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   1132篇
  免费   23篇
  国内免费   4篇
电工技术   71篇
化学工业   360篇
金属工艺   37篇
机械仪表   33篇
建筑科学   23篇
能源动力   54篇
轻工业   129篇
水利工程   1篇
石油天然气   2篇
无线电   65篇
一般工业技术   147篇
冶金工业   76篇
原子能技术   79篇
自动化技术   82篇
  2023年   9篇
  2022年   6篇
  2021年   14篇
  2020年   9篇
  2019年   13篇
  2018年   18篇
  2017年   16篇
  2016年   20篇
  2015年   13篇
  2014年   22篇
  2013年   66篇
  2012年   39篇
  2011年   69篇
  2010年   45篇
  2009年   40篇
  2008年   48篇
  2007年   42篇
  2006年   36篇
  2005年   48篇
  2004年   37篇
  2003年   43篇
  2002年   43篇
  2001年   20篇
  2000年   21篇
  1999年   25篇
  1998年   58篇
  1997年   33篇
  1996年   29篇
  1995年   27篇
  1994年   25篇
  1993年   24篇
  1992年   13篇
  1991年   16篇
  1990年   14篇
  1989年   9篇
  1988年   13篇
  1987年   12篇
  1986年   12篇
  1985年   15篇
  1984年   10篇
  1983年   12篇
  1982年   12篇
  1981年   8篇
  1980年   12篇
  1979年   10篇
  1978年   4篇
  1977年   10篇
  1976年   4篇
  1975年   3篇
  1974年   4篇
排序方式: 共有1159条查询结果,搜索用时 15 毫秒
31.
A molecular valve, consisting of poly(acrylic acid) gel-coated Au mesh, was developed based on volume change of the gel in response to cation concentration. The valve closed when concentration of cations such as H+, Na+, K+, Ca2+, Cu2+, or Al3+ was low, whereas opened upon increase in its concentration. The valve re-closed when water was flowed. The concentration where the valve opens was found to increase in the order of Al3+, Ca2+, and Na+ (2 × 10−4, 5 × 10−4, and 6 × 10−3 M, respectively). The response to Cu2+ ion showed similar behaviour, but the opening concentration was ca. 2 × 10−4 M, which is lower than that of Ca2+ ion. The valve appeared to close over the pH range from 3 to 12, whereas to open below and above it. The fastest response time to open the valve (less than 1 min) was obtained for a solution of pH 1–2. The valve showed repeatability at least 25 cycles upon successive loading of a solution of pH 2 and water. Effects of anions and pressure were also studied.  相似文献   
32.
The virtual diving experience learning system of “Ama”, Japanese traditional female divers, has been developed to simulate how divers move in a virtual space using the diving interface and utilizing an accelerometer and a gyroscope. This interface not only detects the diving motion but also outputs the movement. Diving motion is shown in the ways of hand motion while standing. Although this makes it possible for a learner to understand the divers’ actions more clearly, this system’s difficulty is in visualizing a divers’ actions including their hands or bodies. Therefore, our study focuses on developing the operation system to reproduce actual ways of Amas’ diving with a virtual human body in a virtual space. First, the motion capture was done in an underwater condition. In the next process, the virtual human body was created. Finally, with the motion viewer, the more vivid actions of the Ama were successfully reproduced much more than in previous attempts. Using this system, the effectiveness of the Amas’ movement learning was confirmed, because a learner practices Amas’ movement.  相似文献   
33.
34.
In this paper the ensemble of independent factor analyzers (EIFA) is proposed. This new statistical model assumes that each data point is generated by the sum of outputs of independently activated factor analyzers. A maximum likelihood (ML) estimation algorithm for the parameter is derived using a Monte Carlo EM algorithm with a Gibbs sampler. The EIFA model is applied to natural image data. With the progress of the learning, the independent factor analyzers develop into feature detectors that resemble complex cells in mammalian visual systems. Although this result is similar to the previous one obtained by independent subspace analysis, we observe the emergence of complex cells from natural images in a more general framework of models, including overcomplete models allowing additive noise in the observables.  相似文献   
35.
