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101.
利用神经网络控制连续浇铸过程中的热传导 总被引:2,自引:0,他引:2
In continuous casting, the cooling-solidification process must be based on the adaptation of heat transfer, which is directly connected to casting conditions such as casting speed, casting temperature, and cooling parameters. Most control schemes are based on the static relation between casting speed and water flow rate in each cooling zone; this constitutes an open loop that does not consider the dynamic surface temperature, which is an important parameter for the final slab quality. In steelmaking, the casting-speed changes affect the global heat transfer. An optimal operation requires an adjustment of the process control variables, i.e., global heat transfer. A learning neural network (NN) allows the identification and the control of a nonlinear heat transfer model in the continuous casting process. A heat transfer model was developed using the dynamic heat balance. A comparison between the experimental open loop results and those of the model simulation is considered. Following adaptation, the model is used for controlling the slab surface temperature in closed loop, using NN technology and PID controllers. The NN identification and control strategy gives a stable temperature closed loop control comparatively to the conventional PID. 相似文献
102.
Three new fuzzy neural networks learning algorithms based on clustering, training error and genetic algorithm 总被引:2,自引:2,他引:0
Three new learning algorithms for Takagi-Sugeno-Kang fuzzy system based on training error and genetic algorithm are proposed. The first two algorithms are consisted of two phases. In the first phase, the initial structure of neuro-fuzzy network is created by estimating the optimum points of training data in input-output space using KNN (for the first algorithm) and Mean-Shift methods (for the second algorithm) and keeps adding new neurons based on an error-based algorithm. Then in the second phase, redundant neurons are recognized and removed using a genetic algorithm. The third algorithm then builds the network in one phase using a modified version of error algorithm used in the first two methods. The KNN method is shown to be invariant to parameter K in KNN algorithm and in two simulated examples outperforms other neuro-fuzzy approaches in both performance and network compactness. 相似文献
103.
In human‐centric design, the human reach envelope is one of the most important components to help layout design for workstations, vehicles, and aircrafts. It also can help people to study the range of motion of different body segments. Various methods have been developed to determine human reach envelopes. This article presents different methods and common challenges. Human reach envelopes only give feedback concerning whether a point is reachable. This is not enough for the designers. The more important information the designers need to know is the zones with different discomfort levels. This capability is a powerful tool for ergonomic designers. In addition, a methodology for workspace solid zone differentiation or surface zone differentiation in the three‐dimensional space is presented. © 2008 Wiley Periodicals, Inc. 相似文献
104.
Reza M. Malek Abbaslou Jafar S. Soltan Mohammadzadeh Ajay K. Dalai 《Fuel Processing Technology》2009,90(7-8):849-856
A detailed review of the recent works regarding applications of supercritical media in Fischer–Tropsch synthesis (FTS) is presented. Differences in activity, CH4 and CO2 selectivity, hydrocarbon and olefin distributions, catalyst stability and heat transfer between supercritical Fischer–Tropsch syntheses (SC-FTS) and conventional gas phase Fischer–Tropsch synthesis (GP-FTS) are compared. The effects of temperature, pressure, solvent type, supercritical media/syngas molar ratio on SC-FTS are discussed. Finally selective production of wax via SC-FTS is briefly presented. Experimental analyses reveal that unique properties of supercritical media can improve FTS catalyst activity and selectivity in SC-FTS due to higher heat and mass transfer rates in comparison to GP-FTS. 相似文献
105.
The contribution of fly ash to the physical properties of cementitious mixtures has received considerable attention since its inclusion as an essential ingredient of High Performance Concrete (HPC). However, the chemical contribution to the overall structure development has not been fully understood because of the masking of its hydration products by those of cement. In a mixture of class-F fly ash and lime (Ca/Si=2), portlandite diminishes and C4AH13 forms due to addition of Al to solution. The latter converts to hydrogarnet and C3ASH4. CSH is detected at 3 days and continues to increase in intensity. The 29Si magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR) showed that the Al/Si ratio is 0.24 and the average chain length is 10 units. The presence of Al as approximately one-fifth of the Si in a chain length of 10 units suggests that Al tetrahedra may be present in bridging positions. 相似文献
106.
Manu Malek 《Journal of Network and Systems Management》2006,14(4):609-609
107.
108.
Fast prototyping of high-aspect ratio, high-resolution X-ray masks by gas-assisted focused ion beam 总被引:1,自引:1,他引:0
The capacity of chemically-assisted focused ion beam (FIB) etching systems to undertake direct and highly anisotropic erosion of thin and thick gold (or other high atomic number {Z}) coatings on X-ray mask membranes/substrates provides new levels of precision, flexibility, simplification and rapidity in the manufacture of mask absorber patterns, allowing for fast prototyping of high-aspect ratio, high-resolution masks for deep X-ray lithography for the LIGA process. In preliminary demonstrations, an automated FIB system operating at 30 keV with a gallium liquid metal source and an iodine gas injection system was used for direct milling into a few micrometer thick gold of microstructures into the sub-hundred nanometer regime. Three-dimensional micromachining in bulk diamond is also reported to illustrate the capability of the technique.This work was made possible under funding for California Institute of Technology from NASA general contract (# NAS7-1407), the partial funding for CAMD from the DARPA grant HI-MEMS Development and Manufacturing (contract # N66001-98-1-8926). Patrick Deshaye (Norsam) microsculpting work is also gratefully acknowledged.This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001. 相似文献
109.
Twenty patients with renal cell carcinoma in anatomically or functionally solitary kidneys were treated and followed for up to 18 years. Factors pertinent to management and survival of these patients and 66 other well documented similar patients reported in the literature are analyzed. Most of the patients were unusually young and a significant number had had nephrectomy for contralateral renal cell carcinoma. Survival was closely related to the earlier presence of malignant disease in the other kidney, the duration of the interval between detection of the 2 neoplasms and the stage of the lesion in the solitary kidney. Partial nephrectomy has been the most successful treatment. The mean survival in the Mayo Clinic series has been 6 years for patients still alive and 2.4 years for those dead at the time of this analysis. Results in this and other series emphasize the importance of thorough long-term followup after nephrectomy for hypernephroma and of aggressive therapy when the remaining kidney becomes involved. It is foolhardy to abandon hope merely because there is a malignant tumor in a solitary kidney. 相似文献
110.
Adjouadi M Sanchez D Cabrerizo M Ayala M Jayakar P Yaylali I Barreto A 《IEEE transactions on bio-medical engineering》2004,51(5):868-872
The objective of this study was to evaluate the feasibility of using the Walsh transformation to detect interictal spikes in electroencephalogram (EEG) data. Walsh operators were designed to formulate characteristics drawn from experimental observation, as provided by medical experts. The merits of the algorithm are: 1) in decorrelating the data to form an orthogonal basis and 2) simplicity of implementation. EEG recordings were obtained at a sampling frequency of 500 Hz using standard 10-20 electrode placements. Independent sets of EEG data recorded on 18 patients with focal epilepsy were used to train and test the algorithm. Twenty to thirty minutes of recordings were obtained with each subject awake, supine, and at rest. Spikes were annotated independently by two EEG experts. On evaluation, the algorithm identified 110 out of 139 spikes identified by either expert (True Positives = 79%) and missed 29 spikes (False Negatives = 21%). Evaluation of the algorithm revealed a Precision (Positive Predictive Value) of 85% and a Sensitivity of 79%. The encouraging preliminary results support its further development for prolonged EEG recordings in ambulatory subjects. With these results, the false detection (FD) rate is estimated at 7.2 FD per hour of continuous EEG recording. 相似文献