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   325209篇
  免费   6326篇
  国内免费   3377篇
电工技术   6931篇
技术理论   1篇
综合类   5000篇
化学工业   48955篇
金属工艺   16372篇
机械仪表   10885篇
建筑科学   9815篇
矿业工程   2419篇
能源动力   7871篇
轻工业   24884篇
水利工程   4005篇
石油天然气   5836篇
武器工业   285篇
无线电   36066篇
一般工业技术   61382篇
冶金工业   43320篇
原子能技术   5545篇
自动化技术   45340篇
  2022年   2484篇
  2021年   3640篇
  2020年   2702篇
  2019年   2868篇
  2018年   17848篇
  2017年   16862篇
  2016年   13581篇
  2015年   3942篇
  2014年   5276篇
  2013年   11862篇
  2012年   10678篇
  2011年   18984篇
  2010年   15928篇
  2009年   14334篇
  2008年   15332篇
  2007年   16293篇
  2006年   7603篇
  2005年   7947篇
  2004年   7360篇
  2003年   6976篇
  2002年   6401篇
  2001年   5949篇
  2000年   5445篇
  1999年   5416篇
  1998年   12652篇
  1997年   9159篇
  1996年   7220篇
  1995年   5335篇
  1994年   4448篇
  1993年   4369篇
  1992年   3213篇
  1991年   3130篇
  1990年   2939篇
  1989年   2917篇
  1988年   2730篇
  1987年   2492篇
  1986年   2414篇
  1985年   2706篇
  1984年   2472篇
  1983年   2296篇
  1982年   2156篇
  1981年   2220篇
  1980年   2124篇
  1979年   2116篇
  1978年   2044篇
  1977年   2490篇
  1976年   3270篇
  1975年   1840篇
  1974年   1815篇
  1973年   1877篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
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   
35.
A method for contactless measurement of the shielding critical current density and its dependence on the external magnetic field is described and analyzed. The obtained values are compared with those measured resistively on two different samples. It is shown that the shielding critical current densityJ cs and the intergranular transport current densityJ cr are identical if the measurement conditions are similar. A degradation ofJ cs measured in the external field with AC ripple has been observed.  相似文献   
36.
37.
38.
Containment structures have several regions in which the continuity of the cylindrical pressure boundary is interrupted, e.g., shell penetrations, discontinuous stiffeners, and changes in the shell thickness. Significant strain concentrations can occur in these areas of discontinuity. The Sandia National Laboratories 1:8-scale steel containment equipment hatch was analyzed as an example of an eccentricity at a stiffener intersection.A portion of the as-built 1:8-scale model was modeled with the ANSYS general purpose finite element program using triangular, thin shell finite elements. The overall size of the model was determined from Saint-Venant type considerations of the stress field around the hatch. Shell elements were used to model the ring and formed stiffeners. Geometric and material nonlinear behavior were included. The model was loaded using discrete load steps up to a pressure of 165 psig. At this pressure, the maximum strain was 19.7 percent in the formed stiffener near its intersection with the ring stiffener. The finite element solution demonstrated the very localized nature of the strain field near the ring/formed stiffener intersection.In an attempt to reduce analysis costs, a small portion of the 1:8-scale model immediately surrounding the ring/formed stiffener intersection was selected for further analysis. Two smaller models, a ring/formed stiffener intersection and a ring/circular stiffener intersection, were studied. The models were significantly smaller than the regions used previously. A comparison of the two intersection models showed that the circular stiffener is a more efficient configuration.  相似文献   
39.
40.
Lenin Dnepropetrovsk Pipe Plant. Translated from Metallurg, No. 8, p. 39, August, 1989.  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