全文获取类型
收费全文 | 25835篇 |
免费 | 2893篇 |
国内免费 | 1370篇 |
专业分类
电工技术 | 277篇 |
技术理论 | 1篇 |
综合类 | 1417篇 |
化学工业 | 9338篇 |
金属工艺 | 1223篇 |
机械仪表 | 592篇 |
建筑科学 | 652篇 |
矿业工程 | 447篇 |
能源动力 | 366篇 |
轻工业 | 5649篇 |
水利工程 | 191篇 |
石油天然气 | 2151篇 |
武器工业 | 324篇 |
无线电 | 1448篇 |
一般工业技术 | 2890篇 |
冶金工业 | 1003篇 |
原子能技术 | 250篇 |
自动化技术 | 1879篇 |
出版年
2024年 | 125篇 |
2023年 | 559篇 |
2022年 | 716篇 |
2021年 | 1299篇 |
2020年 | 975篇 |
2019年 | 959篇 |
2018年 | 845篇 |
2017年 | 914篇 |
2016年 | 952篇 |
2015年 | 964篇 |
2014年 | 1411篇 |
2013年 | 1662篇 |
2012年 | 1748篇 |
2011年 | 1815篇 |
2010年 | 1344篇 |
2009年 | 1372篇 |
2008年 | 1160篇 |
2007年 | 1539篇 |
2006年 | 1370篇 |
2005年 | 1209篇 |
2004年 | 1005篇 |
2003年 | 822篇 |
2002年 | 729篇 |
2001年 | 695篇 |
2000年 | 614篇 |
1999年 | 536篇 |
1998年 | 435篇 |
1997年 | 369篇 |
1996年 | 340篇 |
1995年 | 294篇 |
1994年 | 250篇 |
1993年 | 190篇 |
1992年 | 180篇 |
1991年 | 143篇 |
1990年 | 110篇 |
1989年 | 70篇 |
1988年 | 56篇 |
1987年 | 47篇 |
1986年 | 42篇 |
1985年 | 54篇 |
1984年 | 48篇 |
1983年 | 33篇 |
1982年 | 43篇 |
1981年 | 6篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1951年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
M. Guerioune Y. Amiour W. Bounour O. Guellati A. Benaldjia A. Amara N. E. Chakri M. Ali-Rachedi D. Vrel 《International Journal of Self-Propagating High-Temperature Synthesis》2008,17(1):41-48
Aiming at preparation of shape memory alloys (SMAs), we explored the SHS of Cu1 − x
Zn1 − y
Al1 − z
alloys (0.29 < x < 0.30, 0.74 < y < 0.75, and 0.83 < z < 0.96). The most pronounced shape memory effect was exhibited by the alloys of the following compositions (wt %): (1) Cu(70.6)Zn(25.4)Al(4.0),
(2) Cu(70.1)Zn(25.9)Al(4.0), and (3) Cu(69.9)Zn(26.1)Al(4.0). The effect of process parameters on the synthesis of CuZnAl
alloys was studied by XRD, optical microscopy, and scanning electron microscopy (SEM). The grain size of CuZnAl was found
to depend on the relative amount of the primary CuZn and AlZn phases. Changes in the transformation temperature and heat of
transformation are discussed in terms of ignition intensity and compaction. Mechanism of the process depends on the level
of the temperature attained relative to the melting point of components. At the melting point of AlZn, the process is controlled
by the solid-state diffusion of AlZn into a product layer. The ignition temperature for this system depends on the temperature
of the austenite-martensite transformation in CuZnAl alloys. The composition and structure of the products was found to markedly
depend on process parameters. The SHS technique has been successfully used to prepare a variety of SMAs.
相似文献
82.
83.
84.
85.
The changes in surface composition of metallic alloys caused by segregation can be very efficiently studied by low-energy ion scattering (LEIS) due to the specific surface sensitivity of this technique. Investigations of single-crystal surfaces of ordered alloys are of particular interest because they provide the possibility to investigate the interplay between segregation effects and the order-disorder phase transition when passing through the transition temperature. Exemplifying these effects for bimetallic alloys we consider in particular the CuAu-system.For the quantitative interpretation of energy and angle resolved LEIS intensity distributions we compare experimental results with those from numerical simulations using the MARLOWE code which we extended with a detailed trajectory analysis. This allows us to apply various discrimination criteria, such as number of collisions, distance of closest approach, identification of the scattering crystal layer, total path length, etc. On this basis structural effects, ion survival probabilities and the influence of thermal vibrations can be studied.We demonstrate this potential by using CuAu(1 0 0) as a special example. The scattering potential parameters were calibrated with elemental single crystals of known structures and the anisotropic Debye temperatures taken from the literature showed good agreement, neutralization was of minor importance in this case. Our procedure could be successfully used for the quantitative analysis of the composition of the first and second layer as a function of temperature. These results are in good agreement with theoretical predictions. 相似文献
86.
In the present study a continuum model for one-dimensional plane Couette-Poiseuille flow is implemented to turbomolecular pumps in different flow regimes. Pumping performance of various turbomolecular pumps including 6 single rotors, a rotor-stator row, a rotor-stator-rotor row, and a multi-row with 13 alternative rotor-stator rows is considered here. The obtained results show that the model provides good quantitative values for pumping performance of turbomolecular pumps over the whole regimes ranging from molecular flow to transition to slip flow. 相似文献
87.
88.
高分子量丙烯酰胺-DAC共聚物的研制 总被引:7,自引:0,他引:7
采用复合引发体系 ,以丙烯酰胺 (AM)和阳离子单体丙烯酰氧乙基三甲基氯化铵(DAC)为共聚体 ,进行水溶液绝热聚合 ,研制了一种DAC单体含量为 4 0 %~ 5 0 %、相对分子质量大于 1× 10 7的阳离子型聚丙烯酰胺。 相似文献
89.
We present our machine learning system, that uses inductive logic programming techniques to learn how to identify transmembrane
domains from amino acid sequences. Our system facilitates the use of operators such as ‘contains’, that act on entire sequences,
rather than on individual elements of a sequence. The prediction accuracy of our new system is around 93%, and this compares
favourably with earlier results.
This work was carried out with the support of a research grant from ISIS, Fujitsu Laboratories. 相似文献
90.
从冷却曲线上相变段倾角最小原则出发,研究了新型激冷剂的配比与热分析法检测铸铁成分精度的关系,实验结果表明,能使相变段倾角最小的成分配比,也能提高对铸铁成分的热分析和检测精度。 相似文献