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71.
Mechanical and optical properties in precipitated regions of alumina‐rich magnesium aluminate spinel 下载免费PDF全文
Jesse Miller Ivar Reimanis Weiguo Miao Jonathan Salem 《International Journal of Applied Ceramic Technology》2017,14(2):236-244
The toughening and strengthening of transparent ceramics is challenging because microstructural alterations typically lead to light scattering. Here, controlled precipitation of α‐Al2O3 from nonstoichiometric spinel is explored to demonstrate unique control over the evolution of second phase Al2O3 and how the microstructure might be altered to enhance fracture toughness while minimizing light scatter. Alumina‐rich magnesium aluminate spinel, MgO·nAl2O3, where n=2, was hot pressed and HIPed to produce fully dense, single‐phase material. The material was then heat treated in air at 1573 K for up to 20 hours to create a two‐phase spinel‐Al2O3 composite. The fracture toughness varies from 0.88 to 2.47 MPa√m depending on the microstructure; enhanced toughness at the surface was due to increased crack tortuosity at phase boundaries, but residual tensile stresses were observed in the interior of the material. Precipitation causes local volume contraction and the formation of porosity, decreasing optical transmission, especially for heat treatment times longer than 5 hours. 相似文献
72.
As the minimum feature size of interconnect lines decreases below 0.5 urn, the need to control the line microstructure becomes
increasingly important. The alloy content, deposition process, fabrication method, and thermal history all determine the microstructure
of an interconnect, which, in turn, affects its performance and reliability. The motivation for this work was to characterize
the microstructure of various sputtered Al-Pd alloys (Al-0.3wt.%Pd, Al-2Cu-0.3Pd, and Al-0.3Nb-0.3Pd) vs sputtered Al-Cu control
samples (Al-0.5Cu and Al-2Cu) and to assess the role of grain size, mechanical stress, and crystallographic texture on the
electromigration behavior of submicrometer wide lines. The grain size, mechanical stress, and texture of blanket films were
measured as a function of annealing. The as-deposited film stress was tensile and followed a similar stress history on heating
for all of the films; on cooling, however, significant differences were observed between the Al-Pd and Al-Cu films in the
shape of their stress-temperature-curves. A strong (111) crystallographic texture was typically found for Al-Cu films deposited
on SiO2. A stronger (111) texture resulted when Al-Cu was deposited on 25 nm titanium. Al-0.3Pd films, however, exhibited either
a weak (111) or (220) texture when deposited on SiO2, which reverted to a strong (111) texture when deposited on 25 nm titanium. The electromigration lifetimes of passivated,
≈0.7 μm wide lines at 250°C and 2.5 × 106 A/cm2 for both single and multi-level samples (separated with W studs) are reported. The electromigration behavior of Al-0.3Pd
was found to be less dependent on film microstructure than on the annealing atmosphere used, i.e. forming gas (90% N2-10%H2) annealed Al-0.3Pd films were superior to all of the alloys investigated, while annealing in only N2 resulted in poor lifetimes. 相似文献
73.
W. Wijaranakula 《Journal of Electronic Materials》1993,22(1):105-110
The morphology of oxide precipitation induced defects in Czochralski silicon degenerately doped with boron and annealed at
800° and 1050°C, respectively, was examined using a transmission electron microscope. After an extended annealing at 800°C,
the predominantly observed defects were the oxide precipitate platelets having the {001}-type habit planes and sides parallel
to <110> and <112> crystallographic directions. The morphology of the oxide precipitates as derived from the residual oxygen
calculation is suggested to be that of a thin octahedral shape. During a subsequent high temperature annealing, the octahedral
precipitate platelets became thermodynamically unstable and dissolved. Based upon the defect morphology observed after a 1050°C
anneal, it is suggested that the dissolving precipitate introduces a tensile strain into the surrounding silicon lattice.
Contrary to precipitate growth, the lattice strain introduced by precipitate dissolution is relieved primarily through mechanisms
involving vacancy injection from the precipitate interface and a condensation of excess silicon interstitials via a formation
of an interstitial-type dislocation loop. 相似文献
74.
