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431.
S. S. Wang Y. Zhou Y. L. Lam C. H. Kam Y. C. Chan X. Yao 《Materials Research Innovations》1997,1(2):92-96
Neodymium-doped silica glass possesses many properties ideal for high-power laser applications. These include low thermal
expansion coefficient, high temperature stability, and low nonlinear index of refraction. For the first time, the sol-gel
process has been successfully employed to prepare highly doped neodymia silica glass, up to 5wt% Nd for homogeneous dopant
distribution. The optical characteristics of the silica glass and its in-process gel, including the UV/VIS absorption spectra,
infrared absorption spectra, fluorescence emission spectrum and the fluorescence lifetime, are measured and analyzed. The
structure of the sample is also characterized by means of XRD and SEM. A porous gel is observed to have formed when the heat
treatment temperature reaches 300oC. Wavelength shifts in the absorption peak corresponding to the 4I9/2 to 4F5/2 transition have been observed during the densification process and for different Nd weig
ht contents. The FTIR spectra have shown that high temperature heat treatment can greatly reduce the amount of OH groups and
organic residue in the silica. We have also shown that a high OH content contributes to weak fluorescence intensity and short
fluorescence lifetimes.
Received: 3 March 1997 / Accepted: 27 May 1997 相似文献
432.
Angel Vegas 《Crystallography Reviews》2013,19(3):189-283
Abstract Until recently, cations have been considered as small “isolated” entities, occupying the spaces in close-packed arrays of large anions. An inspection however of cation subarrays reveals that some kind of interaction must exist between them, as they reproduce both the topology and the distances of their parent metal structures. Up to now, the existence of clusters has been identified with metal-rich compounds or with compounds in which the metal atoms have unsaturated valences. However, from the results reported here, it can be stated that cations recognize themselves in forming aggregates in such a way that the world of clusters also comes into the field of fully ionic compounds, wherein metal atoms have saturated valences. This kind of interaction has already been observed in silver(I) and gold(I) compounds (and is known as the auriphilic effect or as d 10-d 10 interactions); but examples are reported here of similar interactions between cations of the alkaline-earth metals. Group 13 elements, lanthanides, Sc, Ti and Y, indicating that this effect is a general feature of inorganic solids. Although some explanations have been reported, the reasons for such interactions remain unclear. This is an open question challenging theoretical chemists. These new ideas are placed in the context of similar ones developed recently, which give to cations a more relevant ôle in determining crystal structures. Thus, the old ideas of Lebedev regarding the protagonism of “large” cations in the formation of crystal structures is discussed together with the more recent ideas of O'Keeffe and Hyde which describe the crystal structures of oxides as oxygen-stuffed alloys. In many oxides, the cations occupy octahedral or tetrahedral holes in close-packed arrays of anions. It is true that in many other structures, the cations reproduce the topology of the structures of elements or simple alloys, but it is also true that the structure of the parent metal is often preserved in its oxides. 相似文献
433.
434.
《Advanced Powder Technology》2022,33(10):103769
It is a challenge to develop a new type of non-contact temperature sensor and the related materials with the advantages of high detection sensitivity, spatial resolution, non-invasive and fast response. In this work, a moderate solid-state method was utilized to prepare a novel Ce3+/Eu2+ co-doped KSr4B3O9 phosphor for efficient dual-emission temperature-sensing application. According to the different activation energy and the energy transfer process from Ce3+ to Eu2+, two non-overlapping emission bands with respectively distinctive temperature responses were realized. By using the significant difference in the fluorescence intensity ratio between Eu2+ and Ce3+, a strong shift of the CIE coordinate from (0.3701, 0.4311) at 293 K to (0.2623, 0.2465) at 443 K could be read out. Meanwhile, the maximum absolute (Sa) and relative sensitivities (Sr) were fitted to be 0.0118 and 2.25 % K?1 with a large chromaticity shift from 293 to 443 K (ΔE = 0.1652). The configuration coordinate diagram in KSr4B3O9 was adopted to explain the temperature quenching mechanism in detail. The outstanding temperature-sensing characteristic indicates that KSr4B3O9: 1.75 %Ce3+/1.75 %Eu2+ phosphor has the potential to be applied in a thermometric probe. 相似文献
435.
《工程(英文)》2020,6(2):148-153
Multiscale simulation is a key research tool in the quest for new permanent magnets. Starting with first principles methods, a sequence of simulation methods can be applied to calculate the maximum possible coercive field and expected energy density product of a magnet made from a novel magnetic material composition. Iron (Fe)-rich magnetic phases suitable for permanent magnets can be found by means of adaptive genetic algorithms. The intrinsic properties computed by ab initio simulations are used as input for micromagnetic simulations of the hysteresis properties of permanent magnets with a realistic structure. Using machine learning techniques, the magnet’s structure can be optimized so that the upper limits for coercivity and energy density product for a given phase can be estimated. Structure property relations of synthetic permanent magnets were computed for several candidate hard magnetic phases. The following pairs (coercive field (T), energy density product (kJ·m−3)) were obtained for iron-tin-antimony (Fe3Sn0.75Sb0.25): (0.49, 290), L10-ordered iron-nickel (L10 FeNi): (1, 400), cobalt-iron-tantalum (CoFe6Ta): (0.87, 425), and manganese-aluminum (MnAl): (0.53, 80). 相似文献
436.
稀土氧化物在功能陶瓷中的应用分析 总被引:1,自引:0,他引:1
综述了稀土氧化物在压电陶瓷,导电陶瓷,AlN陶瓷,ZrO2氧敏陶瓷,微波介质陶瓷中的应用现状,详细讨论了稀土的作用机理,再现了稀土氧化物掺杂改性的规律,为利用稀土氧化物掺改性功能陶瓷提供一定的参考和指导作用,并且为稀土氧化物的应用指明了方向,简述了该领域应用研究的发展方向。 相似文献
437.
用程序升温表面裂解和程序升温表面反应的方法研究催化剂上CH4裂解和沉积炭与水汽反应过程。试验结果表明:在转化催化剂上,CH4裂解从220℃开始,360℃时明显加速,540℃时速度达极大值; 相似文献
438.
掺稀土纳米发光材料的研究进展 总被引:5,自引:0,他引:5
概述了掺稀土纳米发光材料的理论研究价值和应用前景,介绍了此类材料的制备方法、结构测试方法及光谱研究情况,对掺稀土纳米发光材料的发展前景进行了展望. 相似文献
439.
本文通过色差分析,pH 电位滴定、电导滴定、红外光谱等一系列分析方法,研究了稀土元素 Nd(Ⅲ)与多种染料的作用机理。结果表明,染料加入稀土 Nd(Ⅲ)后,可以改善染料的性质,提高染色效果。染料与金属离子 Nd~(3+)之间能够发生络合反应,染料不同,络合情况也不同,稀土 Nd(Ⅲ)主要是与染料分子中的磺酸基发生络合。 相似文献
440.
添加稀土铈对HSn70-1冷凝管耐蚀性能的影响 总被引:5,自引:0,他引:5
采用拉伸试验、金相显微分析、经典腐蚀试验方法及阳极极化曲线的测定,研究了电厂用锡黄铜冷凝管的力学性能、组织和耐蚀性能。结果表明,添加适量的B、Ni、Mn、Ce等合金元素可提高HSn70-1AB的强度,耐蚀性能也进一步改善。 相似文献