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   3898篇
  免费   150篇
  国内免费   16篇
电工技术   31篇
综合类   10篇
化学工业   1145篇
金属工艺   108篇
机械仪表   115篇
建筑科学   65篇
矿业工程   10篇
能源动力   239篇
轻工业   414篇
水利工程   20篇
石油天然气   6篇
无线电   268篇
一般工业技术   784篇
冶金工业   240篇
原子能技术   29篇
自动化技术   580篇
  2024年   11篇
  2023年   55篇
  2022年   162篇
  2021年   174篇
  2020年   138篇
  2019年   155篇
  2018年   170篇
  2017年   165篇
  2016年   136篇
  2015年   82篇
  2014年   176篇
  2013年   468篇
  2012年   185篇
  2011年   212篇
  2010年   179篇
  2009年   153篇
  2008年   148篇
  2007年   137篇
  2006年   106篇
  2005年   97篇
  2004年   56篇
  2003年   69篇
  2002年   63篇
  2001年   41篇
  2000年   45篇
  1999年   45篇
  1998年   60篇
  1997年   47篇
  1996年   45篇
  1995年   34篇
  1994年   34篇
  1993年   33篇
  1992年   30篇
  1991年   30篇
  1990年   32篇
  1989年   39篇
  1988年   26篇
  1987年   25篇
  1986年   18篇
  1985年   18篇
  1984年   14篇
  1983年   20篇
  1982年   15篇
  1981年   16篇
  1980年   9篇
  1979年   16篇
  1978年   12篇
  1976年   19篇
  1974年   9篇
  1973年   9篇
排序方式: 共有4064条查询结果,搜索用时 15 毫秒
1.
2.
Multimedia Tools and Applications - A secret sharing scheme partitions a secret into a set of shares and distributes them among the eligible participants, with each participant receiving one share...  相似文献   
3.
Wireless Personal Communications - In this paper, cooperative communication (CC) assisted cognitive wireless sensor network (CWSN) is presented for monitoring health and activity of an end-user in...  相似文献   
4.
5.
This paper presents the design criteria, procedure, and implementation of a soft-switched power-factor-correction (PFC) circuit based on the extended-period quasi-resonant (EPQR) principles. All power electronic devices including switches and diodes in the circuit are fully soft switched. The design method is demonstrated in a prototype circuit. The operating principles are confirmed with computer simulation and experimental results. A comparison of the EP-QR operation and zero-voltage-transition (ZVT) pulse-width modulation (PWM) method  相似文献   
6.
7.
8.
We report on the use of pulsed plasma-enhanced chemical vapor deposition (P-PECVD) technique and show that “state-of-the-art” amorphous silicon (a-Si:H) materials and solar cells can be produced at a deposition rate of up to 15 Å/s using a modulation frequency in the range 1–100 kHz. The approach has also been developed to deposit materials and devices onto large area, 30 cm×40 cm, substrates with thickness uniformity (<5%), and gas utilization rate (>25%). We have developed a new “hot wire” chemical vapor deposition (HWCVD) method and report that our new filament material, graphite, has so far shown no appreciable degradation even after deposition of 500 μm of amorphous silicon. We report that this technique can produce “state-of-the-art” a-Si:H and that a solar cell of p/i/n configuration exhibited an initial efficiency approaching 9%. The use of microcrystalline silicon (μc-Si) materials to produce low-cost stable solar cells is gaining considerable attention. We show that both of these techniques can produce thin film μc-Si, dependent on process conditions, with 1 1 1 and/or 2 2 0 orientations and with a grain size of approx. 500 A. Inclusion of these types of materials into a solar cell configuration will be discussed.  相似文献   
9.
High purity gallium oxide nanopowders have been synthesized by using a simple precipitation technique with calcination at elevated temperature. From the X-ray pattern, the phase purity of the synthesized powders was confirmed as β-Ga2O3. Elemental quantification (stoichiometry) of Ga2O3 was also examined from the X-ray energy dispersive analysis (EDAX). Based on the recorded Fourier Transform Infrared (FTIR) spectrum of Ga2O3, the IR bands due to Ga–O bond and crystal lattice vibrations have been identified in the wavenumber range 400–4,000 cm−1. From the measured SEM images, it is obvious to notice that the pH value has been playing a dominant role in obtaining morphologically different gallium oxide nanopowders. Thermogravimetric analysis reveals 8.3% of weight loss when the sample was heated to the temperature of 1,100 °C from the room temperature, which also shows a crystalline phase transformation. It is very interesting to report that a broad blue emission at 455 nm has been measured from the synthesized gallium oxide nanopowders.  相似文献   
10.
A standard metric conventionally employed to compare the performance of different multiprocessor systems is speedup. Although providing a measure of the improvement in execution speed achievable on a system, this metric does not yield any insight into the factors responsible for limiting the potential improvement in speed. This paper studies the performance degradation in shared-memory multiprocessors as a result of contention for shared-memory resources. A replicate workload framework with a flexible mechanism for workload specification is proposed for measuring performance. Two normalized performance metrics—efficiency and overhead factor—are introduced to quantify the factors limiting performance and facilitate comparison across architectures. Finally, the proposed model is employed to measure and compare the performance of three contemporary shared-memory systems, with special emphasis on the newly released BBN Butterfly-II (TC2000), currently undergoing Beta test.  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