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   199342篇
  免费   10672篇
  国内免费   5388篇
电工技术   7834篇
技术理论   7篇
综合类   9675篇
化学工业   31352篇
金属工艺   11133篇
机械仪表   10233篇
建筑科学   11734篇
矿业工程   3981篇
能源动力   4567篇
轻工业   11151篇
水利工程   3335篇
石油天然气   7604篇
武器工业   878篇
无线电   22306篇
一般工业技术   30073篇
冶金工业   8063篇
原子能技术   1532篇
自动化技术   39944篇
  2024年   553篇
  2023年   2035篇
  2022年   3527篇
  2021年   4871篇
  2020年   3734篇
  2019年   3149篇
  2018年   17318篇
  2017年   16846篇
  2016年   12916篇
  2015年   5268篇
  2014年   5926篇
  2013年   6957篇
  2012年   10449篇
  2011年   17109篇
  2010年   15003篇
  2009年   11977篇
  2008年   13011篇
  2007年   13688篇
  2006年   6452篇
  2005年   6702篇
  2004年   4864篇
  2003年   4444篇
  2002年   3597篇
  2001年   2895篇
  2000年   3118篇
  1999年   3215篇
  1998年   2720篇
  1997年   2300篇
  1996年   2141篇
  1995年   1833篇
  1994年   1484篇
  1993年   1064篇
  1992年   871篇
  1991年   699篇
  1990年   491篇
  1989年   436篇
  1988年   362篇
  1987年   245篇
  1986年   167篇
  1985年   97篇
  1984年   65篇
  1983年   50篇
  1982年   63篇
  1981年   39篇
  1968年   43篇
  1966年   42篇
  1965年   47篇
  1959年   39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
101.
The paper describes some geotechnical properties of the soft soils in Guangzhou College City, China, which are difficult to both sample and test. Laboratory and in situ tests were carried out to assess the physical and mechanical indices of the soils. The data were statistically analyzed and linear regression undertaken such that equations could be developed by which the geotechnical properties of the soft soils can be predicted. The statistical validity of the degree of correlation confirmed that using these equations, the mechanical indices can be estimated from physical indices determined by routine testing.   相似文献   
102.
Clathrate compounds are crystalline materials formed by a physical interaction between host and relatively light guest molecules. Various types of nano-sized cages surrounded by host frameworks exist in the highly unique crystalline structures and free guest molecules are entrapped in an open host-guest network. Recently, we reported two peculiar phenomena, swapping and tuning, naturally occurring in the hydrate cages. Helium, one of the smallest light guest molecules, must be the challengeable material in the sense of physics and moreover possesses versatile applications in the field of superconductivity technology and thermonuclear industry. In this regard, we attempted for the first time to synthesize helium hydrates at moderate temperature and pressure conditions. According to inclusion phenomena, helium itself normally cannot form clathrate hydrates due to being too small molecularly without the help of hydrate former molecules (sI, sII, and sH formers). In this study, the hydrate equilibria of the binary clathrate hydrate containing tetrahydrofuran, helium, and water were determined at 2, 3, 5.56 THF mol%. Direct volumetric measurements were also carried out to confirm the exact amount of helium captured in the hydrate cages. Finally, the crystalline structure of the formed mixed hydrates was identified by powder X-ray diffraction, resulting in structure II.  相似文献   
103.
104.
A variant of the High Multiplicity Multiprocessor Scheduling Problem with C job lengths is considered, in which jobs can be processed only by machines not greater than a given index. When C=2, polynomial algorithms are proposed, for the feasibility version of the problem and for maximizing the number of scheduled jobs.  相似文献   
105.
106.
When deploying TTCN-3 at Nokia, we converted two TTCN-2 test systems to TTCN-3. We explain to which extend we have been able to do the conversion automatically. The conversion tool used provided a syntactically and semantically correct conversion of the TTCN-2 code. We define some improvements made on the tool to increase readability and maintainability of the resulting code. We cover aspects of converting also the non-TTCN-2 parts and describe the experiences we made as a set of lessons learnt.  相似文献   
107.
108.
109.
110.
The effect of carbon surface oxidation on platinum supported carbon particles (Pt/C) with nitric acid was investigated by cyclic voltammetry, electrochemical impedance spectroscopy, polarization experiments and chronoamperometry. Cyclic voltammograms, polarization curves and electrochemical impedance spectra showed that the treated catalyst had much larger active surface area and higher ionic conductivity than the untreated catalyst, and provided enhanced performance for oxygen reduction. The formation of acidic groups was examined by IR spectra. The Pt/C surface oxidation had a large effect on the performance of a gas diffusion electrode for oxygen reduction reaction.  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