全文获取类型
收费全文 | 192210篇 |
免费 | 17189篇 |
国内免费 | 13360篇 |
专业分类
电工技术 | 29862篇 |
技术理论 | 7篇 |
综合类 | 18412篇 |
化学工业 | 9938篇 |
金属工艺 | 10450篇 |
机械仪表 | 17777篇 |
建筑科学 | 19193篇 |
矿业工程 | 8635篇 |
能源动力 | 5125篇 |
轻工业 | 4814篇 |
水利工程 | 7115篇 |
石油天然气 | 6206篇 |
武器工业 | 2824篇 |
无线电 | 13383篇 |
一般工业技术 | 10897篇 |
冶金工业 | 9255篇 |
原子能技术 | 1264篇 |
自动化技术 | 47602篇 |
出版年
2024年 | 825篇 |
2023年 | 2275篇 |
2022年 | 3655篇 |
2021年 | 4603篇 |
2020年 | 5468篇 |
2019年 | 4314篇 |
2018年 | 3933篇 |
2017年 | 5635篇 |
2016年 | 6264篇 |
2015年 | 6868篇 |
2014年 | 12725篇 |
2013年 | 11129篇 |
2012年 | 14011篇 |
2011年 | 15094篇 |
2010年 | 11328篇 |
2009年 | 11652篇 |
2008年 | 11510篇 |
2007年 | 14198篇 |
2006年 | 12752篇 |
2005年 | 11036篇 |
2004年 | 9152篇 |
2003年 | 8137篇 |
2002年 | 6528篇 |
2001年 | 5432篇 |
2000年 | 4745篇 |
1999年 | 3842篇 |
1998年 | 2920篇 |
1997年 | 2588篇 |
1996年 | 2025篇 |
1995年 | 1681篇 |
1994年 | 1433篇 |
1993年 | 1020篇 |
1992年 | 835篇 |
1991年 | 633篇 |
1990年 | 505篇 |
1989年 | 437篇 |
1988年 | 313篇 |
1987年 | 178篇 |
1986年 | 130篇 |
1985年 | 118篇 |
1984年 | 162篇 |
1983年 | 126篇 |
1982年 | 125篇 |
1981年 | 82篇 |
1980年 | 58篇 |
1979年 | 75篇 |
1978年 | 48篇 |
1977年 | 48篇 |
1964年 | 13篇 |
1959年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The flame front deformation instability of low-velocity filtration combustion within an inert packed bed is studied based on the initial preheating non-uniformity. Based on the experimental phenomena, an initial thermal perturbation model is numerically proposed so as to predict the deformation behaviors of the flame front instabilities. The numerical prediction indicates that the assumption of an initial thermal perturbation is a feasible explanation as the cause of the flame front inclination instability. As the initial thermal perturbation increases, the phenomena of the flame front break and shrinking instabilities could easily occur at high filtration velocity or low equivalence ratio. Moreover, the evolutions of the flame front break rate and the shrinking rate are quantitatively analyzed. 相似文献
52.
Rui
Zhang Junmin Li Jianmin Jiao 《International Journal of Adaptive Control and Signal Processing》2020,34(7):919-936
This article investigates an adaptive fuzzy tracking control problem for a class of nontriangular form systems with asymmetric time-varying full state constraints. Unknown functions are approximated by the fuzzy logic systems. A domination approach is employed to tackle the nontriangular form structure. Time-varying asymmetric barrier Lyapunov functions (ABLFs) are adopted to ensure full-state constraints satisfaction. Based on the backstepping technique and time-varying ABLFs, an adaptive controller is proposed and guarantees that all the signals in the closed-loop system are ultimately bounded and the time-varying full state constraints are met. Simulation examples are presented to further demonstrate the effectiveness of the proposed approach. 相似文献
53.
54.
分析了冶炼烟气制酸工艺的特点,介绍了由PROFIBUS-DP现场总线构建的冶炼厂烟气制酸监控系统,详细介绍了其硬件配置及相应的软件设计。 相似文献
55.
56.
马钢二烧结配料计算机控制系统 总被引:1,自引:0,他引:1
阐明了马钢二烧结配科计算机控制系统的目的、控制形式、控制原理;根据烧结配料控制对象的特点对信号采样和控制算法进行了探讨;提供了系统的主要硬件结构,软件功能和程序框图。 相似文献
57.
