全文获取类型
收费全文 | 4213篇 |
免费 | 64篇 |
国内免费 | 214篇 |
专业分类
电工技术 | 32篇 |
综合类 | 63篇 |
化学工业 | 824篇 |
金属工艺 | 1228篇 |
机械仪表 | 292篇 |
建筑科学 | 79篇 |
矿业工程 | 71篇 |
能源动力 | 246篇 |
轻工业 | 25篇 |
水利工程 | 5篇 |
石油天然气 | 34篇 |
武器工业 | 23篇 |
无线电 | 150篇 |
一般工业技术 | 1101篇 |
冶金工业 | 241篇 |
原子能技术 | 25篇 |
自动化技术 | 52篇 |
出版年
2024年 | 2篇 |
2023年 | 51篇 |
2022年 | 63篇 |
2021年 | 94篇 |
2020年 | 120篇 |
2019年 | 82篇 |
2018年 | 92篇 |
2017年 | 96篇 |
2016年 | 87篇 |
2015年 | 114篇 |
2014年 | 228篇 |
2013年 | 174篇 |
2012年 | 253篇 |
2011年 | 380篇 |
2010年 | 249篇 |
2009年 | 290篇 |
2008年 | 292篇 |
2007年 | 299篇 |
2006年 | 242篇 |
2005年 | 189篇 |
2004年 | 156篇 |
2003年 | 183篇 |
2002年 | 153篇 |
2001年 | 127篇 |
2000年 | 111篇 |
1999年 | 96篇 |
1998年 | 70篇 |
1997年 | 54篇 |
1996年 | 23篇 |
1995年 | 20篇 |
1994年 | 19篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 14篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1975年 | 2篇 |
排序方式: 共有4491条查询结果,搜索用时 31 毫秒
31.
32.
S. Garcia A. Amrouche G. Mesmacque X. Decoopman C. Rubio 《International Journal of Fatigue》2005,27(10-12):1347
Fatigue damage accumulation of cold expanded hole in aluminum alloys used in land transportation components was investigated. Tests were carried out using pre-cracked SENT specimens and inserting an expanded hole at the crack tip. The degree of the cold expansion was chosen equal to 4.3%. Tests were performed in two and four block loading under constant amplitude. Two sequences were compared.The increasing and the decreasing magnitude were compared. The experimental results were compared to the damage calculated by the Miner's rule and a new simple fatigue damage indicator. This comparison shows that the ‘model of the damage stress’, which take into account of the loading history, yields a good estimation of the experimental results. Moreover, the error is minimized in comparison to the Miner's model. 相似文献
33.
引入组件对象模型,阐述了组件的结构及实现,对多传感器数据融合系统体系结构进行了分析,基于COM技术,以一种新的体系结构对铝电解槽健康诊断系统软件平台进行设计与实现。通过引入COM技术,简化了铝电解槽健康诊断软件平台的设计和实现。 相似文献
34.
35.
Yong Ju Lee 《Thin solid films》2004,446(2):227-231
Aluminum nitride (AlN) thin films were deposited by atomic layer deposition from aluminum chloride (AlCl3) and an ammonia/hydrogen plasma. The most important role of the ammonia/hydrogen plasma was to act as a reducing agent to extract Cl from AlCl3, and to form AlN subsequently. The growth rate was saturated at ∼0.042 nm/cycle, and the thickness was proportional to the number of reaction cycles. Repeating this reaction cycle led to precisely controlled growth. The film properties were analyzed using Auger electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy and time-of-flight elastic recoil detection analysis. The concentration of chlorine and hydrogen impurities was 0.23 and 2.01 at.%, respectively. AlN films showed good anti-oxidation properties when O2 was annealed at 650 °C for 30 min. 相似文献
36.
The damage and rupture mechanisms of thin sheets of 2024 aluminum alloy (Al containing Cu, Mn, and Mg elements) are investigated. Two grades are studied: a standard alloy and a high damage tolerance alloy. The microstructure of each material is characterized to obtain the second phase volume content, the dimensions of particles and the initial void volume fraction. The largest particles consist of intermetallics. Mechanical tests are carried out on flat specimens including U-notched (with various notch radii), sharply V-notched and smooth tensile samples. Stable crack growth was studied using “Kahn samples” and pre-cracked large center-cracked tension panels M(T). The macroscopic fracture surface of the different specimens is observed using scanning electron microscopy. Smooth and moderately notched samples exhibit a slant fracture surface, which has an angle of about 45° with respect to the loading direction. With increasing notch severity, the fracture mode changes significantly. Failure initiates at the notch root in a small triangular region perpendicular to the loading direction. Outside this zone, slant fracture is observed. Microscopic observations show two failure micromechanisms. Primary voids are first initiated at intermetallic particles in both cases. In flat regions, i.e. near the notch root of severely notched samples, void growth is promoted and final rupture is caused by “internal necking” between the large cavities. In slanted regions these voids tend to coalesce rapidly according to a “void sheet mechanism” which leads to the formation of smaller secondary voids in the ligaments between the primary voids. These observations can be interpreted using finite element simulations. In particular, it is shown that crack growth occurs under plane strain conditions along the propagation direction. 相似文献
37.
38.
用阿基米德实验方法,采用二次正交回归实验设计,研究了低温铝电解质Na3AlF6-AlF3-Al2O3-CaF2-MgF2-NaCl体系的密度.得到密度(ρ)与温度(t/℃)、分子比(CR)和NaCl质量分数(B/%)关系的简化方程:ρ=2.7305-1.225×10-3t 2.204×10-1 (CR)-2.014×10-3 (B-8.292)2.绘制了低温铝电解质密度的等值面图,并讨论了各因素对低温铝电解质密度的影响.经计算得出了实验条件下的密度为1.80~2.05 g/cm3,并与该电解工艺条件下的铝液密度对比,讨论了铝液与低温铝电解质的分离效果. 相似文献
39.
利用差示扫描量热仪(DSC)和H-90型膨胀仪,对潜热储能材料Al-34%Mg-6%Zn和Al-28%Mg-14%Zn合金的热物性参数--固液态时的比热容、30~500℃间的质量密度、熔化温度和熔化潜热等进行了测定.测试结果表明,两种合金的熔化温度和熔化潜热分别为454和447℃及314.4和303.2kJ/kg.从室温加热到熔化温度时,两种合金的密度分别减少1.05%和1.09%.在相变之前,两种合金的比热容随温度的升高而增大,在445℃时,分别为1 368.5和1 203.6 J/(kg·K).在相变过程中,由于熔化潜热的原因,合金的比热容变化很大.对合金组元和合金相对热物性参数的影响进行了讨论. 相似文献
40.
以中铝集团有限责任公司PS版基在国内的营销为研究对象和研究内容,运用营销管理的理论和方法,在系统分析中铝公司PS版基产品国内营销环境的基础上,从理论和实际两个方面来探讨中铝公司在国内市场营销中面临的竞争和存在的问题,提出了中铝公司国内市场PS版基产品的营销策略。 相似文献