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991.
The oxidation of six oxide dispersion strengthened (ODS) ferritic alloys was investigated at 1050 °C in air up to 200 h. Al plays the dominant role in improving the oxidation resistance of the ODS alloys. Cr and Y are of importance in forming the stable Al2O3 scale. To produce the dense alumina layer with enhanced adherence to the metal substrate, the concentrations of Al and Cr should be larger than 2 and 14 wt.%, respectively. 相似文献
992.
《Materials Science & Technology》2013,29(12):1578-1584
AbstractDiffusion bonding was carried out to produce transition joints between commercially pure titanium and 304 stainless steel at a temperature of 800°C for different times ranging from 30 to 180 min. in steps of 30 min under load in vacuum. The diffusion couples thus produced were studied using optical microscopy, scanning electron microscopy, and electron probe microanalysis to characterise the reaction layers formed in the diffusion zone. The chemical compositions of these layers indicate that intermetallics like σ phase, Fe2 Ti, Cr2 Ti, χ phase, FeTi, β-Ti, and Fe2 Ti4 O are formed in the reaction zone. The presence of these intermetallic compounds was also confirmed by the X-ray diffraction technique. Maximum bond strength of ~242 MPa was obtained for diffusion welded joints processed for 120 min. At this joining time, the plastic collapse of the surface asperities reaches near completion, favouring the interdiffusion of chemical species. Reduction in the bond strength of the transition joint processed for 180 min is due to the formation of a large volume fraction of voids in the reaction zone. Under tensile loading, failure takes place through α-Fe + χ phase mixture for transition joints processed in the time range of 30 – 90 min and through β titanium for joining times greater than 120 min. 相似文献
993.
Thomas L. Kao Crystal Y. Shi Junyue Wang Wendy L. Mao Yijin Liu Wenge Yang 《Microscopy research and technique》2013,76(11):1112-1117
Transmission X‐ray microscopy (TXM) is a rapidly developing technique with the capability of nanoscale three dimensional (3D) real‐space imaging. Combined with the wide range in energy tunability from synchrotron sources, TXM enables the retrieval of 3D microstructural information with elemental/chemical sensitivity that would otherwise be inaccessible. The differential absorption contrast above and below absorption edges has been used to reconstruct the distributions of different elements, assuming the absorption edges of the interested elements are fairly well separated. Here we present an “Absorption Correlation Tomography” (ACT) method based on the correlation of the material absorption across multiple edges. ACT overcomes the significant limitation caused by overlapping absorption edges, significantly expands the capabilities of TXM, and makes it possible for fully quantitative nano‐scale 3D structural investigation with chemical/elemental sensitivity. The capability and robustness of this new methodology is demonstrated in a case study of an important type of rare earth magnet (Nd2Fe14B). Microsc. Res. Tech. 76:1112–1117, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
994.
AbstractA lamellar zinc dimolybdate hydroxide Zn3Mo2O8(OH)2 was prepared for the first time by a facile hydrothermal synthesis. The electrochemical properties of the lamellar Zn3Mo2O8(OH)2 as an anode material were investigated by cyclic voltammetry (CV), reversible capacity, cycling stability and rate capability for lithium ion batteries (LIB). The lamellar zinc dimolybdate hydroxide exhibits a reversible capacity of 404.6 mAh g?1 at a current density of 100?mA g?1 after 200 cycles. The reversible capacity of the lamellar Zn3Mo2O8(OH)2 remained at 60 mAh g?1 even at a current density of 3000?mA g?1. When the current density was returned to 100?mA g?1, a discharge capacity of 380 mAh g?1 was maintained after 200 discharge/charge cycles. The excellent electrochemical performance may be due to its unique lamellar structure, which buffers the volume change during the Li+ intercalation/de-intercalation and provides the electrode with convenient lithium ions and electron transport pathways. These results suggest the promising potential application of the lamellar zinc dimolybdate hydroxide in lithium-ion batteries. 相似文献
995.
