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   87633篇
  免费   1166篇
  国内免费   415篇
电工技术   837篇
综合类   2318篇
化学工业   12499篇
金属工艺   4861篇
机械仪表   3084篇
建筑科学   2322篇
矿业工程   566篇
能源动力   1246篇
轻工业   3903篇
水利工程   1285篇
石油天然气   354篇
武器工业   1篇
无线电   9739篇
一般工业技术   16976篇
冶金工业   2951篇
原子能技术   282篇
自动化技术   25990篇
  2022年   64篇
  2021年   79篇
  2020年   71篇
  2019年   84篇
  2018年   14516篇
  2017年   13448篇
  2016年   10051篇
  2015年   705篇
  2014年   375篇
  2013年   457篇
  2012年   3346篇
  2011年   9657篇
  2010年   8470篇
  2009年   5693篇
  2008年   6960篇
  2007年   7936篇
  2006年   288篇
  2005年   1350篇
  2004年   1249篇
  2003年   1279篇
  2002年   662篇
  2001年   153篇
  2000年   253篇
  1999年   121篇
  1998年   120篇
  1997年   111篇
  1996年   112篇
  1995年   77篇
  1994年   75篇
  1993年   51篇
  1992年   55篇
  1991年   60篇
  1990年   48篇
  1989年   41篇
  1988年   37篇
  1985年   42篇
  1984年   41篇
  1983年   38篇
  1982年   44篇
  1968年   46篇
  1967年   38篇
  1966年   54篇
  1965年   47篇
  1960年   41篇
  1959年   43篇
  1958年   44篇
  1957年   43篇
  1956年   39篇
  1955年   64篇
  1954年   72篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
We analysed the ground deformation across two blocks defined by the Rio-Patras fault from 1993 to 2017 using multi-temporal Synthetic Aperture Radar Interferometry (InSAR) techniques. Our main objective was to contribute to the assessment of seismic hazard near the large city of Patras. Multiple data-sets were used, each one covering different temporal periods. Descending and ascending acquisitions, providing different viewing geometries contribute to fully determine the ground displacement in 3D. The data-sets used are from the European Space Agency’s (ESA) European Remote Sensing (ERS), Environmental Satellite (ENVISAT) and SENTINEL-1 as well as German Aerospace Center (DLR) ’s TERRASAR-X missions. Considering ESA’s missions covering both acquisition geometries and long periods, the southern block, showing lack of a sufficient number of scatterers does not allow the displacement characterization. In contrary, the northern block is characterized by a high number of scatterers having values of maximum likehood ranging from ?3.5 to ?4.3 mm year?1 for ascending geometry and from ?1.6 to ?2.7 mm year?1 for the descending one. The fact that both geometries show negative values of displacements are consistent with downlift movement and at the same time the quantitative differentiation probably indicates an horizontal component as well.  相似文献   
2.
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   
3.
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   
4.
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   
5.
6.
7.
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   
8.
9.
Understanding semantic word shifts in scientific domains is essential for facilitating interdisciplinary communication. Using a data set of published papers in the field of information retrieval (IR), this paper studies the semantic shifts of words in IR based on mining per-word topic distribution over time. We propose that semantic word shifts not only occur over time, but also over topics. The shifts are examined from two perspectives, the topic-level and the context-level. According to the over-time word-topic distribution, stable words and unstable words are recognized. The diverging and converging trends in the unstable type reveal characteristics of the topic evolution process. The context-level shifts are further detected by similarities between word vectors. Our work associates semantic word shifts with the evolving of topics, which facilitates a better understanding of semantic word shifts from both topics and contexts.  相似文献   
10.
Research funding has been seen as one of the most important resource in the reward system of science. And usage of publications denotes an interesting perspective of user behavior in scientific communication. This study aims to address the relationship between funding and Usage Count, which is a new metrics item established on the platform of Web of Science. Full records of 300,010 articles published in 2013 were downloaded in October 2015, and divided into six disciplines, including information science library science, education educational research, economics, computer science, materials science, and chemistry. Seven indicators were proposed to measure the impact, including Funding rate, Citation per paper, Usage rate, Usage per paper, Citation difference, Usage difference, and Conversion rate. It concluded funding has impact on usage and citation, and funded papers attract more usage, but varying in different disciplines. Usage Count can be used in the extension of citation metrics but with limits. This study originally engages with usage metrics and detected that there is positive correlation between usage and funding.  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