首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   278650篇
  免费   3068篇
  国内免费   1402篇
电工技术   5881篇
综合类   262篇
化学工业   38674篇
金属工艺   11463篇
机械仪表   9130篇
建筑科学   5816篇
矿业工程   1452篇
能源动力   6445篇
轻工业   20482篇
水利工程   2780篇
石油天然气   5501篇
武器工业   59篇
无线电   35081篇
一般工业技术   55389篇
冶金工业   57499篇
原子能技术   6257篇
自动化技术   20949篇
  2021年   2427篇
  2020年   1849篇
  2019年   2381篇
  2018年   4315篇
  2017年   4350篇
  2016年   4706篇
  2015年   2935篇
  2014年   4859篇
  2013年   12228篇
  2012年   7538篇
  2011年   9507篇
  2010年   7895篇
  2009年   9097篇
  2008年   9385篇
  2007年   9329篇
  2006年   8262篇
  2005年   7372篇
  2004年   7113篇
  2003年   6793篇
  2002年   6529篇
  2001年   6869篇
  2000年   6696篇
  1999年   7053篇
  1998年   18909篇
  1997年   12737篇
  1996年   9629篇
  1995年   7095篇
  1994年   6196篇
  1993年   6237篇
  1992年   4278篇
  1991年   4205篇
  1990年   4190篇
  1989年   3970篇
  1988年   3616篇
  1987年   3033篇
  1986年   3096篇
  1985年   3434篇
  1984年   3028篇
  1983年   2756篇
  1982年   2507篇
  1981年   2658篇
  1980年   2412篇
  1979年   2245篇
  1978年   2229篇
  1977年   2724篇
  1976年   3570篇
  1975年   1958篇
  1974年   1882篇
  1973年   1825篇
  1972年   1566篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
We propose an asynchronous structure for implementation on a SoC. An intersegment topological arrangement preserves parallelization and, through a so-called central arbiter, efficiently organizes communication with high signaling speed in the proposed structure. Researchers proposed the concept of segmenting buses primarily for multicomputer architectures. More recent approaches address on-chip implementation of segmented buses. We present an asynchronous segmented-bus architecture targeted for the modular design of high-performance SoC applications. The structure not only enables faster operation than a conventional bus system but also offers lower power consumption per transferred data item. This is possible because segmentation is realized in such a way that the majority of data transfers in the system are intrasegment transactions on relatively short wires with low or moderate capacitive loads.  相似文献   
72.
With the creation of balancing authorities by the North American Reliability Council that span large portions of the North American interconnection, and stringent requirements for real time monitoring of power system evolution, faster and more accurate state estimation algorithms that can efficiently handle systems of very large sizes are needed in the present environment. This paper presents a distributed state estimation algorithm suitable for large-scale power systems. Synchronized phasor measurements are applied to aggregate the voltage phase angles of each decomposed subsystem in the distributed state estimation solution. The aggregated state estimation solution is obtained from the distributed solution using a sensitivity analysis based update at chosen boundary buses. Placement of synchronized phasor measurements in the decomposed subsystems is also investigated in this paper. Test results on the IEEE 118-bus test bed are provided  相似文献   
73.
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General Motors Corporation is reviewed.  相似文献   
74.
Zusammenfassung Aufnahmen von Lichtenbergschen Figuren mit kurzen Spannungsstößen zeigen, daß bisher bekanntgewordene Bilder solcher Entladungsfiguren bereits ein verhältnismäßig weit vorgeschrittenes Stadium darstellen. Es gelingt mittels kurzer Stöße erste lawinenartige Anfänge der Figuren festzuhalten und einiges über Vorgänge im Anfangsstadium herauszulesen. Die negative Figur beginnt lawinenförmig an bevorzugten Stellen der Kathode. Bei nebeneinander entstandenen Lawinen ist sehr gut die gegenseitige Abstoßung infolge gleicher Ladung zu beobachten. Die Entladung hat einen geschichteten Aufbau. Die positiven Figuren bilden sich später aus. Es sprechen jedoch bisher keinerlei Anzeichen für ein Hinwachsen der Fäden zur Anode. Die Kanäle verjüngen sich zur Anode hin und selbst bei kurzen Stoßzeiten endet kein einziger vor der Anode. Auch die Art der gegenseitigen Abstoßung der positiven Fäden spricht mehr für ein Vorwachsen von der Anode aus. Aus den Farbaufnahmen ergibt sich für die filmschwärzende Strahlung eine Wellenlänge unter 450 m.  相似文献   
75.
Heat removal problems, thermal effects, and self-heating phenomena occurring during operation of planar power SOI MOS transistors are considered. Using device-technological simulating methods, the transistor characteristics and safe operation range were studied. It was shown that limitations of the safe operation range are mostly associated with structure self-heating rather than with the parasitic bipolar transistor.  相似文献   
76.
We consider a distributed source coding system in which several observations must be encoded separately and communicated to the decoder by using limited transmission rate. We introduce a robust distributed coding scheme which flexibly trades off between system robustness and compression efficiency. The optimality of this coding scheme is proved for various special cases.  相似文献   
77.
Sol–gel films are actively investigated during the last decade as possible candidates for environmentally friendly pre-treatments. However, the important drawback in this case is the lack of active corrosion protection and self-healing ability.  相似文献   
78.
The cooling and solidification of melted drops during their movement in an immiscible cooling medium is widely employed for granulation in the chemical industry, and a study of these processes to provides a basis for the design of the granulation tower height and the temperature of the cooling medium is reported. A physical model of the cooling and solidification of the drop is established and the numerical calculation is performed. The influences of the key factors in the solidification, i.e., Bi number, drop diameter, temperature of the cooling medium, etc. are presented. The cooling and solidification during wax granulation in a water‐cooling tower and during urea granulation in an air‐cooling tower (spraying tower) are described in detail. Characteristics of the solidification and temperature distribution within the particle at different times are shown. The model and calculations can be used for structure design of the granulation tower and optimization of the operation parameters.  相似文献   
79.
ProKappa is an expert system tool kit developed by IntelliCorp in C using X-Windows for graphical interface. The SUN 3 or 4 version costs $9995/£7000 and $2595/£1800 for the interactive C environment.
This review covers ProKappa version 1.1, installed on a colour SUN SPARC Station 1 with the minimum recommended values of 12 Mb of memory and 30 Mb of swap space.
IntelliCorp can be contacted in the USA at 1975 El Camino Real West, Mountain View, CA 94040-2216 (+1 (415) 965-5500) and in the UK at 10 Jewry Street, Winchester, Hampshire SO23 8RZ (+44 (0)962 735348).  相似文献   
80.
Conclusions The change in some properties of polyvinyl fluoride during the process of fibre spinning has been investigated.It has been found that during the process of converting PVF powder into fibre, the degree of polymer crystallinity plus its resistance to thermal and thermooxidative degradation is increased; depending on the spinning regime, the densities and physicomechanical properties of PVF fibres are different.Translated from Khimicheskie Volokna, No. 4, pp. 34–35, July–August, 1984.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号