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   62509篇
  免费   6050篇
  国内免费   3332篇
电工技术   3683篇
技术理论   1篇
综合类   5330篇
化学工业   7699篇
金属工艺   2498篇
机械仪表   4319篇
建筑科学   11361篇
矿业工程   1774篇
能源动力   3735篇
轻工业   5705篇
水利工程   1207篇
石油天然气   2859篇
武器工业   901篇
无线电   3708篇
一般工业技术   7156篇
冶金工业   2616篇
原子能技术   433篇
自动化技术   6906篇
  2024年   392篇
  2023年   1152篇
  2022年   2164篇
  2021年   2560篇
  2020年   2667篇
  2019年   2279篇
  2018年   2194篇
  2017年   2555篇
  2016年   2649篇
  2015年   2682篇
  2014年   4066篇
  2013年   3950篇
  2012年   4675篇
  2011年   4845篇
  2010年   3640篇
  2009年   3663篇
  2008年   3225篇
  2007年   4033篇
  2006年   3391篇
  2005年   2873篇
  2004年   2238篇
  2003年   1873篇
  2002年   1551篇
  2001年   1299篇
  2000年   1012篇
  1999年   787篇
  1998年   610篇
  1997年   483篇
  1996年   461篇
  1995年   325篇
  1994年   258篇
  1993年   188篇
  1992年   149篇
  1991年   129篇
  1990年   105篇
  1989年   74篇
  1988年   62篇
  1987年   52篇
  1986年   30篇
  1985年   43篇
  1984年   54篇
  1983年   37篇
  1982年   36篇
  1981年   21篇
  1980年   52篇
  1964年   28篇
  1963年   26篇
  1961年   22篇
  1959年   21篇
  1955年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
A simple measurement system is described for evaluating damage to graphite-epoxy panels, such as those used in high-performance aircraft. The system uses a heating laser and infrared imaging system to measure thermal performance. Thermal conductivity or diffusivity is a sensitive indicator of damage in materials, allowing this thermal measurement to show various degrees of damage in graphite-epoxy composites. Our measurements track well with heat-flux damage to graphite epoxy panels. This measurement system, including analysis software, could easily be used in the field, such as on the deck of an aircraft carrier or at remote air strips.  相似文献   
52.
53.
In this paper, we describe a comprehensive layout methodology for bonded three-dimensional integrated circuits (3D ICs). In bonded 3D integration technology, parts of a circuit are fabricated on different wafers, and then, the wafers are bonded with a glue layer of Cu or polymer based adhesive. Using our layout methodology, designers can layout such 3D circuits with necessary information on inter-wafer via/contact and orientation of each wafer embedded in the layout. We have implemented the layout methodology in 3DMagic. Availability of 3DMagic has led to interesting research with a wide range of layout-specific circuit evaluation, from performance comparison of 2D and 3D circuits to layout-specific reliability analyses in 3D circuits. Using 3DMagic, researchers have designed and simulated an 8-bit encryption processor mapped into 2D and 3D FPGA layouts. Moreover, the layout methodology is an essential element of our ongoing research for the framework of a novel Reliability Computer Aided Design tool, ERNI-3D.  相似文献   
54.
David Mills 《Granular Matter》2004,6(2-3):173-177
For fine powdered materials, capable of being conveyed in dense phase, a conveying region exists in which instability in flow and pipeline blockage can occur if the pressure gradient available is insufficient to maintain a minimum value of solids loading ratio. A reduction in material flow rate can also lead to pipeline blockage in this region. Conveying trials under-taken with cement are used to illustrate the nature of the problem.  相似文献   
55.
The relationship between teachers' judgments versus actual performance on curriculum-based measures in reading was examined. A total of 30 regular education teachers were asked to predict the oral reading fluency score of students along with a rating scale of reading subskills. Correlations between teacher judgment measures and student performance found that teachers were accurate reporters of student performance levels in reading. However, some questions were raised whether teachers were accurate at predicting the actual level of student oral reading fluency when effect sizes were used to compare teacher judgment and actual student performance. Recommendations for continued research in understanding the parameters of the accuracy of teacher judgment are made. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
56.
This study investigated the relationship between self-appraisals of performance, symptom severity and post-event rumination in social phobia, and evaluated the effect of treatment on these variables. A socially phobic group and a nonanxious control group performed an impromptu speech and were told that their performance would be evaluated. Participants appraised their performance immediately after the speech and 1 week later, and the frequency of post-event rumination during the week following the speech was assessed. The socially phobic group maintained the negative appraisals of their speech over the week, whereas the nonclinical group showed increased positivity about their performance The socially phobic group also engaged in more negative rumination than controls. Treatment improved perceptions of performance and reduced negative rumination. These results are discussed in the light of cognitive models of social phobia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
57.
Since computer networks play an important role in distributed computing environments, an application's performance depends heavily on the quality of service provided by the communication networks. To ensure a high performance, the characteristics of wide area networks, WANs, must be well understood. This paper presents methodologies to characterize WAN traffic based on real measurements from Bellcore's backbone network that connects remote sites using dedicated T1 links. This paper also suggests some workload models that can be used for wide area network sizing and performance evaluation studies. It is found that the inter-site traffic pattern depends on the time of the day and the day of the week. Furthermore, the traffic between two sites is found to be reasonably symmetric, except for those sites designated as back-up sites. The coefficient of variation is used as a measure for the traffic burstiness and it is found to be 1·5 degree during working hours. The methods presented here are easy to use and cost-effective.  相似文献   
58.
Evaluating the design of flexible manufacturing systems is complex. Developing a measure of performance useful for evaluating alternate designs continues to be interesting. Here, total productivity of the system is proposed as an appropriate measure. Specification of parameters based upon strategic considerations for this measure are discussed. Finally, the usefulness of the measure is demonstrated through an example.  相似文献   
59.
以往双侧向测井仪动态范围小,测量精度低,为此开发了DLL23XA双侧向测井仪。该仪器主要单元采用厚膜电路,稳定性、一致性好;深、浅屏流源采用可变功率控制,提高了仪器的动态范围。仪器采用3506P例进行数据传输,可方便地配接各种地面系统。  相似文献   
60.
本文介绍了可在微机上实现大规模电信网践模拟的实用化软件SIMUNET,及基所采用的无时钟事件追踪法。该软件可用规划中的电信网络和实际网路的模拟及性能评价,也可用于不同流量控制算法的评价。文中给出一个评价实例。  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