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   1142篇
  免费   45篇
  国内免费   1篇
电工技术   8篇
综合类   1篇
化学工业   227篇
金属工艺   23篇
机械仪表   13篇
建筑科学   72篇
矿业工程   3篇
能源动力   24篇
轻工业   83篇
水利工程   5篇
无线电   124篇
一般工业技术   213篇
冶金工业   258篇
原子能技术   17篇
自动化技术   117篇
  2023年   14篇
  2022年   8篇
  2021年   34篇
  2020年   21篇
  2019年   27篇
  2018年   24篇
  2017年   26篇
  2016年   19篇
  2015年   33篇
  2014年   58篇
  2013年   60篇
  2012年   51篇
  2011年   59篇
  2010年   43篇
  2009年   27篇
  2008年   54篇
  2007年   44篇
  2006年   30篇
  2005年   23篇
  2004年   10篇
  2003年   21篇
  2002年   22篇
  2001年   12篇
  2000年   15篇
  1999年   24篇
  1998年   80篇
  1997年   52篇
  1996年   46篇
  1995年   19篇
  1994年   21篇
  1993年   18篇
  1992年   10篇
  1991年   15篇
  1990年   8篇
  1989年   13篇
  1988年   8篇
  1987年   7篇
  1986年   8篇
  1984年   6篇
  1983年   8篇
  1982年   5篇
  1980年   9篇
  1978年   8篇
  1977年   6篇
  1976年   12篇
  1975年   4篇
  1974年   8篇
  1972年   7篇
  1969年   4篇
  1909年   4篇
排序方式: 共有1188条查询结果,搜索用时 15 毫秒
31.
This paper discusses the design, implementation, and deployment of a secure and practical payment system for electronic commerce on the Internet. The system is based on the iKP family of protocols-(i=1,2,3)-developed at IBM Research. The protocols implement credit card-based transactions between buyers and merchants while the existing financial network is used for payment clearing and authorization. The protocols are extensible and can be readily applied to other account-based payment models, such as debit cards. They are based on careful and minimal use of public-key cryptography, and can be implemented in either software or hardware. Individual protocols differ in both complexity and degree of security. In addition to being both a precursor and a direct ancestor of the well-known SET standard, iKP-based payment systems have been in continuous operation on the Internet since mid-1996. This longevity-as well as the security and relative simplicity of the underlying mechanisms-makes the iKP experience unique. For this reason, this paper also reports on, and addresses, a number of practical issues arising in the course of implementation and real-world deployment of a secure payment system  相似文献   
32.
In the field of humidity quantities, the first CIPM key comparison, CCT-K6 is at its end. The corresponding European regional key comparison, EUROMET.T-K6, was completed in early 2008, about 4?years after the starting initial measurements in the project. In total, 24 NMIs from different countries took part in the comparison. This number includes 22 EURAMET countries, and Russia and South Africa. The comparison covered the dew-point temperature range from ?50?°C to +20?°C. It was carried out in three parallel loops, each with two chilled mirror hygrometers as transfer standards in each loop. The comparison scheme was designed to ensure high quality results with evenly spread workload for the participants. It is shown that the standard uncertainty due to the long-term instability was smaller than 0.008?°C in all loops. The standard uncertainties due to links between the loops were found to be smaller than 0.025?°C at ?50?°C and 0.010?°C elsewhere. Conclusions on the equivalence of the dew-point temperature standards are drawn on the basis of calculated bilateral degrees of equivalence and deviations from the EURAMET comparison reference values (ERV). Taking into account 16 different primary dew-point realizations and 8 secondary realizations, the results demonstrate the equivalence of a large number of laboratories at an uncertainty level that is better than achieved in other multilateral comparisons so far in the humidity field.  相似文献   
33.
34.
35.
通过调查得知,包括虚拟现实技术在机床制造中应用可能性的应用方法、策略和工具在产品开发中的现状.对调查结果进行了讨论,考虑到研究理论的可移植性和对企业内部实战的依赖性.讨论的结果为基础研究领域的命题"基于职能单位的产品开发"提供结论.  相似文献   
36.
正科帕卡格拉纳位于新多瑙河12.5公里处,毗邻Reichsbrücke大桥。出于同旧有设计保持协调性考虑,力求能让大楼融入当地环境,迎合自身功能性需要,GERNER GERNER PLUS团队充分考虑现有周边环境,对大楼重新规划设计。新的设计突显建筑的特殊性和重要性,面向河流的立面是科帕卡格拉纳大楼最重要的部分,所以设计的重点也放在了这里。现有的城市中轴线是一个参照物,为了视觉上和氛围上形成一体化城市的感  相似文献   
37.
As part of a cooperation project, Daimler AG and the Institute of Machine Elements, Gears, and Transmissions (MEGT) at the Technische Universität Kaiserslautern are carrying out detailed investigations on a valve train with roller lever. The aim of the project is to develop a detailed simulation method that allows the secondary movement of the valve train to be modeled and thus represents an extension of the classic valve train dynamics simulation. This opens up the opportunity to evaluate the processes within the valve train in detail in the early stages of the product development process. This report introduces the validation of the methodology based on experimental results. First, the focus is placed on the cam-roller contact, which induces the secondary movement of the valve train. This movement takes place in the axial direction of the camshaft so that the validation takes place on the basis of the measured force in this direction. The force is dependent on the load, i.?e. the combination of speed and normal force, as well as the angular misalignments between cam and roller. Following the validation of the detailed modeling of the cam-roller contact, the gained knowledge is transferred into the extended valve train simulations. Finally the valve train simulation is validated.  相似文献   
38.
39.
Forschung im Ingenieurwesen - Die mechanischen Verluste von Verbrennungsmotoren hängen maßgeblich von den auftretenden Reibkräften innerhalb der Kolbengruppe ab. Da die Kolbengruppe...  相似文献   
40.
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