全文获取类型
收费全文 | 52550篇 |
免费 | 4770篇 |
国内免费 | 4868篇 |
专业分类
电工技术 | 959篇 |
综合类 | 2690篇 |
化学工业 | 5295篇 |
金属工艺 | 27174篇 |
机械仪表 | 2816篇 |
建筑科学 | 594篇 |
矿业工程 | 1229篇 |
能源动力 | 1013篇 |
轻工业 | 401篇 |
水利工程 | 20篇 |
石油天然气 | 588篇 |
武器工业 | 793篇 |
无线电 | 1309篇 |
一般工业技术 | 9991篇 |
冶金工业 | 6631篇 |
原子能技术 | 412篇 |
自动化技术 | 273篇 |
出版年
2024年 | 245篇 |
2023年 | 867篇 |
2022年 | 1526篇 |
2021年 | 1750篇 |
2020年 | 1892篇 |
2019年 | 1447篇 |
2018年 | 1490篇 |
2017年 | 1922篇 |
2016年 | 1716篇 |
2015年 | 1818篇 |
2014年 | 2610篇 |
2013年 | 2727篇 |
2012年 | 3205篇 |
2011年 | 3991篇 |
2010年 | 2876篇 |
2009年 | 3143篇 |
2008年 | 2541篇 |
2007年 | 3642篇 |
2006年 | 3740篇 |
2005年 | 2967篇 |
2004年 | 2605篇 |
2003年 | 2265篇 |
2002年 | 1820篇 |
2001年 | 1672篇 |
2000年 | 1378篇 |
1999年 | 1154篇 |
1998年 | 847篇 |
1997年 | 804篇 |
1996年 | 771篇 |
1995年 | 571篇 |
1994年 | 507篇 |
1993年 | 363篇 |
1992年 | 349篇 |
1991年 | 253篇 |
1990年 | 229篇 |
1989年 | 198篇 |
1988年 | 98篇 |
1987年 | 39篇 |
1986年 | 20篇 |
1985年 | 11篇 |
1984年 | 21篇 |
1983年 | 9篇 |
1982年 | 27篇 |
1981年 | 22篇 |
1980年 | 8篇 |
1978年 | 9篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1959年 | 5篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
141.
Ti-45Al-10Nb合金的高温氧化行为 总被引:4,自引:0,他引:4
研究了Ti—45A1—10Nb(原子分数,%)合金在800-960℃在氧气和空气中的氧化行为.结果表明,该合金具有较好的高温抗氧化性能,其氧化增重速率与铁基耐热不锈钢相似或略优.与Ti—50A1合金相反,Ti-45A1-10Nb合金在空气中的氧化增重速率明显低于在纯氧中的氧化增重速率.X射线衍射与能谱分析表明,Ti-45Al一10Nb合金在氧气中的氧化产物主要有TiO2和Al2O3,但在空气中的氧化产物中有TiN相.这是降低氧化速率的主要原因,同时,合金元素Nb稳定了氧化层中的TiN相,因而提高了合金在空气中的抗氧化性能. 相似文献
142.
Hitoshi Kurokawa Taku Nakayama Yasunori Kobayashi Ken Suzuki Mutsumi Takahashi Seiichi Takami Momoji Kubo Naotsugu Itoh Parasuraman Selvam Akira Miyamoto 《Catalysis Today》2003,82(1-4):233-240
A modified Monte Carlo (MC) simulation was performed to investigate the hydrogen absorption behavior in Pd and Pd–Ag alloys of the composition PdxAg1−x (x=0.7–0.8) under H2 pressure (0.1 MPa) at different temperatures. The present method employed can consider the dissociative adsorption of hydrogen molecule and the subsequent absorption of hydrogen atom by formalizing the relationship between the pressure of hydrogen molecule and hydrogen atom. The potential parameters were determined to reproduce the solution enthalpy of hydrogen in pure metals. The results are in good agreement with experimental findings as well as previous theoretical studies. We confirmed that our method is useful to simulate the absorption of hydrogen in metals and alloys. 相似文献
143.
分析了山西焦化股份有限公司振动筛合金篦条磨损情况,对合金篦条磨损机理进行了研究,提出控制磨蚀和提高材料耐磨洼的方法。 相似文献
144.
论述了参数设计法在铝电解电容器设计开发阶段的应用。文中阐明了铝电解电容器的主要质量特性(损耗因子、电容量)及芯包外径的参数设计原理,并建立了归一化函数作为优选设计方案的判据。实例证明在铝电解电容器的设计过程中应用参数设计法以减小产品质量特性变异是有效的。 相似文献
145.
We have studied properties of quaternary alloy magnetic semiconductor (InGaMn)As grown on InP substrates by low-temperature molecular-beam epitaxy (LT-MBE). A large MCD peak whose intensity is larger than 500 mdeg for (InGaMn)As was observed. This peak intensity was about three times larger than that of typical (GaMn)As films. Relatively high Curie temperature of 83 K of [(In0.53Ga0.47)0.88Mn0.12]As was observed by Hall measurements. The carrier concentration of [(In0.53Ga0.47)0.88Mn0.12]As was estimated to be more than 1.0 × 1021 cm–3 by using the Curie–Weiss fitting of the Hall coefficient R
H, indicating that more than 40% of Mn atoms are activated. This means that (InGaMn)As has a higher activation ratio of Mn as acceptors than (GaMn)As. 相似文献
146.
G. G. Martin 《Journal of Failure Analysis and Prevention》2004,4(1):37-39
Piston failures are not a common occurrence, but they do occur, and failure is usually associated with fatigue crack growth.
Most failures initiate at the gudgeon pin hole or in the skirt of the piston. Occasionally they fail elsewhere. In the example
covered in this paper, failure initiated in the crown and progressed down to the gudgeon pin before final failure occurred.
This paper outlines the cause and mode of failure and shows that small metallurgical discontinuities can contribute to these
failures under the right circumstances. 相似文献
147.
148.
The effect of heat treatments on the tensile properties and microstructures of wrought Mg–Zn–Zr-Rare earth alloys MB25 and MB26 have been studied in this paper. It was shown that the homogenization of the cast ingots decreased the strength of the extruded bars because some grain boundary phases were dissolved during the process of this treatment, while the ageing treatment of the extruded bars increased the strength due to the dispersive precipitation of MgZn2 phase. The quenching + ageing treatments of the extruded bars decreases the strength and plasticity because of the growing up of the grains.Abbreviations ED
electron diffraction
- GB
grain boundary
- RE
rare earth
- TEM
transmission electron microscope 相似文献
149.
This paper is a summary of an extensive research program carried out by the authors on the structure of rapidly solidified aluminum alloys; and a comparison with the work of others also involved in this field. The paper discusses the changes in the dendritic and non-dendritic structure of the matrix at cooling rates from 10–3 to 1010 K/s and discusses the hetergeneity of the structure caused by interdendritic-segretion during solidification. 相似文献
150.