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91.
Ebrahim Fayyazi Seyed Mohamad Mousavi Gholamhassan Najafi 《Energy Sources, Part A: Recovery, Utilization, and Environmental Effects》2018,40(9):1125-1136
Nowadays, Biodiesel as an alternative, sustainable and less toxic fuel has been accepted by both researchers and industry. Developing process intensification reactors with the aim of reaching more efficient process has captured the attention of many researchers recently. In order to examine a novel reactor for biodiesel production using Waste Cooking Oil as a cost-effective feedstock, and KOH as an efficient homogeneous catalyst, the present study was developed to investigate three effective parameters (Oil flow rate, catalyst concentration and reaction temperature) focusing on transesterification reaction yield in the Simultaneous Mixer-Separator (SMS) reactor, designed and fabricated exclusively for biodiesel production at Tarbiat Modares University (TMU). As the findings indicated, rising the flow rate presented an increasing trend up to 15 mL/min and a decreasing trend was found after this level. Also, catalyst concentration up to 1% w/w showed an increasing trend which was significant. Analysis of reaction temperature showed that at 60°C the maximum yield is obtained. Furthermore, 15 mL/min oil flow rate, 1% w/w KOH concentration and 60?C were selected as the optimal reaction conditions for continuous biodiesel production. At this point, the produced biodiesel followed by the purification step reached the yield of 96%. The produced biodiesel physicochemical properties were found to meet ASTM D6751 standard. All in all, continuous production capability, higher productivity, simultaneous separation of products, and the successful handling of waste resources distinguish the SMS reactor as a potential and efficient process intensification reactor. 相似文献
92.
93.
A robust direct current control of DFIG wind turbine with low current THD based predictive approach 下载免费PDF全文
This paper presents a simple and robust direct current control based predictive approach for rotor side converter (RSC) of the doubly fed induction generator (DFIG), which operates at a constant switching frequency and has a fast dynamic response. First, sector of required rotor voltage vector is predicted in this strategy, and according to this predicted sector, two active vectors and two zero vectors are elected in each switching period. Derivatives of rotor current in the synchronous frame are determined for each predicted voltage vector in every period. These derivatives are used to compute the duration of the vectors in such a way that the current error at the end of the switching period gets minimized. The accuracy of the proposed control strategy under variation of rotor speed is evaluated in Matlab/Simulink environment for a 2 MW DFIG. Moreover, the impact of parameter variations on the system is examined for this suggested technique. Furthermore, the dynamic response and stator current total harmonic distortion (THD) of proposed strategy is compared with traditional vector control (VC), direct power control (DPC) and predictive direct power control (PDPC) methods. Finally, the performance of the proposed method is evaluated under disturbance voltage. The results demonstrate that suggested control technique has the lowest stator current THD and operates perfectly near the synchronous speed and under grid voltage dip. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
94.
Ebrahim Jahanshahi Javaran Mohammad Rahnama Saeed Jafari 《Advanced Powder Technology》2013,24(6):1109-1118
Using walls to introduce shear into a domain causes wall effects in the calculation of rheological properties of suspensions. Employing Lees–Edwards boundary conditions as an alternative method, removes these effects. Earlier methods of solid–fluid interactions in the framework of lattice Boltzmann method, such as Ladd and ALD methods, violate conservation law of the translational and rotational momentum (Galilean invariance). In the present study, Lees–Edwards boundary condition has been combined with smoothed profile method (SPM) intending to eliminate Galilean invariance errors. The combined method is validated by allowing a particle to cross a Lees–Edwards boundary. Moreover, third-order interpolation is used for particle distribution functions leaving the domain in the velocity gradient direction to eliminate bumps in the angular velocity of the particle when crossing the Lees–Edwards boundary. As another test case, two interacting circular cylinders placed in a sheared domain using Lees–Edwards boundary condition. Comparing results with the ones presented in the literature shows good agreement. 相似文献
95.
Divsalar A Damavandi SE Saboury AA Seyedarabi A Moosavi-Movahedi AA 《The Journal of dairy research》2012,79(2):209-215
The effect of copper(II) ions (Cu(+2)) on the structure of β-lactoglobulin (β-lg) was investigated spectroscopically using UV-visible, fluorescence and circular dichroism (CD) and calorimetrically using isothermal titration calorimetry (ITC), at different temperatures. Results of the UV-visible studies showed that adding Cu(+2) to β-lg solution caused increasing turbidity, indicative of protein aggregation. It was noticeable that the rate of increasing turbidity was directly proportional to increasing temperature. The far-UV CD studies displayed that the Cu(+2) cannot induce any significant changes in the secondary structures of β-lg at different temperatures. Also, the ITC data indicated that the binding process of Cu(+2) to β-lg is mainly entropically driven. The results highlight that copper ions cause the tertiary structure of β-lg to change and induce a slightly open structure leading to the formation of supramolecular aggregates in β-lg which may result in the reduced allergenicity of β-lg and its increased use in industrial applications. 相似文献
96.
