全文获取类型
收费全文 | 1250篇 |
免费 | 81篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 20篇 |
综合类 | 3篇 |
化学工业 | 355篇 |
金属工艺 | 14篇 |
机械仪表 | 21篇 |
建筑科学 | 36篇 |
能源动力 | 120篇 |
轻工业 | 88篇 |
水利工程 | 17篇 |
石油天然气 | 21篇 |
无线电 | 124篇 |
一般工业技术 | 218篇 |
冶金工业 | 120篇 |
原子能技术 | 3篇 |
自动化技术 | 177篇 |
出版年
2024年 | 3篇 |
2023年 | 28篇 |
2022年 | 57篇 |
2021年 | 69篇 |
2020年 | 43篇 |
2019年 | 52篇 |
2018年 | 67篇 |
2017年 | 57篇 |
2016年 | 69篇 |
2015年 | 43篇 |
2014年 | 86篇 |
2013年 | 95篇 |
2012年 | 64篇 |
2011年 | 81篇 |
2010年 | 40篇 |
2009年 | 46篇 |
2008年 | 41篇 |
2007年 | 27篇 |
2006年 | 29篇 |
2005年 | 38篇 |
2004年 | 25篇 |
2003年 | 14篇 |
2002年 | 17篇 |
2001年 | 19篇 |
2000年 | 8篇 |
1999年 | 12篇 |
1998年 | 21篇 |
1997年 | 10篇 |
1996年 | 22篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1980年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1971年 | 4篇 |
排序方式: 共有1337条查询结果,搜索用时 15 毫秒
11.
Yaser Pourmohammadi Fallah Samer El-Housseini Hussein Alnuweiri 《Wireless Personal Communications》2008,47(2):235-245
The main service differentiation mechanism introduced by the IEEE 802.11e standard is described in terms of prioritized contention
access. Analyzing the performance and service differentiation ability of each of the priority features of the 802.11e standard
is an important task, and considerable research effort has recently been dedicated to this subject. In this article, we present
a generalized and comprehensive analysis of the prioritized access scheme of the 802.11e standard. Our model corrects and
extends the existing models and considers all priority features of the 802.11e Medium Access Control (MAC) protocol. We consider
an arbitrary number of priority levels, and provide a detailed parametric analysis of the MAC behavior for the main priority
parameters of inter frame spacing, contention window size, and transmission opportunity. We validate the accuracy of our analysis
with simulation experiments.
相似文献
Hussein AlnuweiriEmail: |
12.
Jing Wu Delfin Y. Montuno Hussein T. Mouftah Guoqiang Wang Abel C. Dasylva 《International Journal of Communication Systems》2002,15(7):573-592
The health status of the control plane and the data plane of a GMPLS‐controlled optical network is independent in the physically separated control network implementation. In most control plane designs, besides the topology information, the entities of the routing protocol only record the number of available wavelengths on each link. However, the status of each wavelength is maintained by the entities of the signalling protocol. Without recovery ability of the signalling protocol CR‐LDP, a failure in the control plane will result in the permanent loss of the status information of wavelengths. A mechanism to recover the status information of the wavelengths is proposed. A downstream node maintains a label information database (LID) about assignable (free) labels in each incoming link. A copy of LID is redundantly stored in the upstream node as a label information mirror (LIM). A systematic procedure is proposed to synchronize the contents of a LIM and the corresponding LID. The initialization of a new LDP session with the enhanced recovery mechanism will guarantee the revival of the status information of wavelengths. It can recover multiple control channel failures, but it only applies to single node failure among any pair of adjacent nodes. © Crown copyright 2002. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. 相似文献
13.
14.
15.
Hussein Fakhoury Papy Ndungidi Carlos Valderrama 《Analog Integrated Circuits and Signal Processing》2011,67(3):273-284
A low-power, low-pass continuous-time sigma-delta A/D modulator with 1-MHz bandwidth is implemented in a 130-nm CMOS process. The circuit is targeted for an IEEE 802.15.4 direct conversion receiver operating in the 2.4-GHz band. It has a third-order feedforward single-loop filter and a 1-bit quantizer to minimize power consumption. Non-return-to-zero DAC pulse shaping is used to reduce sensitivity to clock jitter. Clocked at 64 MHz, the prototype chip achieves 62-dB peak SNR, −70-dB peak THD, 63-dB dynamic range with an oversampling ratio of 32. The built-in anti-alias filter provides alias attenuation greater than 57 dB, which improves coexistence of the receiver with other devices that operate in the 2.4-GHz band. The circuit dissipates 1.44 mW from the 1.2-V supply and the active die area is 0.1 mm2. 相似文献
16.
