首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   80351篇
  免费   6862篇
  国内免费   2962篇
电工技术   4086篇
技术理论   6篇
综合类   4059篇
化学工业   13848篇
金属工艺   4206篇
机械仪表   4794篇
建筑科学   4743篇
矿业工程   2064篇
能源动力   2506篇
轻工业   5156篇
水利工程   1107篇
石油天然气   3477篇
武器工业   481篇
无线电   11197篇
一般工业技术   11260篇
冶金工业   5384篇
原子能技术   894篇
自动化技术   10907篇
  2024年   595篇
  2023年   1402篇
  2022年   2404篇
  2021年   3361篇
  2020年   2556篇
  2019年   2257篇
  2018年   2472篇
  2017年   2545篇
  2016年   2393篇
  2015年   3009篇
  2014年   3708篇
  2013年   4946篇
  2012年   4797篇
  2011年   5496篇
  2010年   4363篇
  2009年   4375篇
  2008年   4445篇
  2007年   3983篇
  2006年   3886篇
  2005年   3108篇
  2004年   2467篇
  2003年   2433篇
  2002年   2543篇
  2001年   2183篇
  2000年   1786篇
  1999年   1742篇
  1998年   1891篇
  1997年   1448篇
  1996年   1243篇
  1995年   1036篇
  1994年   827篇
  1993年   634篇
  1992年   489篇
  1991年   446篇
  1990年   404篇
  1989年   372篇
  1988年   281篇
  1987年   248篇
  1986年   196篇
  1985年   185篇
  1984年   145篇
  1983年   111篇
  1982年   103篇
  1981年   90篇
  1980年   111篇
  1979年   65篇
  1978年   75篇
  1977年   74篇
  1976年   99篇
  1975年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
对光交叉连接 (OXC)节点中采用半导体光放大器 (SOA)功率均衡技术的方案性能进行了理论分析。首先模拟计算了链路中引入SOA后的功率代价 ;然后逐一讨论了发射机消光比 ,信号码率 ,SOA的噪声系数对系统性能的影响 ;最后计算了OXC节点级联链路的误码率性能。从而为OXC节点和网络设计提供了理论分析和指导依据。  相似文献   
992.
We present a C-band monolithic microwave integrated circuit (MMIC) transmitter module development for multichannel RF/optical subcarrier multiplexed (OSCM) communication applications. The C-band MMIC transmitter module consists of one fully monolithic four-channel OSCM transmitter IC and four coupled-line filters. This MMIC is designed and implemented in a commercial GaAs MESFET process and coupled line bandpass filters are fabricated on the module board. We present the design and performance of the first fully monolithic IC transmitter module for OSCM packet switched applications  相似文献   
993.
There are many challenges for a direct application of graphene as the electrodes in organic electronics due to its hydrophobic surfaces, low work function (WF) and poor conductance. The authors demonstrate a modified single-layer graphene (SLG) as the anode in organic light-emitting diodes (OLEDs). The SLG, doped with the solution-processed titanium suboxide (TiOx) and poly(3,4-ethylenedio-xythiophene)/poly(styrene sulfonic acid) (PEDOT:PSS), exhibits excellent optoelectronic characteristics with reduced sheet resistance (Rsq), increased work function, as well as over 92% transmittance in the visible region. It is notable that the Rsq of graphene decreased by ∼86% from 628 Ω/sq to 86 Ω/sq and the WF of graphene increased about 0.82 eV from 4.30 eV to 5.12 eV after a modification by using the TiOx–PEDOT:PSS double interlayers. In addition, the existence of additional TiOx and PEDOT:PSS layers offers a good coverage to the PMMA residuals on SLG, which are often introduced during graphene transfer processes. As a result, the electrical shorting due to the PMMA residues in the device can be effectively suppressed. By using the modified SLG as a bottom anode in OLEDs, the device exhibited comparable current efficiency and power efficiency to those of the ITO based reference OLEDs. The approach demonstrated in this work could potentially provide a viable way to fabricate highly efficient and flexible OLEDs based on graphene anode.  相似文献   
994.
In this paper, we describe the change in barrier heights (ϕB) and ideality factors (n) of Ni/Au contacts to p-GaN determined from current-voltage measurements as a result of (a) rapid thermal annealing between 400–700°C under flowing nitrogen, and (b) testing at temperatures of 20–300°C. The lowest barrier height and ideality factor values were obtained from samples annealed at 500–600°C. These results provide supporting evidence that thermal processing helps to remove contaminants at the contact-GaN interface, thus decreasing effective barrier height and consequently, contact resistance.  相似文献   
995.
本文主要介绍一种便于在微机上运行的耦合腔行波管综合计算程序 ,尽可能详细地给出了有关的计算公式 ,并对所采用的图形坐标显示系统和简易数据库系统进行了简要介绍。  相似文献   
996.
This paper presents a control strategy that incorporates an auto-tuning neuron into the sliding mode control (SMC) in order to eliminate the high control activity and chattering due to the SMC. The main difference between the auto-tuning neuron and the general one is that a modified hyperbolic tangent function with adjustable parameters is employed. In this proposed control structure, an auto-tuning neuron is then used as the neural controller without any connection weights.. The control law will be switched from the sliding control to the neural control, when the state trajectory of system enters in some boundary layer. In this way, the chattering phenomenon will not occur. The results of numerical simulations are provided to show the control performance of our proposed method.  相似文献   
997.
Electroluminescence (EL) of organic and polymeric fluorescent materials programmable in the luminance is extremely useful as a non‐volatile EL memory with the great potential in the variety of emerging information storage applications for imaging and motion sensors. In this work, a novel non‐volatile EL memory in which arbitrarily chosen EL states are programmed and erased repetitively with long EL retention is demonstrated. The memory is based on utilizing the built‐in electric field arising from the remnant polarization of a ferroelectric polymer which in turn controls the carrier injection of an EL device. A device with vertically stacked components of a transparent bottom electrode/a ferroelectric polymer/a hole injection layer/a light emitting layer/a top electrode successfully emits light upon alternating current (AC) operation. Interestingly, the device exhibits two distinctive non‐volatile EL intensities at constant reading AC voltage, depending upon the programmed direct current (DC) voltage on the ferroelectric layer. DC programmed and AC read EL memories are also realized with different EL colors of red, green and blue. Furthermore, more than four distinguishable EL states are precisely addressed upon the programmed voltage input each of which shows excellent EL retention and multiple cycle endurance of more than 105 s and 102 cycles, respectively.  相似文献   
998.
999.
We have investigated a Cu-doped MoOx/GdOx bilayer film for nonvolatile memory applications. By adopting an ultrathin GdOx layer, we obtained excellent device characteristics such as resistance ratio of three orders of magnitude, uniform distribution of set and reset voltages, switching endurance up to 104 cycles, and ten years of data retention at 85degC. By adopting bilayer films of Cu-doped MoOx/GdOx, a local filament was formed by a two-step process. Improved memory characteristics can be explained by the formation of nanoscale local filament in the ultrathin GdOx layer.  相似文献   
1000.
为了提高工业仪表的开发效率,降低人机界面的设计难度,设计了一种具有通用接口的彩色液晶驱动终端。利用高性能ARM9微控制器与嵌入式Linux操作系统相结合的方法通过S1D13506液晶控制器实现驱动TFT LCD。使用该终端仅通过串口指令即可设计出丰富的图形界面。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号