Kurjenniemi Janne Hämäläinen Seppo Ristaniemi Tapani 《Wireless Personal Communications》2003,27(4):337-351
In this article we consider the performance of the 3.84 Mcpstime-division duplex (TDD) mode of UTRA (Universal TerrestrialRadio Access) network. We emphasize two of the radio resourcemanagement algorithms, handover and uplink power control, whoserole in the overall system performance is studied extensively.First, a handover algorithm used in WCDMA (Wideband Code DivisionMultiple Access) standard is considered in a TDD-mode operation.This gives rise to a careful setting of different handoverparameters, and the evaluation of the effects to the systemperformance. Secondly, the specified uplink power controlalgorithm is considered. Since it is based on several user-mademeasurements which may involve both random and systematic errors acareful study about the suitability of the power control scheme iscarried out. 相似文献
58.
移动通信系统中功率控制研究 总被引:2,自引:0,他引:2
在阐述功率控制在移动通信系统中的发展过程的基础上,着重研究了WCDMA系统的功率控制,最后对功率控制未来的研究方向做了简要的分析。 相似文献
59.
Deformation behavior of stoichiometric blends made from poly(styrene-co-styrenesulfonic acid) (SPS) and poly(styrene-co-4-vinylpyridine) (SVP) was investigated by TEM observation of strained thin films. An FTIR investigation revealed that ionic cross-links were formed between the component polymers upon blending due to intermolecular ion-ion interactions, which arose from proton transfer from sulfonic acid groups to pyridine groups. TEM observations indicate that the deformation mode of the blends changed from crazing only to crazing plus shear deformation, with the shear contribution becoming larger, as the ion content in the blends increased. Such changes in deformation mode can be understood as arising from an increase in the ‘effective’ strand density due to the formation of ionic cross-links upon blending. It was also found that the ionic cross-links via pyridinium cation/sulfonate anion ion pairs were more effective in inducing the transition of deformation mode than ionic cross-links via -SO3−/Na+ or -SO3−/Ca2+ ion pairs. 相似文献
60.
Depending on whether bidirectional links or unidirectional links are used for communications, the network topology under a
given range assignment is either an undirected graph referred to as the bidirectional topology, or a directed graph referred
to as the unidirectional topology. The Min-Power Bidirectional (resp., Unidirectional) k-Node Connectivity problem seeks a range assignment of minimum total power subject to the constraint that the produced bidirectional
(resp. unidirectional) topology is k-vertex connected. Similarly, the Min-Power Bidirectional (resp., Unidirectional) k-Edge Connectivity problem seeks a range assignment of minimum total power subject to the constraint the produced bidirectional
(resp., unidirectional) topology is k-edge connected.
The Min-Power Bidirectional Biconnectivity problem and the Min-Power Bidirectional Edge-Biconnectivity problem have been studied
by Lloyd et al. [23]. They show that range assignment based the approximation algorithm of Khuller and Raghavachari [18],
which we refer to as Algorithm KR, has an approximation ratio of at most 2(2 – 2/n)(2 + 1/n) for Min-Power Bidirectional Biconnectivity, and range assignment based on the approximation algorithm of Khuller and Vishkin [19],
which we refer to as Algorithm KV, has an approximation ratio of at most 8(1 – 1/n) for Min-Power Bidirectional Edge-Biconnectivity.
In this paper, we first establish the NP-hardness of Min-Power Bidirectional (Edge-) Biconnectivity. Then we show that Algorithm KR has an approximation ratio of at most 4 for both Min-Power Bidirectional Biconnectivity and Min-Power Unidirectional Biconnectivity,
and Algorithm KV has an approximation ratio of at most 2k for both Min-Power Bidirectional k-Edge Connectivity and Min-Power Unidirectional k-Edge Connectivity. We also propose a new simple constant-approximation algorithm for both Min-Power Bidirectional Biconnectivity
and Min-Power Unidirectional Biconnectivity. This new algorithm applies only to Euclidean instances, but is best suited for
distributed implementation.
A preliminary version of this work appeared in the proceedings of the 2nd International Conference on AD-HOC Network and Wireless
(Adhoc-Now 2003).
Research performed in part while visiting the Max-Plank-Institut fur Informatik.
Gruia Calinescu is an Assistant Professor of Computer Science at the Illinois Institute of Technology since 2000. He held postdoc or visiting
researcher positions at DIMACS, University of Waterloo, and Max-Plank Institut fur Informatik. Gruia has a Diploma from University
of Bucharest and a Ph.D. from Georgia Insitute of Technology. His research interests are in the area of algorithms.
Peng-Jun Wan has joined the Computer Science Department at Illinois Institute of Technology in 1997 and has been an Associate Professor
since 2004. He received his Ph.D. in Computer Science from University of Minnesota in 1997, M.S. in Operations Research and
Control Theory from Chinese Academy of Science in 1993, and B.S. in Applied Mathematics from Tsinghua University in 1990.
His research interests include optical networks and wireless networks. 相似文献