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   96202篇
  免费   2109篇
  国内免费   808篇
电工技术   1427篇
综合类   2793篇
化学工业   13436篇
金属工艺   5272篇
机械仪表   3592篇
建筑科学   2872篇
矿业工程   711篇
能源动力   1519篇
轻工业   4777篇
水利工程   1474篇
石油天然气   611篇
武器工业   75篇
无线电   10978篇
一般工业技术   17924篇
冶金工业   4135篇
原子能技术   409篇
自动化技术   27114篇
  2024年   64篇
  2023年   227篇
  2022年   446篇
  2021年   678篇
  2020年   487篇
  2019年   429篇
  2018年   14836篇
  2017年   13764篇
  2016年   10394篇
  2015年   1105篇
  2014年   870篇
  2013年   990篇
  2012年   3934篇
  2011年   10275篇
  2010年   8917篇
  2009年   6134篇
  2008年   7358篇
  2007年   8266篇
  2006年   555篇
  2005年   1548篇
  2004年   1417篇
  2003年   1426篇
  2002年   819篇
  2001年   319篇
  2000年   363篇
  1999年   256篇
  1998年   565篇
  1997年   360篇
  1996年   303篇
  1995年   151篇
  1994年   161篇
  1993年   139篇
  1992年   90篇
  1991年   101篇
  1990年   66篇
  1989年   77篇
  1988年   54篇
  1987年   40篇
  1986年   45篇
  1985年   48篇
  1982年   40篇
  1977年   48篇
  1976年   65篇
  1968年   46篇
  1967年   40篇
  1966年   46篇
  1965年   46篇
  1958年   41篇
  1955年   63篇
  1954年   69篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
简单介绍了碳氧比测井的原理及通常的数据处理方法。分析了由常规数据处理所得曲线仍然存在的问题及可能的成因 ,并给出了可行的修正办法。讨论了另一种可行的曲线异常数据的检测、剔除方法。实践表明 :文章讨论的两点建议都是可行的 ,并且在提高测量曲线质量的同时也提高了地层含油饱和度的解释精度。  相似文献   
62.
Microbiological denitrification of red beet juice   总被引:1,自引:0,他引:1  
The purpose of study was the determination of optimal conditions for red beet juice denitrification by Paracoccus denitrificans bacteria as well as the evaluation of the usefulness of microbiologically treated juice for the production of a natural colouring preparation for foods. Total reduction of nitrates was found during bacterial culturing at 25 and 30 °C, at an initial pH of 7.0-8.0 and juice osmotic pressure of 900-1100 mOsm/kg. Microbiological denitrification procedure affected colour, taste and aroma of the juice. However, the use of juice as food colouring and component was made feasible by acidification and partial evaporation of water together with volatile substances.  相似文献   
63.
64.
论述了电磁铁铁芯 (硅钢片 )模具的设计要点及其线切割加工的技巧 ,提出了提高模具加工精度和使用寿命的有效措施。  相似文献   
65.
The paper discusses the postulated suspension force, by which it is possible to explain some enigmatic phenomena observed in different types of mass movements. This force is generated in thick suspensions as a result of friction between sinking solid particles and static water. The suspension force is related to the seepage force but they have opposite directions. Both forces form flow networks. Having explained the suspension force, the paper describes how this influences the movement of material, particularly in debris flows. Enigmatic features and the mechanism of debris flows and lahars are explained by virtue of the suspension force. Electronic Publication  相似文献   
66.
We consider the problem of rescheduling trains in the case where one track of a railway section consisting of two tracks in opposing directions is closed due to construction activities. After presenting an appropriate model for this situation we derive a polynomial algorithm for the subproblem of finding an optimal schedule with minimal latenesss if the subsequences of trains for both directions outside the construction site are fixed. Based on this algorithm we propose a local search procedure for the general problem of finding good schedules and report test results for some real world instances. Received: December 8, 1999 / Accepted: May 2, 2001  相似文献   
67.
Three interesterified vegetable oils (IVOs) prepared from palm, cottonseed, and olive oil, respectively, have been studied for application to Frankfurters. Beef fat (10%) was replaced by one of the IVOs at 20, 60 or 100%. Fatty acid composition of the lipid fraction in the Frankfurters and saturated/unsaturated ratios were established for all batches. We found that total or partial replacement of beef fat by IVOs did not lead to significant changes in appearance, colour, texture, flavour or sensory score. We conclude that IVOs may be successfully applied as beef fat substitutes in Frankfurters.  相似文献   
68.
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   
69.
70.
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