全文获取类型
收费全文 | 3453篇 |
免费 | 78篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 40篇 |
综合类 | 7篇 |
化学工业 | 380篇 |
金属工艺 | 57篇 |
机械仪表 | 53篇 |
建筑科学 | 116篇 |
矿业工程 | 10篇 |
能源动力 | 104篇 |
轻工业 | 337篇 |
水利工程 | 16篇 |
石油天然气 | 19篇 |
无线电 | 235篇 |
一般工业技术 | 344篇 |
冶金工业 | 1389篇 |
原子能技术 | 24篇 |
自动化技术 | 412篇 |
出版年
2022年 | 22篇 |
2021年 | 35篇 |
2020年 | 26篇 |
2019年 | 19篇 |
2018年 | 42篇 |
2017年 | 33篇 |
2016年 | 41篇 |
2015年 | 44篇 |
2014年 | 80篇 |
2013年 | 127篇 |
2012年 | 90篇 |
2011年 | 113篇 |
2010年 | 92篇 |
2009年 | 83篇 |
2008年 | 100篇 |
2007年 | 110篇 |
2006年 | 100篇 |
2005年 | 62篇 |
2004年 | 68篇 |
2003年 | 81篇 |
2002年 | 61篇 |
2001年 | 61篇 |
2000年 | 60篇 |
1999年 | 73篇 |
1998年 | 431篇 |
1997年 | 248篇 |
1996年 | 168篇 |
1995年 | 119篇 |
1994年 | 122篇 |
1993年 | 111篇 |
1992年 | 47篇 |
1991年 | 49篇 |
1990年 | 40篇 |
1989年 | 48篇 |
1988年 | 50篇 |
1987年 | 53篇 |
1986年 | 31篇 |
1985年 | 40篇 |
1984年 | 20篇 |
1983年 | 23篇 |
1982年 | 15篇 |
1981年 | 20篇 |
1980年 | 25篇 |
1978年 | 16篇 |
1977年 | 38篇 |
1976年 | 64篇 |
1975年 | 13篇 |
1974年 | 14篇 |
1973年 | 18篇 |
1972年 | 13篇 |
排序方式: 共有3543条查询结果,搜索用时 218 毫秒
101.
G. Ramadorai M. E. Wadsworth C. K. Hansen 《Metallurgical and Materials Transactions B》1975,6(4):579-584
Powdered molybdenum dioxide was oxidized to MoO3 in the temperature range 390 to 465°C under oxygen partial pressures of 0.016 and 0.18 atmospheres* and under 0.009 atmospheres in the temperature interval 465 to 529°C. The course of the reaction was followed by observing weight change with time. Parabolic kinetics were evident for oxidation below 460°C. Above 460°C linear kinetics were observed. The partial pressure dependence at 407°C and 455°C was found to be approximately \(P_{O_2 }^{1/5} \) . Oxidation tests were restricted to an oxygen partial pressure of 0.009 atmosphere in the temperature range between 460°C and 530°C since above this partial pressure excessive heating occurred. For the low temperature range the oxidation was explained in terms of the diffusion of mono-and divalent oxygen interstitials. Activation enthalpies of 159±8 and 105±8 kJ/mole were obtained respectively for parabolic and linear rate processes. 相似文献
102.
Monga S. Gorur R.S. Hansen P. Massey W. 《Dielectrics and Electrical Insulation, IEEE Transactions on》2006,13(6):1217-1224
This paper illustrates the use of electric field computation to optimize the design of gas filled high voltage composite bushings. The United States Navy employs these bushings in high power very low frequency/low frequency transmitting stations. Commercially available 2D and 3D computational packages based on the boundary element method were employed to analyze the electric fields. The optimized design uses both internal and external elements for electric stress grading at critical parts of the bushing. It has been shown that the location and magnitude of the maximum electric field have been optimized which should result in a substantially higher corona free operating voltage 相似文献
103.
