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   107417篇
  免费   1862篇
  国内免费   438篇
电工技术   1098篇
综合类   2352篇
化学工业   16876篇
金属工艺   5125篇
机械仪表   3483篇
建筑科学   3433篇
矿业工程   656篇
能源动力   1716篇
轻工业   5421篇
水利工程   1490篇
石油天然气   412篇
无线电   10988篇
一般工业技术   20553篇
冶金工业   7151篇
原子能技术   449篇
自动化技术   28514篇
  2023年   214篇
  2022年   360篇
  2021年   568篇
  2020年   340篇
  2019年   434篇
  2018年   14823篇
  2017年   13714篇
  2016年   10466篇
  2015年   1155篇
  2014年   964篇
  2013年   1601篇
  2012年   4255篇
  2011年   10772篇
  2010年   9261篇
  2009年   6481篇
  2008年   7822篇
  2007年   8762篇
  2006年   1057篇
  2005年   1961篇
  2004年   1860篇
  2003年   1810篇
  2002年   1091篇
  2001年   524篇
  2000年   539篇
  1999年   462篇
  1998年   814篇
  1997年   589篇
  1996年   487篇
  1995年   422篇
  1994年   395篇
  1993年   374篇
  1992年   280篇
  1991年   219篇
  1990年   269篇
  1989年   262篇
  1988年   226篇
  1987年   226篇
  1986年   227篇
  1985年   268篇
  1984年   225篇
  1983年   225篇
  1982年   209篇
  1981年   199篇
  1980年   175篇
  1979年   195篇
  1978年   165篇
  1977年   185篇
  1976年   236篇
  1975年   161篇
  1974年   123篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology.  相似文献   
2.
The primary objective of this project is to identify gaps, whether real or perceived, that hinder effective groundwater management in New Zealand. These gaps show as gaps in information, gaps in implementation, gaps in technological and management tools, and gaps in understanding of fundamental processes. The secondary objective is to propose a management strategy to close the identified gaps. Several methods are used to meet these objectives: surveys distributed to selected staff in each regional council; the review of various written reports; the analysis of land-use databases; and private consultation within each regional council. Results show that groundwater management in New Zealand is generally reactionary with the main gaps being in strategic planning and national guidelines. Most gaps appear to be predominantly information and implementation issues. In some cases there are gaps in the understanding of fundamental processes within an aquifer system, including the long-term effects of land-use on groundwater quality. An adaptive management approach is suggested as a means of closing these gaps.  相似文献   
3.
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   
4.
5.
6.
7.
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   
8.
9.
The hot blow forming of magnesium sheet offers significant opportunity for forming complex, lightweight parts for automotive applications. This paper characterizes the elevated-temperature formability of AZ31 magnesium sheet materials and the effect of processing conditions on the performance of these materials. In addition, magnesium sheet application development at General Motors Corporation is reviewed.  相似文献   
10.
Strength of ground ceramics may be affected by residual stress as well as surface flaws induced by grinding. Strength prediction for ground ceramics is convenient for mechanical design of ceramic components. In this article, a numerical procedure based on fracture mechanics was proposed to estimate strength distribution of ground ceramics by considering grinding-induced residual stress. Bending strength and residual stress of ground ceramics were measured for three grinding-conditions. By comparison of simulated results with experimental ones, it was revealed that strength characteristics in experiments were well simulated by using the proposed procedure.  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