
水利工程 | 239篇 |
石油天然气 | 100篇 |
武器工业 | 36篇 |
无线电 | 317篇 |
一般工业技术 | 1033篇 |
冶金工业 | 1279篇 |
原子能技术 | 25篇 |
自动化技术 | 3260篇 |
出版年
2024年 | 27篇 |
2023年 | 57篇 |
2022年 | 121篇 |
2021年 | 174篇 |
2020年 | 198篇 |
2019年 | 183篇 |
2018年 | 182篇 |
2017年 | 198篇 |
2016年 | 240篇 |
2015年 | 281篇 |
2014年 | 802篇 |
2013年 | 611篇 |
2012年 | 765篇 |
2011年 | 782篇 |
2010年 | 607篇 |
2009年 | 651篇 |
2008年 | 569篇 |
2007年 | 640篇 |
2006年 | 552篇 |
2005年 | 484篇 |
2004年 | 470篇 |
2003年 | 419篇 |
2002年 | 351篇 |
2001年 | 262篇 |
2000年 | 182篇 |
1999年 | 141篇 |
1998年 | 139篇 |
1997年 | 112篇 |
1996年 | 96篇 |
1995年 | 98篇 |
1994年 | 61篇 |
1993年 | 41篇 |
1992年 | 31篇 |
1991年 | 22篇 |
1990年 | 38篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1984年 | 12篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1976年 | 8篇 |
1966年 | 16篇 |
1965年 | 16篇 |
1964年 | 8篇 |
1963年 | 13篇 |
1959年 | 10篇 |
1957年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Business publications and the popular press have stressed the importance of creating conditions for meaningful employee expression in work roles, also known as engagement. Few empirical studies, however, have examined how individual or situational factors relate to engagement. Consequently, this study examines the interplay between employee age, perceived coworker age composition, and satisfaction with older (older than 55) and younger (younger than 40) coworkers on engagement using a sample of 901 individuals employed in the United Kingdom. Results indicated that satisfaction with one's coworkers related significantly to engagement. Moreover, perceived age similarity was associated with higher levels of engagement among older workers when they were highly satisfied with their coworkers over 55 and lower levels of engagement when they were not. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
22.
Many problems consist in splitting a set of objects into different groups so that each group verifies some properties. In practice, a partitioning is often encoded by an array mapping each object to its group numbering. In fact, the group number of an object does not really matter, and one can simply rename each group to obtain a new encoding. That is what we call the symmetry of the search space in a partitioning problem. This property may be prejudicial for optimization methods such as evolutionary algorithms (EA) which require some diversity during the search. 相似文献
23.
Garth Isaak 《Information Processing Letters》2004,92(3):107-111
Given a tournament with an acyclic tournament as a feedback arc set we give necessary and sufficient conditions for this feedback arc set to have minimum size. 相似文献
24.
Minglun Gong Author Vitae Author Vitae 《Pattern recognition》2004,37(8):1723-1733
Many computer vision problems can be formulated as optimization problems. Presented in this paper is a new framework based on the quadtree-based genetic algorithm that can be applied to solve many of these problems. The proposed algorithm incorporates the quadtree structure into the conventional genetic algorithm. The solutions of image-related problems are encoded through encoding the corresponding quadtrees, and therefore, the 2D locality within a solution can be preserved. Examples addressed using the proposed framework include image segmentation, stereo vision, and motion estimation. In all cases, encouraging results are obtained. 相似文献
25.
We study the computational complexity of the qualitative algebra which is a temporal constraint formalism that combines the point algebra, the point-interval algebra and Allen's interval algebra. We identify all tractable fragments and show that every other fragment is NP-complete. 相似文献
26.
Ferdinando Auricchio Lorenza Petrini 《International journal for numerical methods in engineering》2004,61(6):807-836
An always increasing knowledge on material properties as well as a progressively more sophisticated production technology make shape memory alloys (SMA) extremely interesting for the industrial world. At the same time, SMA devices are typically characterized by complex multi‐axial stress states as well as non‐homogeneous and non‐isothermal conditions both in space and time. This aspect suggests the finite element method as a useful tool to help and improve application design and realization. With this aim, we focus on a three‐dimensional macroscopic thermo‐mechanical model able to reproduce the most significant SMA features (Int. J. Numer. Methods Eng. 2002; 55 : 1255–1264), proposing a simple modification of such a model. However, the suggested modification allows the development of a time‐discrete solution algorithm, which is more effective and robust than the one previously discussed in the literature. We verify the computational tool ability to simulate realistic mechanical boundary value problems with prescribed temperature dependence, studying three SMA applications: a spring actuator, a self‐expanding stent, a coupling device for vacuum tightness. The effectiveness of the model to solve thermo‐mechanical coupled problems will be discussed in a forthcoming work. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
27.
周俭铁 《广东工业大学高等工程教育研究》2007,7(B06):126-127
文章根据作者的实践,从教材、学生、教师三个方面分析了目前高校在电子商务教学中存在的问题,并提出了自己相应的解决办法. 相似文献
28.
29.
Susskind Alex M.; Kacmar K. Michele; Borchgrevink Carl P. 《Canadian Metallurgical Quarterly》2003,88(1):179
The authors proposed and tested a model describing the relationship between customer service providers' perceptions and attitudes toward their service-related duties and their customers' perceptions of satisfaction with their service experiences. Results indicated that the perception of having standards for service delivery in an organization is strongly related to line-level employees' perceptions of support from coworkers and supervisors. Perceived support from coworker, was significantly related to service providers' customer orientation, whereas perceived support from supervisors showed a weaker relationship to a customer orientation. Ultimately, service providers' customer orientation was strongly related to customers' satisfaction with service. Finally, a set of post hoc analyses indicated that coworker and supervisory support explained a greater proportion of incremental variance in the model than did perceived organizational support alone. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
提出了映射半解析边界元法解百轴对称瞬态弹性动力问题时存在解析方向不能正确反映波的传播现象的问题,产生该问题的原因和如何解决该问题的建议。 相似文献