全文获取类型
收费全文 | 4117篇 |
免费 | 157篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 53篇 |
综合类 | 6篇 |
化学工业 | 944篇 |
金属工艺 | 108篇 |
机械仪表 | 113篇 |
建筑科学 | 96篇 |
矿业工程 | 1篇 |
能源动力 | 142篇 |
轻工业 | 167篇 |
水利工程 | 26篇 |
石油天然气 | 3篇 |
武器工业 | 2篇 |
无线电 | 929篇 |
一般工业技术 | 659篇 |
冶金工业 | 390篇 |
原子能技术 | 22篇 |
自动化技术 | 621篇 |
出版年
2023年 | 19篇 |
2022年 | 67篇 |
2021年 | 91篇 |
2020年 | 59篇 |
2019年 | 52篇 |
2018年 | 84篇 |
2017年 | 68篇 |
2016年 | 87篇 |
2015年 | 83篇 |
2014年 | 125篇 |
2013年 | 305篇 |
2012年 | 220篇 |
2011年 | 236篇 |
2010年 | 220篇 |
2009年 | 229篇 |
2008年 | 236篇 |
2007年 | 202篇 |
2006年 | 175篇 |
2005年 | 153篇 |
2004年 | 141篇 |
2003年 | 125篇 |
2002年 | 113篇 |
2001年 | 102篇 |
2000年 | 92篇 |
1999年 | 84篇 |
1998年 | 175篇 |
1997年 | 120篇 |
1996年 | 82篇 |
1995年 | 67篇 |
1994年 | 58篇 |
1993年 | 43篇 |
1992年 | 38篇 |
1991年 | 30篇 |
1990年 | 25篇 |
1989年 | 31篇 |
1988年 | 22篇 |
1987年 | 18篇 |
1986年 | 8篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 12篇 |
1977年 | 16篇 |
1976年 | 15篇 |
1975年 | 13篇 |
1973年 | 10篇 |
1967年 | 7篇 |
排序方式: 共有4282条查询结果,搜索用时 0 毫秒
81.
Sung Hun Wee Yanfei Gao Yuri L. Zuev Karren L. More Jianyong Meng Jianxin Zhong George M. Stocks Amit Goyal 《Advanced functional materials》2013,23(15):1912-1918
Spontaneous self‐assembly of a multication nanophase in another multication matrix phase is a promising bottom‐up approach to fabricate novel, nanocomposite structures for a range of applications. In an effort to understand the mechanisms for such self‐assembly, complimentary experimental and theoretical studies are reported to first understand and then control or guide the self‐assembly of insulating BaZrO3 (BZO) nanodots within REBa2Cu3O7–δ (RE = rare earth elements including Y, REBCO) superconducting films. The strain field developed around BZO nanodots embedded in the REBCO matrix is a key driving force dictating the self‐assembly of BZO nanodots along REBCO c‐axis. The size selection and spatial ordering of BZO self‐assembly are simulated using thermodynamic and kinetic models. The BZO self‐assembly is controllable by tuning the interphase strain field. REBCO superconducting films with BZO defect arrays self‐assembled to align in both vertical (REBCO c‐axis) and horizontal (REBCO ab‐planes) directions result in the maximized pinning and Jc performance for all field angles with smaller angular Jc anisotropy. The work has broad implications for the fabrication of controlled self‐assembled nanostructures for a range of applications via strain‐tuning. 相似文献
82.
Kuo-Hui Yeh 《Wireless Personal Communications》2014,79(3):1621-1634
With the rapid growth of electronic commerce and demand on variants of Internet based applications, the system providing resources and business services often consists of many servers around the world. So far, a variety of authentication schemes have been published to achieve remote user authentication on multi-server communication environment. Recently, Pippal et al. proposed a multi-server based authentication protocol to pursue the system security and computation efficiency. Nevertheless, based on our analysis, the proposed scheme is insecure against user impersonation attack, server counterfeit attack, and man-in-the-middle attack. In this study, we first demonstrate how these malicious attacks can be invoked by an adversary. Then, a security enhanced authentication protocol is developed to eliminate all identified weaknesses. Meanwhile, the proposed protocol can achieve the same order of computation complexity as Pippal et al.’s protocol does. 相似文献
83.
