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   459篇
  免费   15篇
工业技术   474篇
  2024年   2篇
  2023年   2篇
  2022年   2篇
  2021年   12篇
  2020年   4篇
  2019年   12篇
  2018年   14篇
  2017年   15篇
  2016年   15篇
  2015年   5篇
  2014年   15篇
  2013年   38篇
  2012年   24篇
  2011年   39篇
  2010年   24篇
  2009年   26篇
  2008年   29篇
  2007年   25篇
  2006年   22篇
  2005年   18篇
  2004年   13篇
  2003年   14篇
  2002年   8篇
  2001年   6篇
  2000年   8篇
  1999年   7篇
  1998年   15篇
  1997年   5篇
  1996年   10篇
  1995年   5篇
  1994年   5篇
  1993年   6篇
  1992年   1篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   2篇
  1987年   2篇
  1986年   4篇
  1985年   2篇
  1983年   1篇
  1982年   2篇
  1981年   1篇
  1979年   1篇
  1978年   3篇
  1977年   1篇
  1976年   1篇
  1974年   1篇
  1973年   3篇
排序方式: 共有474条查询结果,搜索用时 125 毫秒
1.
Superconductivity in a tungsten-containing carbon-oxide film was reported. The film with 500 nm thickness was deposited onto polycrystalline silicon oxides using chemical vapor deposition and the co-sputtering of a tungsten metal target. The bonding state of the carbon atoms and the macroscopic and microscopic crystal structure of the film were investigated by Raman spectroscopy, X-ray diffraction and transmission electron microscopy measurements. From the experimental results, we determined that this film essentially had an amorphous structure. The temperature dependence on resistivity was measured in the temperature range of 2–300 K. Resistive superconducting transition was observed at 3.8 K. The dc magnetizations were measured in the temperature range of 1.8–6.5 K. The diamagnetism resulting from a superconductive state was observed below 3.75 K, which is consistent with a resistive superconducting transition. It is thought that the finite sized clusters of the different superconductive transition temperatures cooperatively produce a macroscopic superconducting phenomenon.  相似文献   
2.
In the first half of the paper, various types of processing pertaining to a polygon, using the 4×4 determinant theories are explained along with a new containment test algorithm of a point in a polygon. In the latter half of the paper, a general-purpose geometric processor, the POLYGON ENGINE, is presented which can deal with various types of interference problems, such as Boolean operations in solid modelling, hidden line and surface eliminations, ray tracing and so on. It is, a successor of the TRIANGLE PROCESSOR and is also based upon the 4×4 determinant theories [4–6]. While the TRIANGLE PROCESSOR processes a triangulated polygon on a triangle-by-triangle basis, the POLYGON ENGINE can treat a polygon without triangulation. The latter is expected to be more functional, more efficient and easier to use.  相似文献   
3.
Temperature dependence of the Raman spectrum of lithium oxide single crystal has been measured over a temperature range of 80 to 1073 K. The frequency shift and the line width of the Raman spectrum in lithium oxide were about 531 and 4.5 cm-1 at 80 K, respectively. At 1073 K, the frequency shift and the line width attained the values of 464 and 112 cm-1, respectively. The strong temperature dependence of the frequency shift and line width was compared with data from some crystals with a fluorite structure.  相似文献   
4.
The electrode characteristics of perovskite-type oxides, La0.6Sr0.4CoO3 and La0.6Sr0.4MnO3, on ceria-based oxide and stabilized zirconia were analysed by the a.c. impedance method. The ionic conductivities of the electrolyte and electrode conductivities from the a.c. impedance analysis agreed with those obtained from the current interruption and d.c. four-probe methods. Two semicircles from the charge transfer and diffusion processes appeared as the electrode resistance. The relative contribution of these two processes to the overall electrode resistance strongly depended on the microstructure of the electrode. The electrode microstructure could be controlled by the dispersion medium used for the electrode slurry. The La0.6Sr0.4MnO3 electrode coated with n-butyl acetate slurry exhibited the smallest electrode resistance.  相似文献   
5.
6.
