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   1079篇
  免费   34篇
  国内免费   3篇
电工技术   32篇
化学工业   254篇
金属工艺   27篇
机械仪表   28篇
建筑科学   26篇
矿业工程   2篇
能源动力   30篇
轻工业   104篇
水利工程   7篇
石油天然气   3篇
无线电   41篇
一般工业技术   187篇
冶金工业   241篇
原子能技术   25篇
自动化技术   109篇
  2023年   7篇
  2022年   29篇
  2021年   21篇
  2020年   12篇
  2019年   24篇
  2018年   20篇
  2017年   17篇
  2016年   25篇
  2015年   13篇
  2014年   38篇
  2013年   47篇
  2012年   56篇
  2011年   67篇
  2010年   40篇
  2009年   46篇
  2008年   51篇
  2007年   51篇
  2006年   40篇
  2005年   37篇
  2004年   32篇
  2003年   21篇
  2002年   31篇
  2001年   19篇
  2000年   13篇
  1999年   26篇
  1998年   88篇
  1997年   48篇
  1996年   34篇
  1995年   23篇
  1994年   25篇
  1993年   18篇
  1992年   8篇
  1991年   7篇
  1990年   3篇
  1989年   14篇
  1988年   11篇
  1987年   7篇
  1986年   3篇
  1985年   4篇
  1984年   4篇
  1983年   3篇
  1981年   2篇
  1980年   3篇
  1979年   3篇
  1977年   4篇
  1976年   5篇
  1974年   2篇
  1973年   4篇
  1971年   2篇
  1969年   3篇
排序方式: 共有1116条查询结果,搜索用时 15 毫秒
41.
The structure and composition of the 1/4{110} twin boundary in alpha-Zn7Sb2O12 have been determined by using quantitative high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) analysis. The noise in the experimental HAADF STEM images is reduced by using the maximum entropy method and average processing, and the parameters used in dynamical simulations are experimentally determined. From the analysis, it has been found that octahedral sites in the twin boundary slightly shift parallel to the [110] direction, and a reduction of the Sb concentration at the octahedral sites on the plane adjacent to the twin boundary was detected. The reduction was measured from three regions in the same twin boundary, and the Sb concentrations were 4 +/- 3, 8 +/- 3 and 19 +/-2 at% from 33 at%.  相似文献   
42.
Epitaxial multilayer thin films of infinite-layer (Sr, Ca)CuO2 and perovskite (Sr, Ca)RuO3 have been prepared on (100) SrTiO3 substrates by multitarget rf magnetron sputtering. X-ray diffraction analyses revealed that the multilayer structure of (Sr, Ca)CuO3/(Sr, Ca)RuO3 was successfully fabricated with a minimum layer thickness of 20 Å. Transmission electron microscopy measurements of the multilayers indicated that there was no dislocation which normally exists in single-layer films with an infinite-layer structure. Resistivities of multilayer films at room temperature ranged from 1 to 10 m cm and showed semiconductor-like dependence against the temperature.  相似文献   
43.
The co–enzyme specificity of 3–isopropylmalate dehydrogenasefrom an extreme thermophile, Thermus thermophilus HB8, was changedfrom NAD to NADP by site–directed mutagenesis Based onsequence comparison of 3–isopropylmalate dehydrogenasesfrom various organisms with NAD– and NADP–dependentisocitrate dehydrogenases, Ser226, Ser253 and De279 of 3–isopropylmalatedehydrogenase were suggested as determining the co–enzymespecificity. These residues were replaced with the correspondingresidues of NADP–dependent isocitrate dehydrogenases;Arg, Gly and Tyr respectively. The single–mutated enzymes,S226R and I279Y, enhanced the activities towards NADP 10–and 3–fold respectively, whereas S253G reduced the activity.Among the multiple–mutated enzymes, the double–mutatedS226R/I279Y increased the catalytic efficiency against NADP( fold) and shifted the specificity for NAD towards NADP mostsignificantly ( 173–fold).  相似文献   
44.