Two-way grillage or waffle floors are used extensively in semiconductor factories as they provide high impedance mounts for manufacturing equipment that is extremely vibration sensitive. This paper presents a mathematical model for the analysis of vibration at the center of a bay and the transmission of vibration along a waffle floor. The mathematical model is compared with finite element models and experimental results from several manufacturing buildings, and shows good agreement. Trends are shown for the displacement and resonance frequency of the floor as the thickness of the floor, size of the bays and the stiffness of the columns are varied. 相似文献
104.
Conan C. Albrecht Douglas D. Dean James V. Hansen 《Expert systems with applications》2003,24(4):391-397
As the Internet grows, it is becoming less feasible for customers and merchants to manually visit each web site, analyze the information there, and make sound business decisions regarding the trading of goods or services. To cope with this evolution, software agents can be designed that are capable of automating the more routine, tedious, and time-consuming tasks involved in current trading processes. At a higher level agents may also be able to negotiate and make autonomous decisions and commitments on behalf of their owners.
This paper describes an agent implementation using the situation calculus, which offers a possibly unifying paradigm for dynamic agents. Interesting applications are currently being developed. Our contribution is a situation calculus agent system developed for e-business. Ongoing work is focused on implementing this system in an open marketplace environment. 相似文献
105.
A model for volume lighting and modeling 总被引:4,自引:0,他引:4
Kniss J. Premoze S. Hansen C. Shirley P. McPherson A. 《IEEE transactions on visualization and computer graphics》2003,9(2):150-162
Direct volume rendering is a commonly used technique in visualization applications. Many of these applications require sophisticated shading models to capture subtle lighting effects and characteristics of volumetric data and materials. For many volumes, homogeneous regions pose problems for typical gradient-based surface shading. Many common objects and natural phenomena exhibit visual quality that cannot be captured using simple lighting models or cannot be solved at interactive rates using more sophisticated methods. We present a simple yet effective interactive shading model which captures volumetric light attenuation effects that incorporates volumetric shadows, an approximation to phase functions, an approximation to forward scattering, and chromatic attenuation that provides the subtle appearance of translucency. We also present a technique for volume displacement or perturbation that allows realistic interactive modeling of high frequency detail for both real and synthetic volumetric data. 相似文献
106.
Hansen K.M. Ravn A.P. Stavridou V. 《IEEE transactions on pattern analysis and machine intelligence》1998,24(7):573-584
Software for safety critical systems must deal with the hazards identified by safety analysis. This paper investigates, how the results of one safety analysis technique, fault trees, are interpreted as software safety requirements to be used in the program design process. We propose that fault tree analysis and program development use the same system model. This model is formalized in a real-time, interval logic, based on a conventional dynamic systems model with state evolving over time. Fault trees are interpreted as temporal formulas, and it is shown how such formulas can be used for deriving safety requirements for software components 相似文献
107.
Z. -S. Liu J. S. Hansen D. C. D. Oguamanam 《Structural and Multidisciplinary Optimization》1998,16(2-3):155-161
This paper formulates the eigenvalue sensitivity of a stiffened plate with respect to stiffener location; the analysis is based on the generalized Rayleigh quotient of the combined platebeam system. The results show that the eigenvalue sensitivity is proportional to the force between the plate and the stiffener as well as to the slope of the eigenfunction at the interface between the plate and the stiffener. 相似文献
108.
Most network applications assume continuous connectivity-an assumption that does not “migrate” to wireless environments. The authors present the design of a communication layer for mobile computing that dynamically adapts to changes in network connections. Our work was part of AMIGOS (Advanced Mobile Integration in General Operating Systems), a collaboration between researchers at the University of Copenhagen in Denmark and the University of Minho in Portugal. The AMIGOS project provides transparent support for semi connected operations on mobile computers running a standard operating system; the project home page is at http://www.econ.cbs.dk/people/birger/AMIGOS/. Briefly, our design lets a mobile user connect a mobile host to a LAN, then disconnect the host from it. The user then can reconnect, for example, via a Global System for Mobile Communications (GSM) cellular modem without losing TCP/IP connections. We want to allow existing TCP/IP based applications to be used in a mobile environment, without application modifications 相似文献
109.
110.