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   455509篇
  免费   6192篇
  国内免费   1948篇
电工技术   8446篇
综合类   429篇
化学工业   66908篇
金属工艺   17174篇
机械仪表   12875篇
建筑科学   12054篇
矿业工程   959篇
能源动力   12439篇
轻工业   48043篇
水利工程   3553篇
石油天然气   3050篇
武器工业   8篇
无线电   58038篇
一般工业技术   82500篇
冶金工业   91146篇
原子能技术   6520篇
自动化技术   39507篇
  2021年   3101篇
  2020年   2263篇
  2019年   2867篇
  2018年   4475篇
  2017年   4417篇
  2016年   4930篇
  2015年   3723篇
  2014年   6202篇
  2013年   21014篇
  2012年   11051篇
  2011年   15777篇
  2010年   12472篇
  2009年   14020篇
  2008年   14896篇
  2007年   14913篇
  2006年   13845篇
  2005年   12610篇
  2004年   12166篇
  2003年   12134篇
  2002年   11612篇
  2001年   12140篇
  2000年   10924篇
  1999年   12116篇
  1998年   30705篇
  1997年   21336篇
  1996年   16265篇
  1995年   12185篇
  1994年   10732篇
  1993年   10485篇
  1992年   7418篇
  1991年   7142篇
  1990年   6590篇
  1989年   6340篇
  1988年   6229篇
  1987年   5117篇
  1986年   4998篇
  1985年   6109篇
  1984年   5480篇
  1983年   4951篇
  1982年   4599篇
  1981年   4668篇
  1980年   4343篇
  1979年   4017篇
  1978年   3834篇
  1977年   4693篇
  1976年   6525篇
  1975年   3249篇
  1974年   3061篇
  1973年   3110篇
  1972年   2441篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
The purpose of this paper is to introduce a new I DDQ measurement technique based on active successive approximations, called ASA-I DDQ. This technique has unique features facilitating a speed-up in I DDQ measurement. Experimental results suggest that a significant speed-up factor (up to 4) can be obtained over the QuiC-Mon technique. Such a speed-up is a key element in the replacement of single-threshold I DDQ testing since it amplifies the effectiveness of post-processing techniques.  相似文献   
42.
43.
The current Internet and wireless networks are harsh environments for transporting high-bandwidth multimedia data. We examine the technical issues involved, and describe an end-to-end solution to support a Web-based learn-on-demand system that operates in a wireless campus environment.  相似文献   
44.
This paper describes a novel planar antenna sensor created for the purpose of noninvasive temperature measurements using microwave radiometry. In order to improve radiometric measurements in industrial applications, a new generation of sensors is introduced, composed of a metallic sheet. Simulations based upon the method of moments is used both to design and to determine their electromagnetic performances. This paper also describes a radiometric device using these sensors to measure and control the temperature of food products during deep freezing processes. The results and discussions are presented.  相似文献   
45.
46.
47.
48.
Accurate and reliable decision making in oncological prognosis can help in the planning of suitable surgery and therapy, and generally, improve patient management through the different stages of the disease. In recent years, several prognostic markers have been used as indicators of disease progression in oncology. However, the rapid increase in the discovery of novel prognostic markers resulting from the development in medical technology, has dictated the need for developing reliable methods for extracting clinically significant markers where complex and nonlinear interactions between these markers naturally exist. The aim of this paper is to investigate the fuzzy k-nearest neighbor (FK-NN) classifier as a fuzzy logic method that provides a certainty degree for prognostic decision and assessment of the markers, and to compare it with: 1) logistic regression as a statistical method and 2) multilayer feedforward backpropagation neural networks an artificial neural-network tool, the latter two techniques having been widely used for oncological prognosis. In order to achieve this aim, breast and prostate cancer data sets are considered as benchmarks for this analysis. The overall results obtained indicate that the FK-NN-based method yields the highest predictive accuracy, and that it has produced a more reliable prognostic marker model than both the statistical and artificial neural-network-based methods.  相似文献   
49.
The recent advancement in high- performance semiconductor packages has been driven by the need for higher pin count and superior heat dissipation. A one-piece cavity lid flip chip ball grid array (BGA) package with high pin count and targeted reliability has emerged as a popular choice. The flip chip technology can accommodate an I/O count of more than five hundreds500, and the die junction temperature can be reduced to a minimum level by a metal heat spreader attachment. None the less, greater expectations on these high-performance packages arose such as better substrate real estate utilization for multiple chips, ease in handling for thinner core substrates, and improved board- level solder joint reliability. A new design of the flip chip BGA package has been looked into for meeting such requirements. By encapsulating the flip chip with molding compound leaving the die top exposed, a planar top surface can be formed. A, and a flat lid can then be mounted on the planar mold/die top surface. In this manner the direct interaction of the metal lid with the substrate can be removed. The new package is thus less rigid under thermal loading and solder joint reliability enhancement is expected. This paper discusses the process development of the new package and its advantages for improved solder joint fatigue life, and being a multichip package and thin core substrate options. Finite-element simulations have been employed for the study of its structural integrity, thermal, and electrical performances. Detailed package and board-level reliability test results will also be reported  相似文献   
50.
In this brief, the well-known switched-current (SI) filtering technique is revisited using the concept of the square-root domain (SRD) filtering. It is proved that SI filters are a subclass of the SRD filters, where sampled-data signal processing is performed. This is achieved by considering typical lossless and lossy SRD sampled-data integrator configurations, using a set of complementary SRD operators which are based on the quadratic I-V relationship of MOS transistor operated in the saturation. Circuit examples are given, where linear-domain integrator and third-order filter configurations were derived using appropriate SRD sampled-data building blocks  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