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101.
The current efficiency of polymer light-emitting diodes (PLEDs) were improved using a quantum dot interlayer between a hole transport layer and an emitting layer. The quantum dot interlayer played a role of controlling the hole transport in the PLEDs and enhanced the charge balance in the emitting layer. The current efficiency of the PLEDs was increased by more than 20% by the quantum dot interlayer. In particular, the efficiency improvement was significant at high luminance due to reduced efficiency roll-off in the quantum dot-embedded PLEDs. 相似文献
102.
Byung-Man Kwak Ji Eun Lee Jang-Hyuk Ahn Tae-Hong Jeon 《Journal of food engineering》2009,92(3):324-330
A laser diffraction particle sizing method involving wet analysis could be adapted effectively to measure the accurate particle size distribution of a spray-dried infant formula. Polar, polar aprotic and non-polar solvents, such as ethanol, methanol, acetone, pentane, heptane and hexane, were tested as dispersants for wet analysis. Non-polar solvents such as pentane, heptane and hexane found to be suitable dispersant because the shape of the infant formula particles in non-polar solvents was similar before and after the measurement while the particles had dissolved in the other solvents. The particle size distributions (PSD) of the infant formula determined by laser diffraction (Malvern Master Sizer, UK) using the dry analysis method with air was unsuitable because some parts of the primary and aggregated infant formula particles had been destroyed. The PSD graph of the air dispersion was shifted toward a smaller particle size from that of hexane dispersion. Overall, it is believed that laser diffraction particle sizing involving wet analysis with non-polar solvents may provide a suitable particle sizing method for infant formula products that is better than an air dispersion method. 相似文献
103.
Min-Soo Kim Sohyun Jeon Dae-Su Lee Soon-Jong Jeong Jae-Sung Song 《Journal of Electroceramics》2009,23(2-4):372-375
As a candidate for lead-free piezoelectric materials, Li2O excess 0.95(Na0.5K0.5)NbO3–0.05LiTaO3 (NKN-5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding Li2O as a sintering aid. Abnormal grain growth in NKN-5LT ceramics was observed with varying Li2O content. In the 1 mol% Li2O excess NKN-5LT samples sintered at 1000°C for 4 h in air, electromechanical coupling factor and piezoelectric constant of NKN-5LT ceramics were found to reach the highest values of 0.37 and 250 pC/N, respectively. Lead-free piezoelectric ceramic, Li2O excess NKN-5LT, multilayer ceramic actuators (MLCA) were fabricated. 10?×?10?×?1 mm3 size MLCAs were fabricated by conventional tape casting method. The displacement of Li2O excess NKN-5LT MLCA with 3 mm thickness was ~1 μm at 150 V. 相似文献
104.
Increasing the energy efficiency of manufacturing plants will reduce the production costs and environmental impact. In order to analyse and improve the energy efficiency of manufacturing plants, however, we need models to evaluate the energy footprints of the plants. A key challenge of estimating plant-level footprints is that systemic methods of connecting information on the product, machine and plant levels are not available. Thus, we propose methods to parameterise product-level elements and to model machine-level factors based on those elements. From the machine-level models, the proposed approach performs simulation experiments and provides the energy footprints in closed-form equations for the plant level. We also suggest that the resulting model can be combined with probabilistic techniques to benchmark the energy efficiency of plants at the industry level. In a case study, we demonstrate how to apply the proposed methods to estimate the energy footprint of a hypothetical plant. The procedures introduced here enable manufacturers to evaluate the energy consumption of their facilities at early stages of manufacturing, and provide tools to assess the energy efficiency of their plant by comparison with peers. 相似文献
105.
Triclosan (TCS), an antimicrobial agent, is an emerging and persistent environmental pollutant that is often found as a contaminant in surface waters and sediments; hence, knowledge of its degradability is important. In this study we investigated laccase-mediated TCS transformation and detoxification, using laccase (from the fungus Ganoderma lucidum) in the presence and absence of redox mediators. Transformation products were identified using HPLC, ESI-MS and GC-MS, and transformation mechanisms were proposed. In the absence of redox mediator, 56.5% TCS removal was observed within 24 h, concomitant with formation of new products with molecular weights greater than that of TCS. These products were dimers and trimers of TCS, as confirmed by ESI-MS analysis. Among the various mediators tested, 1-hydroxybenzotriazole (HBT) and syringaldehyde (SYD) significantly enhanced TCS transformation (∼90%). The presence of these mediators resulted in products with lower molecular weights than TCS, including 2,4-dichlorophenol (2,4-DCP; confirmed by GC-MS) and dechlorinated forms of 2,4-DCP. When SYD was used as the mediator, dechlorination resulted in 2-chlorohydroquinone (2-CHQ). Bacterial growth inhibition studies revealed that laccase-mediated transformation of TCS effectively decreased its toxicity, with ultimate conversion to less toxic or nontoxic products. Our results confirmed the involvement of two mechanisms of laccase-catalyzed TCS removal: (i) oligomerization in the absence of redox mediators, and (ii) ether bond cleavage followed by dechlorination in the presence of redox mediators. These results suggest that laccase in combination with natural redox mediator systems may be a useful strategy for the detoxification and elimination of TCS from aqueous systems. 相似文献
106.
