全文获取类型
收费全文 | 1602篇 |
免费 | 129篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 33篇 |
综合类 | 12篇 |
化学工业 | 380篇 |
金属工艺 | 34篇 |
机械仪表 | 84篇 |
建筑科学 | 75篇 |
矿业工程 | 3篇 |
能源动力 | 109篇 |
轻工业 | 104篇 |
水利工程 | 30篇 |
石油天然气 | 67篇 |
无线电 | 112篇 |
一般工业技术 | 297篇 |
冶金工业 | 46篇 |
原子能技术 | 11篇 |
自动化技术 | 348篇 |
出版年
2024年 | 8篇 |
2023年 | 28篇 |
2022年 | 48篇 |
2021年 | 84篇 |
2020年 | 92篇 |
2019年 | 115篇 |
2018年 | 165篇 |
2017年 | 138篇 |
2016年 | 137篇 |
2015年 | 80篇 |
2014年 | 128篇 |
2013年 | 183篇 |
2012年 | 117篇 |
2011年 | 121篇 |
2010年 | 85篇 |
2009年 | 73篇 |
2008年 | 46篇 |
2007年 | 35篇 |
2006年 | 16篇 |
2005年 | 6篇 |
2004年 | 13篇 |
2003年 | 4篇 |
2002年 | 6篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1998年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有1745条查询结果,搜索用时 0 毫秒
991.
On Local Phase Equilibria and the Appearance of Nanoparticles in the Microstructure of Single‐Crystal Ni‐Base Superalloys 下载免费PDF全文
992.
Amirhossein Khodabakhshi Alireza Mashreghi Yazdan Shajari Seyed Hossein Razavi 《Transactions of the Indian Institute of Metals》2018,71(4):849-859
In this study, the effect of etchant type and etching conditions on the root and airfoil microstructure of a service-exposed IN738 turbine blade has been investigated. The microstructure of superalloy components used at high temperatures, in addition to the usual microstructural changes, experiences deterioration in micrometer dimensions. In order to investigate these changes, electrochemical etching was performed on the samples with the chemical solution including 80% phosphoric acid, solution containing Cr2O3 and 55% glycerol. Chemical etching was performed with marble and etchant solution containing 60% glycerol. The results in terms of specifying the deterioration effects on microstructure of the blade applied at high temperature, the amount of γ′ phase and the best etchant were investigated. Among the solutions used for chemical etching, the solution containing 10 ml HNO3, 50 ml HCl and 60 ml glycerol was appropriate for detection of segregations and dendrites, and among the electrochemical etching solutions, the Cr2O3 solution was found suitable for specifying γ′ precipitates’ morphology by scanning electron microscopy. In this research, the results of the quantitative analysis of the images provided by these etchants were also investigated. 相似文献
993.
Neural Processing Letters - In this paper, a class of infinite-horizon nonlinear optimal control problems is considered. The main idea is to convert the infinite horizon problem to an equivalent... 相似文献
994.
Energy‐cost‐aware flow shop scheduling considering intermittent renewables,energy storage,and real‐time electricity pricing 下载免费PDF全文
The industrial sector is one of the major energy consumers that contribute to global climate change. Demand response programs and on‐site renewable energy provide great opportunities for the industrial sector to both go green and lower production costs. In this paper, a 2‐stage stochastic flow shop scheduling problem is proposed to minimize the total electricity purchase cost. The energy demand of the designed manufacturing system is met by on‐site renewables, energy storage, as well as the supply from the power grid. The volatile price, such as day‐ahead and real‐time pricing, applies to the portion supplied by the power grid. The first stage of the formulated model determines optimal job schedules and minimizes day‐ahead purchase commitment cost that considers forecasted renewable generation. The volatility of the real‐time electricity price and the variability of renewable generation are considered in the second stage of the model to compensate for errors of the forecasted renewable supply; the model will also minimize the total cost of real‐time electricity supplied by the real‐time pricing market and maximize the total profit of renewable fed into the grid. Case study results show that cost savings because of on‐site renewables are significant. Seasonal cost saving differences are also observed. The cost saving in summer is higher than that in winter with solar and wind supply in the system. Although the battery system also contributes to the cost saving, its effect is not as significant as the renewables. 相似文献
995.
Evaluation of Data Mining Strategies for Classification of Black Tea Based on Image-Based Features 总被引:1,自引:0,他引:1
Adel Bakhshipour Alireza Sanaeifar Sayed Hossein Payman Miguel de la Guardia 《Food Analytical Methods》2018,11(4):1041-1050
In this study, a new procedure based on computer vision was developed for qualitative classification of black tea. Images of 240 samples from four different classes of black tea, including Orange Pekoe (OP), Flowery Orange Pekoe (FOP), Flowery Broken Orange Pekoe (FBOP), and Pekoe Dust One (PD-ONE), were acquired and processed using a computer vision system. Eighteen color features, 13 gray-image texture features, and 52 wavelet texture features were extracted and assessed. Two common heuristic feature selection methods: correlation-based feature selection (CFS) and principal component analysis (PCA), were used for selecting the most significant features. Seven of the primary features were selected by CFS as the most relevant ones, while PCA converted the original variables into 11 independent components. These final discriminatory vectors were evaluated by using four different classification methods including decision tree (DT), support vector machine (SVM), Bayesian network (BN), and artificial neural networks (ANN) to predict the qualitative category of tea samples. Among the studied classifiers, the ANN with 7–10–4 topology developed by CFS-selected features provided the best classifier with a classification rate of 96.25%. The other methods assayed provided slightly lower accuracies than ANN from 86.25% for BN till 87.50% for SVM and 88.75% for DT. In all the cases, the accuracy of the classifiers increased when using the CFS-selected features as input variables in front of PCA obtained ones. It can be concluded that image-based features are strong characterizing factors which can be effectively applied for tea quality evaluation. 相似文献
996.
