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   86905篇
  免费   1170篇
  国内免费   431篇
电工技术   928篇
综合类   2319篇
化学工业   11857篇
金属工艺   4862篇
机械仪表   3105篇
建筑科学   2329篇
矿业工程   571篇
能源动力   1204篇
轻工业   3853篇
水利工程   1301篇
石油天然气   355篇
武器工业   1篇
无线电   9696篇
一般工业技术   16738篇
冶金工业   3008篇
原子能技术   277篇
自动化技术   26102篇
  2023年   28篇
  2022年   38篇
  2021年   67篇
  2020年   45篇
  2019年   81篇
  2018年   14554篇
  2017年   13452篇
  2016年   10028篇
  2015年   667篇
  2014年   335篇
  2013年   446篇
  2012年   3329篇
  2011年   9572篇
  2010年   8466篇
  2009年   5760篇
  2008年   6984篇
  2007年   7924篇
  2006年   305篇
  2005年   1384篇
  2004年   1224篇
  2003年   1279篇
  2002年   631篇
  2001年   151篇
  2000年   235篇
  1999年   126篇
  1998年   117篇
  1997年   83篇
  1996年   99篇
  1995年   48篇
  1994年   38篇
  1993年   46篇
  1992年   41篇
  1991年   49篇
  1989年   25篇
  1988年   32篇
  1986年   23篇
  1969年   29篇
  1968年   43篇
  1967年   34篇
  1966年   45篇
  1965年   47篇
  1963年   29篇
  1962年   22篇
  1960年   30篇
  1959年   35篇
  1958年   39篇
  1957年   38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.
Colorectal cancer (CRC) is the third most deadly cancer worldwide, and inflammatory bowel disease (IBD) is one of the critical factors in CRC carcinogenesis. IBD is responsible for an unphysiological and sustained chronic inflammation environment favoring the transformation. MicroRNAs (miRNAs) belong to a class of highly conserved short single-stranded segments (18–25 nucleotides) non-coding RNA and have been extensively discussed in both CRC and IBD. However, the role of miRNAs in the development of colitis-associated CRC (CAC) is less clear. The aim of this review is to summarize the major upregulated (miR-18a, miR-19a, miR-21, miR-31, miR-155 and miR-214) and downregulated (miR-124, miR-193a-3p and miR-139-5p) miRNAs in CAC, and their roles in genes’ expression modulation in chronic colonic-inflammation-induced carcinogenesis, including programmed cell-death pathways. These miRNAs dysregulation could be applied for early CAC diagnosis, to predict therapy efficacy and for precision treatment.  相似文献   
2.
Landsiedel  Justus  Root  Waleri  Schramm  Christian  Menzel  Alexander  Witzleben  Steffen  Bechtold  Thomas  Pham  Tung 《Nano Research》2020,13(10):2658-2664
Nano Research - Development of colored surfaces by formation of nano-structured aggregates is a widely used strategy in nature to color lightweight structures (e.g. butterflies) without the use of...  相似文献   
3.
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   
4.
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   
5.
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   
6.
7.
8.
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   
9.
10.
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