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   2047篇
  免费   153篇
  国内免费   1篇
电工技术   11篇
化学工业   617篇
金属工艺   32篇
机械仪表   54篇
建筑科学   77篇
矿业工程   2篇
能源动力   52篇
轻工业   485篇
水利工程   8篇
石油天然气   7篇
无线电   86篇
一般工业技术   280篇
冶金工业   130篇
原子能技术   13篇
自动化技术   347篇
  2024年   5篇
  2023年   19篇
  2022年   97篇
  2021年   119篇
  2020年   66篇
  2019年   73篇
  2018年   74篇
  2017年   71篇
  2016年   85篇
  2015年   68篇
  2014年   89篇
  2013年   154篇
  2012年   153篇
  2011年   138篇
  2010年   125篇
  2009年   133篇
  2008年   121篇
  2007年   90篇
  2006年   77篇
  2005年   57篇
  2004年   57篇
  2003年   42篇
  2002年   39篇
  2001年   34篇
  2000年   14篇
  1999年   22篇
  1998年   14篇
  1997年   20篇
  1996年   19篇
  1995年   17篇
  1994年   9篇
  1993年   12篇
  1992年   5篇
  1991年   4篇
  1990年   10篇
  1989年   6篇
  1988年   5篇
  1987年   5篇
  1986年   5篇
  1985年   5篇
  1984年   8篇
  1983年   6篇
  1982年   3篇
  1979年   7篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1974年   4篇
  1972年   3篇
排序方式: 共有2201条查询结果,搜索用时 31 毫秒
121.
Male pheromones are believed to attract females and repel male mice in open field tests but, when tested in more complex environments, they can attract male mice in usually avoided areas. Females were tested in an apparatus with one dark and one light side, in the absence or presence of male urine or the major urinary proteins (MUPs) bearing the natural ligands. Diestrous females were slower in leaving from the dark area when male urine or MUPs were present in it. Estrogen-primed females showed the opposite behavior, with an increase in the same latency. The light-avoidance behavior of prepubertal females, or females reared without males was not influenced by the presence of male chemosignals. The results show that adult female mice can react to MUP-borne volatiles as to adult male urine and use them as cues of male mice, if they were previously exposed to male cues during infancy. MUP-borne molecules are, thus, the olfactory trace of males in the environment and modulate mice exploratory behavior.  相似文献   
122.
This paper addresses in an integrated and systematic fashion the relatively overlooked but increasingly important issue of measuring and characterizing the geometrical properties of nerve cells and structures, an area often called neuromorphology. After discussing the main motivation for such an endeavour, a comprehensive mathematical framework for characterizing neural shapes, capable of expressing variations over time, is presented and used to underline the main issues in neuromorphology. Three particularly powerful and versatile families of neuromorphological approaches, including differential measures, symmetry axes/skeletons, and complexity, are presented and their respective potentials for applications in neuroscience are identified. Examples of applications of such measures are provided based on experimental investigations related to automated dendrogram extraction, mental retardation characterization, and axon growth analysis.  相似文献   
123.
This paper describes an adaptive neural control system for governing the movements of a robotic wheelchair. It presents a new model of recurrent neural network based on a RBF architecture and combining in its architecture local recurrence and synaptic connections with FIR filters. This model is used in two different control architectures to command the movements of a robotic wheelchair. The training equations and the stability conditions of the control system are obtained. Practical tests show that the results achieved using the proposed method are better than those obtained using PID controllers or other recurrent neural networks models  相似文献   
124.
Consciousness, Agents and the Knowledge Game   总被引:2,自引:0,他引:2  
This paper has three goals. The first is to introduce the “knowledge game”, a new, simple and yet powerful tool for analysing some intriguing philosophical questions. The second is to apply the knowledge game as an informative test to discriminate between conscious (human) and conscious-less agents (zombies and robots), depending on which version of the game they can win. And the third is to use a version of the knowledge game to provide an answer to Dretske’s question “how do you know you are not a zombie?”.  相似文献   
125.
The paper presents a real-time vision system to compute traffic parameters by analyzing monocular image sequences coming from pole-mounted video cameras at urban crossroads. The system uses a combination of segmentation and motion information to localize and track moving objects on the road plane, utilizing a robust background updating, and a feature-based tracking method. It is able to describe the path of each detected vehicle, to estimate its speed and to classify it into seven categories. The classification task relies on a model-based matching technique refined by a feature-based one for distinguishing between classes having similar models, like bicycles and motorcycles. The system is flexible with respect to the intersection geometry and the camera position. Experimental results demonstrate robust, real-time vehicle detection, tracking and classification over several hours of videos taken under different illumination conditions. The system is presently under trial in Trento, a 100,000-people town in northern Italy.  相似文献   
126.
127.
128.
Characterization of the behavior of an asynchronous system depending on the delay of components and wires is a major task facing designers. Some of these delays are outside the designer's control, and in practice may have to be assumed unbounded. The existing literature offers a number of analysis and specification models, but lacks a unified framework to verify directly if the circuit specification admits a correct implementation under these hypotheses.Our aim is to fill exactly this gap, offering both low-level (analysis-oriented) and high-level (specification-oriented) models for asynchronous circuits and the environment where they operate, together with strong equivalence results between the properties at the two levels. One interesting side result is the precise characterization of classical static and dynamic hazards in terms of our model. Consequently the designer can check the specification and directly decide if the behavior of any implementation will depend, e.g., on the delays of the signals described by such specification.We also outline a design methodology based on our models, pointing out how they can be used to select appropriate high and low-level models depending on the desired characteristics of the system.  相似文献   
129.
Chemical signals modulate aggressive behavior in mice. For example, male urinary cues enhance aggression against other adults: a resident mouse attacks a male but not a castrated intruder, unless it is anointed with male urine. Our purpose was to understand whether molecules excreted with urine also act as aggression triggers in a different context. Therefore, the effect of urine, or molecules purified from urine, voided by different animals (males or females), was tested on the aggression of male mice against pups. Latency to the first attack, percentage of pups receiving the first attack, and percentage of attacked pups after 5 and 15 min were recorded. At variance with intermale aggression, male urinary chemosignals sprayed on pups reduced infanticide, while female urine did not. Male urine also delayed infanticide when compared to female urine. Pups anointed with low molecular weight dialyzed urine and with the high molecular weight protein fraction were attacked later than controls. Pups anointed with Major Urinary Proteins (MUPs) also were attacked later. The volatiles retained by MUPs act in the same way as adult male urine. MUPs and their ligands did not modify biting of food items. The results show that mice do not perceive male chemosignals as compulsory aggression triggers but rather can consistently and differentially shape their behavior in response to the same molecules according to different contextual events.  相似文献   
130.
Identification of potent human anti-IL-1RI antagonist antibodies   总被引:4,自引:0,他引:4  
Interleukin-1 (IL-1) blockade by IL-1 receptor antagonist benefits some arthritis patients by reducing joint damage. This fact inspired us to develop antagonist human therapeutic antibodies against IL-1R(I) using phage libraries that display single-chain variable fragment (scFv) antibody fragments. Panning libraries against human IL-1R(I) generated 39 unique scFv-phage whose binding to IL-1R(I) was competed by IL-1 ligands. Fifteen of these scFv-phage, identified using IL-1R(I)-binding assays and dissociation rate ranking, were reformatted as scFv-Fc and IgG(4) molecules. The ease of producing antibodies in the scFv-Fc format permitted rapid identification of four lead clones (C10, C13, C14, C15) that inhibit NF-kappaB nuclear translocation induced by IL-1. Reformatting these clones as IgG(4) molecules increased their inhibition potency by 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