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   927篇
  免费   95篇
  国内免费   9篇
电工技术   23篇
综合类   1篇
化学工业   338篇
金属工艺   10篇
机械仪表   11篇
建筑科学   23篇
矿业工程   2篇
能源动力   34篇
轻工业   167篇
水利工程   9篇
石油天然气   17篇
无线电   70篇
一般工业技术   165篇
冶金工业   32篇
原子能技术   8篇
自动化技术   121篇
  2024年   2篇
  2023年   23篇
  2022年   54篇
  2021年   87篇
  2020年   59篇
  2019年   86篇
  2018年   79篇
  2017年   83篇
  2016年   74篇
  2015年   51篇
  2014年   61篇
  2013年   81篇
  2012年   44篇
  2011年   55篇
  2010年   30篇
  2009年   37篇
  2008年   20篇
  2007年   19篇
  2006年   16篇
  2005年   11篇
  2004年   9篇
  2003年   4篇
  2001年   2篇
  2000年   2篇
  1999年   3篇
  1998年   9篇
  1997年   4篇
  1996年   4篇
  1995年   5篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1987年   1篇
  1986年   1篇
  1984年   1篇
  1982年   2篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
排序方式: 共有1031条查询结果,搜索用时 15 毫秒
31.
32.
We have investigated a TPTQ state as an input state of a non-ideal ferromagnetic detectors. Minimal spin polarization required to demonstrate spin entanglement according to entanglement witness and CHSH inequality with respect to (w.r.t.) their two free parameters have been found, and we have numerically shown that the entanglement witness is less stringent than the direct tests of Bell’s inequality in the form of CHSH in the entangled limits of its free parameters. In addition, the lower limits of spin detection efficiency fulfilling secure cryptographic key against eavesdropping have been derived. Finally, we have considered TPTQ state as an output of spin decoherence channel and the region of ballistic transmission time w.r.t. spin relaxation time and spin dephasing time has been found.  相似文献   
33.
34.
In this study, carrot pomace powder (CPP) with particle sizes of 210 μm (CPP210) and 500 μm (CPP500) was added in the gluten‐free sponge cake recipe. Flour (rice and corn flour, 1:1, w/w) was replaced with 0, 10, 20 and 30% CPP. With increasing the level and particle size of CPP, batter density, viscosity, consistency and firmness increased. The control cake had a dense, hard texture, irregular shape and low sensory scores. These properties improved with addition of CPP so that the cake density, hardness and cohesiveness reduced, while symmetry index and sensory scores increased. Varying the particle size of CPP had no considerable effects on most of the batter and cake properties, while increasing the level of CPP had great positive effects on the quality of batter and cake. Overall, addition of 30% CPP with either of the particle sizes resulted in an acceptable gluten‐free cake.  相似文献   
35.
Inter-fuel substitution in the household sector depends on whether their target energy use is similar or not. To account for the effect of end-use application on energy demand, the concept of useful energy is utilized in which energy carriers are grouped according to their end-use applications. Useful energy is assumed as a commodity demanded to satisfy needs. Therefore, it should possess certain characteristics in accordance with the nature of basic needs. These characteristics were investigated through a two-level budgeting system with demographic variables indicating rural and urban households of Iran. The model has been applied to estimate the behavioural parameters such as income and price elasticities of useful energy demand. The estimated values of income and own-price elasticity show that all categories of useful energy are necessities with a relatively inelastic demand. Among them, cooling and non-substitutable electricity has the highest income and own-price elasticity, while lighting and water heating are ranked as the most necessary types of useful energy due to their low-income elasticity. In addition, small values of cross price elasticities support the idea that different types of useful energy are almost independent. Therefore, the results confirm that useful energy demands could be considered as basic needs.  相似文献   
36.
This study aimed to develop a nanoliposomal formulation containing α‐tocopherol loaded with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and to characterise the formulation by its physical stability. For this purpose, different nanoliposomal formulations with dipalmitoyl phosphocholine were prepared using a modified thin‐film hydration method and evaluated by particle size, polydispersity index (PDI), transmission electron microscopy, differential scanning calorimetry and determining the encapsulation efficiencies of DHA and EPA. A physical stability study was conducted by investigating the change in the vesicle encapsulation efficiency, particle size, PDI and shape when stored at 4, 30 and 40 °C for 3 months. High encapsulation efficiency of DHA and EPA (89.1% ± 0.6% and 81.9% ± 1.4%) and appropriate particle size (82 ± 0.8 nm) were obtained for liposomes composed of α‐tocopherol. The optimum formulation was stable for 90 days when kept at 4 °C. This study demonstrated that α‐tocopherol had a protective effect on the physical stability of the nanoliposomes containing DHA and EPA.  相似文献   
37.
Ni-based/SBA-15 catalysts, were promoted by 3wt % of samaria (Sm2O3), Yttria (Y2O3) and Zirconia (ZrO2), by two-solvent impregnation method. The catalysts characterization was performed by N2 adsorption–desorption, X-ray Diffraction (XRD), X-ray Fluorescence (XRF), High Resolution Transmission Electron Microscopy (HRTEM), Field Emission Electron Scanning Microscopy (FESEM), Temperature Programmed Oxidation/Reduction (TPO/TPR) and NH3-Temperature Programmed Desorption (NH3-TPD) techniques. Then, evaluated by CO2/methane reforming.The CO2/methane reforming outcomes revealed that samaria-promoted catalyst showed excellent activity, stability and cock resistance, while yttria-promoted catalyst just illustrated good activity at high temperature and zirconia-promoted catalyst didn't show any modification in catalytic performance in comparison to Ni-based catalyst with no promoter. Samaria-promoted TEM and TPR analysis, indicated adding samaria improved the NiO particles interaction with SBA-15 support pores wall and NiO dispersion. The TPO analysis displayed that coke deposition in samaria-promoted sample after 12 h reaction is less than yttria-promoted during stream of 5 h. Also, it is suggested that for samaria containing catalyst, cock deposition occurred on the support. Therefore, nickel active sites were preserved for time on stream of 12 h, which is the main reason for samaria-promoted catalyst superior stability than other's.  相似文献   
38.
39.
Electric vehicles (EVs) have a limited driving range compared to conventional vehicles. Accurate estimation of EV's range is therefore a significant need to eliminate “range anxiety” that refers to drivers' fear of running out of energy while driving. However, the range estimators used in the currently available EVs are not sufficiently accurate. To overcome this issue, more accurate range estimation techniques are investigated. Nonetheless, an accurate power‐based EV energy consumption model is crucial to obtain a precise range estimation. This paper describes a study on EV energy consumption modelling. For this purpose, EV modelling is carried out using MATLAB/Simulink software based on a real EV in the market, the BMW i3. The EV model includes vehicle powertrain system and longitudinal vehicle dynamics. The powertrain is modelled using efficiency maps of the electric motor and the power electronics' data available for BMW i3. It also includes a transmission and a battery model (ie, Thevenin equivalent circuit model). A driver model is developed as well to control the vehicle's speed and to represent human driver's behaviour. In addition, a regenerative braking strategy, based on a series brake system, is developed to model the behaviour of a real braking controller. Auxiliary devices are also included in the EV model to improve energy consumption estimation accuracy as they can have a significant impact on that. The vehicle model is validated against published energy consumption values that demonstrates a satisfactory level of accuracy with 2% to 6% error between simulation and experimental results for Environmental Protection Agency and NEDC tests.  相似文献   
40.
Multimedia Tools and Applications - Auto understanding of human activities in video is an increasing necessity in some application realms. The existing methods for human’s activity...  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