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   103378篇
  免费   2493篇
  国内免费   1234篇
电工技术   1841篇
技术理论   4篇
综合类   3345篇
化学工业   14964篇
金属工艺   5708篇
机械仪表   4245篇
建筑科学   3499篇
矿业工程   1115篇
能源动力   1691篇
轻工业   4696篇
水利工程   1561篇
石油天然气   1534篇
武器工业   131篇
无线电   11843篇
一般工业技术   18819篇
冶金工业   3646篇
原子能技术   435篇
自动化技术   28028篇
  2024年   57篇
  2023年   305篇
  2022年   520篇
  2021年   828篇
  2020年   581篇
  2019年   535篇
  2018年   14910篇
  2017年   13909篇
  2016年   10452篇
  2015年   1320篇
  2014年   1163篇
  2013年   1432篇
  2012年   4304篇
  2011年   10672篇
  2010年   9255篇
  2009年   6561篇
  2008年   7785篇
  2007年   8730篇
  2006年   1175篇
  2005年   2138篇
  2004年   1747篇
  2003年   1779篇
  2002年   1066篇
  2001年   552篇
  2000年   708篇
  1999年   645篇
  1998年   590篇
  1997年   487篇
  1996年   489篇
  1995年   333篇
  1994年   309篇
  1993年   223篇
  1992年   183篇
  1991年   161篇
  1990年   125篇
  1989年   95篇
  1988年   86篇
  1987年   48篇
  1986年   46篇
  1985年   35篇
  1968年   44篇
  1967年   34篇
  1966年   43篇
  1965年   45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 562 毫秒
11.
Protection of Metals and Physical Chemistry of Surfaces - The Al2O3 powder was added as a filler to polyurea and the effect of doping amount on Shore hardness and wetting property were...  相似文献   
12.
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   
13.
14.
15.
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   
16.
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being.  相似文献   
17.
18.
Vu  Hoa T.  Nguyen  Manh B.  Vu  Tan M.  Le  Giang H.  Pham  Trang T. T.  Nguyen  Trinh Duy  Vu  Tuan A. 《Topics in Catalysis》2020,63(11-14):1046-1055
Topics in Catalysis - Nano Fe-BTC/graphene oxide (GO) composites were successfully synthesized by hydrothermal treatment with a microwave-assisted method. Samples were characterized by X-ray...  相似文献   
19.
20.
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   
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