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   1810篇
  免费   33篇
  国内免费   84篇
电工技术   55篇
综合类   48篇
化学工业   140篇
金属工艺   62篇
机械仪表   78篇
建筑科学   4篇
矿业工程   10篇
能源动力   103篇
武器工业   12篇
无线电   878篇
一般工业技术   356篇
冶金工业   13篇
原子能技术   37篇
自动化技术   131篇
  2023年   13篇
  2022年   16篇
  2021年   19篇
  2020年   27篇
  2019年   13篇
  2018年   12篇
  2017年   33篇
  2016年   29篇
  2015年   39篇
  2014年   70篇
  2013年   65篇
  2012年   49篇
  2011年   102篇
  2010年   74篇
  2009年   84篇
  2008年   79篇
  2007年   88篇
  2006年   110篇
  2005年   65篇
  2004年   56篇
  2003年   56篇
  2002年   55篇
  2001年   38篇
  2000年   57篇
  1999年   70篇
  1998年   104篇
  1997年   95篇
  1996年   104篇
  1995年   59篇
  1994年   29篇
  1993年   27篇
  1992年   37篇
  1991年   34篇
  1990年   40篇
  1989年   25篇
  1988年   36篇
  1987年   7篇
  1986年   3篇
  1985年   5篇
  1984年   1篇
  1976年   1篇
  1974年   1篇
排序方式: 共有1927条查询结果,搜索用时 234 毫秒
91.
This paper aims to provide a generic quantitative model to comprehensively assess the degree of collaboration with individual horizontal collaboration initiatives with a view to check feasibility for satisfying the customer requirements. The analytic hierarchy process–fuzzy logic model (AHP–FLM) approach is chosen for developing the model, a method that is often used to tackle complex strategic decision making that calls for subjective judgment based on well-established logical reasoning, rather than on simple feeling and intuition. In the process, the complex and unstructured problem for ‘compatibility test’ is broken down into elements, and then a customized hierarchy structure is set up to demonstrate the relationship between different hierarchy levels and among these elements. Each element may have a different level of importance for the horizontal collaboration. A fuzzy rule based collaboration intensity index (CII) is developed to build up the relationships among these evaluation attributes. Synthesizing the generic relative importance and the forecasted degree of collaboration, the proposed approach can determine the success of the collaboration initiative. An illustrative example of a semiconductor industry supply chain (SSC) member that intends to partner with a potential and competing candidate enterprise is developed to demonstrate the applicability of the proposed fuzzy strategic alliance selection framework and to measure the effectiveness of a horizontal collaboration initiative.  相似文献   
92.
An overview of pulsed laser-assisted methods for nanofabrication, which are currently developed in our Institute (LP3), is presented. The methods compass a variety of possibilities for material nanostructuring offered by laser–matter interactions and imply either the nanostructuring of the laser-illuminated surface itself, as in cases of direct laser ablation or laser plasma-assisted treatment of semiconductors to form light-absorbing and light-emitting nano-architectures, as well as periodic nanoarrays, or laser-assisted production of nanoclusters and their controlled growth in gaseous or liquid medium to form nanostructured films or colloidal nanoparticles. Nanomaterials synthesized by laser-assisted methods have a variety of unique properties, not reproducible by any other route, and are of importance for photovoltaics, optoelectronics, biological sensing, imaging and therapeutics.  相似文献   
93.
In this letter, novel hierarchical self-supported micropatterns of Cu2S polygonal laminae assembled on rod-shaped Cu2S crystals are successfully prepared by the template-free reaction of Cu2S and KCN in an aqueous phase. The influence induced by Cl ions on the self-supported micropatterns of Cu2S laminae is discussed on the basis of the experimental results.  相似文献   
94.
The semiconductor capacitances of the nitrogen-doped amorphous carbon (a-C:N) materials with different sp3/sp2 C ratios were studied as a function of electrode potential in a-C:N/aqueous electrolyte systems. This dependence of capacitance on electrode potential in aqueous 0.1 M NaOH shows that the investigated a-C:N materials are intrinsic semiconductors. The space-charge layers inside the a-C:N electrodes behave similar to a Helmholtz layer because of the presence of surface states when the electrolytes contain O2 or anions other than OH. The lower density and mobility of carriers of materials with a higher sp3 C fraction within the a-C:N material causes a suppression of redox reactions, and the lower density of carriers contributes to a lower capacitance.  相似文献   
95.
