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   1012篇
  免费   27篇
  国内免费   3篇
电工技术   53篇
化学工业   328篇
金属工艺   35篇
机械仪表   29篇
建筑科学   17篇
能源动力   37篇
轻工业   49篇
水利工程   3篇
无线电   70篇
一般工业技术   191篇
冶金工业   75篇
原子能技术   39篇
自动化技术   116篇
  2024年   1篇
  2023年   8篇
  2022年   15篇
  2021年   31篇
  2020年   11篇
  2019年   12篇
  2018年   11篇
  2017年   16篇
  2016年   24篇
  2015年   17篇
  2014年   26篇
  2013年   64篇
  2012年   50篇
  2011年   69篇
  2010年   38篇
  2009年   59篇
  2008年   70篇
  2007年   53篇
  2006年   46篇
  2005年   37篇
  2004年   34篇
  2003年   43篇
  2002年   34篇
  2001年   23篇
  2000年   18篇
  1999年   12篇
  1998年   28篇
  1997年   31篇
  1996年   17篇
  1995年   10篇
  1994年   17篇
  1993年   12篇
  1992年   8篇
  1991年   7篇
  1990年   10篇
  1989年   10篇
  1988年   10篇
  1987年   7篇
  1986年   7篇
  1985年   7篇
  1984年   6篇
  1983年   2篇
  1982年   6篇
  1981年   9篇
  1980年   3篇
  1979年   4篇
  1978年   5篇
  1976年   1篇
  1975年   1篇
  1973年   2篇
排序方式: 共有1042条查询结果,搜索用时 15 毫秒
31.
We report experimental results on enhanced backscattering from a plane mirror that is viewed through polymer-film-dispersed nematic liquid crystals. The distribution of the averaged intensity of the light reflected from the mirror placed behind the polymer film is investigated with an image-processing system when a Gaussian beam wave is incident. The enhanced light peak is observed in an incident beam direction, the result of which is predicted by a theory based on the circular Gaussian statistic random-phase-screen model. We pay attention to the enhancement dependence on parameters such as the distance between the polymer film and the flat mirror. The observed result is similar to a previous study by Jakeman et al. in which a random diffusive glass plate was used as a random-phase screen [J. Phys. D 21, 32 (1988)].  相似文献   
32.
In this paper, a streamline display method for magnetic flux density and magnetic field strength vectors in a three-phase induction motor model core is presented, and the relationship between streamlines and magnetic properties is investigated. It is possible to visualize the vector magnetic properties distribution by representing the magnetic flux density and the magnetic field strength vector with the streamlines. In addition, the time variation of the streamlines of the magnetic flux density and magnetic field strength vectors, and magnetic energy was compared. It was clear that the magnetic energy did not necessarily increase in the areas where the magnetic flux density and magnetic field strength increased because these vectors have the spatial phase difference.  相似文献   
33.
We are planning to develop the new Advanced Distribution Automation System (ADAS) equipped with optical communication network and sectionalizer with sensor for more grid reliability and efficiency on maintenance operation. The new system is featured with the function of fault cause or damaged part estimation. The new sectionalizer captures the waveform of electrical line surge originated by fault and the system analyzes the waveform for this function. This paper mainly introduces the system configuration of ADAS and an early stage examination of fault cause estimation technology.  相似文献   
34.
Centrifugal casting is a technology used for manufacturing hybrid rocket paraffin grains. This technology helps avoiding voids formation inside the solid paraffin as it cools. Voids are formed because of air bubbles being entrapped while pouring and because the liquid wax shrinks by 17–19% upon cooling. In this work, the centrifugal casting process for the manufacturing of paraffin cylinders was prototyped at two different scales considering critical casting issues. The effects of process parameters (rotational speed, melt temperature, and flow rate) on the tensile properties of the manufactured grains were analyzed. The results of the optimization conducted at the lower scale (2.5?kg) were up scaled to manufacture 25?kg grains. The resulting mechanical properties complied with the design specifications, and they were better than those characterized from the gravity cast wax. A numerical model of growth and dissolution of bubbles during the process was then developed to predict the quality of the castings. The numerical results showed how increasing the mold rotational speed up to 1800?rpm reduced the removal time. However, compared to grains solidification time, the predicted removal times were much shorter, proving the advantage of centrifugal casting in counteracting voids formation.  相似文献   
35.