Neeraj Jain 《Construction and Building Materials》2012,27(1):39-44
The effects of nonpozzolanic (marble dust) and pozzolanic (rice husk ash) mineral admixtures on the hydration behavior and mechanical properties of ordinary Portland cement (OPC) have been investigated. The blending of both marble dust (20-60%) and rice husk ash (10-30%) in OPC accelerate the setting as compared to control (OPC). Marble dust addition decreases the strength of OPC and the maximum strength of 54.5 MPa has been achieved on 28 days of curing with 20% of marble dust (CM20). Addition of rice husk ash increases the strength and maximum strength of 65.9 MPa has been observed with 20% of RHA (CR20) blended cement. The formation of various crystalline phases and their effects on hydration behavior of mineral admixtures blended cement were examined by X-ray diffraction (XRD). The changes in microstructure of the hydrated samples were also studied using scanning electron microscope (SEM). 相似文献
996.
997.
XRD对表面处理炭纤维表面结构的分析 总被引:1,自引:0,他引:1
利用XRD分析了瞬时高温空气氧化法和气液双效法表面处理对炭纤维表面结构,特别是激昂厚度的变化。结果表明经表面处理后炭纤维表面有细晶化的趋势,这将有利于CFRP的界面粘结。 相似文献
998.
Influence of mineral admixtures on mechanical properties of self‐compacting concrete under elevated temperature 下载免费PDF全文
Self‐compacting concrete (SCC) is a form of concrete that is capable of flowing into the congested interior of formwork and consolidating under the action of its own weight without segregation and bleeding. In the present investigation, an attempt has been made to study the effect of elevated temperature on mechanical properties of SCC specimens made with different mineral admixtures that were heated from 27 to 900 °C and cooled by air or water. Silica fume, flyash, metakaolin were used as mineral admixtures. Master Glenium was used as superplasticizer, and Glenium Stream 2 was used as viscosity modifying agent. Mechanical properties of the cooled specimens such as compressive strength, tensile strength, flexural strength, and modulus of elasticity were found. Compressive, tensile, and flexural strengths of specimens were found to decrease by 73.18%, 65.05%, and 63.2%, and 85.2%, 83.52%, and 83.56% for the specimens with metakaolin that were heated and cooled by air and water, respectively. Similar reductions were found for the SCC specimens made with silica fume and flyash. Microstructure investigation has been carried out on SCC samples using scanning electron microscope and X‐ray diffraction analytical techniques to understand the effect of temperature on decrease in strength. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
999.
《Ceramics International》2016,42(6):6899-6905
In the present article, optical properties and energy upconversion in Er3+/Yb3+ co-doped BiNbO4 matrix were investigated. The BiNbO4 matrix was prepared using the solid-state reaction method. X-ray diffraction of the matrix shows that the crystal structure is consistent with ICSD code 74338. The grain distribution and the behavior of doping with Er3+ and Yb3+ on the sample surface were obtained by scanning electron microscope. Raman spectral characterization was carried out to examine the behavior of the vibrational modes of the samples. Upconversion emissions in the visible region at 484.5, 522, 541.5 and 670.5 nm in the matrices BiNbO4:Er,Yb and BiNbO4:Er were observed and analyzed as a function of 980 nm laser excitation power and rare-earth doping concentration. The results show that BiNbO4 is a promising host material for efficient upconversion phosphors. 相似文献
1000.
Adsorption characteristics of nickel on Bacillus cereus M116 biomass have been studied under varied environmental conditions to explore the potentiality of the biomass for controlling water pollution due to nickel. The optimized parameters for adsorption process are as follows: pH: 7.0, temperature: 40°C, biomass dosage: 2 g L–1. The process is best fitted to Redlich–Peterson isotherm model and follows pseudo-second order rate model. The combination of zeta potential measurement, SEM – EDXA, XRD, XPS, FTIR, TGA, and DSC studies allow a more comprehensive characterization of biomass to understand the mechanisms involved in nickel (II) adsorption in aqueous system. 相似文献