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   5973篇
  免费   489篇
  国内免费   4篇
电工技术   63篇
综合类   3篇
化学工业   1543篇
金属工艺   156篇
机械仪表   160篇
建筑科学   247篇
矿业工程   21篇
能源动力   232篇
轻工业   893篇
水利工程   41篇
石油天然气   40篇
无线电   464篇
一般工业技术   1396篇
冶金工业   112篇
原子能技术   35篇
自动化技术   1060篇
  2024年   32篇
  2023年   69篇
  2022年   117篇
  2021年   235篇
  2020年   204篇
  2019年   170篇
  2018年   313篇
  2017年   348篇
  2016年   390篇
  2015年   238篇
  2014年   309篇
  2013年   674篇
  2012年   355篇
  2011年   413篇
  2010年   338篇
  2009年   325篇
  2008年   300篇
  2007年   286篇
  2006年   191篇
  2005年   152篇
  2004年   131篇
  2003年   115篇
  2002年   124篇
  2001年   49篇
  2000年   58篇
  1999年   39篇
  1998年   40篇
  1997年   34篇
  1996年   41篇
  1995年   32篇
  1994年   26篇
  1993年   25篇
  1992年   19篇
  1991年   19篇
  1990年   9篇
  1989年   15篇
  1988年   13篇
  1986年   8篇
  1985年   27篇
  1984年   11篇
  1983年   11篇
  1982年   17篇
  1981年   15篇
  1980年   11篇
  1979年   14篇
  1978年   14篇
  1977年   9篇
  1975年   8篇
  1974年   10篇
  1973年   10篇
排序方式: 共有6466条查询结果,搜索用时 15 毫秒
61.
In this paper, we consider large loss networks with fixed routing and multirate traffic. We use singlelink formulae and standard results on multidimensional Gaussian distributions to obtain upper bounds for blocking probabilities of new calls under light up to critical loading conditions. This is the loading regime of interest for many practical applications such as admission control in ATM networks. The main advantage of our approach is that the complexity does not scale with the size of the system, making it numerically attractive. Comparison with simulation results show that we get good upper bounds. We conclude by discussing the correlation between links in a network.  相似文献   
62.
We are presenting a fast new method of analysing a dielectric interface which is assumed to be cylindrically symmetrical. It is based on a multimode Gaussian beam development. Then two different cases are considered and we show the kind of results we can expect from this process. Finally, we explain in detail the relationships between the paraxial approximation and further justified simplifications which lead to an important calculation time decrease.  相似文献   
63.
Françis Toutain 《电信纪事》1998,53(9-10):389-405
Providing efficient and flexible quality of service guarantees within interogated services packet networks requires the deployment of advanced scheduling disciplines. This paper concentrates on the class of so-called fair queuing algorithms, firstly reviewing the general principle and its known approximations, then focusing on the service of adaptive applications, shedding light on the need to introduce a new scheduling paradigm, named dgps for decoupled generalized processor sharing; for the latter scheme an approximation technique is introduced and evaluated.  相似文献   
64.
65.
本文描述了运用平均电流模式控制技术来设计和实现全数字功率因数校正(PFC)电路的方法。所述设计中数字信号控制器(DSc)的输入信号与通过升压电感的电流、升压转换器输出电容两端的直流母线电压,以及经整流的交流输入电压成正比,由DSC提供脉宽调制信号来控制PFC开关的导通时间。此技术旨在简化PFC,因而可整合于数字电源转换和电机控制应用中。  相似文献   
66.
Numerical and theoretical investigations are presented for a double screen frequency selective surface (DSFSS) with perfectly conducting Koch fractal patch elements. The work was developed in two steps, in the first step two Koch fractal FSS screens were designed using the commercial software Ansoft DesignerTM. In the second these FSS were cascaded and separated by an air gap layer, forming the so-called DSFSS, to improve the bandwidth behavior. Thereafter, a numerical cascading technique is used to analyze the effect of the air gap on the DSFSS. The results were compared and a good agreement was observed.  相似文献   
67.
68.
69.
We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C60 as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm2/Vs. Devices with pentacene showed a mobility of 0.16 cm2/Vs. Devices using tyrian Purple as semiconductor show low-voltage ambipolar operation with equal electron and hole mobilities of ~0.3 cm2/Vs. These devices demonstrate low hysteresis and operational stability over at least several months. Grazing-angle infrared spectroscopy of evaporated thin films shows that the structure of the polyethylene is similar to solution-cast films. We report also on the morphological and dielectric properties of these films. Our experiments demonstrate that polyethylene is a stable dielectric supporting both hole and electron channels.  相似文献   
70.
Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications.  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