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   728篇
  免费   41篇
  国内免费   1篇
电工技术   9篇
综合类   1篇
化学工业   133篇
金属工艺   23篇
机械仪表   30篇
建筑科学   21篇
矿业工程   3篇
能源动力   40篇
轻工业   78篇
水利工程   9篇
石油天然气   1篇
无线电   77篇
一般工业技术   208篇
冶金工业   74篇
自动化技术   63篇
  2024年   1篇
  2023年   13篇
  2022年   25篇
  2021年   37篇
  2020年   24篇
  2019年   16篇
  2018年   37篇
  2017年   31篇
  2016年   34篇
  2015年   27篇
  2014年   46篇
  2013年   55篇
  2012年   32篇
  2011年   43篇
  2010年   31篇
  2009年   35篇
  2008年   35篇
  2007年   28篇
  2006年   28篇
  2005年   23篇
  2004年   25篇
  2003年   10篇
  2002年   8篇
  2001年   8篇
  2000年   3篇
  1999年   13篇
  1998年   5篇
  1997年   15篇
  1996年   9篇
  1995年   14篇
  1994年   13篇
  1993年   3篇
  1992年   3篇
  1991年   6篇
  1990年   2篇
  1989年   2篇
  1988年   7篇
  1987年   3篇
  1986年   1篇
  1985年   6篇
  1983年   1篇
  1982年   3篇
  1981年   1篇
  1979年   1篇
  1977年   1篇
  1976年   5篇
  1973年   1篇
排序方式: 共有770条查询结果,搜索用时 31 毫秒
761.
This work examines the boundary flow difficulties of the past and the heat transfer properties of Blasius and Sakiadis flows under prescribed concentration flux and prescribed heat flux. The nanofluid is also taken into account in this model, along with impacts from Brownian motion and thermophoresis. The modified system governing partial differential equations is numerically solved by using the R-K method along with the shooting technique. Various values of physical quantities like thermophoresis parameter, Brownian motion parameter, Eckert number, thermal radiation parameter, heat source parameter, and magnetic field parameter along with the C f , N u x , and S h x ${C}_{f},\unicode{x02007}N{u}_{x}\,,\unicode{x02007}\text{and}\unicode{x02007}S{h}_{x}$ were calculated using the temperature, concentration, and velocity profiles. Finally, we demonstrated how the Brownian motion, radiation, and thermophoresis parameters can significantly increase the temperature distributions. The concentration distributions were decelerated with an increase in Brownian motion parameters for both Blasius and Sakiadis cases.  相似文献   
762.
Bottom–up production of semiconductor nanomaterials is often accompanied by inhomogeneity resulting in a spread in electronic properties which may be influenced by the nanoparticle geometry, crystal quality, stoichiometry, or doping. Using photoluminescence spectroscopy of a population of more than 11 000 individual zinc-doped gallium arsenide nanowires, inhomogeneity is revealed in, and correlation between doping and nanowire diameter by use of a Bayesian statistical approach. Recombination of hot-carriers is shown to be responsible for the photoluminescence lineshape; by exploiting lifetime variation across the population, hot-carrier dynamics is revealed at the sub-picosecond timescale showing interband electronic dynamics. High-throughput spectroscopy together with a Bayesian approach are shown to provide unique insight in an inhomogeneous nanomaterial population, and can reveal electronic dynamics otherwise requiring complex pump-probe experiments in highly non-equilibrium conditions.  相似文献   
763.
Sagar  Bhanavath  M.V.N.  Sivakumar 《SILICON》2022,14(3):795-813
Silicon - This study presents the influence of alccofine-1203 (alccofine) on mechanical and microstructure characteristics of High Strength Concrete (HSC). A total of 7 binder proportions were...  相似文献   
764.

In the present research article, authors have experimentally evaluated the shock wave resistant properties of technologically potential materials of the anatase and the rutile phase TiO2 nanoparticles at the dynamic shock wave loaded conditions. The shock wave resistant behavior has been quantitatively drawn utilizing the crystallographic phase stability of the test samples for which the required crystallographic information has been extracted from the powder XRD patterns. Based on our observed experimental results as well as the respective interpretations, it is strongly authenticated that Rutile TiO2 NPs are suitable candidates for aerospace and defense industrial applications of materials fabrications because of the outstanding shock resistant properties than that of Anatase TiO2 NPs which undergo the crystallographic phase transition of rutile-TiO2 at shocked conditions.

  相似文献   
765.