The gamma prime precipitation strengthening behavior and oxide dispersion strengthening behavior of mechanically alloyed oxide dispersion strengthened (ODS) Ni-base superalloys have been investigated. The most important microstructural feature affecting the elevated temperature strength of ODS alloys was found to be the grain aspect ratio. Grain aspect ratio after zone annealing was sensitively related to the primary grain size in as-extruded Ni-base superalloy. There was a suitable range of primary grain size to obtain a coarse elongated grain structure after zone annealing. The large grain aspect ratio above a critical value of about 20 resulted in an increase in stress-rupture life more than two orders of magnitude at 950°C. The size and distribution of the gamma prime precipitates were dependent on the solution heat treatment conditions. The microstructural parameters on the gamma prime precipitates significantly affected on the stress-rupture property of ODS Ni-base superalloy at the intermediate temperature range. 相似文献
75.
76.
Ferrihydrite in water wells and bacterial enrichment cultures 总被引:1,自引:0,他引:1
The chemical and mineralogical composition of Fe(III)-precipitates formed in water wells and laboratory cultures was examined. Ferrihydrite, a poorly ordered Fe(III)-oxide of bulk formula 5Fe2O3 · 9H2O, was detected by X-ray diffraction analysis in all samples. The crystallinity varied from one sample to another. Fe was the only major element detected by energy-dispersive X-ray spectrometry; several other elements were present at minor levels reflecting the chemical composition of the medium. The results suggest that the biologically-catalyzed iron encrustation of water wells begins with the initial formation of ferrihydrite. 相似文献
77.
We report here the identification of a new precipitate phase in thin-film Al-4wt.%Cu metallization used for interconnects
on integrated circuits. The phase is based on a trigonal distortion of a face centered cubic lattice. Computer simulation
of electron diffraction intensities suggests that the basis structure is isomorphous with Al2Ca but with a large and ordered population of vacancies on Cu sites. The reason for the formation of the new phase and its
implications for electromigration reliability are discussed. 相似文献
78.
借助于叠栅图观察了合金钢中细小沉淀相的形貌和分布特征,确定了沉淀相的点阵常数及其同母相(或另一沉淀相)的错配度,并确认了沉淀相或母相中存在的位错及其滑移面。 相似文献
79.
目的 为满足高速列车关键部件的轻量化需求,开发高性能铸造铝合金。方法 熔炼铸造了低锌、低镁且含微量钪的Al-5.78Zn-1.63Mg-1.75Cu-0.17Zr-0.22Sc(质量分数)合金,对合金实施了双级均匀化处理及“固溶+时效”(T6)工艺,结合光镜(OM)、X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪(EDS)及透射电镜(TEM)多种分析测试手段,对比研究合金在铸态、均匀化态及T6处理态下的微观组织特征,重点关注了析出相的演变,并通过室温拉伸性能实验测试合金的力学性能。结果 铸态合金中的析出相以粗大的Mg(Zn,Cu,Al)2相为主,且分布于晶界或枝晶界,在室温拉伸过程中粗大的Mg(Zn,Cu,Al)2相割裂基体,造成合金在弹性变形阶段的脆断,基本无伸长率;双级均匀化处理后,晶界及枝晶间的第二相明显减少,晶内析出了大量的针状相Mg(Zn,Cu,Al)2,而T6处理后,晶内针状相基本消失,时效过程中析出以η''-MgZn2相为主的高密度弥散分布纳米析出相,其平均尺寸为(9.2±0.9)nm,相比于铸态,T6处理后合金的抗拉强度从417 MPa提高到577 MPa,且展现出一定的伸长率。结论 T6处理后合金中析出相由粗大的针状相转变为高密度弥散分布纳米析出相,该析出相可在变形过程中有效钉扎位错,从而提高合金力学性能。 相似文献
80.
为考察热处理工艺对AFA耐热钢组织和力学性能的影响,本文利用光学显微镜、扫描电镜、X射线衍射等技术,研究了新型含铝奥氏体耐热钢(AFA)在不同保温温度和冷却方式下的组织演变规律及力学性能的变化。结果表明:加热温度和冷却方式对试样的显微组织均产生影响。随着保温温度的升高,晶粒的平均尺寸逐渐增大。在1150和1200℃保温冷却后,空冷试样的晶粒尺寸略大于炉冷试样。不同温度下保温冷却后,析出相在晶内和晶界均有分布,晶内析出相形状变为圆形或颗粒状,晶界处变为长条状,但种类并未发生改变。析出相的平均尺寸随着保温温度的升高而增大。在1200℃下炉冷后,析出相的平均尺寸、面密度和晶界覆盖率均高于空冷,此时炉冷试样的硬度值达到170 HV,高于空冷,但抗拉强度和延伸率较低,分别为680 MPa和13.04%。 相似文献