全文获取类型
收费全文 | 5236篇 |
免费 | 398篇 |
国内免费 | 373篇 |
学科分类
工业技术 | 6007篇 |
出版年
2024年 | 9篇 |
2023年 | 132篇 |
2022年 | 125篇 |
2021年 | 185篇 |
2020年 | 205篇 |
2019年 | 164篇 |
2018年 | 156篇 |
2017年 | 176篇 |
2016年 | 197篇 |
2015年 | 191篇 |
2014年 | 264篇 |
2013年 | 293篇 |
2012年 | 363篇 |
2011年 | 383篇 |
2010年 | 256篇 |
2009年 | 342篇 |
2008年 | 270篇 |
2007年 | 335篇 |
2006年 | 292篇 |
2005年 | 238篇 |
2004年 | 193篇 |
2003年 | 207篇 |
2002年 | 189篇 |
2001年 | 183篇 |
2000年 | 140篇 |
1999年 | 98篇 |
1998年 | 75篇 |
1997年 | 97篇 |
1996年 | 52篇 |
1995年 | 46篇 |
1994年 | 48篇 |
1993年 | 15篇 |
1992年 | 25篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有6007条查询结果,搜索用时 46 毫秒
101.
《中国有色金属学会会刊》2021,31(9):2773-2786
W45Cu55, Cr65Cu35, and Cr32W14Cu54 alloys were obtained in order to study the mechanism of “smart response” of the structure of these alloys when using them as arc-resistant circuit-breakers. These alloys differ from industrial ones with frameless packing of Cr and W phases in the copper matrix. The alloy production method is based on the infiltration of copper melt into a mixture of non-compacted Cr and W powders under vibration exposure (80 Hz). The research results show an increase in the arc resistance of contacts when changing from “frame” packing of W to “frameless,” as well as the decisive role of Cr in the processes of self-dispersion of arc-resistant phases and passivation of W and Cu. Based on the obtained results, conclusions are drawn about the advantage of frameless packing of arc-resistant phases in copper and the reasons for the “smart behavior” of the structure of Cr-containing contacts in response to functional loads in the presence of oxygen and an inert atmosphere. 相似文献
102.
Pavel Diko Renáta Pagáčová Katarína Zmorayová Veronika Kuchárová Liudmila Vojtková Vitaliy Antal Viktor Kavečanský 《Journal of the American Ceramic Society》2021,104(2):740-752
Barium cerate (BaCeO3) is one of the possible additions to bulk YBa2Cu3O7 single-grain superconductors to suppress the growth of Y2BaCuO5 (Y211) particles. This paper investigates the synthesis of barium cerate powder and its use in YBa2Cu3O7 bulk superconductors. Crystalline barium cerate was synthesized by solid-state reaction, by co-precipitation of oxalates and by sol-gel method. Final calcination was held in air or in vacuum. It is shown that the most efficient in refining Y211 is nanocrystalline barium cerate prepared by sol-gel method calcined in vacuum. The effective refinement of Y211 particles occurred over the entire interval of nanocrystalline BaCeO3 addition from 0.38 to 1.90 wt%. The optimal concentration of nanosize barium cerate was determined, microstructure and superconducting properties were characterized. The effect of Y211 content on trapped field in YBCO bulks with addition of nanocrystalline barium cerate is shown. 相似文献
103.
Recently, the successful synthesis of wafer-scale single-crystal graphene, hexagonal boron nitride (hBN), and MoS2 on transition metal surfaces with step edges boosted the research interests in synthesizing wafer-scale 2D single crystals on high-index substrate surfaces. Here, using hBN growth on high-index Cu surfaces as an example, a systematic theoretical study to understand the epitaxial growth of 2D materials on various high-index surfaces is performed. It is revealed that hBN orientation on a high-index surface is highly dependent on the alignment of the step edges of the surface as well as the surface roughness. On an ideal high-index surface, well-aligned hBN islands can be easily achieved, whereas curved step edges on a rough surface can lead to the alignment of hBN along with different directions. This study shows that high-index surfaces with a large step density are robust for templating the epitaxial growth of 2D single crystals due to their large tolerance for surface roughness and provides a general guideline for the epitaxial growth of various 2D single crystals. 相似文献
104.