Jin-sung Kim Jong-hyun Jeon Hoon Heo 《Journal of Mechanical Science and Technology》2013,27(2):549-556
The operation of a wind turbine generator involves natural uncertainty due to aerodynamic characteristics, resulting in a system that performs inefficiently. In general, the conventional controller now in wide use is not suitable for every operating point, because its tuning parameters and set-points do not meet the varying system characteristics. A study into an optimal control technique is conducted to reduce the negative effects of inherent uncertainty in system operation. In order to resolve the uncertainty problem, an optimal control method for an effective wind turbine generator is designed on the basis of a sensorless frame by utilizing a hybrid of the direct search optimization method (DSO) and the genetic algorithm (GA). This method is easy to implement and computation of functional derivatives is not necessary. The conventional GA is well known for its high performance in global optimization and its effectiveness in making ideal choices for control variables. The proposed DSO-GA hybrid differs from the conventional GA in terms of the sampling survey and the crossover operation. Moreover, the proposed multivariable optimal control strategy is a sensorless optimization technique that determines the pitch angle of the blades and the yaw angle of the nacelles to produce stable maximum power from a wind turbine system under steady-state operation. The proposed DSO-GA controller is implemented for a lab-scale wind turbine generator exposed to artificial wind, and the experimental results constitute a 3-D performance surface model of output voltage, which is used as an objective function for simulation. The optimization procedure with the objective function is carried out by means of the conventional and proposed methods, whose results reveal that the proposed DSO-GA optimizer yields far better performance in terms of generation number, convergence rate, and robustness. Both techniques are applied to a wind power generator through simulation and experiments. The performances are compared, and conclusions are drawn for each case. 相似文献
107.
A method and device for measuring glucose concentration in a scattering medium have been developed. A spectral range of 800-1800 nm is considered for wavelength selection because of its deeper penetration into biological tissue and the presence of a glucose absorption band. An algorithm based on selected wavelengths is proposed to minimize interference from other components. The optimal distance between the light source and the detector for diffuse reflectance measurement minimizes the influence of medium scattering. The proposed algorithm and measuring device are tested with a solution containing milk with added glucose. Glucose concentrations between 0 and 2000 mg/dl are determined with a correlation coefficient of 0.977. We also investigate the influence of concentration variations of other substances such as water, hemoglobin, albumin, and cholesterol when they are mixed in a scattering medium. 相似文献
108.
During steady state crack growth by diffusive cavitation at grain boundaries, crack tip fields are relaxed due to the presence of a cavitation zone. In the present analysis, analytic solutions for the actual crack tip stress fields and the crack velocity in the presence of cavitation zone consisting of continuously distributed cavities ahead of the crack tip are derived using the smeared volume concept. Results indicate that the r
–1/2 singularity is now attenuated to r
–1/2 + (0<<1/2) singularity. The singularity attenuation parameter is a function of the crack velocity and material parameters. The crack growth rate is related to the mode I stress intensity factor K by K
2 at relatively high load, K
n at intermediate load, and approaches zero at small load near K
th. Meanwhile, the cavitation zone extends further into the material due to the stress relaxation at the crack tip and the subsequent stress redistribution. Such relaxation effects become very distinct at low crack velocity and low applied load.
Key words: Creep crack growth, brittle material, diffusive cavity growth, sintering stress, crack tip stress field. 相似文献
109.
Shin H Lee KM Moon WK Jeon JU Lim G Pak YE Park JH Yoon KH 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2000,47(4):801-807
The feasibility of utilizing PZT films as future data storage media was investigated using a modified AFM. Applying voltages between a conductive AFM tip and the PZT films causes the switching of ferroelectric domains. The domains are observed using an EFM imaging technique. The experimental results and calculations revealed that the electrostatic force generated between the polarized area and the tip is a main contributor for the imaging of the polarized domains. The written features on ferroelectric films were less than 100 nm in diameter, implying the possibility of realizing data storage devices with ultra-high area density. The disappearance of the polarized images without any applied voltage was observed, which is a drawback in this application of PZT thin films. 相似文献
110.
A new technique for designing linear phase quadrature mirror filters (QMF) filters is proposed. These filters have the frequency responses of sharp and symmetrical transition characteristics, and the properties of perfect reconstruction and simple implementation.<> 相似文献