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   121278篇
  免费   12102篇
  国内免费   6814篇
电工技术   8810篇
技术理论   6篇
综合类   8884篇
化学工业   18204篇
金属工艺   7352篇
机械仪表   8509篇
建筑科学   9272篇
矿业工程   4003篇
能源动力   3480篇
轻工业   8431篇
水利工程   2845篇
石油天然气   6729篇
武器工业   1336篇
无线电   14759篇
一般工业技术   12998篇
冶金工业   5095篇
原子能技术   1481篇
自动化技术   18000篇
  2024年   543篇
  2023年   1948篇
  2022年   3714篇
  2021年   5182篇
  2020年   3890篇
  2019年   3199篇
  2018年   3638篇
  2017年   4046篇
  2016年   3703篇
  2015年   5210篇
  2014年   6436篇
  2013年   7590篇
  2012年   8811篇
  2011年   9636篇
  2010年   8342篇
  2009年   7837篇
  2008年   7890篇
  2007年   7602篇
  2006年   7356篇
  2005年   5981篇
  2004年   4181篇
  2003年   3233篇
  2002年   2911篇
  2001年   2572篇
  2000年   2487篇
  1999年   2361篇
  1998年   1884篇
  1997年   1554篇
  1996年   1398篇
  1995年   1173篇
  1994年   999篇
  1993年   678篇
  1992年   522篇
  1991年   419篇
  1990年   296篇
  1989年   241篇
  1988年   205篇
  1987年   127篇
  1986年   102篇
  1985年   63篇
  1984年   30篇
  1983年   20篇
  1982年   31篇
  1981年   23篇
  1980年   37篇
  1979年   20篇
  1976年   14篇
  1975年   9篇
  1959年   7篇
  1951年   7篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
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   
72.
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   
73.
Recently, InE has been regarded as a popular education strategy in Chinese universities. However, problems have been exposed in the adoption of InE, for example, in InE courses and competitions. The purpose of this paper is to provide a possible solution to the problems, which is to organize effective InE courses by integrating InE with Inter-Course-level Problem-Based Learning (ICPBL). A detailed case is demonstrated by an ICPBL elective course design with deep integration of InE in the teaching, learning, and assessments. This paper contributes to a new curriculum design for promoting InE education in practically for Chinese universities.  相似文献   
74.
75.
锰粉料制块是解决铁合金冶炼精料入炉的主要途径之一,生产过程中为解决锰粉料粘附计量斗的问题,介绍了一种新型计量斗,阐述他的结构特点和工作原理,实施改进后下料流畅,降低了劳动强度,提高了生产效率。  相似文献   
76.
NO2 fission is regarded to be the most important initial decomposition process of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20). In this study, four CL-20 conformers based on the ε-CL-20 were obtained after the optimization at m062x/cc-pvtz level, and the bond length, bond order and bond dissociation energy of the N-N bonds were examined to investigate the stability of these bonds. In addition, the rate constants and activation energy of the NO2 fission were evaluated using the microcanonical variational transition state theory (μVT). The calculation results have shown that N-N bonds in the case of pseudo-equatorial and axial of nitro groups are the most stable and the least stable, respectively, by evaluating the bond length, bond order and minimum energy path (MEP). The NO2 fission rate constants are affected by not only the stability of N-N bonds but also the repulsion forces from the other nitro groups, and the fission process for pseudo-equatorial positioning of nitro groups is easier to be accelerated due to the increase of the repulsion forces. The decomposition of CL-20 conformer may mainly originate from the fission of the pseudo-equatorial positioning of nitro groups, especially for CL-20 III conformer because of the significant low activation energy.  相似文献   
77.
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   
78.
79.
Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics.  相似文献   
80.
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