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   135775篇
  免费   6172篇
  国内免费   2889篇
电工技术   3764篇
技术理论   1篇
综合类   5580篇
化学工业   20302篇
金属工艺   8025篇
机械仪表   6736篇
建筑科学   5809篇
矿业工程   2199篇
能源动力   2730篇
轻工业   7421篇
水利工程   2196篇
石油天然气   2998篇
武器工业   354篇
无线电   15722篇
一般工业技术   23135篇
冶金工业   5100篇
原子能技术   849篇
自动化技术   31915篇
  2024年   426篇
  2023年   1053篇
  2022年   1854篇
  2021年   2610篇
  2020年   2023篇
  2019年   1664篇
  2018年   16020篇
  2017年   15028篇
  2016年   11655篇
  2015年   2950篇
  2014年   3148篇
  2013年   3599篇
  2012年   6764篇
  2011年   13270篇
  2010年   11618篇
  2009年   8797篇
  2008年   9795篇
  2007年   10395篇
  2006年   2640篇
  2005年   3197篇
  2004年   2658篇
  2003年   2656篇
  2002年   2160篇
  2001年   1474篇
  2000年   1256篇
  1999年   1134篇
  1998年   907篇
  1997年   687篇
  1996年   662篇
  1995年   515篇
  1994年   405篇
  1993年   284篇
  1992年   193篇
  1991年   157篇
  1990年   124篇
  1989年   111篇
  1988年   86篇
  1987年   54篇
  1986年   45篇
  1985年   33篇
  1968年   43篇
  1967年   33篇
  1966年   43篇
  1965年   45篇
  1959年   38篇
  1958年   37篇
  1957年   36篇
  1956年   34篇
  1955年   63篇
  1954年   68篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
A new excimer laser annealing (ELA) process that uses a floating amorphous-Silicon (a-Si) thin film with a multichannel structure is proposed for high-performance poly-Si thin-film transistors (TFTs). The proposed ELA method produces two-dimensional (2-D) grain growth, which can result in a high-quality grain structure. The dual-gate structure was employed to eliminate the grain boundaries perpendicular to the current flow in the channel. A multichannel structure was adapted in order to arrange the grain boundary to be parallel to the current flow. The proposed poly-Si TFT exhibits high-performance electrical characteristics, which are a high mobility of 504 cm/sup 2//Vsec and a low subthreshold slope of 0.337 V/dec.  相似文献   
2.
The purpose of this paper is to evaluate two methods of assessing the productivity and quality impact of Computer Aided Software Engineering (CASE) and Fourth Generation Language (4GL) technologies: (1) by the retrospective method; and (2) the cross-sectional method. Both methods involve the use of questionnaire surveys. Developers' perceptions depend on the context in which they are expressed and this includes expectations about the effectiveness of a given software product. Consequently, it is generally not reliable to base inferences about the relative merits of CASE and 4GLs on a cross-sectional comparison of two separate samples of users. The retrospective method that requires each respondent to directly compare different products is shown to be more reliable. However, there may be scope to employ cross-sectional comparisons of the findings from different samples where both sets of respondents use the same reference point for their judgements, and where numerical rather than verbal rating scales are used to measure perceptions.  相似文献   
3.
4.
5.
This study empirically examined the organisational learning effects of the nonfinancial performance information provided by management accounting information systems (MAISs) under advanced manufacturing technology (AMT). In this study, a target costing system and the frequent and quick reporting of information were considered the facilitators of learning. First, we examined the relationships between AMT level and the amount of nonfinancial performance information produced by MAISs. The empirical results showed that there are significant positive relationships between the level of AMT and nonfinancial performance information. With a systems approach, we also proved the impact of the relationships among AMT levels, nonfinancial performance information and learning facilitators on the organisational performance of a firm. The results of our research suggest that under a high level of AMT, for the provision of information to result in an increase of performance through organisational learning, a target costing system must be introduced and a large amount of information should be provided frequently and quickly. The results of this study also showed that although AMT level may be low, fairly well-arranged facilitators and a moderately large amount of information may be necessary for the improvement of performance. In conclusion, effective organisational learning depends on the provision of relevant information as well as efficient learning support mechanisms.  相似文献   
6.
7.
The ennoblement of corrosion potential (Ecorr) of passive metal immersed in seawater was investigated with electrochemical technology and epifluorescence microscopy. The in situ observation showed that the bacteria number increased on the metal surface according to an exponential law which was in the same way with the ennoblement of Ecorr. At the same time, the anodic polarization current of high‐Mo stainless steel decreased in the initial days. According to the mix‐potential theory and the characteristics of polarization curves of high‐Mo steel in natural seawater, the ennoblement of corrosion potential may be induced by the decrease of the passive current density.  相似文献   
8.
新的启迪     
说点心里的话,建筑设计对青年人来讲是一条漫长的道路。建筑是一个载体,有精神一面,也有物质一面。有些建筑师拿着模型或未建成的设计来炒作,为了求名,生怕别人不知道。这对个人是小事,但若贻误了青年学子,那就是不可取的。  相似文献   
9.
10.
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