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   49414篇
  免费   4730篇
  国内免费   2742篇
电工技术   2074篇
技术理论   2篇
综合类   4015篇
化学工业   4937篇
金属工艺   3028篇
机械仪表   3609篇
建筑科学   1090篇
矿业工程   1723篇
能源动力   636篇
轻工业   6071篇
水利工程   476篇
石油天然气   1570篇
武器工业   914篇
无线电   7939篇
一般工业技术   4383篇
冶金工业   2549篇
原子能技术   379篇
自动化技术   11491篇
  2024年   210篇
  2023年   705篇
  2022年   1083篇
  2021年   1427篇
  2020年   1411篇
  2019年   1134篇
  2018年   1079篇
  2017年   1444篇
  2016年   1516篇
  2015年   1858篇
  2014年   2579篇
  2013年   2639篇
  2012年   3250篇
  2011年   3656篇
  2010年   2659篇
  2009年   2736篇
  2008年   2787篇
  2007年   3329篇
  2006年   3079篇
  2005年   2718篇
  2004年   2281篇
  2003年   2098篇
  2002年   1711篇
  2001年   1410篇
  2000年   1342篇
  1999年   1009篇
  1998年   890篇
  1997年   782篇
  1996年   701篇
  1995年   551篇
  1994年   516篇
  1993年   432篇
  1992年   337篇
  1991年   270篇
  1990年   243篇
  1989年   213篇
  1988年   156篇
  1987年   88篇
  1986年   72篇
  1985年   83篇
  1984年   67篇
  1983年   82篇
  1982年   59篇
  1981年   41篇
  1980年   36篇
  1979年   29篇
  1978年   19篇
  1977年   25篇
  1976年   12篇
  1973年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
32.
The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
33.
This paper presents the main current theoretical issues in Information Retrieval. The principles of conceptual modelling, as they have emerged in the database area, are presented and their application to document modelling in order to enhance document retrieval is discussed. Finally, the main features of the MULTOS project are presented and critically reviewed confronting them with the requirements which have been identified during the general discussion on document conceptual modelling for information retrieval.  相似文献   
34.
35.
The paper describes a prototype system called HiSQL (Historical SQL) which extends the functionality of SQL in manipulating historical data, by providing functions for spatial and temporal processing. Conceptually the paper is divided into three parts: the first part deals with the design and architecture of the system; the second part introduces a case study (the defters); and the third part describes specific functions for spatial and temporal processing of serial documents. The paper concludes with a comparison between HiSQL and SQL and suggestions for further work. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
36.
In many applications electronic sensors are used toimprove performance and reliability of measurement systems. Suchsensors should provide a correct transfer from the physical signalto be measured to the electrical output signal. One importantstep to achieve this, is to calibrate each sensor by applyingdifferent reference input signals and adjusting the sensor transferaccordingly. Besides expensive reference equipment the calibrationprocess takes much time and attention per individual sensor,which means a considerable increase in sensor production costs.By including at the sensor or sensor interface chip a programmablecalibration facility the calibration of such smart sensors caneasily be automated and can be executed for a batch of sensorsat a time, thus minimizing the calibration time and costs. Thispaper presents a calibration method and options for integrationin the smart sensor concept, in hardware as well as in software.An advantage of the proposed method is that it does not needa large matrix of calibration data, which needs to be storedin a look-up table or converted into a correction formula, butinstead it uses a step-by-step approach to correct the sensortransfer at each calibration measurement until the error is sufficientlysmall.  相似文献   
37.
1.引言 在人工智能领域中,产生式系统是一种比较有效的知识表示方法,并得到了广泛应用。目前许多较为成功的专家系统都是用产生式系统实现的~[1]。随着应用领域的不断扩士其知识座的抓橄称渐增  相似文献   
38.
论述了无线电引信多普勒信号增速器的实现原理及意义,介绍了采用TMS320C30作为CPU、多片大容量静态RAM芯片构成海量存储体的信号增速器硬件结构和软件设计,并提出了今后的研究方向。  相似文献   
39.
通过LD22-l构造地震资料目标处理,搞清了“模糊带”,引进交互处理系统是成功的.  相似文献   
40.
二元复合驱采出液矿场处理试验   总被引:1,自引:0,他引:1  
利用研制的二元复合驱采出液矿场处理装置,对辽河油田兴28块兴191井采出液进行了矿场处理试验。结果表明,采用适宜的破乳剂及处理工艺技术,可以使矿场采出液处理达到净化油含水≤0.5%的指标。  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