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   18948篇
  免费   705篇
  国内免费   44篇
电工技术   237篇
综合类   24篇
化学工业   3739篇
金属工艺   467篇
机械仪表   397篇
建筑科学   948篇
矿业工程   108篇
能源动力   600篇
轻工业   1634篇
水利工程   172篇
石油天然气   68篇
无线电   1457篇
一般工业技术   3364篇
冶金工业   3425篇
原子能技术   116篇
自动化技术   2941篇
  2023年   123篇
  2022年   210篇
  2021年   329篇
  2020年   234篇
  2019年   270篇
  2018年   368篇
  2017年   378篇
  2016年   413篇
  2015年   338篇
  2014年   513篇
  2013年   1218篇
  2012年   825篇
  2011年   1166篇
  2010年   799篇
  2009年   829篇
  2008年   930篇
  2007年   871篇
  2006年   759篇
  2005年   743篇
  2004年   594篇
  2003年   541篇
  2002年   526篇
  2001年   332篇
  2000年   303篇
  1999年   328篇
  1998年   355篇
  1997年   298篇
  1996年   326篇
  1995年   304篇
  1994年   289篇
  1993年   262篇
  1992年   259篇
  1991年   161篇
  1990年   230篇
  1989年   203篇
  1988年   167篇
  1987年   166篇
  1986年   156篇
  1985年   187篇
  1984年   197篇
  1983年   162篇
  1982年   170篇
  1981年   168篇
  1980年   143篇
  1979年   165篇
  1978年   123篇
  1977年   121篇
  1976年   162篇
  1975年   125篇
  1973年   108篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Interfacial microstructures in βP-Si3N4( w )-Si-Al-Y-O-N-glass systems were investigated by systematically varying the nitrogen content and the Al:Y ratio of the glass matrix. High-resolution and analytical transmission electron microscopy (HREM and AEM) studies revealed that the interfacial microstructure is a function of the glass composition. No interfacial phases were formed in glasses with low Al:Y ratios and in glasses with high Al:Y ratios and low nitrogen content, whereas epitaxial growth of an interfacial layer (100–200 μm thick) on the βP-Si3N4( w ) occurred in a glass matrix with high Al:Y ratio and high nitrogen content. The interfacial layer was identified to be a β'-SiAION phase. Interfaces containing the SiAION layer exhibited high debonding energy compared to Si3N4( w )–glass interfaces. HREM studies indicated that the lattice-mismatch strain in the SiAION layer was relieved by dislocation formation at the SiAION–Si3N4( w ) interface. The difference in interfacial debonding energy was, hence, attributed to the local atomic structure and bonding between the glass-β-Si3N4 and the glass–β'-SiAION phases. This observation was clear evidence of the strong influence of glass chemistry on the interfacial debonding behavior by altering the interfacial microstructure.  相似文献   
52.
53.
54.
55.
56.
In the verified architecture microprocessor (VAMP) project we have designed, functionally verified, and synthesized a processor with full DLX instruction set, delayed branch, Tomasulo scheduler, maskable nested precise interrupts, pipelined fully IEEE compatible dual precision floating point unit with variable latency, and separate instruction and data caches. The verification has been carried out in the theorem proving system PVS. The processor has been implemented on a Xilinx FPGA. A shorter version of this article with the title “Instantiating uninterpreted functional units and memory system: functional verification of the VAMP” appeared in [8]. The work reported here was done while all the authors were with Saarland University.  相似文献   
57.
Examined the job performance of 420 credit managers (mean age at hiring 25 yrs) from a large finance company who either quit their job, were fired, or were promoted to a higher position in the company. Six biographical variables and 12 performance appraisal scores accumulated from data in employee files were used in a cross-validated multiple discriminant analysis to predict membership in the 3 classification groups. Results reveal a systematic relation between the performance appraisal variables and the classification groups: The performance of promoted Ss was significantly superior to that of Ss who quit, which in turn was significantly superior to the performance of the fired Ss. 18 discriminating variables accounted for a 46.7% hit rate in group membership. Findings are discussed in the context of research on performance antecedents of voluntary and involuntary turnover, as well as the feedback properties of performance appraisal information. It is suggested that no single performance–turnover relation exists. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
58.
In various medium‐to‐large‐scale fire test equipments like the ISO room corner test (RC), and more recently, the single burning item test (SBI) the mass flow rate measurement of the combustion gases plays a key role in the determination of the heat‐release rate and smoke‐production rate. With the knowledge of the velocity profile and the temperature of the flow, the mass flow rate is obtained by measuring the velocity on the axis of the duct. This is done by means of a bi‐directional probe based on the pitot principle. However, due to the variation of the mean temperature and the temperature gradient in any cross section of the duct, introduced by ever changing combustion gas temperatures, the velocity nor the density profile are constant in time. This paper examines the resulting uncertainty on the mass flow rate. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
59.
60.
This article describes the application, at the team and individual level, of findings from the positive psychology research. An overview of this research is presented focusing on several areas generally included in the positive psychology domain: flow, appreciative inquiry, the broaden and build theory, and other strategies for increasing the experience of positive emotions and the identification and deployment of strengths. The authors propose that these applications show promise in consulting psychology engagements and may have merit when utilized by practitioners themselves. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  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