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   2891篇
  免费   105篇
  国内免费   2篇
电工技术   12篇
综合类   1篇
化学工业   579篇
金属工艺   20篇
机械仪表   36篇
建筑科学   147篇
矿业工程   5篇
能源动力   61篇
轻工业   338篇
水利工程   23篇
石油天然气   5篇
无线电   139篇
一般工业技术   411篇
冶金工业   928篇
原子能技术   2篇
自动化技术   291篇
  2023年   20篇
  2022年   68篇
  2021年   77篇
  2020年   39篇
  2019年   46篇
  2018年   67篇
  2017年   65篇
  2016年   49篇
  2015年   59篇
  2014年   68篇
  2013年   146篇
  2012年   133篇
  2011年   176篇
  2010年   125篇
  2009年   146篇
  2008年   135篇
  2007年   135篇
  2006年   127篇
  2005年   117篇
  2004年   100篇
  2003年   82篇
  2002年   102篇
  2001年   51篇
  2000年   62篇
  1999年   66篇
  1998年   52篇
  1997年   50篇
  1996年   65篇
  1995年   53篇
  1994年   50篇
  1993年   43篇
  1992年   43篇
  1991年   11篇
  1990年   31篇
  1989年   36篇
  1988年   30篇
  1987年   30篇
  1986年   28篇
  1985年   20篇
  1984年   29篇
  1983年   24篇
  1982年   26篇
  1981年   22篇
  1980年   16篇
  1979年   12篇
  1978年   8篇
  1977年   7篇
  1976年   8篇
  1975年   10篇
  1974年   8篇
排序方式: 共有2998条查询结果,搜索用时 15 毫秒
981.
We propose a powerful video filtering algorithm that exploits temporal and spatial redundancy characterizing natural video sequences. The algorithm implements the paradigm of nonlocal grouping and collaborative filtering, where a higher dimensional transform-domain representation of the observations is leveraged to enforce sparsity, and thus regularize the data: 3-D spatiotemporal volumes are constructed by tracking blocks along trajectories defined by the motion vectors. Mutually similar volumes are then grouped together by stacking them along an additional fourth dimension, thus producing a 4-D structure, termed group, where different types of data correlation exist along the different dimensions: local correlation along the two dimensions of the blocks, temporal correlation along the motion trajectories, and nonlocal spatial correlation (i.e., self-similarity) along the fourth dimension of the group. Collaborative filtering is then realized by transforming each group through a decorrelating 4-D separable transform and then by shrinkage and inverse transformation. In this way, the collaborative filtering provides estimates for each volume stacked in the group, which are then returned and adaptively aggregated to their original positions in the video. The proposed filtering procedure addresses several video processing applications, such as denoising, deblocking, and enhancement of both grayscale and color data. Experimental results prove the effectiveness of our method in terms of both subjective and objective visual quality, and show that it outperforms the state of the art in video denoising.  相似文献   
982.
983.
A new copper plating bath for electroless deposition directly on conductive copper-diffusion barrier layers has been developed. This plating bath can be operated at temperatures between 20 and 50°C and has good stability. High temperature processing allows for increased deposition rates and decreased specific resistivity values for the deposited copper films. Electroless Cu films deposited from this bath showed a conformal step coverage in high aspect ratio trenches and, therefore, are promising as seed layers for copper electroplating. The effect of the bath composition, activation procedure and processing temperature on the plating rate and morphology of the deposited copper has been studied and is presented here.  相似文献   
984.
In this work, mixing and co-gelation of Au nanoparticles (NPs) and highly luminescent CdSe/CdS core/shell nanorods (NRs) are used as tools to obtain noble metal particle-decorated macroscopic semiconductor gel networks. The hybrid nature of the macrostructures facilitates the control over the optical properties: while the holes are trapped in the CdSe cores, the connected CdSe/CdS NRs support the mobility of excited electrons throughout the porous, hyperbranched gel networks. Due to the presence of Au NPs in the mixed gels, electron trapping in the gold NPs leads to a suppressed radiative recombination, namely, quenches the fluorescence in certain fragments of the multicomponent gel. The extent of fluorescence quenching can be influenced by the quantity of the noble metal domains. The optical properties are monitored as a function of the NR:NP ratio of a model system CdSe/CdS:Au. By this correlation, it demonstrates that the spatial extent of quenching initiated by a single Au NP exceeds the dimensions of one NR, which the Au is connected to (with a length of 45.8 nm ± 4.1 nm) and can reach the number of nine NRs per Au NP, which roughly corresponds to 400 nm of total electron travel distance within the network structure.  相似文献   
985.
Free-standing discontinuous Cu-line patterns varying in line widths and interline distances in the range of a few micrometers were manufactured by combining photolithography and electrochemical deposition. Two principally different seed layers, polycrystalline Au and X-ray amorphous Ni-P, were applied prior to electrodeposition of the Cu lines as well as continuous Cu films, which were deposited as reference. The effect of the seed layer and the influence of the pattern design on surface topography and morphology of the deposits were studied by means of light optical and scanning electron microscopy (SEM). The growth behavior is related to the developing crystallographic texture of Cu-line patterns and continuous films, as determined from calculated orientation distribution functions (ODFs) on the basis of X-ray diffraction (XRD) pole figure measurements. While strong crystallographic textures of Cu lines on polycrystalline Au were observed with pattern-dependent differences to continuous films, almost no preferred grain orientations develop both for Cu lines and corresponding continuous films deposited on amorphous Ni-P.  相似文献   
986.