We have proposed the concept of the virtual segment (VS), in which a global communication service is provided by combining a store–carry–forward scheme using vehicles with broadband wireless/wired network infrastructures along roads connected to the Internet. The VS can be a practical framework for non-real-time, asynchronous message transfer (especially for large messages) in a cost-effective manner. In this study, a critical implementation design issue, the message forward scheduling, in the VS approach is discussed and investigated through computer simulation by our developed VS simulator that has reflected the results of the field experiment for realistic performance evaluation.  相似文献   
36.
37.
This paper examines characteristics of interactive learning between human tutors and a robot having a dynamic neural-network model, which is inspired by human parietal cortex functions. A humanoid robot, with a recurrent neural network that has a hierarchical structure, learns to manipulate objects. Robots learn tasks in repeated self-trials with the assistance of human interaction, which provides physical guidance until the tasks are mastered and learning is consolidated within the neural networks. Experimental results and the analyses showed the following: 1) codevelopmental shaping of task behaviors stems from interactions between the robot and a tutor; 2) dynamic structures for articulating and sequencing of behavior primitives are self-organized in the hierarchically organized network; and 3) such structures can afford both generalization and context dependency in generating skilled behaviors.  相似文献   
38.
This paper presents an application of bidirectional transformation to the design and implementation of a novel editor supporting interactive refinement in the development of structured documents. The user performs a sequence of editing operations on a view of the document, and the editor automatically derives an efficient and reliable document source and a transformation that produces the document view. The editor is unique in its programmability, in the sense that transformations can be obtained through editing operations. It uses the view-updating technique developed in the database community and a new bidirectional transformation language that can describe not only the relationship between the document source and its view, but also the data dependency in the view.  相似文献   
39.
A compact electrostatic levitator was developed for the structural analysis of high-temperature liquids by x-ray diffraction methods. The size of the levitator was 200 mm in diameter and 200 mm in height and can be set up on a two axis diffractometer with a laboratory x-ray source, which is very convenient in performing structural measurements of high-temperature liquids. In particular, since the laboratory x-ray source allows a great amount of user time, preliminary or challenging experiments can be performed with trial and error, which prepares and complements synchrotron x-ray experiments. The present small apparatus also provides the advantage of portability and facility of setting. To demonstrate the capability of this electrostatic levitator, the static structure factors of alumina and silicon samples in their liquid phases were successfully measured.  相似文献   
40.
Inspired by recent studies regarding dendritic computation, we constructed a recurrent neural network model incorporating dendritic lateral inhibition. Our model consists of an input layer and a neuron layer that includes excitatory cells and an inhibitory cell; this inhibitory cell is activated by the pooled activities of all the excitatory cells, and it in turn inhibits each dendritic branch of the excitatory cells that receive excitations from the input layer. Dendritic nonlinear operation consisting of branch-specifically rectified inhibition and saturation is described by imposing nonlinear transfer functions before summation over the branches. In this model with sufficiently strong recurrent excitation, on transiently presenting a stimulus that has a high correlation with feed- forward connections of one of the excitatory cells, the corresponding cell becomes highly active, and the activity is sustained after the stimulus is turned off, whereas all the other excitatory cells continue to have low activities. But on transiently presenting a stimulus that does not have high correlations with feedforward connections of any of the excitatory cells, all the excitatory cells continue to have low activities. Interestingly, such stimulus-selective sustained response is preserved for a wide range of stimulus intensity. We derive an analytical formulation of the model in the limit where individual excitatory cells have an infinite number of dendritic branches and prove the existence of an equilibrium point corresponding to such a balanced low-level activity state as observed in the simulations, whose stability depends solely on the signal-to-noise ratio of the stimulus. We propose this model as a model of stimulus selectivity equipped with self-sustainability and intensity-invariance simultaneously, which was difficult in the conventional competitive neural networks with a similar degree of complexity in their network architecture. We discuss the biological relevance of the model in a general framework of computational neuroscience.  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