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   88322篇
  免费   1134篇
  国内免费   418篇
电工技术   834篇
综合类   2321篇
化学工业   12195篇
金属工艺   4866篇
机械仪表   3176篇
建筑科学   2279篇
矿业工程   568篇
能源动力   1298篇
轻工业   3844篇
水利工程   1271篇
石油天然气   357篇
无线电   10096篇
一般工业技术   17157篇
冶金工业   3143篇
原子能技术   279篇
自动化技术   26190篇
  2023年   22篇
  2021年   129篇
  2020年   42篇
  2019年   65篇
  2018年   14508篇
  2017年   13439篇
  2016年   10038篇
  2015年   699篇
  2014年   366篇
  2013年   608篇
  2012年   3375篇
  2011年   9716篇
  2010年   8534篇
  2009年   5862篇
  2008年   7035篇
  2007年   8009篇
  2006年   315篇
  2005年   1367篇
  2004年   1266篇
  2003年   1303篇
  2002年   641篇
  2001年   200篇
  2000年   250篇
  1999年   149篇
  1998年   266篇
  1997年   174篇
  1996年   163篇
  1995年   93篇
  1994年   107篇
  1993年   95篇
  1992年   67篇
  1991年   59篇
  1990年   38篇
  1989年   36篇
  1988年   45篇
  1979年   20篇
  1969年   29篇
  1968年   44篇
  1967年   33篇
  1966年   42篇
  1965年   44篇
  1963年   28篇
  1962年   22篇
  1960年   30篇
  1959年   35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 218 毫秒
1.
2.
3.
4.
d -Glycero-d -manno-heptose-1β,7-bisphosphate (HBP) and d -glycero-d -manno-heptose-1β-phosphate (H1P) are bacterial metabolites that were recently shown to stimulate inflammatory responses in host cells through the activation of the TIFA-dependent NF-κB pathway. To better understand structure-based activity in relation to this process, a family of nonhydrolyzable phosphonate analogues of HBP and H1P was synthesized. The inflammation modulation by which these molecules induce the TIFA-NF-κB signal axis was evaluated in vivo at a low-nanomolar concentration (6 nM) and compared to that of the natural metabolites. Our data showed that three phosphonate analogues had similar stimulatory activity to HBP, whereas two phosphonates antagonized HBP-induced TIFA-NF-κB signaling. These results open new horizons for the design of pro-inflammatory and innate immune modulators that could be used as vaccine adjuvant.  相似文献   
5.
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   
6.
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   
7.
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   
8.
9.
10.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before.  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