Abstract— A polymer‐dispersed liquid‐crystal (PDLC) matrix template embedded with nano/microparticles can be backfilled/infiltrated with a dye‐doped liquid crystal for a paper‐like reflective display. In this way, a desirable degree of diffusion can be realized to reduce the viewing‐angle dependency of a gain reflector and metallic glare without changing other electro‐optical properties.  相似文献   
36.
Due to the opportunities provided by the Internet, more and more people are taking advantage of distance learning courses and during the last few years enormous research efforts have been dedicated to the development of distance learning systems. So far, many e-learning systems are proposed and used practically. However, in these systems the e-learning completion rate is about 30%. One of the reasons is the low study desire when the learner studies the learning materials. In this research, we propose an interactive Web-based e-learning system. The purpose of our system is to increase the e-learning completion rate by stimulating learner’s motivation. The proposed system has three subsystems: the learning subsystem, learner support subsystem, and teacher support subsystem. The learning subsystem improves the learner’s study desire. The learner support subsystem supports the learner during the study, and the teacher support subsystem supports the teacher to get the learner’s study state. To evaluate the proposed system, we developed several experiments and surveys. By using new features such as: display of learner’s study history, change of interface color, encourage function, ranking function, self-determination of the study materials, and grouping of learners, the proposed system can increase the learning efficiency.
Giuseppe De MarcoEmail:
  相似文献   
37.
During iron-carbon eutectic solidification, the coefficients for partition of a third element between the eutectic liquid and its solid were evaluated thermodynamically. The coefficientk M A/L for the equilibrium partition of the third element (M) between austenite and liquid iron largely depended on the interaction between carbon and the third element and a simplified method for the evaluation ofk M A/L was introduced. The coefficients,K S andK M, for the partition of the element between the eutectic liquid and its solid in the stable and metastable eutectic solidification, respectively, were also calculated fromk M A/L and the coefficientk M C/A for the equilibrium partition of the element between cementite and austenite. It was indicated by the thermodynamics of the free energy for the co-existing phases that the effect of a third element on graphitization occurring during eutectic solidification was related quantitatively to the value of K which was represented byK S-K M. The effect of a third element on the difference between the stable and metastable eutectic temperatures and on the carbon activity of liquid iron was closely related to K or the equilibrium partition coefficient,k M C/A .  相似文献   
38.
众所周知,微生物,如藻类、细菌、霉菌(真菌和酵母)以及病毒可在物品的表面寄生和存活,尤其是当死角、粗糙的表面或微缝中有残存的营养物质时,微生物…在聚合物表面的生长可导致褪色、污渍、臭味、生物膜、交叉感染并最终降低机械强度,降低产品使用寿命。汽巴可为解决上述的问  相似文献   
39.
Safety demonstration tests using the High Temperature Engineering Test Reactor (HTTR) will be conducted for the purpose of demonstrating inherent safety features of High Temperature Gas-cooled Reactors (HTGRs) as well as providing the core and plant transient data for validation of HTGR safety analysis codes. The first phase safety demonstration test items include the reactivity insertion test and the coolant flow reduction test. In the reactivity insertion test, which is the control rod withdrawal test, one pair out of 16 pairs of control rods is withdrawn, simulating a reactivity insertion event. The coolant flow reduction test consists of the partial loss of coolant flow test and the gas circulators trip test. In the partial loss of coolant flow test, primary coolant flow rate is slightly reduced by control system. In the gas circulators trip test one and two out of three gas circulators are run down, simulating coolant flow reduction events. The gas circulators trip tests, in which position of control rods are kept unchanged, are simulation tests of anticipated transients without scram (ATWS).  相似文献   
40.
Magnetic properties were investigated for the rare-earth 3d-transition metal oxides with the perovskite structure. Intriguing magnetic phenomena were reviewed for a few systems:magnetization peak effect in the titanates, magnetization reversal in the chromites and metallic ferromagnetism in the cobahites. The results suggest an important role of the rare-earth ions for the magnetic properties of such complex oxides.  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