全文获取类型
收费全文 | 215037篇 |
免费 | 2787篇 |
国内免费 | 650篇 |
专业分类
电工技术 | 4258篇 |
综合类 | 141篇 |
化学工业 | 30316篇 |
金属工艺 | 7817篇 |
机械仪表 | 5838篇 |
建筑科学 | 5021篇 |
矿业工程 | 796篇 |
能源动力 | 5150篇 |
轻工业 | 15934篇 |
水利工程 | 1792篇 |
石油天然气 | 2894篇 |
武器工业 | 8篇 |
无线电 | 28780篇 |
一般工业技术 | 40296篇 |
冶金工业 | 48206篇 |
原子能技术 | 3731篇 |
自动化技术 | 17496篇 |
出版年
2021年 | 1697篇 |
2020年 | 1267篇 |
2019年 | 1629篇 |
2018年 | 2532篇 |
2017年 | 2483篇 |
2016年 | 2649篇 |
2015年 | 1898篇 |
2014年 | 3120篇 |
2013年 | 8977篇 |
2012年 | 5294篇 |
2011年 | 7180篇 |
2010年 | 5674篇 |
2009年 | 6566篇 |
2008年 | 6974篇 |
2007年 | 6918篇 |
2006年 | 6302篇 |
2005年 | 5868篇 |
2004年 | 5701篇 |
2003年 | 5491篇 |
2002年 | 5302篇 |
2001年 | 5576篇 |
2000年 | 5207篇 |
1999年 | 5760篇 |
1998年 | 16293篇 |
1997年 | 10751篇 |
1996年 | 8292篇 |
1995年 | 6053篇 |
1994年 | 5270篇 |
1993年 | 5268篇 |
1992年 | 3547篇 |
1991年 | 3403篇 |
1990年 | 3343篇 |
1989年 | 3167篇 |
1988年 | 2896篇 |
1987年 | 2338篇 |
1986年 | 2409篇 |
1985年 | 2738篇 |
1984年 | 2441篇 |
1983年 | 2170篇 |
1982年 | 1979篇 |
1981年 | 2134篇 |
1980年 | 1869篇 |
1979年 | 1751篇 |
1978年 | 1739篇 |
1977年 | 2127篇 |
1976年 | 2832篇 |
1975年 | 1497篇 |
1974年 | 1438篇 |
1973年 | 1376篇 |
1972年 | 1173篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
161.
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
162.
Jon T. Carter Paul E. Krajewski Ravi Verma 《JOM Journal of the Minerals, Metals and Materials Society》2008,60(11):77-81
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
163.
W. Rogowski VDE O. Martin H. Thielen VDE 《Electrical Engineering (Archiv fur Elektrotechnik)》1941,35(7):424-430
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
164.
Yu. A. Chaplygin E. A. Artamonova A. Yu. Krasyukov T. Yu. Krupkina 《Semiconductors》2008,42(13):1522-1526
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
165.
Jun Chen Berger T. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2008,54(8):3385-3398
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
166.
Martin T. P. Azvine B. 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2003,8(2):93-101
With the burgeoning complexity and capabilities of modern information appliances and services, user modelling is becoming an increasingly important research area. Simple user profiles already personalise many software products and consumer goods such as digital TV recorders and mobile phones. A user model should be easy to initialise, and it must adapt in the light of interaction with the user. In many cases, a large amount of training data is needed to generate a user model, and adaptation is equivalent to retraining the system. This paper briefly outlines the user modelling problem and work done at BTexact on an intelligent personal assistant (IPA) which incorporates a user profile. We go on to describe FILUM, a more flexible method of user modelling, and show its application to the telephone assistant and email assistant components of the IPA, with tests to illustrate its usefulness. 相似文献
167.
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
168.
A. T. Joseph 《Expert Systems》1991,8(2):119-127
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
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
169.
In this article, we describe a new approach to applying distributed artificial intelligence techniques to manufacturing processes. The construction of intelligent systems is one of the most important techniques among artificial intelligence research. Our goal is to develop an integrated intelligent system for real time manufacturing processes. An integrated intelligent system is a large knowledge integration environment that consists of several symbolic reasoning systems (expert systems) and numerical computation packages. These software programs are controlled by a meta-system which manages the selection, operation and communication of these programs. A meta-system can be implemented in different language environments and applied to many disciplines. This new architecture can serve as a universal configuration to develop high performance intelligent systems for many complicated industrial applications in real world domains.To whom all correspondence should be addressed. 相似文献
170.
J.A. Bakken L. Barone D. Braun M. Caillat C. Dionisi C. Dor H. Elmamouni F. Ferroni G.L. Grazer J.T. He R. Herbiet B. Ille P. Lecomte E. Longo P.F. Loverre Y.S. Lu J.P. Martin U. Micke R.P. Mount P.A. Pirou H.-G. Sander D. Schmitz M. Schneegans D.P. Stickland R.L. Sumner K.L. Tung E. Valente M. Vivargent 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1985,228(2-3):294-302
A calorimeter of 25 bismuth germanate (BGO) crystals equipped with silicon photodiode readout has been tested at the CERN SPS in the energy range 1–50 GeV. The response for electrons has been shown to be linear in this energy range and the rms resolution obtained (
) is approximately 1%, for E > 4 GeV. The electron/pion separation was found to be better than 1:500 in the energy range 1–20 GeV. Data on lateral and longitudinal shower development were compared with the results of a Monte Carlo simulation using the SLAC-EGS program and found to be in good agreement. 相似文献