《Calphad》2015
The viscosity database for the Al–Cu–Mg–Si system was constructed using the CALPHAD (CALculation of PHAse Diagram)-type formalism. Viscosities of pure elements were described with the Arrhenius formula based on the experimental data. Subsequently, viscosities of the Al–Cu, Al–Si, Al–Mg and Cu–Si binary systems were assessed via CALPHAD technique and compared with the corresponding experimental data. Due to the lack of experimental data, viscosities in the Mg–Si and Cu–Mg systems were estimated by means of the Hirai's equation. The viscosities of the ternary Al–Cu–Si system were then predicted based on the binary parameters and compared with the experimental results. Using the established viscosity database for the quaternary Al–Cu–Mg–Si system, the viscosities of some commercial aluminum alloys were predicted. The reasonable agreement between calculations and experiments in Al-rich corner indicates that the CALPHAD-type database for the viscosity is valid and the database is suitable for predicting the viscosity of the commercial Al–Cu–Mg–Si based alloys. 相似文献
105.
106.
The superoxide anions in the human body are reduced into hydrogen peroxide and molecular oxygen by the metallo enzyme Cu–Zn superoxide dismutase 1. The disulfide bond in SOD1 is essential to maintain the structural stability of protein and its proper folding. A computational study on the disulfide bond with the addition of residues was made using three different level of theories viz., B3LYP/6-31G (d,p), M052X/6-31G (d,p) and MP2/6-31G (d,p). The nature of disulfide bond was found to be unaffected with the additional residues being attached to the termini of cysteine residues. This result was found to be in agreement with the experimental values. The results of Molecular Dynamics simulation illustrate the crinkled appearance caused in the disulfide loop of A4V mutation. The conformational change in the disulfide loop was found to have significant effect on the loss of dimerization, metal binding affinity and overall protein stability. It is also noted that the disulfide loop with more number of residues is found to have no effect on the disulfide bond characteristics, but the disulfide loop with less number of residues is found to have remarkable effect for mutation in any position of the wild type protein. 相似文献
107.
采用芘为荧光基团、肼为连接臂,根据席夫碱反应,制备芘-邻香兰素类Cu(II)荧光传感器(TM),其结构经熔点、1HNMR、13CNMR、IR、MS和元素分析表征。TM在乙腈体系中对Cu(II)有很好的紫外、荧光和比色响应,响应时间为12 min,不受其他金属离子干扰且对Cu(II)的识别可视、可逆。通过荧光滴定法计算出TM对Cu(II)的检出限为0.48 μmol/L。TM具有桔黄色的固体荧光,但其乙腈溶液荧光很弱,通过对比加水或Cu(II)的荧光强度,结合紫外和荧光滴定以及量子化学计算,探讨了TM的聚集诱导发光(AIE)识别机理。TM可用于自来水中Cu(II)的检测,回收率为91.2%~107.3%,相对误差为6.3%~8.8%。高选择性和对Cu(II)的快速响应使TM有望成为新的AIE型荧光传感器,用于实际样品中Cu(II)的检测。 相似文献
108.
109.
110.
The different types of metal powder used for selective laser melting(SLM) process would cause distinct corrosion behavior due to the uniformity of the obtained microstructure.The SLM-produced Ti–5Cu alloy using atomized Ti–5Cu metal powder(SLMed Ti–5Cu) in this work reveals a relatively uniform microstructure with overwhelming acicular α/α′ phase and shows great advantages on corrosion resistance compared with the SLM-produced Ti–5Cu alloy using the mixture powder(SLMedM Ti–5Cu).The effect of the micro-galvanic cells decreases due to the undetectable Ti_2Cu phase in the microstructure of the SLMed Ti–5Cu.An apparent passivation behavior was observed for SLMed Ti–5Cu instead of severe pitting phenomenon for the SLMed-M Ti–5Cu.The charge transfer resistance of SLMed Ti–5Cu in this work is 10.09 ± 2.63 MΩ cm~2, which is significantly higher than that of SLMed-M Ti–5Cu(4.76 MΩ cm~2).The above result indicates the atomized Ti–5Cu powder plays an important role in the formation of the uniform microstructure of SLMed product, thereby enhancing its corrosion resistance in Hank's solution at 37 ℃. 相似文献