W.-R. Liou T.-H. Chen M.-L. Yeh J.-J. Ho G. E. Jan 《International Journal of Electronics》2013,100(6):623-632
A fully integrated dual-band LC voltage control oscillator, designed in a 0.18-µm CMOS technology for 5.8-GHz/2.0-GHz wireless communication applications, is described. The frequency band switching is accomplished with switched-inductor technique. The dual-band oscillator can be operated in 5.38–6.23?GHz and 1.78–2.07?GHz with 15% frequency tuning range. Two different inductors are used for the frequency band switching. Frequency tuning is implemented by varying the capacitance of a MOS varactor. The measured phase noise is ?109?dBc/Hz @ 1?MHz and ?112?dBc/Hz @ 1?MHz for frequency at 5.8?GHz and 2?GHz, respectively. This oscillator is fabricated in UMC's 0.18-µm one-poly-six-metal 1.8?V process. The power dissipation of this dual-band VCO is 11.7 and 9.3?mW for oscillation frequency of 2?GHz and 5.8?GHz, respectively. 相似文献
84.
Tae Chul Hong Sungmoon Yeo Sooyoung Kim Kun‐Seok Kang Bon‐Jun Ku 《International Journal of Satellite Communications and Networking》2012,30(5):221-234
The adaptive modulation and coding (AMC) scheme is mandatory for modern wireless communication systems to overcome inevitable channel impairments. Many of the limitations using AMC are due to the long round‐trip delay of a satellite system. This paper proposes an efficient AMC scheme with power control and symbol interleaving that can be effectively applied to satellite systems. In particular, we focus on mobile satellite systems that have maximum compatibility in a Long Term Evolution system. Simulations reveal that the proposed scheme can provide a maximum 10.2% increase of average beam spectral efficiency and a maximum of 8‐dB power gain compared with a conventional AMC scheme. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
85.
Funai AK Fessler JA Yeo DT Olafsson VT Noll DC 《IEEE transactions on medical imaging》2008,27(10):1484-1494
86.
Mohammad Mahdi Tavakoli Giovanni Azzellino Marek Hempel Ang‐Yu Lu Francisco J. Martin‐Martinez Jiayuan Zhao Jingjie Yeo Tomas Palacios Markus J. Buehler Jing Kong 《Advanced functional materials》2020,30(31)
A roll‐to‐roll (R2R) transfer technique is employed to improve the electrical properties of transferred graphene on flexible substrates using parylene as an interfacial layer. A layer of parylene is deposited on graphene/copper (Cu) foils grown by chemical vapor deposition and are laminated onto ethylene vinyl acetate (EVA)/poly(ethylene terephthalate). Then, the samples are delaminated from the Cu using an electrochemical transfer process, resulting in flexible and conductive substrates with sheet resistances of below 300 Ω sq?1, which is significantly better (fourfold) than the sample transferred by R2R without parylene (1200 Ω sq?1). The characterization results indicate that parylene C and D dope graphene due to the presence of chlorine atoms in their structure, resulting in higher carrier density and thus lower sheet resistance. Density functional theory calculations reveal that the binding energy between parylene and graphene is stronger than that of EVA and graphene, which may lead to less tear in graphene during the R2R transfer. Finally, organic solar cells are fabricated on the ultrathin and flexible parylene/graphene substrates and an ultra‐lightweight device is achieved with a power conversion efficiency of 5.86%. Additionally, the device shows a high power per weight of 6.46 W g?1 with superior air stability. 相似文献
87.
