全文获取类型
收费全文 | 206004篇 |
免费 | 15397篇 |
国内免费 | 7819篇 |
专业分类
电工技术 | 11257篇 |
技术理论 | 14篇 |
综合类 | 11221篇 |
化学工业 | 35748篇 |
金属工艺 | 10558篇 |
机械仪表 | 12000篇 |
建筑科学 | 16426篇 |
矿业工程 | 4947篇 |
能源动力 | 5862篇 |
轻工业 | 12698篇 |
水利工程 | 3225篇 |
石油天然气 | 11139篇 |
武器工业 | 1345篇 |
无线电 | 25496篇 |
一般工业技术 | 26760篇 |
冶金工业 | 10948篇 |
原子能技术 | 2116篇 |
自动化技术 | 27460篇 |
出版年
2024年 | 882篇 |
2023年 | 3267篇 |
2022年 | 5836篇 |
2021年 | 7942篇 |
2020年 | 5807篇 |
2019年 | 5018篇 |
2018年 | 5426篇 |
2017年 | 6204篇 |
2016年 | 5702篇 |
2015年 | 7300篇 |
2014年 | 9542篇 |
2013年 | 12283篇 |
2012年 | 12243篇 |
2011年 | 13898篇 |
2010年 | 11628篇 |
2009年 | 11479篇 |
2008年 | 10884篇 |
2007年 | 10479篇 |
2006年 | 10871篇 |
2005年 | 9636篇 |
2004年 | 6566篇 |
2003年 | 5785篇 |
2002年 | 5254篇 |
2001年 | 4728篇 |
2000年 | 4878篇 |
1999年 | 5642篇 |
1998年 | 5289篇 |
1997年 | 4352篇 |
1996年 | 3960篇 |
1995年 | 3312篇 |
1994年 | 2775篇 |
1993年 | 2193篇 |
1992年 | 1700篇 |
1991年 | 1278篇 |
1990年 | 1019篇 |
1989年 | 877篇 |
1988年 | 682篇 |
1987年 | 496篇 |
1986年 | 394篇 |
1985年 | 334篇 |
1984年 | 212篇 |
1983年 | 198篇 |
1982年 | 163篇 |
1981年 | 145篇 |
1980年 | 131篇 |
1979年 | 97篇 |
1978年 | 63篇 |
1977年 | 63篇 |
1976年 | 77篇 |
1975年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Microstructure evolution of AZ31 magnesium alloy during equal channel angular extrusion 总被引:3,自引:0,他引:3
Li Yuanyuan Zhang Datong Chen Weiping Liu Ying Guo Guowen 《Journal of Materials Science》2004,39(11):3759-3761
63.
64.
65.
66.
印染废水处理工艺研究及实例 总被引:1,自引:0,他引:1
本文简要介绍了印染废水水质特征,提出了处理工艺,并利用两个工程实例说明了该工艺的可行性. 相似文献
67.
Stress analysis of spontaneous Sn whisker growth 总被引:5,自引:0,他引:5
K. N. Tu Chih Chen Albert T. Wu 《Journal of Materials Science: Materials in Electronics》2007,18(1-3):269-281
Spontaneous Sn whisker growth is a surface relief phenomenon of creep, driven by a compressive stress gradient. No externally
applied stress is required for the growth, and the compressive stress is generated within, from the chemical reaction between
Sn and Cu to form the intermetallic compound Cu6Sn5 at room temperature. To obtain the compressive stress gradient, a break of the protective oxide on the Sn surface is required
because the free surface of the break is stress-free. Thus, spontaneous Sn whisker growth is unique that stress relaxation
accompanies stress generation. One of the whisker challenging issues in understanding and in finding effective methods to
prevent spontaneous Sn whisker growth is to develop accelerated tests of whisker growth. Use of electromigration on short
Sn stripes can facilitate this. The stress distribution around the vicinity and the root of a whisker can be obtained by using
the micro-beam X-ray diffraction utilizing synchrotron radiation. A discussion of how to prevent spontaneous Sn whisker growth
by blocking both stress generation and stress relaxation is given. 相似文献
68.
Effect of boron on the low-cycle fatigue behavior and deformation structure of INCONEL 718 at 650 °C
L. Xiao M. C. Chaturvedi D. L. Chen 《Metallurgical and Materials Transactions A》2004,35(11):3477-3487
Symmetrical push-pull low-cycle fatigue (LCF) tests were performed on INCONEL 718 (IN718) containing 12, 29, 60, and 100 ppm
B at 650 °C. The results showed that all the alloys experienced a relatively short period of initial cyclic hardening at low
strain amplitudes, followed by a regime of saturation or slightly continuous cyclic softening. The initial cyclic hardening
phase decreased with increasing strain amplitudes, and disappeared at the high strain amplitudes. A serrated flow was observed
in the plastic regions of cyclic stress-strain hysteresis loops. The saturated cyclic stress amplitude at a given strain amplitude
was highest for the alloy with 60 ppm B, and lowest for the alloy with 12 ppm B. The LCF lifetime increased with increasing
B concentration up to 60 ppm, and then decreased as the B content increased from 60 to 100 ppm. Fractographic analysis suggested
that the fracture mode changed from intergranular to transgranular cracking as the B concentration increased. The characteristic
deformation microstructures produced by LCF tests at 650 °C, examined via transmission electron microscopy, were regularly spaced arrays of planar deformation bands on {111} slip planes in all four
alloys. A ladderlike structure was observed in some local regions in the alloy with 12 ppm B. Heavily deformed planar deformation
bands were observed in the fatigued specimens with 100 ppm B. The mechanism of improvement in the LCF life of IN718 due to
B addition is discussed. 相似文献
69.
This study used different metals to modify Rh/Al2O3 catalysts for NO reduction in a simulated waste incineration flue gas containing 6% O2. The characteristics of the modified catalysts were analyzed using BET, TEM and XRD. The results of the experiment reveal that Na addition can significantly affect the properties of Rh/Al2O3 catalysts on the BET surface area and Rh metal dispersion. Furthermore, Na addition was found to significantly enhance the NO conversion of Rh/Al2O3 at 250–350 °C. On the contrary, Cu, Ni, and Co addition was found to have slight suppression effects. 相似文献
70.