This article considers the nature of online religion by examining the websites and religious counseling activities conducted by new Japanese religions. Beginning with an overview of the widespread use of the Internet in Japan and its use in religion, the article examines the cultural and social factors that keep the religious use of the Internet from becoming as pervasive in Japan as it is in the U.S. The article then describes a website with elements of online religion and the Internet-based religious counseling services being provided by ministers of the new Shintō-derived religions of Konkōkyō and Tenrikyō. These activities have successfully given some people who need religious assistance access to religious teaching. In concluding, the article examines the reasons for the success of these efforts, as well as the reasons why they have not expanded in scope, in light of the cultural and organizational advantages and disadvantages that affect Internet use.  相似文献   
7.
The human pelvis is such a unique structure that enables our upper body to work so perfectly with the two legs so as to control the body's balance in the complicated postures. The aim of this study is to establish a new dynamic body sway control model in the upright standing body position in coronal plane, and to reveal the possible control mechanisms underlying the body sway with special concerns on the roles that the pelvis and its muscles are performing during the sway. The plant of control model, the dynamics of human body, includes five parts, i.e. two ankles, two hips and one lumbosacral joint, which makes up a multi‐link inverted pendulum system, and is driven by two pairs of muscles, the psoas major (PM) and glutaeus medius (GM). Body sway records from eight healthy young subjects showed that the angular sway scopes of the ankle on roll (lateral) plane are 0.94±0.36± (eye‐open) and 1.35±0.52± (eye‐closed) respectively, while in lumbosacral plane, the scopes are 0.99±0.41± (eye‐open) and 1.27±0.72± (eye‐closed). The ankle and lumbosacral sways were almost in the same degree, yet their phase difference was near ±n, which means that the body trunk maintains perpendicular to horizon during the upright stance. Surface electromyographic (sEMG) activity from GM also showed the same evidence: the activated GM was always in the same side as the deviated center‐of‐pressure (COP). By assuming the corrective torque of posture is regulated by PID (proportional, integral and derivative) control, the body sway can be simulated by applying human physical parameters. Our study results demonstrated that the simulated traces are consistent with the experimental recorded, suggesting that the pelvis is an important structure for the posture maintenance and control, and the mechanism of balance keeping control during upright stance can be approximately taken as a PID control. The result also suggests a novel means for postural stability assessment in individual in the future.  相似文献   
8.
Platinum nanowires and nanoparticles were selectively synthesized in mesoporous silicas FSM-16 and HMM-1. The nanowires are 3 nm in diameter and several hundred nm to μm in length with high crystallinity. Pt nanowires and nanoparticles can be isolated by dissolving silica matrix with HF. The Pt wires extracted from organosilica HMM-1 have a nanonecklace structure, while the wires from siliceous FSM-16 have a nanorod structure. The extracted Pt nanoparticles (3 nm in size) on HOPG show the Coulomb staircase phenomena in STM/STS analysis. The mechanism for formation of the Pt nanowires is based on the migration of Pt ions in the mesoporous channels.  相似文献   
9.
This work faces the redundancy problem, a central concern in robotics, in a particular force-producing task by using muscle synergies to simplify the control. We extracted muscle synergies from human electromyograph signals and interpreted the physical meaning of the identified muscle synergies. Based on the human analysis results, we hypothesized a novel control framework that can explain the mechanism of the human motor control. The framework was tested in controlling a pneumatic-driven robotic arm to perform a reaching task. This control method, which uses only two synergies as manipulated variables for driving antagonistic pneumatic artificial muscles to generate desired movements, would be useful to deal with the redundancy problem; thus, suggesting a simple but efficient control for human-like robots to work safely and compliantly with humans.  相似文献   
10.
Attention has been increasingly paid to the partial oxidation of lower alkanes to synthesis gas, due to its intrinsic energy saving process. We studied the partial oxidation of ethane (POE) on Co loaded on various supports. The POE performance varied as follows: Y2O3, CeO2, ZrO2, La2O3  SiO2, Al2O3, TiO2 > MgO. Comparing Y2O3 and CeO2, the carbon deposition during the POE was negligible on CeO2 and therefore CeO2 was the most preferable support. By changing space velocity and O2 partial pressure, reaction mechanism of POE was studied and it was revealed that two-step mechanism was prevailing; combustion of ethane to H2O and CO2 and subsequent reforming of ethane with H2O and CO2 to synthesis gas. Co/CeO2 catalyst exhibited high and stable catalytic activity for 10 h; high ethane conversion of 18% (maximum ethane conversion 20% at O2/C2H6 = 0.2) with H2 and CO selectivities of 93 and 84%, respectively.  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