全文获取类型
收费全文 | 127873篇 |
免费 | 14626篇 |
国内免费 | 7423篇 |
学科分类
工业技术 | 149922篇 |
出版年
2024年 | 369篇 |
2023年 | 1689篇 |
2022年 | 2601篇 |
2021年 | 3299篇 |
2020年 | 3990篇 |
2019年 | 3509篇 |
2018年 | 3205篇 |
2017年 | 4547篇 |
2016年 | 4909篇 |
2015年 | 5202篇 |
2014年 | 8868篇 |
2013年 | 8723篇 |
2012年 | 9276篇 |
2011年 | 10382篇 |
2010年 | 7571篇 |
2009年 | 8070篇 |
2008年 | 8001篇 |
2007年 | 8993篇 |
2006年 | 7960篇 |
2005年 | 6550篇 |
2004年 | 5381篇 |
2003年 | 4520篇 |
2002年 | 3640篇 |
2001年 | 3088篇 |
2000年 | 2702篇 |
1999年 | 2104篇 |
1998年 | 1626篇 |
1997年 | 1363篇 |
1996年 | 1272篇 |
1995年 | 1040篇 |
1994年 | 917篇 |
1993年 | 736篇 |
1992年 | 605篇 |
1991年 | 487篇 |
1990年 | 393篇 |
1989年 | 311篇 |
1988年 | 257篇 |
1987年 | 215篇 |
1986年 | 172篇 |
1985年 | 207篇 |
1984年 | 225篇 |
1983年 | 197篇 |
1982年 | 183篇 |
1981年 | 114篇 |
1980年 | 80篇 |
1979年 | 97篇 |
1978年 | 73篇 |
1977年 | 72篇 |
1976年 | 21篇 |
1959年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
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
82.
针对云南富源县辖区内大量小型煤矿抽采的低浓度瓦斯未开展有效利用的问题,以区内某小型煤矿为背景,采用现场调研、分析归纳、理论计算相结合的方法对其低浓度瓦斯发电项目展开分析研究。研究表明,某小型煤矿低浓度瓦斯发电项目成功的关键是“瓦斯治理先行”理念主导下的气源保障综合技术体系。在气源得以保障的基础上,该小型煤矿低浓度瓦斯发电项目已经持续高效运行4年,每年创造经济收益约403.2万元,减排CO2约4.47万t;同时促进了煤矿瓦斯治理工作有效落实,提高了煤矿安全生产水平,保障了煤矿产量的达标。 相似文献
83.
多带OFDM-UWB系统峰均功率比降低方法研究 总被引:1,自引:0,他引:1
针对多带OFDM—UWB信号存在高峰均功率比的问题,提出了利用扩展与交织降低系统信号峰均功率比的方法。该方法通过对传输数据进行正交扩展与交织,使得进入多载波调制的数据趋于高斯分布,减小了传输数据自相关函数的旁瓣峰值,降低了OFDM-UWB信号的峰均功率比。由于采用正交矩阵进行扩展,扩展前后的数据传输速率保持不变。仿真结果表明,扩展与交织可以有效地降低信号峰均功率比2-5dB左右。同时该方法还具有抗窄带干扰的鲁棒性。 相似文献
84.
Istvan S. N. Berkeley 《Minds and Machines》2006,16(4):471-478
Berkeley [Minds Machines 10 (2000) 1] described a methodology that showed the subsymbolic nature of an artificial neural network
system that had been trained on a logic problem, originally described by Bechtel and Abrahamsen [Connectionism and the mind.
Blackwells, Cambridge, MA, 1991]. It was also claimed in the conclusion of this paper that the evidence was suggestive that
the network might, in fact, count as a symbolic system. Dawson and Piercey [Minds Machines 11 (2001) 197] took issue with
this latter claim. They described some lesioning studies that they argued showed that Berkeley’s (2000) conclusions were premature.
In this paper, these lesioning studies are replicated and it is shown that the effects that Dawson and Piercey rely upon for
their argument are merely an artifact of a threshold function they chose to employ. When a threshold function much closer
to that deployed in the original studies is used, the significant effects disappear. 相似文献
85.
简述了电动助力转向系统的研究现状及其基本结构、工作原理和主要特点。分析了该系统的主要元件,论述了亥系统的发展趋势。 相似文献
86.
A system is frequently represented by transfer functions in an input–output characterization. However, such a system (under mild assumptions) can also be represented by transfer functions in a port characterization, frequently referred to as a chain-scattering representation. Due to its cascade properties, the chain-scattering representation is used throughout many fields of engineering. This paper studies the relationship between poles and zeros of input–output and chain-scattering representations of the same system. 相似文献
87.
88.
计量用脉冲Nd:YAG倍频激光器及其电源 总被引:2,自引:0,他引:2
介绍了脉冲Nd:YAG倍频激光器双波长(1064/532nm)3种输出的激光光路。1064nm输出的动静比可达0.40;KTP晶体外腔倍频效率可达0.50。介绍了稳定可靠的调Q电路、逻辑控制电路和开关电源的主电路及其参数计算。 相似文献
89.
90.
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