全文获取类型
收费全文 | 4236篇 |
免费 | 313篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 39篇 |
综合类 | 3篇 |
化学工业 | 1197篇 |
金属工艺 | 132篇 |
机械仪表 | 103篇 |
建筑科学 | 149篇 |
矿业工程 | 15篇 |
能源动力 | 152篇 |
轻工业 | 849篇 |
水利工程 | 48篇 |
石油天然气 | 18篇 |
无线电 | 177篇 |
一般工业技术 | 858篇 |
冶金工业 | 124篇 |
原子能技术 | 47篇 |
自动化技术 | 640篇 |
出版年
2023年 | 47篇 |
2022年 | 84篇 |
2021年 | 169篇 |
2020年 | 121篇 |
2019年 | 148篇 |
2018年 | 210篇 |
2017年 | 204篇 |
2016年 | 202篇 |
2015年 | 188篇 |
2014年 | 229篇 |
2013年 | 461篇 |
2012年 | 264篇 |
2011年 | 323篇 |
2010年 | 316篇 |
2009年 | 240篇 |
2008年 | 155篇 |
2007年 | 131篇 |
2006年 | 92篇 |
2005年 | 41篇 |
2004年 | 54篇 |
2003年 | 50篇 |
2002年 | 57篇 |
2001年 | 38篇 |
2000年 | 43篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 30篇 |
1996年 | 26篇 |
1995年 | 24篇 |
1994年 | 20篇 |
1993年 | 29篇 |
1992年 | 25篇 |
1991年 | 13篇 |
1990年 | 13篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1986年 | 11篇 |
1985年 | 23篇 |
1984年 | 29篇 |
1983年 | 27篇 |
1982年 | 26篇 |
1981年 | 43篇 |
1980年 | 29篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1977年 | 23篇 |
1976年 | 34篇 |
1975年 | 25篇 |
1974年 | 20篇 |
1973年 | 23篇 |
排序方式: 共有4551条查询结果,搜索用时 15 毫秒
91.
92.
Urban environments possess many regularities which can be efficiently exploited for 3D dense reconstruction from multiple
widely separated views. We present an approach utilizing properties of piecewise planarity and restricted number of plane
orientations to suppress reconstruction and matching ambiguities causing failures of standard dense stereo methods. We formulate
the problem of the 3D reconstruction in MRF framework built on an image pre-segmented into superpixels. Using this representation,
we propose novel photometric and superpixel boundary consistency terms explicitly derived from superpixels and show that they
overcome many difficulties of standard pixel-based formulations and handle favorably problematic scenarios containing many
repetitive structures and no or low textured regions. We demonstrate our approach on several wide-baseline scenes demonstrating
superior performance compared to previously proposed methods. 相似文献
93.
94.
Aleksandar Kovačević Branko Milosavljević Zora Konjović Milan Vidaković 《Multimedia Tools and Applications》2010,47(3):525-544
This paper presents a tunable content-based music retrieval (CBMR) system suitable the for retrieval of music audio clips. The audio clips are represented as extracted feature vectors. The CBMR system is expert-tunable by altering the feature space. The feature space is tuned according to the expert-specified similarity criteria expressed in terms of clusters of similar audio clips. The main goal of tuning the feature space is to improve retrieval performance, since some features may have more impact on perceived similarity than others. The tuning process utilizes our genetic algorithm. The R-tree index for efficient retrieval of audio clips is based on the clustering of feature vectors. For each cluster a minimal bounding rectangle (MBR) is formed, thus providing objects for indexing. Inserting new nodes into the R-tree is efficiently performed because of the chosen Quadratic Split algorithm. Our CBMR system implements the point query and the n-nearest neighbors query with the O(logn) time complexity. Different objective functions based on cluster similarity and dissimilarity measures are used for the genetic algorithm. We have found that all of them have similar impact on the retrieval performance in terms of precision and recall. The paper includes experimental results in measuring retrieval performance, reporting significant improvement over the untuned feature space. 相似文献
95.
