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61.
Hongsub Bae Tanveer Ahmad Ilsu Rhee Yongmin Chang Seong-Uk Jin Sungwook Hong 《Nanoscale research letters》2012,7(1):44
Coprecipitated ferrite nanoparticles were coated with carbon using a hydrothermal method. From transmission electron microscope
pictures, we could see that the coated iron oxide nanoparticles were spherical in shape with an average diameter of 90 nm.
The strong bonding of carbon on the nanoparticle surfaces was checked by noting the C = O and C = C vibrations in Fourier
transform infrared spectra. The spin-lattice relaxation process [T
1] and spin-spin relaxation process [T
2] relaxivities of hydrogen protons in the aqueous solution of coated nanoparticles were determined to be 1.139 (mM·s)-1 and 1.115 (mM·s)-1, respectively. These results showed that the carbon-coated iron oxide nanoparticles are applicable as both T
1 and T
2 contrast agents in magnetic resonance imaging. 相似文献
62.
63.
64.
Kyoung-Ho Kang Hyun-Sik Park Seok Cho Nam-Hyun Choi Sung-Won Bae Seung-Wook Lee Yeon-Sik Kim Ki-Yong Choi Won-Pil Baek Moo-Yong Kim 《Annals of Nuclear Energy》2011
Integral effect tests using the ATLAS facility were performed to obtain the thermal-hydraulic parameters such as dynamic and static pressures, local temperatures, and flow rates during a feedwater line break of a steam generator. The break of a feedwater line was simulated using a double rupture disc assembly in order to satisfy the requirements for the break opening time of around a few milliseconds. In the present study, estimated break opening time was less than 1.5 ms and broken areas were 48.1% and 93.4% of the feedwater line, respectively. The maximum dynamic pressures of about 1.57 bar were obtained inside of feedwater box that was closest to the break location of the feedwater line. After the break of the feedwater line, propagation of the pressure wave along the distance from the break location inside the steam generator was clearly and pertinently observed in all the tests. From a structural integrity point of view, however, the risk induced by this maximum dynamic load could be treated to be insignificant. 相似文献
65.
An analytical calculation has been performed to predict the turbulent friction factor in a rod bundle. For each subchannel constituting a rod bundle, the geometry parameters are analytically derived by integrating the law of the wall over each subchannel with the consideration of a local shear stress distribution. The correlation equations for a local shear stress distribution are supplied from a numerical simulation for each subchannel. The explicit effect of a subchannel shape on the geometry parameter and the friction factor is reported. The friction factor of a corner subchannel converges to a constant value, while the friction factor of a central subchannel steadily increases with a rod distance ratio. The analysis for a rod bundle shows that the friction factor of a rod bundle is largely affected by the characteristics of each subchannel constituting a rod bundle. The present analytic calculations well predict the experimental results from the literature with rod bundles in circular, hexagonal, and square channels. 相似文献
66.
Kwang-min Kim A-Rong Kim Minwon Park In-Keun Yu Bum-Yong Eom Kidoek Sim Seok-Ho Kim Myung-Hwan Sohn Hae-Jong Kim Joon-Han Bae Ki-Cheol Seong 《低温学》2011,51(6):272-277
The authors designed and manufactured a toroidal-type superconducting magnetic energy storage (SMES) system. The toroidal-type SMES was designed using a 3D CAD program. The toroidal-type magnet consists of 30 double pancake coils (DPCs). The single pancake coils (SPCs), which constitute the double pancake coils, are arranged at an angle of 6° from each other, based on the central axis of the toroidal-type magnet. The cooling method used for the toroidal-type SMES is the conduction cooling type. When the cooling method for the toroidal-type SMES was designed, the two-stage Gifford–McMahon (GM) refrigerator was considered. The Bi-2223 HTS wire, which was made by soldering brass on both sides of the superconductor, is used for the magnet winding. Finally, the authors connected the toroidal-type SMES to a real-time digital simulator (RSCAD/RTDS) to simulate voltage sag compensation in a power utility. 相似文献
67.
Yun Hee Chang Tae Soo Bae Shin Ki Kim Mu Seong Mun Wan-Hee Lee 《International Journal of Precision Engineering and Manufacturing》2011,12(1):129-134
The incidence of osteoarthritis for lower limb amputees, especially unilateral transfemoral amputees, was higher than that
of transtibial amputees. Considering level of amputation and bilateral load asymmetry, we could assumed that joint moments
in the coronal plane during gait were highly related to the risk of osteoarthritis. Therefore, this study aimed to examine
the hip and knee adduction moments in the coronal plane in persons with unilateral transfemoral amputation during walking
through gait analysis. The subjects were 12 unilateral transfemoral amputees and 21 healthy persons. Three-dimensional motion
analysis was measured bilaterally from 33 persons during walking to calculate temporal-spatial parameters and joint moments.