We present an analytic model for the performance evaluation of hierarchical cellular systems, which can provide multiple routes for calls through overflow from one cell layer to another. Our model allows the case where both the call time and the cell residence time are generally distributed. Based on the characterization of the call time by a hyper-Erlang distribution, the Laplace transform of channel occupancy time distribution for each call type (new call, handoff call, and overflow call) is derived as a function of the Laplace transform of cell residence time. In particular, overflow calls are modeled by using a renewal process. Performance measures are derived based on the product form solution of a loss system with capacity limitation. Numerical results show that the distribution type of call time and/or cell residence time has influence on the performance measure and that the exponential case may underestimate the system performance. 相似文献
88.
Highly Stretchable or Transparent Conductor Fabrication by a Hierarchical Multiscale Hybrid Nanocomposite 下载免费PDF全文
Sukjoon Hong Seungyong Han Young Duk Suh Sang Eon Lee Junyeob Yeo Seung Seob Lee Dongjin Lee Seung Hwan Ko 《Advanced functional materials》2014,24(36):5671-5678
As is frequently seen in sci‐fi movies, future electronics are expected to ultimately be in the form of wearable electronics. To realize wearable electronics, the electric components should be soft, flexible, and even stretchable to be human‐friendly. An important step is presented toward realization of wearable electronics by developing a hierarchical multiscale hybrid nanocomposite for highly flexible, stretchable, or transparent conductors. The hybrid nanocomposite combines the enhanced mechanical compliance, electrical conductivity, and optical transparency of small CNTs (d ≈ 1.2 nm) and the enhanced electrical conductivity of relatively bigger Ag nanowire (d ≈ 150 nm) backbone to provide efficient multiscale electron transport path with Ag nanowire current backbone collector and local CNT percolation network. The highly elastic hybrid nanocomposite conductors and highly transparent flexible conductors can be mounted on any non‐planar or soft surfaces to realize human‐friendly electronics interface for future wearable electronics. 相似文献
89.
Nitride-Based ultraviolet metal-semiconductor-metal photodetectors with a low-temperature GaN layer 总被引:1,自引:0,他引:1
J. K. Sheu C. J. Kao M. L. Lee W. C. Lai L. S. Yeh G. C. Chi S. J. Chang Y. K. Su J. M. Tsai 《Journal of Electronic Materials》2003,32(5):400-402
The GaN metal-semiconductor-metal (MSM) ultraviolet (UV) photodetectors with a low-temperature (LT)-GaN layer have been demonstrated.
It was found that we could achieve a two orders of magnitude smaller, photodetector-dark current by introducing a LT-GaN layer,
which could be attributed to the larger Schottky-barrier height between the Ni/Au metal contact and the LT-GaN layer. It was
also found that photodetectors with the LT-GaN layer could provide a larger photocurrent to dark-current contrast ratio and
a larger UV-to-visible rejection ratio. The maximum responsivity was found to be 3.3 A/W and 0.13 A/W when the photodetector
with a LT-GaN layer was biased at 5 V and 1 V, respectively. 相似文献
90.
Dual-band planar inverted F antenna for GSM/DCS mobile phones 总被引:2,自引:0,他引:2
Shih-Huang Yeh Kin-Lu Wong Tzung-Wern Chiou Shyh-Tirng Fang 《Antennas and Propagation, IEEE Transactions on》2003,51(5):1124-1126
A compact dual-band planar inverted F antenna suitable for the application as a global system for mobile communication/digital communication system (GSM/DCS) dual-band mobile phone internal antenna is proposed and implemented. The proposed antenna has three resonant elements, two meandered metallic strips of slightly different lengths and one nearly-rectangular patch, which are printed on a supporting FR4 substrate and arranged in a compact configuration. These three resonant elements share a common shorting pin, and for the GSM (890-960 MHz) operation, the proposed antenna is operated with the two meandered strips both resonated as a quarter-wavelength structure, leading to a wide bandwidth formed by two resonant modes. For the upper band of the proposed antenna, three resonant modes are generated, two from the second higher-order modes of the two meandered strips and one from the nearly-rectangular patch, leading to a wide bandwidth covering the DCS band (1710-1880 MHz). The antenna design and experimental results are presented. 相似文献