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   83614篇
  免费   5467篇
  国内免费   1660篇
电工技术   2639篇
技术理论   2篇
综合类   2098篇
化学工业   15197篇
金属工艺   3690篇
机械仪表   4798篇
建筑科学   3197篇
矿业工程   753篇
能源动力   3098篇
轻工业   6281篇
水利工程   857篇
石油天然气   1629篇
武器工业   195篇
无线电   13174篇
一般工业技术   14423篇
冶金工业   6929篇
原子能技术   968篇
自动化技术   10813篇
  2024年   350篇
  2023年   1106篇
  2022年   1728篇
  2021年   2547篇
  2020年   1864篇
  2019年   1810篇
  2018年   2231篇
  2017年   2233篇
  2016年   2601篇
  2015年   2400篇
  2014年   3391篇
  2013年   5048篇
  2012年   4849篇
  2011年   5749篇
  2010年   4563篇
  2009年   4675篇
  2008年   4386篇
  2007年   3926篇
  2006年   3632篇
  2005年   3155篇
  2004年   2758篇
  2003年   2673篇
  2002年   2798篇
  2001年   2324篇
  2000年   1900篇
  1999年   1807篇
  1998年   2595篇
  1997年   1821篇
  1996年   1563篇
  1995年   1263篇
  1994年   921篇
  1993年   843篇
  1992年   635篇
  1991年   591篇
  1990年   488篇
  1989年   461篇
  1988年   373篇
  1987年   316篇
  1986年   288篇
  1985年   247篇
  1984年   212篇
  1983年   160篇
  1982年   165篇
  1981年   138篇
  1980年   140篇
  1979年   111篇
  1978年   96篇
  1977年   124篇
  1976年   161篇
  1975年   83篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
To ensure the core status can meet the requirements of thermal limits, stability and other constraints during the power ascension process of a nuclear power plant, operators usually gradually increase power based on onsite measurements and experience. To reduce the operator’s burden, this research develops a method to find an optimal power ascension path that can be followed by operators. The power ascension path is formulated as a multiobjective optimization problem with the following constraints: power ascension time, thermal limits, core stability and maximum rod line. A genetic algorithm is adopted to obtain the optimal power ascension path. The results show that using our approach full power can be achieved quickly, while maintaining reasonable margins of thermal limit and stability, in addition to satisfying maximum rod line criteria.  相似文献   
103.
The purpose of this study was to analyze the symbolization of colors as cultural codes, based on costume colors. In order to study the significance of colors in cultural changes, we carried out a quantitative analysis and interpreted it from the perspective of cultural semiotics. The range of this study was focused on Korean costume colors, over diverse diachronic stages of Korean culture. For this study 1535 color samples were collected, measured with a spectrophotometer, and analyzed quantitatively according their diachronic stages of origin. As a result, red, blue, and yellow were found to be the most frequently used colors during the Chosun Dynasty, a period based on Confucianism. These colors acted as cultural codes with cultural significance. During the Modern times pink, light blue, and black increased in frequency and represented the reception of western culture, the changing sex role of women in society, and utilitarianism. In these days, neutral colors and grayish tones of all colors are the most significant colors of high frequency. The use of such colors is closely related to industrialization, mechanization, functionalism, and the changes of women's sex roles in the societies. They are used as cultural codes, especially to emphasize a rational and masculine image rather than a feminine image. © 2006 Wiley Periodicals, Inc. Col Res Appl, 32, 71–79, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20290  相似文献   
104.
The final closed-form expression for bit error probability (BEP) is presented for a DS-CDMA system using a maximal ratio combining (MRC) diversity over a Rician fading channel. The accuracy of the BEP estimate evaluated by this expression is verified by comparison with a semi-analytic simulation result. The effect that diversity order has on the BEP is also considered for typical multipath delay profiles with different Rician ratios  相似文献   
105.
The electrical properties of thin-film ferroelectric capacitors are known to degrade severely when exposed to hydrogen. In this study, we directly measured the effects of the grain boundary on the hydrogen-induced degradation in ferroelectric Pb(Zr, Ti)O3 (PZT) thin films by the location of the top Pt electrode either inside the grains or at the grain boundary. A strong relationship between the grain boundary and the electrical properties of ferroelectric capacitors as a result of hydrogen annealing was found. The degradation of the electrical properties in thin-film ferroelectric capacitors after hydrogen annealing is mainly due to the presence of the grain boundary in the ferroelectric thin film  相似文献   
106.
Language-level support for object persistence frees programmers from having to confront a broad class of database issues from within their applications. By virtue of its metaobject protocol, CLOS is a language whose semantics can be tailored by individual programmers. We used the metaobject protocol to extend CLOS with support for object persistence. Our goal was to obtain a version of CLOS with persistence to which we could easily port a commercial geometric CAD modeling system. We describe the design and implementation of our persistence extension and highlight the strengths and weaknesses exhibited by the CLOS metaobject protocol during our experiment. For many aspects of the implementation we found that the metaobject protocol was ideal. In other cases we had to choose among paying a large performance penalty, extending the protocol, and bypassing the protocol by modifying the language implementation directly.  相似文献   
107.
108.
109.
Density-Induced Support Vector Data Description   总被引:6,自引:0,他引:6  
  相似文献   
110.
In this letter, we examined whether the parasitic bipolar junction transistors (BJTs) in the MOSFET fabricated by the standard CMOS process can play a role as a fluorescence detector. To suppress the action of two vertical parasitic BJTs, the gate and n-well were tied in the parasitic BJTs, and the body node was connected to the drain. The proposed device was compared with the inherent and the parasitic diodes in the MOSFET. It had 100 times higher photocurrents than the diodes in the MOSFET. In addition, it was applied for the detection of the fluorescent signal, and could detect near 10 nM of Alexa 546. Therefore, CMOS-process-compatible parasitic BJTs can be used as a photodetector in an integrated fluorescence detector.  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