全文获取类型
收费全文 | 12824篇 |
免费 | 878篇 |
国内免费 | 780篇 |
专业分类
电工技术 | 237篇 |
综合类 | 535篇 |
化学工业 | 1296篇 |
金属工艺 | 5090篇 |
机械仪表 | 351篇 |
建筑科学 | 47篇 |
矿业工程 | 302篇 |
能源动力 | 486篇 |
轻工业 | 23篇 |
水利工程 | 2篇 |
石油天然气 | 145篇 |
武器工业 | 77篇 |
无线电 | 450篇 |
一般工业技术 | 3465篇 |
冶金工业 | 1701篇 |
原子能技术 | 124篇 |
自动化技术 | 151篇 |
出版年
2024年 | 40篇 |
2023年 | 269篇 |
2022年 | 221篇 |
2021年 | 429篇 |
2020年 | 416篇 |
2019年 | 415篇 |
2018年 | 376篇 |
2017年 | 409篇 |
2016年 | 376篇 |
2015年 | 387篇 |
2014年 | 587篇 |
2013年 | 940篇 |
2012年 | 644篇 |
2011年 | 1133篇 |
2010年 | 665篇 |
2009年 | 774篇 |
2008年 | 667篇 |
2007年 | 706篇 |
2006年 | 725篇 |
2005年 | 574篇 |
2004年 | 549篇 |
2003年 | 514篇 |
2002年 | 374篇 |
2001年 | 321篇 |
2000年 | 304篇 |
1999年 | 258篇 |
1998年 | 197篇 |
1997年 | 218篇 |
1996年 | 147篇 |
1995年 | 139篇 |
1994年 | 126篇 |
1993年 | 93篇 |
1992年 | 82篇 |
1991年 | 58篇 |
1990年 | 58篇 |
1989年 | 43篇 |
1988年 | 30篇 |
1987年 | 31篇 |
1986年 | 31篇 |
1985年 | 16篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 25篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 9篇 |
1978年 | 14篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
HU Wei WANG Yanbin CHU WuYang XIAO Jimei University of Science Technology Beijing China Associate Professor Department of Materials Physics University of Science Technology Beijing Beijing China 《金属学报(英文版)》1992,5(6):443-448
The ductility loss and threshold stress intensity,K_(IH)during hydrogen charging were measuredfor pure Ni and four Ni-Fe fcc alloys.The results show that ductility loss in 40Ni60Fe alloyand K_(IH)a 50Ni50Fe alloy have a minimum value.The variations of the amounts of hydride,hydrogen evolution and dislocation structure with composition have been investigated.The va-riation of hydrogen embrittlement susceptibility with composition measured by ductility lossand by K_(IH)or K_(IH)/K_C can be explained by means of the synthetical effects of amount ofhydride,solutionized hydrogen and the extent of dislocation planarity on hydrogenembrittlement susceptibility. 相似文献
72.
Internal nitridation of Co containing 3 a/o of either Cr, Al, or Ti was studied over the range of 700–1100° C in NH3/H2 (694 ratio). The kinetics of thickening of the reaction zone followed the parabolic rate law, suggesting that solidstate diffusion was rate controlling. Activation energies obtained were 51.2 Kcal/molfor Co-3Cr, 46.6 Kcal/mol for Co-3Ti, and 27.9 Kcal/mol for Co-3Al. XRD showed only CrN, AlN, and TiN. Deep etching revealed that AlN formed hexagonal plates near the surface when formed at high temperature, the precipitates becoming more massive (blocky morphology) near the reaction front. TiN formed elongated dendritic precipitates, whereas CrN tended to form spheroids. The precipitate size varied with temperature, decreasing with decreasing temperature. In some cases, nitriding formed a case but no visible precipitates even at very high magnifications in the SEM. The solubility of nitrogen in cobalt was determined by long-time equilibration and subsequent chemical analyses. The diffusivity of nitrogen in cobalt was determined from measured permeabilities and the experimentally determined solubilities. Mechanisms are discussed, and the behavior of internal nitridation is compared with internal carburization and oxidation in cobalt alloys. 相似文献
73.
在铝合金与氧化膜的界面的富集化合金层,对阳极氧化膜的局部和整体结构、膜的组成以及性能有重大影响。因此,对铝合金富集化进行预测很有必要。 相似文献
74.
