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991.
992.
Nong Xu Sang Moon Lee Sung Su Kim Anwu Li C. Jim Lim Farzam Fotovat 《Chemical Engineering Communications》2017,204(10):1157-1166
Different from traditional seeded method, NaA zeolite membranes (NZMs) were prepared by in situ synthesis onto the inner side of porous α-alumina tubular supports in a hydrothermal synthesis reactor. The influences of pretreatment of porous tubular support, temperature, time, and synthetic cycle for the synthesis of the zeolite membranes were investigated. The operating conditions were optimized. Characterization of the membranes by scanning electron microscopy and X-ray diffraction showed that the crystalline materials on the inner surface of the porous α-alumina tubes were NaA-type zeolite. Single- and binary-gas permeation tests were conducted. Single-component permeabilities of hydrogen and nitrogen through the NZM changed slightly when the transmembrane pressure difference varied from 80 to 420?kPa. Its selectivity for H2 relative to N2 was about 5.3, which was greater than that of the Knudsen diffusion. The separation factors of binary gases H2/N2 and H2/CO2 at 473?K were 3.9 and 5.7, respectively, again exceeding the Knudsen diffusion level. The separation of binary gases suggests that the NaA-type zeolite membranes on α-alumina substrate were defect free and able to provide molecular sieving. The results demonstrate that the unseeded synthetic method presented in this work is successful and reliable. 相似文献
993.
Mingyu Shin Hyun-Soo Lee Moonseo Park Myunggi Moon Sangwon Han 《Accident; analysis and prevention》2014
Construction accidents are caused by an unsafe act (i.e., a person's behavior or activity that deviates from normal accepted safe procedure) and/or an unsafe condition (i.e., a hazard or an unsafe mechanical or physical environment). While there has been dramatic improvement in creating safer construction environments, relatively little is known regarding the elimination of construction workers’ unsafe acts. To address this deficiency, this paper aims to develop a system dynamics (SD)-based model of construction workers’ mental processes that can help analyze the feedback mechanisms and the resultant dynamics regarding the workers’ safety attitudes and safe behaviors. The developed model is applied to examine the effectiveness of three safety improvement policies: incentives for safe behaviors, and increased levels of communication and immersion in accidents. Application of the model verifies the strong potential of the developed model to provide a better understanding of how to eliminate unsafe acts, and to function as a robust test-bed to assess the effectiveness of safety programs or training sessions before their implementation. 相似文献
994.
Dong-Seob Tark Dong Chan Moon Hee Young Kang Su-Ran Kim Hyang-Mi Nam Hee-Soo Lee Suk-Chan Jung Suk-Kyung Lim 《Journal of dairy science》2017,100(5):3463-3469
In this study, we aimed to assess trends in antimicrobial resistance and to investigate the characteristics of extended-spectrum β-lactamase (ESBL)-producing isolates from bovine mastitic milk from 2012 to 2015. A total of 374 Escherichia coli isolates were analyzed (154 in 2012, 113 in 2013, 76 in 2014, and 31 in 2015). No consistent trends in antimicrobial resistance of E. coli isolates occurred during the 4-yr period. The most frequently observed resistance was tetracycline (23.3%), followed by streptomycin (17.1%), ampicillin (16.6%), neomycin (11.8%), and trimethoprim/sulfamethoxazole (11.2%). Multidrug resistance was observed in 15.5% of isolates. Among these isolates, 15 (4.0%) carried one or more blaCTX-M and AmpC ESBL genes from 11 different farms, including blaCTX-M-15 at 4 farms, blaCTX-M-3 at 2 farms, blaCTX-M-1 at 3 farms, and blaCMY-2 at 3 farms. This study is the first report of blaCTX-M-3-producing E. coli in dairy milk. Transfer of ESBL was observed in 3 blaCTX-M-3-producing isolates, 1 blaCTX-M-1-producing isolate, and all 3 blaCMY-2-producing isolates. Almost all blaCTX-M-15 and blaCTX-M-1 genes possessed an insertion sequence, ISECP1, upstream of the blaCTX-M gene. Identical pulsed-field gel electrophoresis profiles were also observed in blaCTX-M-producing E. coli from the same farm. These results suggested that ESBL might spread by both clonal and horizontal spread in dairy farms in South Korea. Although no significant changes occurred in the antimicrobial resistance of E. coli during the 4-yr study period, the resistance rates and presence of ESBL were high compared with those in other countries. Thus, these findings suggest the importance of control measures for E. coli, particularly ESBL-producing bacteria, on dairy farms to reduce treatment failure and transmission to humans. 相似文献
995.
