全文获取类型
收费全文 | 99065篇 |
免费 | 12127篇 |
国内免费 | 4762篇 |
专业分类
电工技术 | 49755篇 |
技术理论 | 3篇 |
综合类 | 7599篇 |
化学工业 | 4956篇 |
金属工艺 | 2116篇 |
机械仪表 | 3816篇 |
建筑科学 | 3105篇 |
矿业工程 | 2027篇 |
能源动力 | 8073篇 |
轻工业 | 2263篇 |
水利工程 | 2538篇 |
石油天然气 | 863篇 |
武器工业 | 669篇 |
无线电 | 12838篇 |
一般工业技术 | 3643篇 |
冶金工业 | 1803篇 |
原子能技术 | 2151篇 |
自动化技术 | 7736篇 |
出版年
2024年 | 453篇 |
2023年 | 1326篇 |
2022年 | 2544篇 |
2021年 | 3010篇 |
2020年 | 3297篇 |
2019年 | 2671篇 |
2018年 | 2399篇 |
2017年 | 3465篇 |
2016年 | 3708篇 |
2015年 | 4195篇 |
2014年 | 7056篇 |
2013年 | 5832篇 |
2012年 | 8024篇 |
2011年 | 8624篇 |
2010年 | 6261篇 |
2009年 | 6356篇 |
2008年 | 6238篇 |
2007年 | 7454篇 |
2006年 | 6623篇 |
2005年 | 5350篇 |
2004年 | 4359篇 |
2003年 | 3490篇 |
2002年 | 2665篇 |
2001年 | 2333篇 |
2000年 | 1918篇 |
1999年 | 1398篇 |
1998年 | 935篇 |
1997年 | 734篇 |
1996年 | 694篇 |
1995年 | 543篇 |
1994年 | 487篇 |
1993年 | 301篇 |
1992年 | 269篇 |
1991年 | 167篇 |
1990年 | 137篇 |
1989年 | 111篇 |
1988年 | 84篇 |
1987年 | 63篇 |
1986年 | 40篇 |
1985年 | 39篇 |
1984年 | 63篇 |
1983年 | 51篇 |
1982年 | 54篇 |
1981年 | 23篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1978年 | 15篇 |
1977年 | 8篇 |
1959年 | 15篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
A novel hierarchical intelligent controller configuration is proposed using an artificial neural network as a control-mode classifier in the supervisory level and a set of pre-designed controllers in the lower level. Controller outputs are modified nonlinearly by the classifying signals in a structure resembling one artificial neuron with adaptively changed weights. The lower-level local controllers are implemented using neural networks. An illustrative example of this approach is based on the transient stabilization of a single-machine infinite-bus system studied in Flexible AC Transmission Systems (FACTS) research. 相似文献
72.
数字调幅制式是当前国际上较先进的调制技术,DX系列全固态数字调幅中波发射机的电声指标和工业效率都是很先进的,过去的DX大功率机采用风冷方式,本文介绍了最新水冷DX-600发射机的设备情况和技术特点。 相似文献
73.
Marcus T. Schmitz Bashir M. Al-Hashimi Petru Eles 《Design Automation for Embedded Systems》2002,6(4):401-424
In this paper, we introduce the LOPOCOS (Low Power Co-synthesis) system, a prototype CAD tool for system level co-design. LOPOCOS targets the design of energy-efficient embedded systems implemented as heterogeneous distributed architectures. In particular, it is designed to solve the specific problems involved in architectures that include dynamic voltage scalable (DVS) processors. The aim of this paper is to demonstrate how LOPOCOS can support the system designer in identifying energy-efficient hardware/software implementations for the desired embedded systems. Hence, highlighting the necessary optimization steps during design space exploration for DVS enable architectures. The optimization steps carried out in LOPOCOS involve component allocation and task/communication mapping as well as scheduling and dynamic voltage scaling. LOPOCOS has the following key features, which contribute to this energy efficiency. During the voltage scaling valuable power profile information of task execution is taken into account, hence, the accuracy of the energy estimation is improved. A combined optimization for scheduling and communication mapping based on genetic algorithm, optimizes simultaneously execution order and communication mapping towards the utilization of the DVS processors and timing behaviour. Furthermore, a separation of task and communication mapping allows a more effective implementation of both task and communication mapping optimizationsteps. Extensive experiments are conducted to demonstrate the efficiency of LOPOCOS. We report up to 38% higher energy reductions compared to previous co-synthesis techniques for DVS systems. The investigations include a real-life example of an optical flow detection algorithm. 相似文献
74.
