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   110323篇
  免费   3338篇
  国内免费   1598篇
电工技术   2436篇
技术理论   3篇
综合类   3953篇
化学工业   15929篇
金属工艺   6376篇
机械仪表   4756篇
建筑科学   4182篇
矿业工程   1620篇
能源动力   1912篇
轻工业   5438篇
水利工程   1807篇
石油天然气   2147篇
武器工业   190篇
无线电   12080篇
一般工业技术   19511篇
冶金工业   4100篇
原子能技术   555篇
自动化技术   28264篇
  2024年   147篇
  2023年   525篇
  2022年   844篇
  2021年   1208篇
  2020年   926篇
  2019年   777篇
  2018年   15219篇
  2017年   14224篇
  2016年   10742篇
  2015年   1677篇
  2014年   1618篇
  2013年   1874篇
  2012年   4839篇
  2011年   11207篇
  2010年   9873篇
  2009年   7014篇
  2008年   8236篇
  2007年   9120篇
  2006年   1469篇
  2005年   2412篇
  2004年   1952篇
  2003年   1919篇
  2002年   1308篇
  2001年   741篇
  2000年   788篇
  1999年   734篇
  1998年   590篇
  1997年   483篇
  1996年   474篇
  1995年   357篇
  1994年   329篇
  1993年   242篇
  1992年   194篇
  1991年   143篇
  1990年   68篇
  1989年   71篇
  1988年   83篇
  1987年   49篇
  1986年   37篇
  1968年   44篇
  1967年   33篇
  1966年   42篇
  1965年   45篇
  1960年   32篇
  1959年   37篇
  1958年   38篇
  1957年   37篇
  1956年   36篇
  1955年   66篇
  1954年   72篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
In order to predict the wearing of stellite alloys,the related methods of rare metals data processing were discussed. The method of opposite degree(OD) algorithm was put forward to predict the wearing of stellite alloys.OD algorithm is based on prior numerical data, posterior numerical data and the opposite degree between numerical forecast data. To compare the performance of predicted results based on different algorithms, the back propagation(BP) and radial basis function(RBF) neural network methods were introduced. Predicted results show that the relative error of OD algorithm is smaller than those of BP and RBF neural network methods. OD algorithm is an effective method to predict the wearing of stellite alloys and it can be applied in practice.  相似文献   
22.
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   
23.
综采工作面在推进过程中经常会受到断层的影响,严重制约了矿井的安全生产及经济效益。以寺河煤矿西井区W2303工作面采用留顶煤、割底矸等手段过逆断层群为工程实例,分析了综采工作面安全、快速过逆断层群技术的应用效果,对于类似矿山也有一定的借鉴价值。  相似文献   
24.
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   
25.
26.
27.
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   
28.
29.
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   
30.
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