全文获取类型
收费全文 | 743篇 |
免费 | 16篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 73篇 |
金属工艺 | 22篇 |
机械仪表 | 38篇 |
建筑科学 | 26篇 |
矿业工程 | 3篇 |
能源动力 | 4篇 |
轻工业 | 92篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 43篇 |
一般工业技术 | 107篇 |
冶金工业 | 271篇 |
原子能技术 | 7篇 |
自动化技术 | 57篇 |
出版年
2022年 | 5篇 |
2021年 | 7篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 31篇 |
2012年 | 21篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 21篇 |
2007年 | 24篇 |
2006年 | 19篇 |
2005年 | 15篇 |
2004年 | 10篇 |
2003年 | 13篇 |
2002年 | 20篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 24篇 |
1998年 | 77篇 |
1997年 | 35篇 |
1996年 | 29篇 |
1995年 | 25篇 |
1994年 | 22篇 |
1993年 | 24篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1987年 | 7篇 |
1986年 | 13篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1982年 | 9篇 |
1981年 | 4篇 |
1980年 | 5篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1966年 | 5篇 |
1965年 | 4篇 |
排序方式: 共有759条查询结果,搜索用时 15 毫秒
1.
Sequential maximum a posteriori (SMAP) and the extraction and classification of homogeneous objects (ECHO), two spectral/spatial scene segmentation algorithms, were compared with traditional maximum likelihood (ML) estimation in a supervised classification of multispectral data. SMAP generalized better than both ECHO and ML. Significant differences were found in all mean class classification accuracies: SMAP>ECHO>ML 相似文献
2.
This paper describes the work done by the Autonomous Systems Lab of Ecole Polytechnique Federale de Lausanne (EPFL) on the global design of an unmanned solar airplane that can fly continuously over days and night. Part of the Sky-Sailor Project, a first prototype was designed and demonstrated to have very good flight characteristics. The prototype achieved an autonomous flight of five hours with its energy only from the sun. A lightweight control and navigation system was also designed for the aircraft. 相似文献
3.
4.
5.
Within the framework of research that describes the processes of collaborative knowledge construction in computer-supported collaborative learning (CSCL) environments, the present work has three objectives: (i) the identification of the strategies of six small groups of university students for the elaboration of written products in a CSCL environment; (ii) seek relations between the identified writing strategies and the processes and phases of collaborative knowledge construction in the groups; and (iii) relate these strategies and phases with the learning results obtained by the groups. We carried out a multiple-case study, with the analysis of four different didactic sequences, in two different virtual learning and teaching settings. In each setting, three student groups were studied, where each had to collaboratively develop between four and eight written products. For all the studied groups, the analysis enabled the identification of five types of strategies in the preparation of the elaboration of written products, and four types of phases of collaborative knowledge construction, which are interrelated and also connected with the grades that the groups obtained in each case. 相似文献
6.
7.
Eric N. Hanson I.-Cheng Chen Roxana Dastur Kurt Engel Vijay Ramaswamy Wendy Tan Chun Xu 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(1):12-24
A software architecture is presented that allows client application programs to interact with a DBMS server in a flexible
and powerful way, using either direct, volatile messages, or messages sent via recoverable queues. Normal requests from clients
to the server and replies from the server to clients can be transmitted using direct or recoverable messages. In addition,
an application event notification mechanism is provided, whereby client applications running anywhere on the network can register
for events, and when those events are raised, the clients are notified. A novel parameter passing mechanism allows a set of
tuples to be included in an event notification. The event mechanism is particularly useful in an active DBMS, where events
can be raised by triggers to signal running application programs.
Received July 21, 1995 / Accepted May 30, 1996 相似文献
8.
Controlling Spin Qubits in Quantum Dots 总被引:1,自引:0,他引:1
Hans-Andreas Engel L. P. Kouwenhoven Daniel Loss C. M. Marcus 《Quantum Information Processing》2004,3(1-5):115-132
We review progress on the spintronics proposal for quantum computing where the quantum bits (qubits) are implemented with electron spins. We calculate the exchange interaction of coupled quantum dots and present experiments, where the exchange coupling is measured via transport. Then, experiments on single spins on dots are described, where long spin relaxation times, on the order of a millisecond, are observed. We consider spin-orbit interaction as sources of spin decoherence and find theoretically that also long decoherence times are expected. Further, we describe the concept of spin filtering using quantum dots and show data of successful experiments. We also show an implementation of a read out scheme for spin qubits and define how qubits can be measured with high precision. Then, we propose new experiments, where the spin decoherence time and the Rabi oscillations of single electrons can be measured via charge transport through quantum dots. Finally, all these achievements have promising applications both in conventional and quantum information processing.
PACS: 03.67.Lx, 03.67.Mn, 73.23.Hk, 85.35.Be 相似文献
9.
Molten salt reactors (MSR) have many non-proliferation attributes. They can operate on the thorium-uranium fuel cycle which protects the fissile material by the daughter products of the inseparable U-232. MSRs can completely fission all plutonium and HEU, and as desired, ‘convert’ them to U-233. This also results in high, and efficient resource utilization, while diminishing the plutonium stock. On line processing, when applied, could free the waste from all fissile material. The fuel in the reactor stays protected by the intense radiation of the fission products. Fuel can also be protected in the reactor as well as outside the reactor by denaturing with natural uranium. A wide variety of MSRs are available, from ‘once through’ minimum processing reactors to ones with fuel processing which can breed fuel for converters. MSRs are extremely safe and simple reactors with good economic potential. 相似文献
10.