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   162906篇
  免费   9106篇
  国内免费   4968篇
电工技术   7080篇
技术理论   2篇
综合类   8279篇
化学工业   22873篇
金属工艺   9729篇
机械仪表   8376篇
建筑科学   7710篇
矿业工程   2775篇
能源动力   3766篇
轻工业   9054篇
水利工程   3168篇
石油天然气   3811篇
武器工业   1015篇
无线电   19441篇
一般工业技术   25276篇
冶金工业   6412篇
原子能技术   1274篇
自动化技术   36939篇
  2024年   274篇
  2023年   968篇
  2022年   1988篇
  2021年   2925篇
  2020年   2188篇
  2019年   1795篇
  2018年   16245篇
  2017年   15580篇
  2016年   12207篇
  2015年   3797篇
  2014年   4421篇
  2013年   5223篇
  2012年   9288篇
  2011年   15816篇
  2010年   14234篇
  2009年   11345篇
  2008年   12453篇
  2007年   13022篇
  2006年   5007篇
  2005年   5263篇
  2004年   4273篇
  2003年   4117篇
  2002年   3616篇
  2001年   2782篇
  2000年   1863篇
  1999年   1288篇
  1998年   904篇
  1997年   700篇
  1996年   616篇
  1995年   469篇
  1994年   355篇
  1993年   269篇
  1992年   195篇
  1991年   171篇
  1990年   139篇
  1989年   113篇
  1988年   80篇
  1987年   70篇
  1986年   50篇
  1984年   38篇
  1968年   45篇
  1967年   34篇
  1966年   43篇
  1965年   45篇
  1959年   40篇
  1958年   37篇
  1957年   36篇
  1956年   34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 15 毫秒
1.
2.
Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter‐species, and inter‐kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles—with immune‐modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF‐α and IL‐6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM‐1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post‐injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo.  相似文献   
3.
针对不合格品的高效处置、数据的有效分析对企业质量控制具有深远的意义,其是装备制造领域质量管理研究的重点。文章以SAP接口二次开发、IQS流程建模、数据库建立、系统实用价值等方面展开详细论述,确保质量信息可追溯分析。  相似文献   
4.
5.
6.
7.
8.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms.  相似文献   
9.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials.  相似文献   
10.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards.  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