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   285811篇
  免费   16324篇
  国内免费   8212篇
电工技术   12133篇
技术理论   14篇
综合类   13251篇
化学工业   46674篇
金属工艺   15091篇
机械仪表   14901篇
建筑科学   18597篇
矿业工程   5508篇
能源动力   6931篇
轻工业   16149篇
水利工程   4442篇
石油天然气   11415篇
武器工业   1352篇
无线电   34187篇
一般工业技术   42149篇
冶金工业   13482篇
原子能技术   2377篇
自动化技术   51694篇
  2024年   887篇
  2023年   3277篇
  2022年   5872篇
  2021年   7980篇
  2020年   5845篇
  2019年   5044篇
  2018年   18946篇
  2017年   18823篇
  2016年   15056篇
  2015年   7895篇
  2014年   9786篇
  2013年   12506篇
  2012年   15270篇
  2011年   22852篇
  2010年   19540篇
  2009年   16722篇
  2008年   17357篇
  2007年   17975篇
  2006年   11025篇
  2005年   10811篇
  2004年   7652篇
  2003年   6906篇
  2002年   5792篇
  2001年   4848篇
  2000年   5055篇
  1999年   5725篇
  1998年   5351篇
  1997年   4395篇
  1996年   4014篇
  1995年   3332篇
  1994年   2791篇
  1993年   2200篇
  1992年   1718篇
  1991年   1304篇
  1990年   1024篇
  1989年   881篇
  1988年   690篇
  1987年   496篇
  1986年   395篇
  1985年   334篇
  1984年   212篇
  1983年   198篇
  1982年   163篇
  1981年   145篇
  1980年   131篇
  1979年   97篇
  1977年   63篇
  1976年   77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 9 毫秒
31.
32.
33.
印染废水处理工艺研究及实例   总被引:1,自引:0,他引:1  
本文简要介绍了印染废水水质特征,提出了处理工艺,并利用两个工程实例说明了该工艺的可行性.  相似文献   
34.
This study used different metals to modify Rh/Al2O3 catalysts for NO reduction in a simulated waste incineration flue gas containing 6% O2. The characteristics of the modified catalysts were analyzed using BET, TEM and XRD. The results of the experiment reveal that Na addition can significantly affect the properties of Rh/Al2O3 catalysts on the BET surface area and Rh metal dispersion. Furthermore, Na addition was found to significantly enhance the NO conversion of Rh/Al2O3 at 250–350 °C. On the contrary, Cu, Ni, and Co addition was found to have slight suppression effects.  相似文献   
35.
Nanocrystalline LaFeO3 is prepared by the dehydration of coprecipitated lanthanum and iron(III) hydroxides. It is shown that the behavior of the samples during heating and the size distribution of LaFeO3 nanocrystals can be considerably different depending on the scheme used for coprecipitation of lanthanum and iron hydroxides; independently of the method employed for coprecipitation of the initial compounds, sintering of the samples at 950°C leads to the formation of lanthanum orthoferrite crystals up to 100 nm in size.  相似文献   
36.
37.
38.
A Kanban system facilitates lean principles in a simple and effective way. While reportedly successful in many manufacturing firms, the conventional Kanban systems using physical cards suffer from human errors, limited tracking capability, and so on. To make the information flow leaner, software providers add new features to their existing programs for manufacturing systems to computerize Kanban activities. As Web-based technologies advance rapidly, developing an entirely Web-based Kanban system appears to be feasible and promising. This paper presents the advantages, limitations, and challenges of Web-based Kanban systems. An experimental program has been developed based on PHP+MySQL, a popular Web programming platform. The server-executed program features cross-platform compatibility, real-time tracking and performance monitoring, and greatly enhanced information contents compared to physical Kanbans. Human errors are minimized by the automated transactions; nevertheless, the interfacing and data maintenance require further research efforts.  相似文献   
39.
Rapid advances in wireless mobile network technologies and mobile handsets (MHs) facilitate ubiquitous infrastructure that can support a range of mobile services and applications in addition to conventional mobile Internet access. One recent trend is to effectively run desktop PC-oriented heavier applications on MHs. However, due to their miniature, portable size, MHs are resource-constrained and therefore, running these applications directly on an MH is not satisfactory given a user's expectations. To cope with this problem, this article proposes a novel offloading service that can seamlessly offload some of the tasks of a mobile application from an MH to nearby, resource-rich PCs (called surrogates). The system architecture and key components of the proposed offloading service are presented, prototyped, and evaluated. The results of experiments and simulations have demonstrated the effectiveness and efficiency of this offloading service for mobile applications.  相似文献   
40.
In the ideal A2B2O6O′ pyrochlore structure, the x-value of O atom position is a variable parameter. In Bi1.5ZnNb1.5−xTaxO7 (BZNT) cubic pyrochlores, the x-values alter with the different compositions of Nb/Ta. In this work, a series of initial models for BZNT were established by analyzing X-ray diffraction data. Then three structure modifying methods, including Rietveld refinement, Rietveld refinement with energy and geometry optimization based on quantum mechanics, were employed to obtain the precise models using Materials Studio. Moreover, the reflectivities of BZNT were computed by quantum mechanical simulation based on the refined models. Comparing the simulation results from different modifying models with the experimental results, it is found that Rietveld refinement with energy optimization is the most accurate method for BZNT pyrochlores. According to the simulation results, the different reflectivities correspond well with various x-values of O atom positions in BZNT pyrochlores.  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