Maria Helena L.B. Braz Sean W.M. SiqueiraDiva de S. e S. Rodrigues Rubens N. Melo 《Computers in human behavior》2011,27(4):1344-1351
The development of instructional content using Information Technologies is an expensive, time-consuming and complex process that requires new methodologies. It was in this context that the concept of Learning Objects (LOs) was proposed in order to promote reuse. However, this goal is not yet fully attained and new contributions to increase reuse are still welcome. Besides, if content is conveyed in LOs that are easier to reuse, they must be combined and sequenced in order to build more elaborated and complex content. This paper presents a strategy to deal with these problems based on the definition of small LOs here called Component Objects (COs). These COs are structured and combined according to a conceptual metamodel, which is the basis for the definition of conceptual schemas representing the existing material, including not only content but also practice. This strategy for searching, extracting, and sequencing COs, supports a teacher to better control the implementation of complex content, reducing errors in the authoring process. This approach includes a specification language and an algorithm for semi-automatic sequencing learning content and practice. Finally, a case study that shows the proposed approach and some results of using the algorithm are presented. 相似文献
96.
Ney Sodr Pablo Guillermo Gonzales-Ormeo Helena Maria Petrilli Cludio Geraldo Schn 《Calphad》2009,33(3):576-583
The metastable phase diagram of the BCC-based ordering equilibria in the Fe–Al–Mo system has been calculated via a truncated cluster expansion, through the combination of Full-Potential-Linear augmented Plane Wave (FP-LAPW) electronic structure calculations and of Cluster Variation Method (CVM) thermodynamic calculations in the irregular tetrahedron approximation. Four isothermal sections at 1750 K, 2000 K, 2250 K and 2500 K are calculated and correlated with recently published experimental data on the system. The results confirm that the critical temperature for the order–disorder equilibrium between Fe3Al–D03 and FeAl–B2 is increased by Mo additions, while the critical temperature for the FeAl–B2/A2 equilibrium is kept approximately invariant with increasing Mo contents. The stabilization of the Al-rich A2 phase in equilibrium with overstoichiometric B2–(Fe,Mo)Al is also consistent with the attribution of the A2 structure to the τ2 phase, stable at high temperatures in overstoichiometric B2–FeAl. 相似文献
97.
98.
Lena Cibulski Denis Gračanin Alexandra Diehl Rainer Splechtna Mai Elshehaly Claudio Delrieux Krešimir Matković 《The Visual computer》2016,32(6-8):847-857
Widespread use of GPS and similar technologies makes it possible to collect extensive amounts of trajectory data. These data sets are essential for reasonable decision making in various application domains. Additional information, such as events taking place along a trajectory, makes data analysis challenging, due to data size and complexity. We present an integrated solution for interactive visual analysis and exploration of events along trajectories data. Our approach supports analysis of event sequences at three different levels of abstraction, namely spatial, temporal, and events themselves. Customized views as well as standard views are combined to form a coordinated multiple views system. In addition to trajectories and events, we include on-the-fly derived data in the analysis. We evaluate our integrated solution using the IEEE VAST 2015 Challenge data set. A successful detection and characterization of malicious activity indicate the usefulness and efficiency of the presented approach. 相似文献
99.
100.
Mobile Virtual Reality provides a gateway for marketers to innovatively reach consumers. This study examines the impact of Virtual Reality in the context of transformational brand experience appeals, focussing specifically on the determining role of vividness. A three-dimensional conceptual framework is presented, offering a systematic review of the literature on vividness effects in marketing communications, revealing the major gap that most available studies only focus on informational messages. We conducted an experiment to address this gap and demonstrate in the context of a transformational ad that Virtual Reality generates higher perceptions of vividness and presence than a regular two-dimensional video, with vividness positively affecting attitude toward the ad, both directly and indirectly via presence. Our study also reveals that vividness in turn elicits a positive effect on brand attitudes which stimulates consumers’ purchase intentions. As such, the strategic potential of Virtual Reality for marketing communications is highlighted. 相似文献