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71.
Solid-solution hardening and softening by Fe additions to NiAl 总被引:3,自引:0,他引:3
Solid-solution hardening in the case of a ternary alloy addition to a B2 compound with the triple defect structure has been investigated. The fact that the ternary element may occupy either of two sublattices or may affect the concentration of other types of point defects present in the material makes this a very interesting problem to consider. Ni-rich (40 at% Al), stoichiometric (50 at% Al), and Al-rich (52 at% Al) alloys were doped with up to 12 at% Fe. Lattice parameter, bulk density and hardness measurements were performed on samples quenched from 1000 °C. It was found that solid-solution softening actually occurs in the Ni-rich alloys, while hardening was observed in the stoichiometric and Al-rich alloys. The vacancy concentration was determined from the experimental data, and the site occupancies of the Fe atoms were estimated from a thermodynamic model. Through careful consideration of all point defect concentrations the solid-solution hardening and softening behaviors could be effectively rationalized. 相似文献
72.
研究了活性填料纳米Ni粉对陶瓷先驱体聚硅氮烷连接反应烧结SiC陶瓷接头性能的影响,同时与惰性填料纳米SiC粉及活性填料微米Ni粉进行了对比,指出填料的种类及颗粒度对连接强度均有较大影响。活性填料纳米Ni粉的加入可减少连接层内的孔隙和裂纹,同时还可以与聚硅氮烷的裂解产物及母材发生反应,促进聚硅氮烷的裂解,从而降低连接温度,提高连接强度。当连接温度为1200℃时,其最大抗弯强度达到251.6MPa。微观研究表明,连接层结构较为均匀致密,且与母材间界面结合良好。惰性填料纳米SiC粉对连接强度没有明显改善。微米Ni粉因不能与先驱体形成均匀的连接层而导致连接强度降低。 相似文献
73.
PREPARATIONOFULTRAFINENICKELPOWDERChaiLiyuan;ZhongHaiyun(DepartmentofNonferrousMetallurgy,CentralSouthUniversityofTechnology,... 相似文献
74.
The chemical composition, defect structure, and diffusion in nickel sulfide -Ni3S2 have been investigated in H2S-H2 mixtures containing between 1 and 65% H2S between 560 and 700°C. Gravimetric, density, and X-ray studies were carried out. In the thermodynamically stable compound the ratio of Ni/S varied between 1.3 and 1.75. The X-ray examination showed a step change in the lattice parameter at the Ni/S ratio 1.4. A linear dependence of the density values (between 5.5 and 6.2 g/cm3) on the composition was observed. On the basis of the chemical composition and density measurements the number of nickel and sulfur atoms in 1 cm3 were determined. It has been shown that the Ni3S2 phase is defected in both anion and cation sublattices and that its chemical formula may be described as follows: Ni3±yS2x, where y 2x. It has been found that in the mixture containing 10% H2S the process of defect formation is determined by their diffusion in the sulfide. The temperature dependence of the diffusion coefficient is described by the equation D = 13.15 exp(-30,000/RT) cm2/sec. No dependence of D on the sulfur partial pressure was observed, but this may be due to the relatively large uncertainties in the measurement of the diffusion coefficients. 相似文献
75.
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77.
镁合金化学镀镍层的结合机理 总被引:15,自引:4,他引:15
镁合金在直接化学镀前的活化处理时,表面生成一层氟化物保护膜,溶解度计算及XPS分析表明,氟化物膜在镀液中可稳定存在,用SEM,XPS,SAM考察了初始沉积Ni,镀层横截面以及开裂后的断面形貌与成分,发现在镀层与基体之间存在着氟化物,镀液成分与Ni的混杂层,这一混杂层是镀层与基体结合的最薄弱环节,镀层开裂通常首先发生在此混杂层内。 相似文献
78.
The effect of nickel and molybdenum concentrations on the phase transformation and mechanical properties of conventional 18Ni(350)
maraging steel has been investigated. Both of these elements act as strong austenite stabilizers. When the concentration of
molybdenum or nickel is greater than 7.5 or 24 wt %, respectively, the austenite phase remains stable up to room temperature.
In both molybdenum- and nickel-alloyed steels, the austenite phase could be transformed to martensite by either dipping the
material in liquid nitrogen or subjecting it to cold working. When 7.5 wt% Mo and 24 wt% Ni were added in combination, however,
the austenite phase obtained at room temperature did not transform to martensite when liquid-nitrogen quenched or even when
cold rolled to greater than 95% reduction. The aging response of these materials has also been investigated using optical,
scanning electron, and scanning transmission electron microscopy. 相似文献
79.
The aim of this study was to improve the understanding of the deleterious effect of sulfur impurities on the adherence of the thermally-grown oxide on the boundary layer in thermal-barrier-coating systems. In Part I, the sulfur segregation on the free surface of NiAl(001) and at different interfaces between metal and transient alumina scales has been characterized by AES, XPS and LEED. The sulfur diffusion coefficient in the alloy has been determined (D = 0.15 exp(–218,000/RT) cm2/s). It is by three orders of magnitude larger than the nickel and aluminum self-diffusion coefficients. It has also been observed that the sulfur de-segregates upon Al enrichment of the metallic surface. The saturation of the metallic surface with an amorphous alumina layer formed at room temperature blocks the segregation of S. However, in the initial stages of oxidation where the transient -alumina grows by cationic transport and inject vacancies at the interface, S segregates at the interface between the alumina thin films and the metallic substrate. 相似文献
80.
薛福连 《有色金属再生与利用》2006,(9):24-25
本文采用酸溶,除渣,分离及蒸发浓缩,冷却,过滤等操作步骤从废镍触媒中回收有实用价值的硫酸镍,硫酸镁晶体,其回收率分别为75%和90%,经济效益也比较好。 相似文献