The rotating dilution refrigerator has been built up and tested to study topology and dynamics of vortices in thin helium films in porous glasses. The torsional oscillator method is considered as the basic technique to be used. We are able to rotate the cryostat with angular velocity up to 6.3 rad/s and resolve changes of about 0.3 mrad/s. The 40mK minimum temperature of the cryostat does not change up to the highest angular velocities.  相似文献   
45.
Computational Visual Media - The exact shape of intracranial aneurysms is critical in medical diagnosis and surgical planning. While voxel-based deep learning frameworks have been proposed for this...  相似文献   
46.
Tamada  Tsutomu  Ueda  Yu  Kido  Ayumu  Yoneyama  Masami  Takeuchi  Mitsuru  Sanai  Hiroyasu  Ono  Kentaro  Yamamoto  Akira  Sone  Teruki 《Magma (New York, N.Y.)》2022,35(4):549-556
Magnetic Resonance Materials in Physics, Biology and Medicine - Image quality (IQ) of diffusion-weighted imaging (DWI) with single-shot echo-planar imaging (ssEPI) suffers from low signal-to-noise...  相似文献   
47.
48.
Abstract— To understand actual viewing conditions at home is important for TV design. And the preferred luminance level of LCD TVs under actual viewing conditions is also important in order to obtain both good picture quality and low power consumption. The actual viewing conditions of households and the preferred luminance levels was investigated. In a field test of 83 households, the display luminance, screen illuminance, and viewing locations were measured on site. In laboratory experiments, young and elderly subjects adjusted the luminance of an LCD‐TV screen to their preferred levels under different screen illuminance levels, angular screen sizes, and average luminance levels (ALL) of the images. As a result, two equations, which represent the preferred luminance level of LCD‐TV screens corresponding to different viewing conditions for young and elderly subjects were obtained. When the ALL of the images was 25% and the screen illuminance and angular screen size were set at 100 lx and 20°, respectively, the preferred luminance was 1 60 cd/m2 for the young subjects and 248 cd/m2 for the elderly subjects. By using the setting of the preferred luminance of an LCD TV under actual viewing conditions, it is possible to conserve energy consumption.  相似文献   
49.
This article presents the micro-electro-mechanical systems (MEMS) microrobot which demonstrates locomotion controlled by hardware neural networks (HNN). The size of the microrobot fabricated by the MEMS technology is 4 × 4 × 3.5 mm. The frame of the robot is made of silicon wafer, and it is equipped with a rotary-type actuator, a link mechanism, and six legs. The rotary-type actuator generates rotational movement by applying an electrical current to artificial muscle wires. The locomotion of the microrobot is obtained by the rotation of the rotary-type actuator. As in a living organism, the HNN realized robot control without using any software programs, A/D converters, or additional driving circuits. A central pattern generator (CPG) model was implemented as an HNN system to emulate the locomotion pattern. The MEMS microrobot emulated the locomotion method and the neural networks of an insect with the rotary-type actuator, the link mechanism, and the HNN. The microrobot performed forward and backward locomotion, and also changed direction by inputting an external trigger pulse. The locomotion speed was 0.325 mm/s and the step width was 1.3 mm.  相似文献   
50.
Animations of characters with flexible bodies such as jellyfish, snails, and, hearts are difficult to design using traditional skeleton‐based approaches. A standard approach is keyframing, but adjusting the shape of the flexible body for each key frame is tedious. In addition, the character cannot dynamically adjust its motion to respond to the environment or user input. This paper introduces a new procedural deformation framework (ProcDef) for designing and driving animations of such flexible objects. Our approach is to synthesize global motions procedurally by integrating local deformations. ProcDef provides an efficient design scheme for local deformation patterns; the user can control the orientation and magnitude of local deformations as well as the propagation of deformation signals by specifying line charts and volumetric fields. We also present a fast and robust deformation algorithm based on shape‐matching dynamics and show some example animations to illustrate the feasibility of our framework.  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