全文获取类型
收费全文 | 799篇 |
免费 | 32篇 |
专业分类
电工技术 | 12篇 |
化学工业 | 177篇 |
金属工艺 | 12篇 |
机械仪表 | 22篇 |
建筑科学 | 56篇 |
能源动力 | 30篇 |
轻工业 | 124篇 |
水利工程 | 11篇 |
石油天然气 | 3篇 |
无线电 | 70篇 |
一般工业技术 | 85篇 |
冶金工业 | 58篇 |
原子能技术 | 2篇 |
自动化技术 | 169篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 20篇 |
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 14篇 |
2017年 | 17篇 |
2016年 | 20篇 |
2015年 | 21篇 |
2014年 | 20篇 |
2013年 | 44篇 |
2012年 | 51篇 |
2011年 | 76篇 |
2010年 | 65篇 |
2009年 | 59篇 |
2008年 | 58篇 |
2007年 | 52篇 |
2006年 | 33篇 |
2005年 | 37篇 |
2004年 | 28篇 |
2003年 | 25篇 |
2002年 | 26篇 |
2001年 | 11篇 |
2000年 | 4篇 |
1999年 | 13篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 4篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
排序方式: 共有831条查询结果,搜索用时 15 毫秒
21.
Bart Goethals Dominique Laurent Wim Le Page Cheikh Tidiane Dieng 《Knowledge and Information Systems》2012,33(3):655-684
We present an approach for mining frequent conjunctive in arbitrary relational databases. Our pattern class is the simple, but appealing subclass of simple conjunctive queries. Our algorithm, called Conqueror $^+$ , is capable of detecting previously unknown functional and inclusion dependencies that hold on the database relations as well as on joins of relations. These newly detected dependencies are then used to prune redundant queries. We propose an efficient database-oriented implementation of our algorithm using SQL and provide several promising experimental results. 相似文献
22.
Pieter Samyn Ludo Van Schepdael Wim Van Paepegem J. S. Leendertz Eric Suister Patrick De Baets Joris Degrieck 《Applied Composite Materials》2006,13(2):57-85
Carbon fibre/epoxy rings are used as radial reinforcement for polymer bearing elements with nominal diameter 250 mm functioning under 150 MPa. Full-scale static and dynamic testing revealed no catastrophic failure for loading to 400 MPa, although there was circumferential splitting of carbon fibres at the machined top edge causing counterface wear under sliding. A combined numerical–experimental analysis was applied for design improvement with a representative small-scale qualification test on the real ring geometry, inducing additional stress concentrations compared to ASTM standards. Full-scale modelling revealed high radial–axial shear stresses (33 MPa) in non-hydrostatically loaded zones, while it increased towards 104 MPa under hydrostatic load conditions. The former is the most critical and should be simulated either on a small-scale unidirectional compression test or on a representative short beam shear test, respectively, measuring the radial–axial or radial–tangential shear strength. A relation between both small-scale states of stress was experimentally and numerically studied, experiencing that the composite ring has lower radial–tangential shear stress compared to radial–axial shear stress as a different hydrostatic stress state is observed in the bulk of the composite ring. As a compressive test is however more difficult to perform than a short-beam-shear test, a representative design criterion for shear fracture is determined from failure at 27 kN normal load in a short-beam-shear test. Finally, fracture is avoided by optimising the cross-sectional geometry of the composite reinforcing ring and close control of the processing parameters. 相似文献
23.
24.
25.
26.
Francesco
Borgioli David Hajdu Tamas Insperger Gabor Stepan Wim Michiels 《International journal for numerical methods in engineering》2020,121(16):3505-3528
The article presents a pseudospectral approach to assess the stability robustness of linear time-periodic delay systems, where periodic functions potentially present discontinuities and the delays may also periodically vary in time. The considered systems are subject to linear real-valued time-periodic uncertainties affecting the coefficient matrices, and the presented method is able to fully exploit structure and potential interdependencies among the uncertainties. The assessment of robustness relies on the computation of the pseudospectral radius of the monodromy operator, namely, the largest Floquet multiplier that the system can attain within a given range of perturbations. Instrumental to the adopted novel approach, a solver for the computation of Floquet multipliers is introduced, which results into the solution of a generalized eigenvalue problem which is linear w.r.t. (samples of) the original system matrices. We provide numerical simulations for popular applications modeled by time-periodic delay systems, such as the inverted pendulum subject to an act-and-wait controller, a single-degree-of-freedom milling model and a turning operation with spindle speed variation. 相似文献
27.