Hamed Delfan Abazari Seyed Mohammad Hossein Seyedkashi Mohammad Hoseinpour Gollo Young Hoon Moon 《Metals and Materials International》2017,23(5):865-876
Multilayered sheet metals have been widely used to achieve a wide range of favorable mechanical, physical, thermal and electrical properties. Laser beam irradiation over these materials creates extreme temperature changes that can lead to changes in the microstructural properties. Microstructure plays a very crucial role in determining the mechanical property of the irradiated region, thus determining the optimum laser processing conditions. In this study, metallographic studies, as well as tensile, fatigue and hardness tests, are undertaken on SUS430/C11000/SUS430 laminated composites that have been exposed to laser irradiation with different number of passes. This composite can be used in the microelectronics industry since it has the anti-corrosion and strength capability of stainless steel, and the electrical superiority of copper. Ytterbium fiber laser is used in such a way that the governing mechanism of the process is the temperature gradient mechanism. Evolution of the microstructure is revealed by metallography, and the fracture levels of tension and fatigue test specimens are further evaluated by SEM. This study illustrates the significant effects of successive laser irradiation on the evolution of microstructure and mechanical properties, which lead to some suggestions for improving the properties of laser-formed SUS430/C11000/SUS430 composites. 相似文献
996.
Modular assembly is being applied to an increasing number of vehicles and part manufacturers to manage the ever-changing demands of the automotive industry. In spite of many researches performed on the supply chain management and logistics aspects of modular production, there is no research discussing modular production line concepts used by module suppliers. In this paper, labour productivity of two assembly line concepts including the conveyor line and box assembly line is studied under modular production environment. Both line concepts and respective assembly processes are described in detail. Mathematical models showing the total work faced by these two assembly line concepts are developed and compared. Two productivity scales are defined: the maximum achievable productivity and the actual productivity. The labour productivity rates of these assembly line concepts on above productivity scales obtained from calculations and a simulation are compared as a performance measure. 相似文献
997.
Dawei Chang Shabbar Abbas Khizar Hayat Shuqin Xia Xiaoming Zhang Mingyong Xie Jin Moon Kim 《International Journal of Food Science & Technology》2010,45(9):1895-1901
Ascorbic acid (AA) was encapsulated in glassy low‐dextrose equivalent maltodextrin matrix by extrusion. The effects of formulation parameters, i.e., core/matrix ratio and water content were mainly investigated on Tg of extrudate. The AA yield, AA content and water content of the products together with extrusion parameters were also determined and compared for different formulations. The Tg of extrudates containing water content from 7.860% to 10.430% ranged from 43.17 to 27.48 °C, and the Tg of extrudates which core to matrix from 1:4 to 1:8 ranged from 35.79 to 41.64 °C. AA yield of all extrudates is above 96%, and with increasing water content, there was a slight decrease in the AA yield. The increased water level and core/matrix ratio reduce specific mechanical energy and die head pressure. X‐ray diffraction and scanning electron microscopy suggested that AA was most likely molecularly dispersed within the maltodextrin indicating the miscibility of AA and maltodextrin. 相似文献
998.
Yield, fatigue and buckling characteristics are often used as evaluation indexes for the performance of engine connecting rods in weight reduction design. There are, however, a limited number of studies on the buckling of connecting rods. Even the widely used field equations for the buckling have limitations in the application since they are derived from ideal support conditions. This study first presents an evaluation procedure for the buckling of a connecting rod via finite element analysis (FEA). The FEA approach allows us to treat the first and second modes of buckling collectively. The buckling stresses from the suggested FEA approach are closer to those measured in rig experiments than those from classical formula are. The stress sensitivities to the area reduction of rod shank are then examined in lights of yield, fatigue and buckling. The stress sensitivity in buckling indicates to be relatively higher than or comparable to those of yield and fatigue. Consequently, when weight reduction of connection rod shank is attempted, buckling should be considered as an essential factor along with the other criteria such as yield and fatigue. 相似文献
999.
Donghyun Hwang Deuk-Kyu Lee Jaehwa Jeong Moon G. Lee 《Journal of Mechanical Science and Technology》2010,24(1):223-226
In many mechanical operations, vibrations from personal tools may cause serious injuries to the human body. This is particularly
true in the case of vibrations that are constantly and repeatedly transferred to humans. In fact, a serious physical problem,
Raynaud’s phenomenon, may occur. In this paper, we propose a vibration transmissibility reduction module with a flexure mechanism
for personal tools. First, a target personal tool, that is, a grass cutter is selected, and the level of vibration transmissibility
to the hand is measured. Subsequently, we develop a concept design of the module with stiffness to reduce the vibration transmissibility
by more than 20%. The vibration transmissibility is measured by an accelerometer. In addition, the vibration reduction is
enhanced when the gap between the inner and outer bodies is filled with silicone gel. Finally, this is verified experimentally. 相似文献
1000.
To increase the precision and reliability of process control, random uncertainty factors affecting the control system must be accounted for. We propose a novel approach based on the operational matrix technique for robust PI controller design for dead-time processes with stochastic uncertainties in both process parameters and inputs. The use of the operational matrix drastically reduces computational time in controller design and statistical analysis with a desired accuracy over that of the traditional Monte-Carlo method. Examples with deterministic and stochastic inputs were considered to demonstrate the validity of the proposed method. The computational effectiveness of the proposed method was shown by comparison with the Monte-Carlo method. The proposed approach was mainly derived based on the integrator plus dead-time process, but can be easily extended to other types of more complex stochastic systems with dead-time, such as a first-order plus dead-time or a second-order plus dead-time system. 相似文献