This paper presents the thermodynamic evaluation of A390 hypereutectic Al–Si alloy (Al–17% Si–4.5% Cu–0.5% Mg) and alloys up to 10% Mg, using the Factsage® software. Two critical compositions were detected at 4.2% and 7.2% Mg where the temperatures of the liquidus, the start of the binary and of the ternary eutectic reaction are changed. These critical compositions show differences in the formation of Mg2Si intermetallic particles during the solidification interval. For compositions up to 4.2% Mg, the Mg2Si intermetallic phase first appears in the ternary eutectic zone. With Mg contents between 4.2% and 7.2%, Mg2Si particle appears in both the binary and ternary eutectic reactions. Above 7.2% Mg, it solidifies as a primary phase and also during the binary and ternary reactions. The calculated liquid fraction vs. temperature curves also showed a decrease of the eutectic formation temperature (knee point temperature) with the addition of Mg content up to 4.2% Mg. This temperature becomes almost constant up to 10% Mg. The calculation of eutectic formation temperature shows a good agreement with differential scanning calorimetry (DSC) tests. 相似文献
997.
In this paper, the polymer chain of rotator (PCOR) equation of state (EOS) was used together with an EOS/GE mixing rule (MHV1) and the Wilson's equation as an excess-Gibbs-energy model in the proposed approach to extend the capability and improve the accuracy of the PCOR EOS for predicting the Henry's constant of solutions containing polymers. The results of the proposed method compared with two equation of state (van der Waals and GC-Flory) and three activity coefficient models (UNIFAC, UNIFAC-FV and Entropic-FV) indicated that the PCOR EOS/Wilson's equation provided more accurate results. The interaction parameters of Wilson's equation were fitted with Henry's constant experimental data and the property parameters of PCOR, a and b, were fitted with experimental volume data (Tait equation). As a result, the present work provided a simple and useful model for prediction of Henry's constant for polymer solutions. 相似文献
998.
This paper presents the combined influence of heat-loss and radiation on the pyrolysis of biomass parti-cles by considering the structure of one-dimensional, laminar and steady state flame propagation in uniformly pre-mixed wood particles. The assumed flame structure consists of a broad preheat-vaporization zone where the rate of gas-phase chemical reaction is small, a thin reaction zone composed of three regions:gas, tar and char combustion where convection and the vaporization rate of the fuel particles are small, and a broad convection zone. The analy-sis is performed in the asymptotic limit, where the value of the characteristic Zeldovich number is large and the equivalence ratio is larger than unity (i.e. u 1? ≥ ). The principal attention is made on the determination of a non-linear burning velocity correlation. Consequently, the impacts of radiation, heat loss and particle size as the de-termining factors on the flame temperature and burning velocity of biomass particles are declared in this research. 相似文献
999.
Alireza Talebitaher Stuart Victor Springham Paul Maurice Edmund Shutler Paul Lee Rajdeep Singh Rawat 《Journal of Fusion Energy》2012,31(3):234-241
The coded aperture imaging (CAI) technique has been applied to investigate the spatial distribution of DD fusion in a deuterium
filled 1.6 kJ plasma focus (PF) device operated in its neutron-optimized regime. The coded mask has been fabricated in Havar
alloy with 20 × 20 pixels and 57 square holes (14% open area) using a Singer-set Cyclic Difference pattern. Five CAI cameras
were employed simultaneously: one placed on-axis (0°) and four at 45° to the PF axis. CR-39 polymer nuclear track detectors
were used to register proton tracks from D(d,p)T reactions. The detectors were covered by 75 μm Kapton film to stop all energetic
charged particles (mostly deuterons) other than the 3 MeV fusion protons. A de-convolution algorithm was applied to the measured
proton track coordinates to obtain images of the fusion source from the five directions. Typically (2–8) × 104 proton tracks were registered by each detector per shot. Also two beryllium fast-neutron detectors were employed simultaneously
to measure the associated neutron yield and anisotropy. The CAI images show the fusion source is a cigar-shaped region around
the pinch column with no indication of plasma column instabilities. The proton anisotropy is comparable to the measured neutron
anisotropy. 相似文献
1000.
Alireza MOHAMMADREZAEI Sadegh PAPARI Mousa ASADI Abas NADERIFAR Reza GOLHOSSEINI 《Frontiers of Chemical Science and Engineering》2012,6(3):253
The effect of iridium and iron impregnation of HZSM-5 zeolite on the methanol to propylene reaction (MTP) was investigated. The selectivities of propylene and other hydrocarbons, and the conversion of methanol were compared by performing MTP in a small pilot plant. The results indicate that HZSM-5 zeolite modified by iron and iridium increased propylene selectivity by 6.3% and 8%, respectively. The selectivity of propylene was higher for Ir/H-ZSM-5 than for Fe/H-ZSM-5, where Fe/H-ZSM-5 was more stable than Ir/H-ZSM-5. Analytic techniques, including X-ray diffraction, BET surface area, temperature-programmed desorption of ammonia, and inductively coupled plasma atomic emission spectroscopy, were used to characterize the modified zeolites as well as the parent zeolites. 相似文献