Cdric H. G. Neutel Jhana O. Hendrickx Wim Martinet Guido R. Y. De Meyer Pieter-Jan Guns 《International journal of molecular sciences》2020,21(23)
Background: Autophagy is a highly conserved catabolic homeostatic process, crucial for cell survival. It has been shown that autophagy can modulate different cardiovascular pathologies, including vascular calcification (VCN). Objective: To assess how modulation of autophagy, either through induction or inhibition, affects vascular and valvular calcification and to determine the therapeutic applicability of inducing autophagy. Data sources: A systematic review of English language articles using MEDLINE/PubMed, Web of Science (WoS) and the Cochrane library. The search terms included autophagy, autolysosome, mitophagy, endoplasmic reticulum (ER)-phagy, lysosomal, calcification and calcinosis. Study characteristics: Thirty-seven articles were selected based on pre-defined eligibility criteria. Thirty-three studies (89%) studied vascular smooth muscle cell (VSMC) calcification of which 27 (82%) studies investigated autophagy and six (18%) studies lysosomal function in VCN. Four studies (11%) studied aortic valve calcification (AVCN). Thirty-four studies were published in the time period 2015–2020 (92%). Conclusion: There is compelling evidence that both autophagy and lysosomal function are critical regulators of VCN, which opens new perspectives for treatment strategies. However, there are still challenges to overcome, such as the development of more selective pharmacological agents and standardization of methods to measure autophagic flux. 相似文献
28.
An abstract file system is defined here as a partial function from (absolute) paths to data. Such a file system determines
the set of valid paths. It allows the file system to be read and written at a valid path, and it allows the system to be modified
by the Unix operations for creation, removal, and moving of files and directories. We present abstract definitions (axioms)
for these operations. This specification is refined towards a pointer implementation. The challenge is to have a natural abstraction
function from the implementation to the specification, to define operations on the concrete store that behave exactly in the
same way as the corresponding functions on the abstract store, and to prove these facts. To mitigate the problems attached
to partial functions, we do this in two steps: first a refinement towards a pointer implementation with total functions, followed
by one that allows partial functions. These two refinements are proved correct by means of a number of invariants. Indeed,
the insights gained consist, on the one hand, of the invariants of the pointer implementation that are needed for the refinement
functions, and on the other hand of the precise enabling conditions of the operations on the different levels of abstraction.
Each of the three specification levels is enriched with a permission system for reading, writing, or executing, and the refinement
relations between these permission systems are explored. Files and directories are distinguished from the outset, but this
rarely affects our part of the specifications. All results have been verified with the proof assistant PVS, in particular,
that the invariants are preserved by the operations, and that, where the invariants hold, the operations commute with the
refinement functions. 相似文献
29.
Davy Van Deursen Wim Van Lancker Erik Mannens Rik Van de Walle 《Multimedia Tools and Applications》2014,70(2):827-846
W3C’s Video in the Web activity aims at a better integration of media within the Web. In this paper, we show how two specifications currently under development within this activity, i.e., Media Fragment URIs and Media Annotations, can be combined within media-enabled HTML5 Web applications. In particular, we introduce a number of extensions for the Media Annotations ontology in order to close the gap with Media Fragment URIs. Additionally, we show how rich media fragment annotations can be converted into a WebVTT file. The latter can be used by HTML5-enabled players to show the annotations in a synchronized way. Further, a fully integrated Web application has been developed that shows how both specifications can work together within an HTML5 environment. This application relies on NinSuna, our media delivery platform targeted at multichannel publication that provides server-side support for both Media Fragment URIs and Media Annotations. 相似文献
30.
Nico De Clercq Robin Theunis Paul Leroux Patrick Reynaert Wim Dehaene 《Analog Integrated Circuits and Signal Processing》2017,90(2):283-290
A clock-cycle accurate synchronization technique for fully integrated data-converters is presented. Only a single cable is needed to distribute both the required synchronization signal and the converter clock. Different possible implementations, both to generate and decompose the distributed signal, are presented. A discrete component generator circuit is discussed. To avoid setup and hold time violations, on-chip signal reconstruction is unavoidable. A 40 nm CMOS recovery circuit was developed. Simulation results, including layout parasitics, show the wide frequency operating range of the proposed technique. 相似文献