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   40621篇
  免费   3083篇
  国内免费   1578篇
电工技术   2014篇
技术理论   2篇
综合类   2422篇
化学工业   6988篇
金属工艺   2346篇
机械仪表   2437篇
建筑科学   3143篇
矿业工程   997篇
能源动力   965篇
轻工业   2625篇
水利工程   586篇
石油天然气   2883篇
武器工业   217篇
无线电   4824篇
一般工业技术   4993篇
冶金工业   2167篇
原子能技术   470篇
自动化技术   5203篇
  2024年   155篇
  2023年   680篇
  2022年   1056篇
  2021年   1600篇
  2020年   1156篇
  2019年   953篇
  2018年   1044篇
  2017年   1254篇
  2016年   1133篇
  2015年   1492篇
  2014年   1906篇
  2013年   2387篇
  2012年   2356篇
  2011年   2654篇
  2010年   2387篇
  2009年   2224篇
  2008年   2190篇
  2007年   2175篇
  2006年   2191篇
  2005年   1863篇
  2004年   1295篇
  2003年   1133篇
  2002年   1076篇
  2001年   938篇
  2000年   960篇
  1999年   1142篇
  1998年   1001篇
  1997年   859篇
  1996年   850篇
  1995年   654篇
  1994年   561篇
  1993年   383篇
  1992年   343篇
  1991年   256篇
  1990年   199篇
  1989年   169篇
  1988年   137篇
  1987年   104篇
  1986年   77篇
  1985年   58篇
  1984年   57篇
  1983年   30篇
  1982年   37篇
  1981年   24篇
  1980年   19篇
  1979年   11篇
  1977年   7篇
  1976年   7篇
  1973年   5篇
  1970年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Bursts consist of a varying number of asynchronous transfer mode cells corresponding to a datagram. Here, we generalized weighted fair queueing to a burst-based algorithm with preemption. The new algorithm enhances the performance of the switch service for real-time applications, and it preserves the quality of service guarantees. We study this algorithm theoretically and via simulations.  相似文献   
102.
Co-evolution as a computational and cognitive model of design   总被引:6,自引:0,他引:6  
Co-evolutionary design has been developed as a computational model that assumes two parallel search spaces: the problem space and the solution space. The design process iteratively searches each space using the other space as the basis for a fitness function when evaluating the alternatives. Co-evolutionary design can also be developed as a cognitive model of design by characterizing the way in which designers iteratively search for a design solution, making revisions to the problem specification. This paper presents the computational model of co-evolutionary design and then describes a protocol study of human designers looking for evidence of co-evolution of problem specifications and design solutions. The study shows that co-evolutionary design is a good cognitive model of design and highlights the similarities and differences between the computational model and the cognitive model. The results show that the two kinds of co-evolutionary design complement each other, having strengths in different aspects of the design process. Electronic Publication  相似文献   
103.
104.
Self-aligned single-dot memory devices and arrays were fabricated based on arsenic-assisted etching and oxidation effects. The resulting device has a floating gate of about 5-10 nm, presenting single-electron memory operation at room temperature. In order to realize the final single-electron memory circuit, this paper investigates process repeatability, device uniformity in single-dot memory arrays, device scalability, and process transferability to an industrial application  相似文献   
105.
This article focuses on the detailed microstructural investigation of the oxide scale formed on a 304 steel in the presence of oxygen and water vapour (40%) at 600 °C. The work has been carried out using a combination of microanalytical techniques including FIB, TEM, EDX and electron diffraction. The local breakdown of the initially protective oxide scale and the growth of island/crater oxide morphology are described. Special consideration is given to the influence of the microstructure of the steel and the oxide scale on the breakdown behaviour.  相似文献   
106.
To investigate the effects of multiple weak interactions on the binding of phenolic compounds by polymeric adsorbents, macroporous polystyrene (PS) resin and PS‐based adsorbents with different hydrogen‐bond acceptor atoms (PS CH2( OCH2CH2)n OCH3, n = 0, 1, 2, and 3, denoted as PS‐EG0, PS‐EG1, PS‐EG2, and PS‐EG3) were prepared. The phenol adsorption strength order on these adsorbents was PS/PS‐EG0 < PS‐EG1 < PS‐EG2 < PS‐EG3, indicating that the adsorption on PS and PS‐EG0 was driven by hydrophobic and π–π interactions, and the adsorption on PS‐EG1, PS‐EG2, and PS‐EG3 was driven by a hydrogen bond in addition to hydrophobic and π–π interactions. PS‐EG2 may adsorb a second phenol molecule on each binding site and PS‐EG3 may adsorb second and third ones. The adsorption strength of resorcinol increased in the order of PS, PS‐EG1, and PS‐EG2, indicating that the adsorption was driven by 0, 1, and 2 hydrogen bonds in addition to hydrophobic and π–π interactions. Similarly, the adsorption of phloroglucinol on PS, PS‐EG1, PS‐EG2, and PS‐EG3 was driven by 0, 1, 2, and 3 hydrogen bonds in addition to hydrophobic and π–π interactions because the adsorption strength increased in this order. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4652–4658, 2006  相似文献   
107.
108.
A shortcut model is developed for predicting the HETP of a structured packed distillation column operating at elevated pressure. The proposed model incorporates the geometrical parameters of the packing, physical properties of the vapor and liquid phases, and the hydrodynamics of the two‐phase flow. The proposed model is tested and validated by comparing the predicted results with the present experimental data and some published HETP data. The results show that the proposed model can predict the experimental data with a deviation smaller than 20 %.  相似文献   
109.
简要地介绍了氢离子敏场效应晶体管(H~+-ISFET)的基本结构和工作原理,提出了一种新型背面接触式H~+-ISFET。对该结构在版图、工艺设计中的有关问题,进行了探讨。最后指出:它在pH值的测量中有较好的实用价值。  相似文献   
110.
雨洪资源利用的必要性及其措施探讨   总被引:2,自引:0,他引:2  
遵循水的规律,坚持防汛抗旱并举,实现防汛工作由单纯的洪水控制向洪水资源化转变和单一农业性抗旱向以保证包括城市供水为重点的全面抗旱转变是新时期治水新思路的重要观点之一.文章在回顾雨洪资源利用发展简史的基础上,就其必要性、可行性和利用方式进行了初步探讨.  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