Hengfei Gu Fei Zhang Shinjae Hwang Anders B. Laursen Xin Liu So Yeon Park Mengjin Yang Rosemary C. Bramante Hussein Hijazi Leila Kasaei Leonard C. Feldman Yao-Wen Yeh Philip E. Batson Bryon W. Larson Mengjun Li Yifei Li Keenan Wyatt James L. Young Krishani Teeluck Kai Zhu Eric Garfunkel G. Charles Dismukes 《Advanced functional materials》2023,33(25):2301196
The rapidly increasing solar conversion efficiency (PCE) of hybrid organic–inorganic perovskite (HOIP) thin-film semiconductors has triggered interest in their use for direct solar-driven water splitting to produce hydrogen. However, application of these low-cost, electronic-structure-tunable HOIP tandem photoabsorbers has been hindered by the instability of the photovoltaic-catalyst-electrolyte (PV+E) interfaces. Here, photolytic water splitting is demonstrated using an integrated configuration consisting of an HOIP/n+silicon single junction photoabsorber and a platinum (Pt) thin film catalyst. An extended electrochemical (EC) lifetime in alkaline media is achieved using titanium nitride on both sides of the Si support to eliminate formation of insulating silicon oxide, and as an effective diffusion barrier to allow high-temperature annealing of the catalyst/TiO2-protected-n+silicon interface necessary to retard electrolytic corrosion. Halide composition is examined in the (FA1-xCsx)PbI3 system with a bandgap suitable for tandem operation. A fill factor of 72.5% is achieved using a Spiro-OMeTAD-hole-transport-layer (HTL)-based HOIP/n+Si solar cell, and a high photocurrent density of −15.9 mA cm−2 (at 0 V vs reversible hydrogen electrode) is attained for the HOIP/n+Si/Pt photocathode in 1 m NaOH under simulated 1-sun illumination. While this thin-film design creates stable interfaces, the intrinsic photo- and electro-degradation of the HOIP photoabsorber remains the main obstacle for future HOIP/Si tandem PEC devices. 相似文献
17.
Ethernet Passive Optical Network (EPON) has been widely considered as a promising technology for implementing the FTTx solutions to the “last mile” bandwidth bottleneck problem. Bandwidth allocation is one of the critical issues in the design of EPON systems. In an EPON system, multiple optical network units (ONUs) share a common upstream channel for data transmission. To efficiently utilize the limited bandwidth of the upstream channel, an EPON system must dynamically allocate the upstream bandwidth among multiple ONUs based on the instantaneous bandwidth demands and quality of service requirements of end users. This paper introduces the fundamental concepts on EPONs, discusses the major issues related to bandwidth allocation in EPON systems, and presents a survey of the state-of-the-art dynamic bandwidth allocation (DBA) algorithms for EPONs. 相似文献
18.
Chiral nematic mesoporous organosilica (CNMO) films are functionalized with a mixture of hydrophobic silanes and spiropyran compounds to create freestanding photochromic films that can be used for reversible photopatterning. The mesoporosity and interconnected pore structure of the films imparted by the cellulose nanocrystal template enables a large cross‐section of the material to be functionalized. Thus, the materials show intense absorption spectra from the tethered spiropyran and rapid color changes when the porous films are irradiated with UV or white light. The spiropyran‐bound CNMO films behave as reversible sensors where metal binding to the spiropyran results in visible color changes detectable by the naked eye. These metals can be removed in the presence of ethanol and white light, regenerating the metal‐free film. The proof‐of‐concept demonstrated in this paper may help to develop new photochromic displays, security features, and patterns. 相似文献
19.
Sivacarendran Balendhran Sumeet Walia Hussein Nili Jian Zhen Ou Serge Zhuiykov Richard B. Kaner Sharath Sriram Madhu Bhaskaran Kourosh Kalantar‐zadeh 《Advanced functional materials》2013,23(32):3952-3970
In the quest to discover the properties of planar semiconductors, two‐dimensional molybdenum trioxide and dichalcogenides have recently attracted a large amount of interest. This family, which includes molybdenum trioxide (MoO3), disulphide (MoS2), diselenide (MoSe2) and ditelluride (MoTe2), possesses many unique properties that make its compounds appealing for a wide range of applications. These properties can be thickness dependent and may be manipulated via a large number of physical and chemical processes. In this Feature Article, a comprehensive review is delivered of the fundamental properties, synthesis techniques and applications of layered and planar MoO3, MoS2, MoSe2, and MoTe2 along with their future prospects. 相似文献
20.
Awad R. Mansour A.M. Hussein 《International Communications in Heat and Mass Transfer》1990,17(6):823-830
An analytical solution for diffusion with homogenous n the order nonlinear chemical reaction in laminar flow of a Newtonian fluid through tubular reactor with unknown boundary conditions is presented. The results of the new solution have been compared with previously published numerical solutions and shown to be accurate. 相似文献