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   7063篇
  免费   201篇
  国内免费   28篇
电工技术   107篇
综合类   2篇
化学工业   1436篇
金属工艺   291篇
机械仪表   188篇
建筑科学   109篇
矿业工程   8篇
能源动力   339篇
轻工业   269篇
水利工程   58篇
石油天然气   14篇
无线电   999篇
一般工业技术   1533篇
冶金工业   861篇
原子能技术   72篇
自动化技术   1006篇
  2023年   71篇
  2022年   151篇
  2021年   184篇
  2020年   162篇
  2019年   153篇
  2018年   244篇
  2017年   203篇
  2016年   199篇
  2015年   108篇
  2014年   206篇
  2013年   414篇
  2012年   239篇
  2011年   317篇
  2010年   241篇
  2009年   281篇
  2008年   256篇
  2007年   207篇
  2006年   216篇
  2005年   155篇
  2004年   128篇
  2003年   129篇
  2002年   129篇
  2001年   126篇
  2000年   129篇
  1999年   112篇
  1998年   264篇
  1997年   183篇
  1996年   131篇
  1995年   130篇
  1994年   105篇
  1993年   133篇
  1992年   108篇
  1991年   97篇
  1990年   84篇
  1989年   75篇
  1988年   72篇
  1987年   75篇
  1986年   88篇
  1985年   106篇
  1984年   99篇
  1983年   95篇
  1982年   78篇
  1981年   63篇
  1980年   50篇
  1979年   46篇
  1978年   49篇
  1977年   62篇
  1976年   82篇
  1975年   43篇
  1973年   42篇
排序方式: 共有7292条查询结果,搜索用时 15 毫秒
31.
32.
In this paper TCAD-based simulation of a novel insulated shallow extension (ISE) cylindrical gate all around (CGAA) Schottky barrier (SB) MOSFET has been reported,to eliminate the suicidal ambipolar behavior (bias-dependent OFF state leakage current) of conventional SB-CGAA MOSFET by blocking the metal-induced gap states as well as unwanted charge sharing between source/channel and drain/channel regions.This novel structure offers low barrier height at the source and offers high ON-state current.The ION/IoFF of ISE-CGAA-SB-MOS-FET increases by 1177 times and offers steeper subthreshold slope (~60 mV/decade).However a little reduction in peak cut off frequency is observed and to further improve the cut-off frequency dual metal gate architecture has been employed and a comparative assessment of single metal gate,dual metal gate,single metal gate with ISE,and dual metal gate with ISE has been presented.The improved performance of Schottky barrier CGAA MOSFET by the incorporation of ISE makes it an attractive candidate for CMOS digital circuit design.The numerical simulation is performed using the ATLAS-3D device simulator.  相似文献   
33.
Wireless Personal Communications - The efficient management of resource sharing plays a crucial role in the cloud execution environment. The constraints such as heterogeneity and dynamic nature of...  相似文献   
34.
An analytical model of Al0.15Ga0.85N/GaN modulation doped field effect transistor (MODFET), which uses an accurate velocity field relationship and incorporates the dominant effect of piezoelectric polarization induced charge at the AlGaN/GaN interface is presented. The effect of traps has also been taken into account. The calculated DC characteristics are in excellent agreement with the measured data. The model is extended to predict the microwave performance of the device. High current levels (>500 mA/mm), large transconductance (160.83 mS/mm) and a high cutoff frequency (9.6 GHz) have been achieved analytically and are in close agreement with the experimental data.  相似文献   
35.
A grounded lamination gate (GLG) structure for high-/spl kappa/ gate-dielectric MOSFETs is proposed, with grounded metal plates in the spacer oxide region. Two-dimensional device simulations performed on the new structure demonstrate a significant improvement with respect to the threshold voltage roll-off with increasing gate-dielectric constant (due to parasitic internal fringe capacitance), keeping the equivalent oxide thickness same. A simple fabrication procedure for the GLG MOSFET is also presented.  相似文献   
36.