The complex structured starch particles were reduced to the nanoscale size range through hydrolysis utilizing low concentration acid assisted by ultrasound irradiation. The synthesized starch nanoparticles (SNPs) were characterized by transmission electron microscopy (TEM), Fourier-transform infrared (FTIR), and X-ray diffraction (XRD) techniques. The synthesized SNPs possessed surface activated entities, as many cationic functional groups were confirmed through the FTIR spectrum. Also, these SNPs were effectively utilized to separate heavy Cu metal ions from the synthetic ion solution. The SNPs were characterized using field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) analysis for the surface modification after the adsorption process. The weak electrostatic interaction between the SNP surface and Cu ion was confirmed by the XPS spectrum and energy-dispersive X-ray spectroscopy. The maximum efficiency of Cu ions removal was about 93% at an optimal pH 5 and 25 mg/ml dosage. The adsorption equilibrium was obtained in 60 min. The nitrogen isotherm BET analysis of SNPs after adsorption shows a higher specific surface area of 18.552 m2/g, attributed to the interaction and presence of Cu ions on the SNP surface. The process feasibility was validated by the Langmuir isotherm model. The process exhibits pseudo-second-order adsorption kinetics and follows the Langmuir isotherm. The RL predicted by the Langmuir isotherm mechanism is 0.017, implying favourable adsorption. The process is reproducible and allows for the separation of heavy metal ions from the wastewater through biosorption effectively.  相似文献   
766.
Cognitive networks are stands out as intelligent technology which evolved to enhance spectrum utilization. Secondary users are allowed to utilize the primary user's frequency bands on idling times. Identifying the idle licensed spectrum is achieved through spectrum sensing. The spectrum holes should be explored such that a suitable spectrum can be selected and allocated to the secondary users. Existing spectrum sensing and selection schemes have limitations due to interferences. Thus, an optimization algorithm based on bio-inspired improved weed optimization was presented in this research work for enhanced channel utilization. The optimization model explores the channel characteristics and reduces the primary network interferences through its optimal solution. Further, Markov greedy-based auction scheme was presented for channel allocation. Considering the channel capacity, delay, and switching rates the allocation is performed to enhance the overall system performance. Simulation analysis demonstrates the superior performance of the proposed model over existing techniques like particle swarm optimization and genetic algorithm.  相似文献   
767.
768.
Sah  Dheeraj  Chitra  Lodhi  Kalpana  Kant  Chander  Srivastava  Sanjay K.  Kumar  Sushil 《SILICON》2022,14(15):9635-9642
Silicon - In the present work, a new process is reported to recover metallic contacts and wafer from the crystalline silicon solar cell through chemical etching. 2 M KOH was used as an...  相似文献   
769.
T.  Gangadharan  C.  Kailasanathan  P. R  Rajkumar  A.  Perumal.  K.R  Chitra Priya Darshini 《SILICON》2022,14(13):7483-7500
Silicon - The inorganic nanomaterial plays a crucial role in bone defect repair. Nano hydroxyapatite (nHAp) is the most important inorganic substance that closely resembles the mineral component of...  相似文献   
770.
Habitat suitability refers to the mechanism that enables organisms to choose suitable habitats to survive. In the present study, we studied the habitat suitability of young golden mahseer (fingerlings and juveniles) in the streams of the Ramganga River, one of the prominent rivers of the western Himalaya. Different habitat types and microhabitat features were documented. Habitat suitability was evaluated by generating habitat suitability criteria curves in response to varying habitat availability and use by young golden mahseer during different seasons. Generalised linear modelling (GLM) was used to analyse environmental characteristics responsible for selecting golden mahseer habitats. We studied mahseer based on body size into two main classes, that is, fingerlings (1.5–10 cm) and juveniles (10–30 cm). Golden mahseer fingerlings preferred mean depth (0.1–0.6 m) and mean stream velocity (0–0.2 m/s) at stream reach dominated by diverse substrate compositions such as sand, gravel, and small cobbles. Similarly, juveniles preferred mean depth (0.1–1.5 m) and mean water velocity (0.1–0.5 m/s), with cobbles, bedrock, and sand dominating their habitats. The GLM results indicated that dissolved oxygen, temperature, and water velocity were the significant factors influencing habitat suitability. High dissolved oxygen positively influenced fingerlings, whereas moderate to high water velocity affected juveniles the most. Therefore, to understand the flow requirement for threatened species like golden mahseer, it is essential to characterise critical habitats and develop criteria based on habitat suitability curves.  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