Sana Sadeghi Alireza Rezvanian Ebrahim Kamrani 《AEUE-International Journal of Electronics and Communications》2012,66(9):772-779
Impulse noise reduction from corrupted images plays an important role in image processing. This problem will also affect on image segmentation, object detection, edge detection, compression, etc. Generally, median filters or nonlinear filters have been used for noise reduction but these methods will destroy the natural texture and important information in the image like the edges. In this paper, to eliminate impulse noises from noisy images, we used a hybrid method based on cellular automata (CA) and fuzzy logic called Fuzzy Cellular Automata (FCA) in two steps. In the first step, based on statistical information, noisy pixels are detected by CA; then using this information, the noisy pixel will change by FCA. Regularly, CA is used for systems with simple components where the behavior of each component will be defined and updated based on its neighbors. The proposed hybrid method is characterized as simple, robust and parallel which keeps the important details of the image effectively. The proposed approach has been performed on well-known gray scale test images and compared with other conventional and famous algorithms, is more effective. 相似文献
97.
Slussarenko S Karimi E Piccirillo B Marrucci L Santamato E 《Journal of the Optical Society of America. A, Optics, image science, and vision》2011,28(1):61-65
We present an optical scheme to encode and decode 2 bits of information into different orbital angular momentum (OAM) states of a paraxial optical beam. Our device generates the four light angular momentum states of order ±2 and ±4 by spin-to-orbital angular momentum conversion in a triangular optical loop arrangement. The switching among the four OAM states is obtained by changing the polarization state of the circulating beam by two quarter-wave plates, and the 2 bit information is transferred to the beam OAM exploiting a single q plate. The polarization of the exit beam is left free for an additional 1 bit of information. The switching among the different OAM states can be as fast as a few nanoseconds, if suitable electro-optical cells are used. This may be particularly useful in communication systems based on light OAM. 相似文献
98.
Mohammadreza Nabavitabatabayi Ebrahim ShiraniMohammad Hassan Rahimian 《International Communications in Heat and Mass Transfer》2011,38(1):128-138
This work investigates the heat transfer performance in an enclosure including nanofluids with a localized heat source. The velocity field is solved by multiple relaxation time lattice Boltzmann modeling (MRT) which has superior numerical advantages to single relaxation time lattice Boltzmann modeling (SRT); however, heat transfer is simulated separately using SRT-lattice Boltzmann modeling. The hydrodynamics and thermal fields are then coupled together using the Boussinesq approximation. The main objective of this study is to investigate the influence of several pertinent parameters such as Rayleigh number, solid particle volume fraction of nanoparticles, and the geometry as well as location of the localized heat source on the heat transfer performance of nanofluids. The results obtained from lattice Boltzmann modeling clearly indicate that heat transfer augmentation is possible using nano-fluids in comparison to conventional fluids, resulting in the compactness of many industrial devices. 相似文献
99.
This paper presents characteristic analysis of without permanent magnet brushless DC (WPMBLDC) motor by using three-dimensional (3-D) finite element method (FEM). The paper describes the complex magnetic structure and principle of the presented WPMBLDC motor in detail. The magnetic field distribution of the presented motor is numerically computed by 3-D FEM. The primary characteristics of the motor including magnetic flux density, flux linkage and inductance profile are obtained. A prototype WPMBLDC machine has also been built and tested; additionally, the accuracy of 3-D FE analysis is verified by comparing the calculated results with the experimental measured values. 相似文献
100.
Mehdi Alzamani Ali Shokuhfar Ebrahim Eghdam Sadegh Mastali 《Materials Science in Semiconductor Processing》2013,16(4):1063-1069
TiO2 photocatalytic film, annealed at temperatures of 500 °C and 700 °C, was prepared on SiO2 pre-coated glass via sol–gel technique for photocatalytic purposes and effects of catalyst-type on its properties were investigated by an X-ray diffractometer (XRD), Scanning Electron Microscope, UV–vis spectrophotometer, and contact angle measurements. The XRD results showed that present phases depend upon catalyst used in the solution and phase transformation behaves in a temperature-dependent manner. For the layers derived from sols containing acidic catalysts, the anatase structure dominated and exhibited much better photocatalytic activity. The results indicated that the sample derived from sol comprises H2SO4 as catalyst, and exhibits anatase grains with the lowest size. This could be the reason for its better photocatalytic activity. Finally, samples derived from sol containing acidic catalysts showed superhydrophilicity and superior cleaning ability. 相似文献