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   2908篇
  免费   373篇
  国内免费   134篇
电工技术   156篇
综合类   209篇
化学工业   465篇
金属工艺   101篇
机械仪表   134篇
建筑科学   180篇
矿业工程   53篇
能源动力   75篇
轻工业   213篇
水利工程   41篇
石油天然气   94篇
武器工业   29篇
无线电   539篇
一般工业技术   474篇
冶金工业   108篇
原子能技术   24篇
自动化技术   520篇
  2024年   5篇
  2023年   49篇
  2022年   60篇
  2021年   118篇
  2020年   115篇
  2019年   109篇
  2018年   130篇
  2017年   101篇
  2016年   106篇
  2015年   113篇
  2014年   131篇
  2013年   192篇
  2012年   189篇
  2011年   201篇
  2010年   185篇
  2009年   206篇
  2008年   185篇
  2007年   176篇
  2006年   145篇
  2005年   135篇
  2004年   103篇
  2003年   112篇
  2002年   99篇
  2001年   68篇
  2000年   56篇
  1999年   63篇
  1998年   51篇
  1997年   30篇
  1996年   26篇
  1995年   31篇
  1994年   22篇
  1993年   5篇
  1992年   13篇
  1991年   8篇
  1990年   8篇
  1989年   6篇
  1988年   13篇
  1987年   4篇
  1986年   10篇
  1985年   2篇
  1984年   5篇
  1983年   4篇
  1982年   5篇
  1981年   6篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1977年   5篇
  1967年   1篇
  1965年   1篇
排序方式: 共有3415条查询结果,搜索用时 156 毫秒
1.
Han  Jing  Xie  Lun  Liu  Jing  Li  Xue 《Multimedia Tools and Applications》2020,79(23-24):16627-16644
Multimedia Tools and Applications - Understanding human emotions through facial expressions is key enabling technology for interactive robots. Most approaches of facial expression recognition are...  相似文献   
2.
This article discloses a new horizon for the application of peroxides in medical chemistry. Stable cyclic peroxides are demonstrated to have cytotoxic activity against cancer cells; in addition a mechanism of cytotoxic action is proposed. Synthetic bridged 1,2,4,5-tetraoxanes and ozonides were effective against HepG2 cancer cells and some ozonides selectively targeted liver cancer cells (the selectivity indexes for compounds 11 b and 12 a are 8 and 5, respectively). In some cases, tetraoxanes and ozonides were more selective than paclitaxel, artemisinin, and artesunic acid. Annexin V flow-cytometry analysis revealed that the active ozonides 22 a and 23 a induced cell death of HepG2 by apoptosis. Further study showed that compounds 22 a and 23 a exhibited a strong inhibitory effect on P-glycoprotein (P-gp/ABCB5)-overexpressing HepG2 cancer cells. ABCB5 is a key player in the multidrug-resistant phenotype of liver cancer. Peroxides failed to demonstrate a direct correlation between oxidative potential and their biological activity. To our knowledge this is the first time that peroxide diastereoisomers have been found to show stereospecific antimalarial action against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum. Stereoisomeric ozonide 12 b is 11 times more active than stereoisomeric ozonide 12 a (IC50=5.81 vs 65.18 μm ). Current findings mean that ozonides merit further investigation as potential therapeutic agents for drug-resistant hepatocellular carcinoma.  相似文献   
3.
Supermedia-enhanced Internet-based telerobotics   总被引:4,自引:0,他引:4  
This paper introduces new planning and control methods for supermedia-enhanced real-time telerobotic operations via the Internet. Supermedia is the collection of video, audio, haptic information, temperature, and other sensory feedback. However, when the communication medium used, such as the Internet, introduces random communication time delay, several challenges and difficulties arise. Most importantly, random communication delay causes instability, loss of transparency, and desynchronization in real-time closed-loop telerobotic systems. Due to the complexity and diversity of such systems, the first challenge is to develop a general and efficient modeling and analysis tool. This paper proposes the use of Petri net modeling to capture the concurrency and complexity of Internet-based teleoperation. Combined with the event-based planning and control method, it also provides an efficient analysis and design tool to study the stability, transparency, and synchronization of such systems. In addition, the concepts of event transparency and event synchronization are introduced and analyzed. This modeling and control method has been applied to the design of several supermedia-enhanced Internet-based telerobotic systems, including the bilateral control of mobile robots and mobile manipulators. These systems have been experimentally implemented in three sites test bed consisting of robotic laboratories in the USA, Hong Kong, and Japan. The experimental results have verified the theoretical development and further demonstrated the stability, event transparency, and event synchronization of the systems.  相似文献   
4.
Kutz  J.N. Wai  P.K.A. 《Electronics letters》1998,34(6):522-523
Based on a variational analysis, the authors demonstrate that the noise-induced Gordon-Haus timing jitter in a dispersion-managed soliton transmission system can be substantially reduced by appropriate placement of the amplifiers  相似文献   
5.
A series of small angle neutron scattering measurements on blends of normal polystyrene (PSH) and labelled (deuterated) polystyrene (PSD) have been made with concentrations of PSD from 5 to 50 mol %. It is shown that the single chain form factor of the polymer in bulk can be obtained from a single concentration measurement for any concentration of labelled molecules, providing the molecular weights of the parent and labelled molecules are the same and the molecular weight distributions are narrow.  相似文献   
6.
文章介绍了SOC设计流程,智能I/O处理器组成,在开发该处理器对VHDL源代码的优化问题。  相似文献   
7.
关于化粪池几个问题的探讨   总被引:1,自引:0,他引:1  
秦伦 《同煤科技》2002,(3):33-33,36
探讨化粪池在设计布置及使用管理中应注意的几个问题,以充分发挥化粪池在保护环境,减轻污染方面的作用。  相似文献   
8.
Current methods in alleviating the wall deposition problem in spray drying emphasize mainly controlling the stickiness of the drying particles and less attention is placed on the properties of the dryer wall. In this experimental study, the effect of wall surface properties on the deposition mechanism has been investigated. Properties considered in classifying different wall materials were surface energy, roughness, and dielectric properties. The model solution contained sucrose, representing low-molecular-weight sugars commonly encountered in spray drying of fruit and vegetable juices. The effect of wall properties on deposition was explored at different drying rates producing particles of different surface rigidity. Larger surface roughness produced higher deposition fluxes for particles with high impact velocity and moisture. Surface energy and surface roughness were found to have no significant effect for dry rigid particles at the middle and bottom elevation of the drying chamber. However, material with lower surface energy (Teflon) exhibited less deposition for rubbery particles at such elevations. Analysis shows that dielectric wall material (Teflon) tends to enhance deposition of dry particles because of attrition at the surface. Higher wall temperature was found to produce slightly more deposition. The results of this work give a general indication of the effect of wall material on the deposition problem and provide the fundamental understanding for further studies along this line. Proper selection of dryer wall material will provide potential alternatives for reducing the deposition problem.  相似文献   
9.
An analytic theory is presented which demonstrates that the noise induced Gordon-Haus timing jitter in arbitrary dispersion-managed transmission systems is reduced by the power-enhancement factor required to support a dispersion-managed solitons provided the path-average soliton period is much greater than the dispersion-map period. The analysis further predicts the behaviour of the amplitude, width, and quadratic chirp fluctuations due to the amplified spontaneous emission (ASE) noise  相似文献   
10.
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