全文获取类型
收费全文 | 663358篇 |
免费 | 8851篇 |
国内免费 | 1948篇 |
专业分类
电工技术 | 12324篇 |
综合类 | 636篇 |
化学工业 | 98441篇 |
金属工艺 | 25124篇 |
机械仪表 | 18980篇 |
建筑科学 | 15848篇 |
矿业工程 | 2864篇 |
能源动力 | 17852篇 |
轻工业 | 56608篇 |
水利工程 | 6378篇 |
石油天然气 | 11167篇 |
武器工业 | 43篇 |
无线电 | 78166篇 |
一般工业技术 | 128183篇 |
冶金工业 | 133518篇 |
原子能技术 | 12856篇 |
自动化技术 | 55169篇 |
出版年
2021年 | 5813篇 |
2020年 | 4230篇 |
2019年 | 5493篇 |
2018年 | 9337篇 |
2017年 | 9115篇 |
2016年 | 9554篇 |
2015年 | 6694篇 |
2014年 | 11144篇 |
2013年 | 30123篇 |
2012年 | 17660篇 |
2011年 | 24339篇 |
2010年 | 19305篇 |
2009年 | 21711篇 |
2008年 | 22342篇 |
2007年 | 22028篇 |
2006年 | 19327篇 |
2005年 | 17825篇 |
2004年 | 17194篇 |
2003年 | 16861篇 |
2002年 | 16032篇 |
2001年 | 16225篇 |
2000年 | 15167篇 |
1999年 | 16256篇 |
1998年 | 42432篇 |
1997年 | 29471篇 |
1996年 | 22684篇 |
1995年 | 16932篇 |
1994年 | 14710篇 |
1993年 | 14423篇 |
1992年 | 10252篇 |
1991年 | 9738篇 |
1990年 | 9515篇 |
1989年 | 9180篇 |
1988年 | 8488篇 |
1987年 | 7386篇 |
1986年 | 7306篇 |
1985年 | 8288篇 |
1984年 | 7621篇 |
1983年 | 6728篇 |
1982年 | 6303篇 |
1981年 | 6505篇 |
1980年 | 6081篇 |
1979年 | 5880篇 |
1978年 | 5658篇 |
1977年 | 6852篇 |
1976年 | 9032篇 |
1975年 | 4896篇 |
1974年 | 4620篇 |
1973年 | 4676篇 |
1972年 | 3852篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A decision support system for interactive decision making - Part II: analysis and output interpretation 总被引:2,自引:0,他引:2
Liping Fang K.W. Hipel D.M. Kilgour Xiaoyong Peng 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2003,33(1):56-66
For pt.I see ibid., p.42-55 (2003). The development of a comprehensive decision support system, GMCR II, for the systematic study of real-world interactive decision problems is presented. The companion paper (Part I), discusses how GMCR II elicits, stores, and manages conflict models; here (Part II), the focus is on GMCR IIs analysis and output interpretation subsystems. Specifically, this paper describes the powerful and efficient analysis engine contained in GMCR II, its informative output presentation and interpretation facilities, and a number of follow-up analyses. Furthermore, an illustrative case study is used to demonstrate how GMCR II can be conveniently applied in practice. 相似文献
62.
S.M. Savaresi F.L. Taroni F. Previdi S. Bittanti 《Mechatronics, IEEE/ASME Transactions on》2004,9(3):569-579
The problem considered in this paper is the design and tuning of the control system of a power-split continuously variable transmission (CVT) used in high-power tractors. Power-split CVTs are characterized by the combination of a traditional mechanical transmission and by a continuously-variable transmission. This guarantees, at the same time, smooth variations of the transmission-ratio and high efficiency of the overall transmission system. The control architecture of an hydrostatic power-split CVT is constituted by three main parts: 1) servo-controller on the current of the valve which drives the hydraulic transmission; 2) a servo-controller on the hydraulic transmission-ratio; and 3) a synchronizer which coordinates the hydraulic and the mechanical parts of the CVT. In this work, these three controllers are fully developed, including: design, implementation, and evaluation on an experimental system. 相似文献
63.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment. 相似文献
64.
Open Shortest Path First (OSPF) traffic engineering (TE) is intended to bring long-awaited traffic management capabilities into IP networks, which still rely on today's prevailing routing protocols: OSPF or IS-IS. In OSPF, traffic is forwarded along, and split equally between, equal cost shortest paths. In this letter, we formulate the basic requirements placed on a practical TE architecture built on top of OSPF and present a theoretical framework meeting these requirements of practicality. The main contribution of our work comes from the recognition that coupled with an instance of the maximum throughput problem there exists a related inverse shortest-path problem yielding optimal OSPF link weights. 相似文献
65.
This paper describes techniques for the on-chip measurement of high-frequency and/or high-bandwidth electrical phenomena in ultra large-scale integration environments. The techniques rely on the integration of multiple compact and robust electronic test devices, or cores, at various locations within an integrated circuit. The cores consist primarily of signal generators that approximate the output of a sigma-delta modulator using finite repetitious bit patterns and a small set of highly robust analog components. They are capable of digitizing on-chip signals at gigahertz rates even using low-cost manufacturing processes. Simple communication between the multiple cores enables the migration of many "board-level" type measurements down to the chip level. 相似文献
66.
67.
68.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients. 相似文献
69.
70.
Rankin D.M. Gulliver T.A. Taylor D.P. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(9):2230-2235
This article investigates the asymptotic performance of single parity-check (SPC) product codes (PCs) from a decoding point of view. Specifically, the probability of bit error is bounded before and after the decoding of each dimension, similar to the analysis of "iterated codes" by Elias (1954). It is shown that the asymptotic probability of bit error can be driven to zero as the number of dimensions, and hence the block length, increases at signal-to-noise ratios (SNRs) within 2 dB of capacity over the additive white Gaussian noise (AWGN) channel. 相似文献