全文获取类型
收费全文 | 540篇 |
免费 | 26篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 145篇 |
金属工艺 | 16篇 |
机械仪表 | 17篇 |
建筑科学 | 20篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 39篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 39篇 |
一般工业技术 | 100篇 |
冶金工业 | 60篇 |
原子能技术 | 1篇 |
自动化技术 | 115篇 |
出版年
2023年 | 7篇 |
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 8篇 |
2019年 | 17篇 |
2018年 | 8篇 |
2017年 | 11篇 |
2016年 | 22篇 |
2015年 | 25篇 |
2014年 | 25篇 |
2013年 | 39篇 |
2012年 | 35篇 |
2011年 | 32篇 |
2010年 | 29篇 |
2009年 | 22篇 |
2008年 | 25篇 |
2007年 | 29篇 |
2006年 | 18篇 |
2005年 | 18篇 |
2004年 | 9篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 8篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1971年 | 2篇 |
1957年 | 1篇 |
1955年 | 1篇 |
1954年 | 2篇 |
1924年 | 2篇 |
1923年 | 1篇 |
排序方式: 共有566条查询结果,搜索用时 15 毫秒
561.
Hakan Cevikalp Diane Larlus Marian Neamtu Bill Triggs Frederic Jurie 《Journal of Signal Processing Systems》2010,61(1):61-73
In case of insufficient data samples in high-dimensional classification problems, sparse scatters of samples tend to have many ‘holes’—regions that have few or no nearby training samples from the class. When such regions lie close to inter-class boundaries, the nearest neighbors of a query may lie in the wrong class, thus leading to errors in the Nearest Neighbor classification rule. The K-local hyperplane distance nearest neighbor (HKNN) algorithm tackles this problem by approximating each class with a smooth nonlinear manifold, which is considered to be locally linear. The method takes advantage of the local linearity assumption by using the distances from a query sample to the affine hulls of query’s nearest neighbors for decision making. However, HKNN is limited to using the Euclidean distance metric, which is a significant limitation in practice. In this paper we reformulate HKNN in terms of subspaces, and propose a variant, the Local Discriminative Common Vector (LDCV) method, that is more suitable for classification tasks where the classes have similar intra-class variations. We then extend both methods to the nonlinear case by mapping the nearest neighbors into a higher-dimensional space where the linear manifolds are constructed. This procedure allows us to use a wide variety of distance functions in the process, while computing distances between the query sample and the nonlinear manifolds remains straightforward owing to the linear nature of the manifolds in the mapped space. We tested the proposed methods on several classification tasks, obtaining better results than both the Support Vector Machines (SVMs) and their local counterpart SVM-KNN on the USPS and Image segmentation databases, and outperforming the local SVM-KNN on the Caltech visual recognition database. 相似文献
562.
Matjaz Valant Taras Kolodiazhnyi Iztok Arčon Frederic Aguesse Anna‐Karin Axelsson Neil M. Alford 《Advanced functional materials》2012,22(10):2114-2122
An analysis of Mn substitution in SrTiO3 is performed in order to understand the origin of reported spin coupling in lightly Mn‐doped SrTiO3. The spin glass state magnetoelectrically coupled to the dipolar glass state has previously been reported for SrTiO3 substituted with only 2% of Mn on the B‐site. An analysis of the substitution mechanism for A‐ and B‐site doping shows a strong influence of processing conditions, such as processing temperature, oxygen partial pressure, and off‐stoichiometry. The required conditions for a site‐selective substitution are defined, which yield a single‐phase and almost defect‐free perovskite. Magnetic measurements show no magnetic anomalies resulting from spin coupling and only a simple paramagnetic behavior. Magnetic anomalies are observed only for the samples in which Mn is misplaced within the cation sublattice of the SrTiO3 perovskite. This occurs due to improper material processing, which causes initially unpredicted changes in the valence state of the Mn and results in the formation of structural defects and irregularities associated with segregation and nucleation of the magnetic species. Previously reported spin coupling in Mn‐doped SrTiO3 is not an intrinsic phenomenon and cannot be treated as a spin glass. 相似文献
563.
FredericJ.Kahn 《现代显示》2001,(3):7-11
数字投影正以比任何其他大屏幕显示技术都快得多的速度在改进,有可能成为竞争中的优胜者,从面统治大屏幕HDTV消费类市场。但这还需要一段时间。 相似文献
564.
There is virtual agreement among geologists that world production of conventional oil will peak at some point in the future. Oil, after all, is a finite resource, while demand will only grow over time. Geologists disagree, however, exactly when the peak will occur. Using data from the International Energy Agency, the US Department of Energy, the Association for the Study of Peak Oil and Gas, and petroleum industry sources, we argue that conventional oil production will reach a worldwide maximum within the next 5–10 years, earlier than generally estimated, thus leaving a very short time frame within which to plan for conversion to alternative sources of energy. Unless planning is initiated immediately, the United States and other Western democracies will see their positions in the global economy undercut as military conflicts over limited energy resources increase, and wealth and power are shifted to authoritarian regimes in Russia, Venezuela, Africa and the Middle East. 相似文献
565.
Wojciech Knap Salman Nadar Hadley Videlier Stephane Boubanga-Tombet Dominique Coquillat Nina Dyakonova Frederic Teppe Kristoph Karpierz Jerzy ?usakowski Maciej Sakowicz Irmantas Kasalynas Dalius Seliuta Gintaras Valusis Taiichi Otsuji Yahya Meziani Abdel El Fatimy Simon Vandenbrouk Kamel Madjour Didier Th��ron Christophe Gaqui��re 《Journal of Infrared, Millimeter and Terahertz Waves》2011,32(5):618-628
Resonant frequencies of the two-dimensional plasma in field effect transistors (FETs) increase with the reduction of the channel dimensions and can reach the Terahertz (THz) range. Nonlinear properties of the plasma/electron gas in the transistor channel can be used for the rectification and detection of THz radiation. The excitation of plasma waves by sub-THz and THz radiation was demonstrated for short gate transistors at cryogenic temperatures. At room temperature plasma oscillations are usually overdamped, but the FETs can still operate as efficient broadband rectifiers/detectors in the THz range. We present a few recent experimental results on THz detection by FETs showing some new ways of improvement of FETs for THz imaging at room temperature as well as the new physical phenomena like detection in quantizing magnetic fields. We also demonstrate THz emission properties of GaN based FETs. 相似文献
566.
Alexander W. Jones Marie‐Laure Louillat‐Habermeyer Frederic W. Patureau 《Advanced Synthesis \u0026amp; Catalysis》2015,357(5):945-949
What does it take to force a rigid and strained dehydrogenative ring closure, for example, in phenylcarbazoles? Since the works of Buchwald and Fagnou, palladium‐catalysed ring‐closing dehydrogenative reactions are legion, but will not operate when the strain at the reductive elimination stage becomes too large. We propose here a “muscled up” super‐oxidative palldium‐catalysed C H activation method for the ring closure of strained phenylcarbazoles.