全文获取类型
收费全文 | 1880篇 |
免费 | 54篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 100篇 |
综合类 | 1篇 |
化学工业 | 679篇 |
金属工艺 | 55篇 |
机械仪表 | 85篇 |
建筑科学 | 30篇 |
能源动力 | 106篇 |
轻工业 | 148篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 104篇 |
一般工业技术 | 341篇 |
冶金工业 | 47篇 |
原子能技术 | 93篇 |
自动化技术 | 148篇 |
出版年
2024年 | 3篇 |
2023年 | 18篇 |
2022年 | 25篇 |
2021年 | 44篇 |
2020年 | 22篇 |
2019年 | 21篇 |
2018年 | 41篇 |
2017年 | 22篇 |
2016年 | 51篇 |
2015年 | 33篇 |
2014年 | 64篇 |
2013年 | 128篇 |
2012年 | 87篇 |
2011年 | 117篇 |
2010年 | 88篇 |
2009年 | 121篇 |
2008年 | 124篇 |
2007年 | 108篇 |
2006年 | 105篇 |
2005年 | 81篇 |
2004年 | 54篇 |
2003年 | 65篇 |
2002年 | 64篇 |
2001年 | 35篇 |
2000年 | 34篇 |
1999年 | 41篇 |
1998年 | 31篇 |
1997年 | 24篇 |
1996年 | 30篇 |
1995年 | 18篇 |
1994年 | 15篇 |
1993年 | 19篇 |
1992年 | 13篇 |
1991年 | 15篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 9篇 |
1985年 | 24篇 |
1984年 | 24篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 15篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1973年 | 6篇 |
排序方式: 共有1942条查询结果,搜索用时 0 毫秒
181.
Koji Sumino 《Metallurgical and Materials Transactions A》1999,30(6):1465-1479
Dynamic processes of individual dislocations in Si, such as generation, motion, and multiplication, are reviewed on the basis
of direct observations by means of X-ray topography and transmission electron microscopy. The characteristics in the reaction
of oxygen impurities with dislocations are clarified by real time observations with these techniques. Immobilization of dislocations
due to the reaction is demonstrated. Stress-strain behavior of Si in the yield deformation is described in detail. It is sensitive
to the deformation temperature, strain rate, and also to the density of dislocations initially contained in the crystal. Though
the yield behavior of Si crystals free from dislocations is not influenced by oxygen impurities contained, that of dislocated
crystals is affected significantly by these impurities. All of these characteristics in the yield deformation of Si are shown
to be successfully described with a model that takes into account the dynamic processes of individual dislocations revealed
by the direct observations. 相似文献
182.
183.
184.
Byung-Nam Kim Keijiro Hiraga Koji Morita Hidehiro Yoshida 《Journal of the European Ceramic Society》2009,29(2):323-327
Commercial alumina powder was densified by spark plasma sintering (SPS) at 1150 °C. During SPS processing, the effects of the heating rate were examined on microstructure and transparency. With decreasing heating rate, the grain size and the residual porosity decreased, while the transparency increased. At a heating rate of 2 °C/min, the grain size was 0.29 μm, and the in-line transmission was 46% for a wavelength of 640 nm. The mechanisms for the fine microstructure and low porosity at slow heating, which are conflicting with some existing results, were explained by considering the role of defect concentration and grain-boundary diffusion during densification. 相似文献
185.
Koji Nakano Motonobu Takahashi Keiko Kawaguchi Kyoko Nozaki 《Synthetic Metals》2009,159(9-10):939-942
New π-conjugated polymers with dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran (DBBDF) unit in the main chains were synthesized. Copolymerization of 6,12-diiodo-DBBDF with p-diethynylbenzene or 2,7-diethynylfluorene derivative under Sonogashira–Hagiwara coupling-reaction condition gave the corresponding copolymer. The resulting copolymers were soluble in organic solvents such as tetrahydrofuran and chloroform. In UV–vis absorption spectra, both copolymers showed red-shifted spectra compared to their monomer units. In the chloroform solutions, the copolymer with DBBDF and p-diethynylbenzene units showed yellowish-green emission, while the copolymer with DBBDF and 2,7-diethynylfluorene units did greenish-blue emission. 相似文献
186.
Isao Yamashita Hitoshi Nagayama Koji Tsukuma 《Journal of the American Ceramic Society》2008,91(8):2611-2616
Effects of residual pores and optical birefringence on transmission through translucent polycrystalline alumina have been studied with the Mie scattering theory. The in-line and total forward transmissions of the translucent polycrystalline alumina were simulated as a function of porosity, pore radius, and grain size. The model revealed that porosity has a significant effect on both the total forward scattering and the in-line transmission, whereas grain size affects only in-line transmission. The calculated transmittance is in good agreement with the experimental values. The in-line transmission gradually increased with a decrease in grain size, and the effect of birefringence on the total forward transmission is negligible in the visible spectrum. The total forward transmission in the visible spectrum is mainly governed by residual pores. 相似文献
187.
Mitsuo Miyazawa Koji Takahashi Hideo Araki 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2006,81(4):674-678
Biotransformation of the isoflavones, 6,7,4′‐trimethoxyisoflavone ( 1 ) and 5,7,4′‐trimethoxyisoflavone ( 2 ) by Aspergillus niger was investigated. Compound 1 was transformed to 4′‐hydroxy‐6,7‐dimethoxyisoflavone ( 3 ) and 2 to 4′‐hydroxy‐5,7‐dimethoxyisoflavone ( 4 ). This suggested that 1 and 2 were demethylated at the C‐4′ position with regioselectivity by Aspergillus niger. Copyright © 2006 Society of Chemical Industry 相似文献
188.
189.
190.
Telechelically bis(hydrodimethylsilyl)-functionalized oligo(dimethylsiloxane)s or aromatics were found to give polymers constituting
of alternating disilylene and oligodimethylsiloxane or 4,4′-diylaromatics as repeating units by dehydrogenative coupling reaction
in the presence of palladium dibenzylideneacetone complex. The same catalyst gave polysilylenes with trisiloxane pendant from
1,1-dihydro-1,3,3,5,5,7,7,7-octamethyltetrasiloxane.
Received: 18 October 1996/Accepted: 31 October 1996 相似文献