A simple wet chemical method has been used to synthesize selenium nanoparticles by the reaction of ionic liquid with sodium selenosulphate, a selenium precursor, in the presence of polyvinyl alcohol stabilizer, in aqueous medium. The method is capable of producing spherical selenium nanoparticles in the size range of 76-150 nm under ambient conditions. This is a first report on the production of nano-selenium assisted by an ionic liquid. The synthesized nanoparticles can be separated easily from the aqueous sol by a high-speed centrifuge machine, and can be re-dispersed in an aqueous medium. The synthesized selenium nanoparticles have been characterized by X-ray diffraction, energy dispersive X-ray analysis, differential scanning calorimetry and transmission electron microscopy techniques.  相似文献   
96.
A phaser-based processing technique was adopted in an UWB over fiber system employing SOA. The target is to simultaneously reduce the ASE noise impact and nonlinear effects inherent to optical amplification. Experimental results prove the effectiveness of chirping in terms of cross correlation and bit error rate.  相似文献   
97.
We investigate the influence of thermal effects on the high-speed performance of 1.3-μm InAs/GaAs quantum-dot lasers in a wide temperature range (5–50°C). Ridge waveguide devices with 1.1 mm cavity length exhibit small signal modulation bandwidths of 7.51 GHz at 5°C and 3.98 GHz at 50°C. Temperature-dependent K-factor, differential gain, and gain compression factor are studied. While the intrinsic damping-limited modulation bandwidth is as high as 23 GHz, the actual modulation bandwidth is limited by carrier thermalization under continuous wave operation. Saturation of the resonance frequency was found to be the result of thermal reduction in the differential gain, which may originate from carrier thermalization.  相似文献   
98.
Iron oxide n-Fe2O3 nanowire photoelectrodes were synthesized by thermal oxidation of Fe metal sheet (Alfa Co. 0.25 mm thick) in an electric oven then tested for their photoactivity. The photoresponse of the n-Fe2O3 nanowires was evaluated by measuring the rate of water splitting reaction to hydrogen and oxygen, which is proportional to photocurrent density, Jp. The optimized electric oven-made n-Fe2O3 nanowire photoelectrodes showed photocurrent densities of 1.46 mA cm−2 at measured potential of 0.1 V/SCE at illumination intensity of 100 mW cm−2 from a Solar simulator with a global AM 1.5 filter. For the optimized carbon modified (CM)-n-TiO2 synthesized by thermal flame oxidation the photocurrent density for water splitting was found to increase by two fold to 3.0 mA cm−2 measured at the same measured potential and the illumination intensity. The carbon modified (CM)-n-Fe2O3 electrode showed a shift of the open circuit potential by −100 mV/SCE compared to undoped n-Fe2O3 nanowires. A maximum photoconversion efficiency of 2.3% at applied potential of 0.5 V/Eaoc was found for CM-n-Fe2O3 compared to 1.69% for n-Fe2O3 nanowires at higher applied potential of 0.7 V/Eaoc. These CM-n- Fe2O3 and n- Fe2O3 nanowires thin films were characterized using photocurrent density measurements under monochromatic light illumination, UV-Vis spectra, X-ray diffraction (XRD) and scanning electron microscopy (SEM).  相似文献   
99.
研制了高功率非对称大光腔半导体激光器。脉冲阈值电流为4-5A,在工作电流为4倍阈值时,激光器单面输出峰值功率为10-12W,其灾变功率大于20W;得到了对称的远场光强分布;器件工作寿命大于1000小时。  相似文献   
100.
试验研究了三种半导体致冷电对金属化系统的拉伸强度,其中铋-镍-锡金属化系统与半导体致冷材料粘接强度最高,超过原始棒状材料的拉伸强度,它是半导体致冷器电对的最好的金属化系统。  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