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   8815篇
  免费   802篇
  国内免费   16篇
电工技术   114篇
综合类   6篇
化学工业   2525篇
金属工艺   385篇
机械仪表   573篇
建筑科学   124篇
矿业工程   5篇
能源动力   393篇
轻工业   629篇
水利工程   16篇
石油天然气   12篇
无线电   1482篇
一般工业技术   2113篇
冶金工业   364篇
原子能技术   120篇
自动化技术   772篇
  2024年   8篇
  2023年   121篇
  2022年   166篇
  2021年   270篇
  2020年   216篇
  2019年   232篇
  2018年   289篇
  2017年   311篇
  2016年   370篇
  2015年   290篇
  2014年   421篇
  2013年   521篇
  2012年   657篇
  2011年   791篇
  2010年   510篇
  2009年   583篇
  2008年   494篇
  2007年   384篇
  2006年   316篇
  2005年   264篇
  2004年   269篇
  2003年   283篇
  2002年   248篇
  2001年   181篇
  2000年   178篇
  1999年   161篇
  1998年   176篇
  1997年   133篇
  1996年   117篇
  1995年   85篇
  1994年   64篇
  1993年   78篇
  1992年   55篇
  1991年   55篇
  1990年   36篇
  1989年   31篇
  1988年   31篇
  1987年   27篇
  1986年   21篇
  1985年   38篇
  1984年   24篇
  1983年   6篇
  1982年   13篇
  1981年   13篇
  1980年   19篇
  1979年   14篇
  1977年   10篇
  1976年   17篇
  1975年   9篇
  1974年   9篇
排序方式: 共有9633条查询结果,搜索用时 15 毫秒
11.
Food Science and Biotechnology - To determine the physiochemical properties of the 4-α-glucanotransferase from Bifidobacterium sp., the bllj_0114 gene encoding 4-α-glucanotransferase was...  相似文献   
12.
Metals and Materials International - This study investigated the influence of the initial grain size on the plastic deformation and tunnel defects that occurred from friction stir welding of...  相似文献   
13.
14.
A new excimer laser annealing (ELA) process that uses a floating amorphous-Silicon (a-Si) thin film with a multichannel structure is proposed for high-performance poly-Si thin-film transistors (TFTs). The proposed ELA method produces two-dimensional (2-D) grain growth, which can result in a high-quality grain structure. The dual-gate structure was employed to eliminate the grain boundaries perpendicular to the current flow in the channel. A multichannel structure was adapted in order to arrange the grain boundary to be parallel to the current flow. The proposed poly-Si TFT exhibits high-performance electrical characteristics, which are a high mobility of 504 cm/sup 2//Vsec and a low subthreshold slope of 0.337 V/dec.  相似文献   
15.
A new /spl lambda//4 bias line combined by a dumb-bell shaped defected ground structure (DGS) is proposed to suppress harmonics in power amplifiers. The proposed DGS bias line maintains the required high impedance even after DGS is inserted, while the width and length of the /spl lambda//4 bias line are broader and shorter than those of conventional bias lines. When the DGS bias line is used in power amplifiers, the third harmonic components as well as the second harmonic are reduced, because of the increased slow-wave effect over wide harmonic band. It is shown that the reduction of the third harmonic component, the improvement of 1 dB compression point, and power added efficiency are 26.5 dB, 0.45 dB, and 9.1%, respectively.  相似文献   
16.
Selective epitaxial growth (SEG) of silicon has attracted considerable attention for its good electrical properties and advantages in building microstructures in high‐density devices. However, SEG problems, such as an unclear process window, selectivity loss, and nonuniformity have often made application difficult. In our study, we derived processing diagrams for SEG from thermodynamics on gas‐phase reactions so that we could predict the SEG process zone for low pressure chemical vapor deposition. In addition, with the help of both the concept of the effective supersaturation ratio and three kinds of E‐beam patterns, we evaluated and controlled selectivity loss and nonuniformity in SEG, which is affected by the loading effect. To optimize the SEG process, we propose two practical methods: One deals with cleaning the wafer, and the other involves inserting dummy active patterns into the wide insulator to prevent the silicon from nucleating.  相似文献   
17.
This paper investigates the catalytic ignition of the H2/O2/CO2 mixture on platinum in a stagnation flow at atmospheric pressure experimentally and numerically. We measure the ignition temperatures of the gas mixtures flowing towards resistively heated platinum with various composition ratios and various diluent gases of N2, Ar and CO2. Compared with N2 or Ar, the CO2 dilution shows higher ignition temperature by about 50 K, even at the same composition ratio. The ignition temperature increase is proportional to the dilution ratio. Through the numerical simulation, it is illustrated that higher ignition temperature is caused by the adsorption of CO2 and following dissociation on platinum surface, which was to date considered negligible in catalytic combustion.  相似文献   
18.
Accidents in different complex sociotechnical systems are rarely compared using the same theoretical framework for risk management. We conducted a comparative analysis of two Canadian public health disasters involving drinking water distribution systems, the North Battleford Cryptosporidium parvum outbreak in April 2001 and the Walkerton E. coli outbreak in May 2000. Both accidents resulted from a complex interaction between all levels of a complex sociotechnical system. However, the low-level physical and individual factors differed in the two cases, whereas, the high-level governmental and regulatory factors tended to be the same. These findings may have implications for the design of public policies to minimize risk in complex sociotechnical systems.  相似文献   
19.
A number of checkpointing and message logging algorithms have been proposed to support fault tolerance of mobile computing systems. However, little attention has been paid to the optimistic message logging scheme. Optimistic logging has a lower failure-free operation cost compared to other logging schemes. It also has a lower failure recovery cost compared to the checkpointing schemes. This paper presents an efficient scheme to implement optimistic logging for the mobile computing environment. In the proposed scheme, the task of logging is assigned to the mobile support station so that volatile logging can be utilized. In addition, to reduce the message overhead, the mobile support station takes care of dependency tracking and the potential dependency between mobile hosts is inferred from the dependency between mobile support stations. The performance of the proposed scheme is evaluated by an extensive simulation study. The results show that the proposed scheme requires a small failure-free overhead and the cost of unnecessary rollback caused by the imprecise dependency is adjustable by properly selecting the logging frequency.  相似文献   
20.
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