Discrete-Event Simulation is a powerful, but underexploited alternative for many kinds of physical experimentation. It permits what is physically impossible or unaffordable, to conduct and run related experiments in parallel, against each other. Comparative and Concurrent Simulation (CCS) is a parallel experimentation method that adds a comparative dimension to discrete-event simulation. As a methodology or style, CCS resembles a many-pronged rake; its effectiveness is proportional to the number of prongs—the number of parallel experiments. It yields information in parallel and in time order, rather than in the arbitrary order of one-pronged serial simulations. CCS takes advantage of the similarities between parallel experiments via the one-for-many simulation of their identical parts; if many experiments are simulated, then it is normally hundreds to thousands times faster than serial simulation. While CCS is a one-dimensional method, a more general, multi-dimensional or multidomain version is MDCCS. MDCCS permits parent experiments to interact and produce offspring experiments, i.e., to produce more, but smaller experiments, and many zero-size/zero-cost experiments. MDCCS is more general, informative, and faster (usually over 100:1) than CCS for most applications. It handles more complex applications and experiments, such as multiple faults, variant executions of a software program, animation, and others.From a forthcoming book by E. Ulrich, V. Agrawal, and J. Arabian, and a Ph.D. thesis on MDCCS by K.P. Lentz, Northeastern University.  相似文献   
987.
Water repellency is often generated by taking advantage of surface textures and low surface energy coatings such as the one afforded by long perfluorinated side‐chains polymers. However, new regulations are phasing out these polymers because of their related health and safety hazard concerns. This is a particular challenge for water‐repellent fabrics as consumers expect safer products with stable performance and new functionalities. In this work, an approach is developed that allows for iCVD deposition of durable, conformal short fluorinated polymers stabilized with a crosslinking agent. As a result, high hydrophobicity and low liquid adhesion are achieved simultaneously while maintaining initial substrate breathability. It is explained why this polymeric coating—1H,1H‐perfluorooctyl methacrylate co divinylbenzene—exhibits remarkable hydrophobic properties amidst a wide range of other possible candidates. In order to further enhance the dynamic water repellency performance, the chemical treatment is combined with physical texturing—obtained through microsandblasting, a process particularly suitable for fabrics—thus making this combined approach a suitable candidate to meet the industrial needs. This work paves the way for the development of environmentally friendly, highly repellent coatings for large volume production and the application of roll‐to‐roll coating techniques, and multifunctionalization of fabrics and wearable devices.  相似文献   
988.
Fabrication of a chemiresistive biosensor for detection of biomolecules is demonstrated on a high surface area, flexible electro‐spun nylon fiber mat. For the first time, the –OH functionalized conducting copolymer of 3,4‐ethylenedioxythiophene (EDOT) and 3‐thiopheneethanol (3‐TE) is synthesized and conformally deposited on the electro‐spun mats by oxidative chemical vapor deposition (oCVD). The free –OH functional groups of the copolymer are available for immobilization of analyte specific biomolecules. Here, avidin and biotin molecules are employed as the analyte‐specific molecule and analyte respectively for their high specificity to each other. The sensitivities of avidin immobilized conducting copolymer on electro‐spun mats are tested against micro‐molar to nano‐molar concentrations of biotin in aqueous solutions. Application of electro‐spun fiber mat in this case enhances the sensor response 6 times when compared to a flat substrate and also significantly lowers the response time. In addition to the experimental studies, current work also includes modeling of the kinetics of the change of response for the biotin‐avidin interactions as a function of time. Most importantly, this fabrication technique promises an extremely sensitive and field deployable method for the detection of other biomolecules, for example, food pathogens.  相似文献   
989.
We report a novel approach for producing carbon nanotube fibers (CNF) composed with the polysaccharide agarose. Current attempts to make CNF's require the use of a polymer or precipitating agent in the coagulating bath that may have negative effects in biomedical applications. We show that by taking advantage of the gelation properties of agarose one can substitute the bath with distilled water or ethanol and hence reduce the complexity associated with alternating the bath components or the use of organic solvents. We also demonstrate that these CNF can be chemically functionalized to express biological moieties through available free hydroxyl groups in agarose. We corroborate that agarose CNF are not only conductive and nontoxic, but their functionalization can facilitate cell attachment and response both in vitro and in vivo. Our findings suggest that agarose/CNT hybrid materials are excellent candidates for applications involving neural tissue engineering and biointerfacing with the nervous system.  相似文献   
990.
ABSTRACT

The explosion in the literature in the area of technology management indicates a need for some integration of concepts and issues. This article defines and discusses a Strategic Technology Management System (STMS), which meets this need. The STMS delineates a systems life cycle approach to technology management, which includes eight phases: creation, monitoring, assessment, transfer, acceptance, utilization, maturity, and decline. Each phase includes critical issues that must be managed in order for a firm to successfully control its product/service and process technology projects and programs. These critical issues are defined, and a number of industry examples are given to substantiate the STMS life cycle concept. Finally, several key performance factors for STMSs are discussed.  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