The analysis compared the prosthetic side and the intact side of the amputee group and then analyzed the moment between both
the intact sides of the transfemoral amputee group and the healthy persons. The results showed that the intact knee adduction
moment of amputees increased by 32% compared to the prosthetic side and more than twice compared to the control group at terminal
stance. But the bilateral hip adduction moment was decreased compared to the control group (p<0.05). Therefore it is expected
that the higher knee adduction moment on the intact side may cause secondary complication to unilateral transfemoral amputees,
but it is difficult to make connection with hip osteoarthritis. 相似文献
68.
Jae Hee Jung Sun Young Park Jung Eun Lee Chu Won Nho Byung Uk Lee Gwi Nam Bae 《Journal of aerosol science》2011,42(10):725-736
Aerosol techniques have recently been used to process natural products for medical, pharmaceutical, and environmental health applications. In particular, electrohydrodynamic spraying, or electrospraying, which is a method of atomizing liquids by means of electrical forces, is a promising aerosol technology because it generates non-agglomerated particles due to repulsive electrical forces between particles with unipolar charges. We investigated the characteristics of natural-product nanoparticles generated via electrospraying. A plant extract containing a natural-product (Sophora flavescens) was sprayed in steady cone-jet mode using a specially designed electrospray system with a point-to-orifice-plate configuration. The electrosprayed natural-product particles maintained their bimodal size distribution with good stability and uniformity for longer than 1 h. Compared to generation characteristics observed using a conventional nebulization process, the electrospray technique produced non-agglomerated, spherical particles and resulted in a narrow size range for both peaks. The size distribution of electrosprayed particles was controlled by varying the suspension flow rate of S. flavescens extract. Also, they had a high average charge per particle and positive polarity. The nanoparticles maintained the major chemical composition of the original S. flavescens ethanolic extract during electrospraying. Our investigation demonstrated that the electrospray process, driven by high-intensity electric fields, can be used to generate nanoscale particles from natural products. 相似文献
69.
Jin Woo Bae Tae Uk Yang Gi Joon Nam Gun Joo Lee Byeong-Uk Nam Jae Young Jho 《Polymer Bulletin》2011,67(4):729-740
Ethylene vinylacetate (EVA) copolymer-based nanocomposites with maleic anhydride-grafted ethylene-vinylacetate (EVAgMA) and
organically modified clay (o-clay) were prepared in a twin screw extruder by following a two-step melt compounding method.
EVAgMA/o-clay masterbatches with various clay contents up to 50 wt% were examined, after which the masterbatch with the highest
clay content was melt compounded with EVA for the preparation of EVA/o-clay nanocomposites containing specific amounts of
clay. Further morphological dispersion of the clay particles by highly polar EVA and shearing was confirmed in the EVA/o-clay
nanocomposites by X-ray diffraction (XRD) and transmission electron microscopy (TEM). These morphologies led to increased
thermal properties in air as well as a considerable decrease in heat release rate (HRR). EVA/o-clay/MDH nanocomposites were
also prepared using a high clay-bearing masterbatch to confirm the synergistic flame retardancy of clay as a co-additive in
EVA/MDH composites. EVA/o-clay/MDH nanocomposites prepared by substituting o-clay for MDH showed significantly lower and wider
HRR during combustion compared to EVA/MDH composite. 相似文献
70.
Eunjoo Bae Hee-Jin Park Jaeyong Yoon Younghun Kim Kyunghee Choi Jongheop Yi 《Korean Journal of Chemical Engineering》2011,28(1):267-271
Silver nanoparticles (AgNPs), potent antibiotic materials, have been found to cause cell-membrane damage and produce reactive oxygen species (ROS). The resultant structural change in the cell-membrane could cause an increase in cell permeability of silver ions and AgNPs. To address this issue further, in-vivo and in-vitro cytotoxicity testing of as-made nanomaterials was conducted to quantify and assess their nanotoxicity. Considering the behavior of AgNPs in the environment, toxicity may be reflected by differences in their physicochemical properties (size, agglomeration rate, adsorption properties on humic acid) dependency and toxicity depression. Therefore, we investigated the effect of the cellular uptake of AgNPs with the kinetics of agglomeration and adsorption. The amount of agglomerated and adsorbed AgNPs with sizes of <14 nm was higher than that for AgNPs with sizes of 90 and 140 nm. For 90 and 140 nm sized AgNPs, adsorption was more significant than agglomeration. It is noteworthy that the normal concept that smaller sized AgNPs are taken up more readily may be in error in cases of interactions of abiotic factors. 相似文献