全文获取类型
收费全文 | 12509篇 |
免费 | 1404篇 |
国内免费 | 608篇 |
专业分类
电工技术 | 158篇 |
综合类 | 667篇 |
化学工业 | 2913篇 |
金属工艺 | 3972篇 |
机械仪表 | 600篇 |
建筑科学 | 196篇 |
矿业工程 | 340篇 |
能源动力 | 131篇 |
轻工业 | 422篇 |
水利工程 | 19篇 |
石油天然气 | 295篇 |
武器工业 | 84篇 |
无线电 | 407篇 |
一般工业技术 | 2179篇 |
冶金工业 | 1894篇 |
原子能技术 | 89篇 |
自动化技术 | 155篇 |
出版年
2024年 | 92篇 |
2023年 | 219篇 |
2022年 | 418篇 |
2021年 | 438篇 |
2020年 | 550篇 |
2019年 | 425篇 |
2018年 | 416篇 |
2017年 | 496篇 |
2016年 | 442篇 |
2015年 | 511篇 |
2014年 | 697篇 |
2013年 | 732篇 |
2012年 | 775篇 |
2011年 | 860篇 |
2010年 | 630篇 |
2009年 | 676篇 |
2008年 | 513篇 |
2007年 | 813篇 |
2006年 | 805篇 |
2005年 | 723篇 |
2004年 | 632篇 |
2003年 | 502篇 |
2002年 | 392篇 |
2001年 | 320篇 |
2000年 | 265篇 |
1999年 | 215篇 |
1998年 | 194篇 |
1997年 | 138篇 |
1996年 | 132篇 |
1995年 | 88篇 |
1994年 | 85篇 |
1993年 | 42篇 |
1992年 | 65篇 |
1991年 | 36篇 |
1990年 | 44篇 |
1989年 | 44篇 |
1988年 | 19篇 |
1987年 | 9篇 |
1986年 | 16篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
研究了Ti14钛合金半固态条件下的变形行为。半固态变形后.由于液相的出现,加快了原子扩散的能力.其变形激活能明显高于钛合金固态变形时的激活能。结果表明,变形后,晶界、晶内液相长大,形成了宽化的晶界和网格状结构。 相似文献
152.
研究了高铬马氏体耐热钢(0.09C-10.2Cr-0.52Ni-1.52Mo-0.22V-0.07Nb-3.0Co-0.01Ti-0.0129N-0.0033B)的显微组织和力学性能.结果表明该钢经1100℃×1h空冷正火处理 750℃×1h空冷回火处理后的显微组织为板条状马氏体,在原奥氏体晶界和板条间分布有M23C6碳化物,并有少量1~3μm的M3B2颗粒,马氏体板条内部有10~30 nm的MX型析出相.短期蠕变试验数据显示其在650℃的蠕变性能优于P92钢. 相似文献
153.
Kiyoshi Kusabiraki Noriaki Kuroda Isao Motohira Takayuki Ooka 《Oxidation of Metals》1997,48(3-4):289-302
The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO2 or Ar-10%CO2. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO2) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed. 相似文献
154.
155.
The α alloy Ti-2Al-2.5Zr and near α alloy Ti-4Al-2V were hydrogenated to various levels. The morphology,orientation relation (OR), and habit plane of the hydrides were studied by means of transmission electron microscopy (TEM). It was found that in the two alloys most of the precipitates are δ-hydrides which have fcc structure with the lattice parameter a = 0.44 nm. Two basic orientation relationships and habit planes of the precipitates are determined. Twin structure was observed in both alloys. 相似文献
156.
Daniel G. Sanders Mamidala Ramulu 《Journal of Materials Engineering and Performance》2004,13(6):744-752
Superplastic forming (SPF) combined with diffusion bonding (DB) has been used successfully for the fabrication of titanium
aerospace hardware. Many of these applications have been for military aircraft, whereby a complex built-up structure has been
replaced with monolithic parts. Several methods for applying the two- and four-sheet titanium SPF/DB processes have been devised,
including the welding of sheets prior to forming and the use of silk-screened stop-off (yttria) to prevent bonding where it
is undesirable. Very little progress has been made in the past few years toward understanding and modeling the SPF/DB process
using constitutive equations and data by laboratory testing. Concerns that engineers face in designing for fatigue life, acceptable
design loads, and damage tolerance are currently being studied, but the database is very limited. This is a summary of past
work found in the literature and forms the foundation for additional research.
This paper was presented at the International Symposium on Superplasticity and Superplastic Forming sponsored by the Manufacturing
Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium
was organized by Daniel G. Sanders, The Boeing Company. 相似文献
157.
固溶条件对一种新型亚稳β钛合金时效响应的影响 总被引:4,自引:0,他引:4
根据近临界钼当量和多元强化原则设计了一种新型亚稳β钛合金(Ti-B20),以室温拉伸性能和显微组织为主要考察内容研究了固溶处理对这种新合金时效响应的影响。结果表明:在同样的时效条件下,该合金的抗拉伸强度随着固溶温度的升高而升高,而固溶后水淬比空冷能产生更高的硬化效应,分析结果揭示了该合金独特的时效响应来自于其亚稳β相较低的稳定性和过剩空位对析出的共同作用。 相似文献
158.
A new metastable beta titanium alloy of Ti-Al-Mo-V-Cr-Fe-Zr-Sn system was designed and named Ti-B20. In order to investigate the aging properties and microstructures of the new alloy .subjected to different solution treatments, the tensile and Vickers hardness tests were carried out and the optical microscope and scanning electron microscope analysis were performed. The results show that the new alloy displays rapid aging response, high age strengthening effect and fine deposition. In addition, beta solution results in ultra high age hardening effect with low tensile ductility, whereas excellent combination of aging strength and ductility can be obtained after solution treated below beta transus temperature. 相似文献
159.
研究了TC4钛合金在柱面-平面接触条件下的微动疲劳行为.通过观察微动区的磨损特征和截面形貌,分析了微动疲劳损伤机制,探讨了磨屑的形成与演变过程及其对微动疲劳行为的影响,考察了摩擦系数随时间的变化.结果表明,TC4钛合金微动区的损伤机制以粘着磨损、磨粒磨损和接触疲劳为主,并伴有氧化磨损.磨屑是基体材料脱落、破碎、氧化形成的,磨屑中的硬质氧化物颗粒促进了合金表面的磨粒磨损,加速了疲劳失效. 相似文献
160.
Advances in fabricating superplastically formed and diffusion bonded components for aerospace structures 总被引:1,自引:0,他引:1
Larry D. Hefti 《Journal of Materials Engineering and Performance》2004,13(6):678-682
Superplastic forming and diffusion bonding (SPF/DB) production hardware is being fabricated today for aerospace applications.
Metal tooling is being used to bring the titanium sheets into contact so diffusion bonding can occur. However, due to material
sheet and tooling tolerances, good bond quality is difficult to achieve over large areas. A better method for achieving DB
is to use “stop-off” inside sealed sheets of titanium, which constitutes a pack, and then the pack is bonded using external
gas pressure. A good method for heating the pack for this process is to use induction heating. Components using “stop-off”
that were diffusion bonded first and then superplastically formed have shown much better bond quality than components that
were produced using matched metal tooling. This type of tooling has been successful at bonding small areas as long as the
exerted pressure is concentrated on the area where bonding is required. Finite element modeling is providing weight effect
solutions for titanium SPF/DB aerospace structures.
This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing
Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium
was organized by Daniel G. Sanders, The Boeing Company. 相似文献