首页 | 官方网站   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   7856篇
  免费   766篇
  国内免费   18篇
工业技术   8640篇
  2024年   9篇
  2023年   109篇
  2022年   84篇
  2021年   307篇
  2020年   260篇
  2019年   281篇
  2018年   343篇
  2017年   353篇
  2016年   405篇
  2015年   316篇
  2014年   454篇
  2013年   579篇
  2012年   577篇
  2011年   721篇
  2010年   525篇
  2009年   551篇
  2008年   454篇
  2007年   317篇
  2006年   309篇
  2005年   246篇
  2004年   228篇
  2003年   190篇
  2002年   178篇
  2001年   113篇
  2000年   132篇
  1999年   121篇
  1998年   110篇
  1997年   84篇
  1996年   67篇
  1995年   53篇
  1994年   28篇
  1993年   18篇
  1992年   24篇
  1991年   18篇
  1990年   17篇
  1989年   9篇
  1988年   10篇
  1987年   8篇
  1986年   4篇
  1985年   8篇
  1984年   3篇
  1982年   3篇
  1981年   2篇
  1980年   4篇
  1979年   1篇
  1977年   2篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1966年   1篇
排序方式: 共有8640条查询结果,搜索用时 31 毫秒
41.
Fast DCT algorithm with fewer multiplication stages   总被引:1,自引:0,他引:1  
A novel fast DCT scheme with reduced multiplication stages and fewer additions and multiplications is proposed. The proposed algorithm is structured so that most multiplications tend to be performed at the final stage, which reduces the propagation error that could occur in the fixed-point computation. Minimisation of the multiplication stages can further decrease the error  相似文献   
42.
Multicomponent mass transfer accompanied by instantaneous chemical reactions in a small drop has been modeled and simulated for the case where two different solutes diffuse from a continuous phase into the drop and react rapidly with a third reactant in the drop. The computational results obtained by Galerkin’s finite element method are reported in terms of concentration profiles, the locations of reaction front, the cumulative mass flux, and the enhancement factor. The effects of physical parameters, such as diffusivities of the solutes and the reactant, the interfacial concentration of solutes, and the relative amount of the reactant, on the calculated quantities are discussed.  相似文献   
43.
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers.  相似文献   
44.
In a high-resolution flat panel system, a conventional interface that directly connects a liquid crystal display (LCD) controller to a flat panel cannot overcome the problems of excess EMI (electromagnetic interference) and power caused by full-swing transmission signals in parallel lines. This paper presents a high-speed digital video interface system implemented with a low-cost standard CMOS (complimentary metal-oxide-semiconductor) technology that can mitigate EMI and power problems in high-resolution flat panel display systems. The combined architecture of the high-speed, small number of parallel lines and low-voltage swing serial interface can support resolutions from VGA (640×480 pixels) up to XGA (1024×768 pixels) with significant power improvement and drastic EMI reduction. To support high-speed, low-voltage swing signaling and overcome channel-to-channel skew problems, a robust data recovery system is required. The proposed digital phase-locked loop enables robust skew-insensitive data recovery of up to 1.04 GBd  相似文献   
45.
The surface of a palladium-barium cathode was studied using scanning probe microscopy techniques. Data from the tunneling spectroscopy showed the pattern of the electron work function distribution over a microscopic region on the emitter surface. This pattern is compared to the distribution of various phases in the palladium-barium alloy employed.  相似文献   
46.
To provide authentication to the Diffie-Hellman key exchange, a few integrated key exchange schemes which provide authentication using the DSA signature have been proposed in the literature. In this letter we point out that all of the previous Diffie-Hellman-DSA schemes do not provide security against session state reveal attacks. We also suggest a strong Diffie-Hellman-DSA scheme providing security against session state reveal attacks as well as forward secrecy and key independence  相似文献   
47.
This study relates to the development of coatings for optical discs in high-density digital versatile disc systems (HD-DVD or blue lay disk) that use a high numerical aperture of 0.85 at 405 nm wavelength and have a protective top layer over a primer layer for protection against damage and dust. Ultraviolet-curable raw materials of two acrylic monofunctional monomers ( isobornylacrylate, IBA and tetrahydrofurfurylacrylate, THFA) and two kinds of urethaneacrylate oligomers (OUMD and OUME) have been easily mixed with photoinitiators. Curing rate of these materials was characterized by FT-IR. In case of top coats, VTES (vinyltriethoxysilane) and acrylic acid were added to enhance the abrasion resistance. These two kinds of UV-curable resinous materials having no solvent were synthesized and investigated as means for making a blue ray disk having good optical and mechanical properties. In addition, dynamic characteristics including reflectivity, fluctuation of RF signal and noise level were also investigated.  相似文献   
48.
This paper presents an investigation on the characteristics of damaged layer in micro-machining by using the ultrahigh-speed air spindle. The damaged layer in metal cutting is derived from plastic deformation and transformation of metal structure. In this study, micro-cutting force, surface roughness, and plastic deformation layer according to the variation of machining conditions were investigated by experiments. The damaged layer was measured using optical microscope for the samples prepared by metallographic techniques. Its scale was dependent on cutting process parameters, especially feed per tooth. According to experimental results, it was verified that the thickness of damaged layer was increased with increasing of feed per tooth and cutting depth, also thickness of damaged layer was reduced in down-milling compared to upmilling during micro-endmilling operation.  相似文献   
49.
In our study, we extracted the market, finance, and government factors determining R&D investment of individual firms in the IT industry in Korea. We collected the financial data of 515 individual firms belonging to IT and non‐IT industries between 1980 and 1999 from the Korea Investors Service's database and investigated the empirical relationship between the factors using an ordinary regression model, a fixed effects model, and a random effects model. The main findings of our study are as follows: i) The Herfindahl Index variable representing the degree of market concentration is statistically insignificant in explaining R&D expenditures in the IT manufacturing industry. ii) Assets, which is used as a proxy variable for firm size, have a positive and statistically significant coefficient. These two results suggest that the Schumpeterian Hypothesis may be only partially applied to the IT manufacturing industry in Korea. iii) The dividend variable has a negative value and is statistically significant, indicating that a tendency of high dividends can restrict the internal cash flow for R&D investment. iv) The sales variable representing growth potential shows a positive coefficient. v) The subsidy as a proxy variable for governmental R&D promotion policies is positively correlated with R&D expenditure. This suggests that government policy has played a significant role in promoting R&D activities of IT firms in Korea since 1980. vi) Using a dummy variable, we verified that firms reduced their R&D investments to secure sufficient liquidity under the restructuring pressure during Korea's 1998 and 1999 economic crisis.  相似文献   
50.
Bias-temperature instabilities (BTI) of HfO/sub 2/ metal oxide semiconductor field effect transistors (MOSFETs) have been systematically studied for the first time. NMOS positive BTI (PBTI) exhibited a more significant V/sub t/ instability than that of PMOS negative BTI (NBTI), and limited the lifetime of HfO/sub 2/ MOSFETs. Although high-temperature forming gas annealing (HT-FGA) improved the interface quality by passivating the interfacial states with hydrogen, BTI behaviors were not strongly affected by the technique. Charge pumping measurements were extensively used to investigate the nature of the BTI degradation, and it was found that V/sub t/ degradation of NMOS PBTI was primarily caused by charge trapping in bulk HfO/sub 2/ rather than interfacial degradation. Deuterium (D/sub 2/) annealing was found to be an excellent technique to improve BTI immunity as well as to enhance the mobility of HfO/sub 2/ MOSFETs.  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-23

京公网安备 11010802026262号