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   141846篇
  免费   6565篇
  国内免费   3437篇
电工技术   4962篇
技术理论   5篇
综合类   6432篇
化学工业   20505篇
金属工艺   8260篇
机械仪表   6470篇
建筑科学   7368篇
矿业工程   2064篇
能源动力   2862篇
轻工业   7281篇
水利工程   2330篇
石油天然气   3458篇
武器工业   506篇
无线电   16396篇
一般工业技术   23338篇
冶金工业   5101篇
原子能技术   1028篇
自动化技术   33482篇
  2024年   246篇
  2023年   1040篇
  2022年   1755篇
  2021年   2565篇
  2020年   1824篇
  2019年   1510篇
  2018年   15926篇
  2017年   15053篇
  2016年   11503篇
  2015年   2921篇
  2014年   3059篇
  2013年   3660篇
  2012年   6884篇
  2011年   13328篇
  2010年   11835篇
  2009年   8844篇
  2008年   10181篇
  2007年   11039篇
  2006年   3461篇
  2005年   4026篇
  2004年   3119篇
  2003年   2955篇
  2002年   2432篇
  2001年   1795篇
  2000年   1661篇
  1999年   1632篇
  1998年   1213篇
  1997年   1050篇
  1996年   1043篇
  1995年   818篇
  1994年   681篇
  1993年   498篇
  1992年   448篇
  1991年   347篇
  1990年   213篇
  1989年   179篇
  1988年   168篇
  1987年   95篇
  1986年   63篇
  1985年   55篇
  1968年   43篇
  1967年   33篇
  1966年   42篇
  1965年   44篇
  1959年   37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 15 毫秒
41.
In this work, the hydrothermally-synthesized sodium niobate nanowires were used to decompose Rhodamine B dye solution through the piezo-catalytic effect. With the sodium niobate catalyst, a high piezo-catalytic degradation ratio of ~80% was achieved under the excitation of vibration for the Rhodamine B dye solution (~5?mg/l). These active species in the catalytic process, hydroxyl radicals and superoxide radicals with the strong oxidation ability, were also observed, which confirmed the key role of piezoelectric effect for piezo-catalysis. The piezo-catalysis of sodium niobate nanowires provides a high-efficiency and reusable tool in application in depredating the dye wastewater.  相似文献   
42.
Proton induced X-ray emission (PIXE) technique and factor analysis were used to study the recovery of making-technology of Chinese Longquan celadon made in the late Southern Song Dynasty (1127–1279 CE). Based on factor analysis, for the raw material for body and the recipe for glaze, there is a close but slightly different relationship between these Longquan celadons unearthed from the core area of Dayao and the non-core area, despite all the Longquan celadons belong to the high-calcium-glaze system. The chemical compositions of most of the tentative body and glaze samples are very close to those of Longquan celadons unearthed from the core area of Dayao and the non-core area. This study can provide a guidance for recovery of making-technology of Longquan celandon.  相似文献   
43.
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   
44.
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   
45.
46.
47.
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   
48.
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   
49.
M1080B无心外圆磨床砂轮及导轮宽度较窄,磨削轴承套圈外圆时,磨削效率低,托板架调整较为繁琐、皮带打滑、磨损较为严重。针对上述问题,提出了相应的解决办法,提高了磨削效率。  相似文献   
50.
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