75.
The results are presented of exposure to a controlled high-temperature erosive gas stream of a series of alloys, which were selected to represent the range of microstructures and mechanical properties available in commercial high-temperature alloys. Analysis of the kinetic and morphological data suggested that the high-temperature oxidation behavior of a given alloy plays a very important role in determining its erosion-corrosion behavior under the conditions studied. In terms of relative behavior, alloys which are weak but ductile at temperature, and which form tenacious oxide scales, exhibited the highest resistance to high-temperature erosion-corrosion. Simple models were developed to describe the expected interaction between high-temperature oxidation and erosion. 相似文献
76.
Corrosion in wet lime/limestone systems used for flue gas desulfurization in thermal power plants is of great concern. The
frequent variations in acidity and in chloride and fluoride ion concentrations experienced by such systems pose a serious
threat to the materials of construction. Currently used materials mostly type 316L stainless steel often fail to meet their
life expectancy. The present study evaluates the performance of advanced Ni- Cr- Mo alloys 59 and C- 276 in a simulated sulfur
dioxide scrubber environment. Accelerated tests showed that high Ni- Cr- Mo alloys have little tendency to leach metal ions
such as chromium, nickel, and molybdenum at different impressed potentials. Scanning electron microscopy was used to examine
the morphology of pitting attack. 相似文献
77.
Fe-30Mo alloys containing up to 9.1 wt% Al were sulfidized at 0.01 atm sulfur vapor over the temperature range of 700–900°C. The sulfidation kinetics followed the parabolic rate law for all alloys at all temperatures. For alloys containing small and intermediate amounts of Al (<4.8 wt.%), a duplex sulfide scale formed. The outer layers of the scales were found to be relatively compact FeS in all cases; whereas the inner layers were composed of the layered compound MoS
2
(intercalated with iron), the Chevrel compound Fe
x
Mo
6
S
8,a spinel double sulfide Al
x
Mo
2
S
4,depending on the Al content of the alloy and the sulfidation temperature. Extremely thin scales were found on the alloys with higher Al contents. Accordingly, extremely slow sulfidation rates were observed—even slower than the sulfidation rate of pure Mo. The transition of the sulfidation kinetics from a high-rate active mode to a low-rate passive mode requires both a critical Al content in the alloy and a critical Mo content. Because of the two-phase nature of the alloys, the latter requirement implies a critical volume fraction of the intermetallic second-phase in the alloy, which has been known as the multiphase effect. Interestingly, the multiphase effect in these alloys was also a function of the Al content in the alloys. 相似文献
78.
以2090 Ce合金为研究对象,对不同时效时间的室温拉伸断口进行了半定量分析,探讨了拉伸性能对断裂特征的响应关系,重点分析合金分层裂纹的形成过程。研究表明:2090 Ce合金的断裂方式以韧窝、分层开裂和沿亚晶界开裂3种为主,随时效时间的延长,韧窝、分层开裂逐渐减少,沿亚晶界开裂比例逐渐加大:分层开裂程度与时效程度有密切关系:分层开裂过程与试样内部受力状态、晶界状态有密切关系。分层最先发生在试样中心,随后在二分之一、四分之一……处反复发生,最终将试样分割成一系列平行的薄板。时效后期由于亚晶界的弱化,使裂纹倾向沿亚晶界扩展,从而抑制分层开裂的发生,同时导致合金强度,尤其是塑性的下降。 相似文献
79.
龙克昌 《稀有金属材料与工程》1992,21(1):8-13
介绍了镍-金属氢化物电池的特性和该类电池所用的稀土贮氢材料及其成份配制、制备工艺、合金添加剂对LaNi_5基合金电极综合性能的影响,以及该类电池的应用开发前景。 相似文献
80.
Ti—Al二元合金的成分对组织和力学性能的影响 总被引:1,自引:0,他引:1
用金相、扫描电镜和X射线衍射研究了6种不同Al含量Ti-Al二元合金铸态和退火态的组织结构和相组成的特征和变化。从结晶动力学的观点,分析了合金的结晶凝固过程。采用三点弯曲方法研究了合金的抗弯性能同Al含量的关系。结果表明,Al含量为34 wt%,经1100℃/30 h退火的合金抗弯性能最好,Al含量偏离34wt%,都对合金的力学性能不利。 相似文献