This paper analyzes the effect of temperature variation on various device architectures i.e. Insulated Shallow Extension Silicon On Nothing (ISESON), ISE and SON MOSFET using ATLAS 3D device simulator for 45 nm gate length. The simulation results obtained with the ATLAS has been validated by comparing it with reported experimental data of SON MOSFET. The simulation results demonstrate that out of three device designs, the ISESON MOSFET is the most suitable device for high speed, low voltage and high temperature applications. The integration of ISE and SON onto the conventional bulk MOSFET leads to the enhancement in analog device performance in terms of device efficiency (gm/Ids), device gain (gm/gd), output resistance (Rout) and early voltage (Vea).  相似文献   
37.
Wireless Personal Communications - The orthogonal frequency division multiplexing (OFDM) is the most encouraging multi-carrier modulation system chosen for the high data rates but the objective is...  相似文献   
38.
Silicon wafers and dies are made of single crystalline material in semiconductor applications which must withstand high stresses within electronic packages. The apparent mechanical strength of single-crystalline Si depends on process induced defects. Mechanical bending tests are the simplest way to obtain the strength of Si dies and wafers and have been used for many years throughout the industry. Some of the bending tests, such as the 3-point-bend (3PB) test, provide a convoluted contribution from both the defects on die surface (caused by backgrinding and mishandling) and defects on die edges (caused by sawing or dicing). However, the ball-on-ring (BOR) test provides a way to single out the contribution of backside grinding defects to the die strength. This paper compares the results of both 3PB and BOR tests on a number of backgrinding and dicing processes. The die strength of the 3PB test is consistently less than that of the BOR test due to the fact that the edge defects are under tension for 3PB tests but not for BOR. It is demonstrated that the BOR test is a good method for backgrinding process optimization. Due to the intrinsic scattering nature of the strength data, a Weibull-based probabilistic mechanics approach is the method of choice to present the data.  相似文献   
39.

Speed control of a DC motor has always been a challenge because of its variable torque. But it becomes more challenging when noise enters the system at its input. Therefore, there is a need of more advanced controllers. In this paper, a multi-resolution proportional integral derivative (MRPID) controller has been proposed to be utilized to control the speed of a DC motor. It works well even in the presence of noise as compared to the conventional PID controller. Also, performance of a PID controller deteriorates when nonlinearity or uncertainty arises in the system. This degraded performance can be improved by utilizing the multi-resolution property of wavelets, which decomposes the error signal into various frequency components. Further, wavelet coefficients of these decompositions are used to generate the control signal for controlling speed of a DC motor. In this paper, performances of a MRPID, a fractional order PID (FOPID) and a conventional PID controllers are compared in the presence of noise for speed control of a DC motor. The results obtained using a MRPID controller are observed to be better in terms of improved transient characteristics and disturbance rejection for a DC motor as compared to those obtained with PID and FOPID controllers.

  相似文献   
40.
InxGa1−xAs (x=0.25–0.35) grown at low temperature on GaAs by molecular beam epitaxy is characterized by Hall effect, transmission electron microscopy, and ultrafast optical testing. As with low temperature (LT) GaAs, the resistivity is generally higher after a brief anneal at 600°C. High-resolution transmission electron microscopy shows all the as-grown epilayers to be heavily dislocated due to the large lattice mismatch (2–3%). When the layers are annealed, in addition to the dislocations, precipitates are also generally observed. As with LT-GaAs, the lifetime shortens as growth temperature is reduced through the range 300–120°C; also, the lifetime in LT-InxGa1−xAs is generally shorter in as-grown samples relative to annealed samples. Metal-semiconductor-metal photodetectors fabricated on the material exhibit response times of 1–2 picoseconds, comparable to results reported on GaAs grown at low temperature, and the fastest ever reported in the wavelength range of 1.0–1.3 μm.  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