首先对OFDM的发展以及应用做了简要的介绍,然后讨论了当前OFDM研究过程中的两个关键技术问题,最后展望了OFDM的未来发展。 相似文献
75.
H. de Groot 《Materialwissenschaft und Werkstofftechnik》2007,38(12):965-968
Ischemia‐reperfusion injury of the bone occurs due to traumatic and non‐traumatic alterations affecting blood supply to the bone. It is likely to occur also upon insertion of an implant. Ischemia‐reperfusion injury of the bone has been studied by interruption of blood supply in situ, in limb replantation/transplantation models, in revascularized bone grafts and non‐vascularized bone fragments, as well as in isolated cultured cells. All cells of the bone are affected, including osteoblasts, osteocytes, osteoclasts, chondrocytes, and bone marrow cells. Critical ischemia times for induction of bone cell death, either in the ischemic period or following reperfusion, are in the range of 3 to 7 h. These critical ischemia times are significantly increased by decreasing the temperature from 37 °C to 0–4 °C. Anoxia is the most likely trigger of cell injury in the ischemic phase. In the reperfusion phase, reactive oxygen species are decisively involved in the injurious process. In general, however, the available information on the mechanism of ischemia‐reperfusion injury of the bone is relatively sparse. On the other hand, there are clear similarities to the mechanisms of ischemia‐reperfusion injury known from other organs, and there is a clear potential for protection against ischemia‐reperfusion injury of the bone. 相似文献
76.
77.
S. M. Nikonov I. V. Elkin I. A. Lipatov A. V. Basov A. V. Kapustin A. A. Rovnov 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2007,41(6):351-354
Results of experiments conducted on a large-scale integral PSB-VVéR bench and directed toward investigation of the performance
of new passive safety systems for nuclear plants with a water-cooled power reactor, an additional system for passive flooding
of the active zone, and a system for the passive removal of heat from steam generators are presented.
__________
Translated from élektricheskie Stantsii, No. 9, September 2007, pp. 7–10. 相似文献
78.
简单回顾了国内外在火电机组运行优化领域的研究历程,列举了目前国内外市场上针对火电机组的各种主流运行优化产品的功能特点和应用情况,分析了国外引进产品和国内自主研发产品在中国当前市场环境下各自的优势和劣势。介绍了当前运行优化系统在国内电站机组的应用现状,阐述了国内外运行优化系统在实际应用中存在的问题,并提出了相应的改进意见。对机组运行优化系统的未来发展进行了展望,指出机组运行优化系统将利用先进技术设备和信息平台,与电站管理紧密结合,在日益规范的市场中不断发展完善,为提高电站经济性发挥更大的作用。 相似文献
79.
Understanding how the structure of the unit-cell affects the cryogenic performance of a Si power Metal Oxide Semiconductor Field Effect Transistor (MOSFET) is an important step toward optimizing of the device for cryogenic operations. In this paper, numerical simulations of the Si power Double Diffused MOSFET’ (DMOS) are performed at room temperature and cryogenic temperatures. Physically based models for temperature dependent silicon properties are employed in the simulations. The performances of power DMOS’ with various unit-cell structures are compared at both room temperature and low temperatures. The effect of the cell structure on the on-resistance and breakdown voltage of the device are analyzed. The simulation results suggest that the device optimized for room temperature operation can be further optimized at cryogenic temperatures. 相似文献
80.
The development of renewable technologies in the last decade has been exceptional. In photovoltaic (PV) for example, efforts were not only limited to merely improving their efficiency but also to the reduction of the cost of cells and modules via volume production for commercial markets. There are many national schemes promoting the use of PV technology and regional targets for a share of renewable energy production. This paper attempts to relay to the reader a journey, based on experience, approaches for enhancing the prospect of utilising solar energy within the society we live in. The issue of expansion or enhancing the utilisation of solar energy can be undertaken by individuals, groups, institutions and governments. The aim of this paper is to provide some examples, which could serve as a framework in which action could be taken to promote solar technology. 相似文献