全文获取类型
收费全文 | 499篇 |
免费 | 37篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 141篇 |
金属工艺 | 25篇 |
机械仪表 | 17篇 |
建筑科学 | 8篇 |
能源动力 | 9篇 |
轻工业 | 34篇 |
水利工程 | 2篇 |
无线电 | 60篇 |
一般工业技术 | 84篇 |
冶金工业 | 67篇 |
原子能技术 | 25篇 |
自动化技术 | 49篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 25篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 18篇 |
2017年 | 16篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 22篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 29篇 |
2009年 | 41篇 |
2008年 | 17篇 |
2007年 | 15篇 |
2006年 | 14篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 23篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1991年 | 5篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有536条查询结果,搜索用时 15 毫秒
101.
A total of fifteen saturated fatty acid esters were newly identified from the secretions of an unidentified Anaulaciulus sp. (Julida: Julidae). The fatty acid components of the esters were composed of normal chain acids (from C10 to C14) and of branched chain acids (from iso-C12 to iso-C15 and anteiso-C15). The alcohol moieties were all composed of normal chain alcohols varying from n-butanol to n-octanol. The most abundant component found in the total esters was n-hexyl laurate (64.7%). Novel compounds identified from the millipede secretion extracts include six branched iso- and anteiso-fatty
esters, an odd-numbered C11-fatty acid ester, a C13-fatty acid ester, and a C7-alcohol ester, all of which were previously undescribed natural products. In addition, a characteristic mixture of benzoquinones,
such as 2-methyl-1,4-benzoquinone, 2-methoxy-3-methyl-1,4-benzoquinone, 2,3-dimethoxy-1,4-benzoquinone, 2-methoxy-6-methyl-1,4-benzoquinone,
and 2,3-dimethoxy-5-methyl-1,4-benzoquinone were identified from the secretions, together with trace amounts of 1,4-benzoquinone. 相似文献
102.
Ryota Hosomi Kenji Fukunaga Midori Fukao Munehiro Yoshida Hirofumi Arai Seiji Kanda Toshimasa Nishiyama Teruyuki Kanada 《Food science and biotechnology》2012,21(5):1335-1342
This study evaluated phospholipids (PLs) containing n-3 polyunsaturated fatty acids (n-3 PUFAs) for their specific inherent effects and effects due to a combination of the presence of glycerophosphate structure and n-3 PUFAs on cholesterol metabolism in rats. Rats were fed a diet of AIN-93G containing soybean oil (SO, 7%), SO (5.8%)+fish oil (1.2%), SO (5.2%)+soybean PLs (1.8%), SO (5.2%)+PLs containing n-3 PUFAs (1.8%), and SO (4.0%)+fish oil (1.2%)+soybean PLs (1.8%). Diets with PLs containing n-3 PUFAs, and soybean PLs in combination with fish oil, resulted in decreased serum and liver cholesterol levels through enhancement of fecal cholesterol excretion and suppression of liver sterol regulatory element binding protein-2 mRNA expression compared with the diet containing soybean oil alone. This study shows that soybean PLs with added triacylglycerol that included n-3 PUFAs have the same effects on cholesterol metabolism as PLs containing n-3 PUFAs, and that these could be of benefit to people. 相似文献
103.
104.
Yoshinobu Nakamura Ryota Yamazaki Tomoyoshi Fukuda Kohei Shitajima Syuji Fujii Mariko Sasaki 《Journal of Adhesion Science and Technology》2013,27(19):1895-1906
The surface treatment of spherical silica particles with silane coupling agents having various organic functional groups was conducted and the effect of the alkoxy group number on the molecular flexibility of the silane chain with multilayer coverage was investigated using 1H-pulse nuclear magnetic resonance spectroscopy. The silica particles were treated with 2-propanol solution and heated at 120?°C for 24?h after solvent evaporation to accelerate the polycondensation reaction of silanol groups. For multilayer coverage, flexible linear chain and rigid network structures were expected to form on the surface from the di- and trialkoxy structures, respectively. However, the rigid network structure was formed from both the di- and trialkoxy structures with glycidoxy, amino, and methacryloxy functional silanes. Ring opening of the epoxy group occurred, followed by reaction to form the network structure, even with the dialkoxy structure of the glycidoxy functionality. Ring opening of the epoxy group could be reduced by pH adjustment of the treatment solution and the linear chain structure was formed from the dialkoxy structure. In the case of amino and methacryloxy functional groups, hydrogen bonds were formed between the amino or methacryloxy groups and the silanol groups on the silica surface or silane molecules. 相似文献
105.
Phromphong Pandee C. M. Gourlay S. A. Belyakov Ryota Ozaki Hideyuki Yasuda Chaowalit Limmaneevichitr 《Metallurgical and Materials Transactions A》2014,45(10):4549-4560
The mechanisms of Al-Si eutectic refinement due to scandium (Sc) additions have been studied in an Al-7Si-0.3Mg foundry alloy. The evolution of eutectic microstructure is studied by thermal analysis and interrupted solidification, and the distribution of Sc is studied by synchrotron micro-XRF mapping. Sc is shown to cause significant refinement of the eutectic silicon. The results show that Sc additions strongly suppress the nucleation of eutectic silicon due to the formation of ScP instead of AlP. Sc additions change the macroscopic eutectic growth mode to the propagation of a defined eutectic front from the mold walls opposite to the heat flux direction similar to past work with Na, Ca, and Y additions. It is found that Sc segregates to the eutectic aluminum and AlSi2Sc2 phases and not to eutectic silicon, suggesting that impurity-induced twinning does not operate. The results suggest that Sc refinement is mostly caused by the significantly reduced silicon nucleation frequency and the resulting increase in mean interface growth rate. 相似文献
106.
107.
A Unique Approach to Characterization of Sol‐Gel‐Derived Rare‐Earth‐Doped Oxyfluoride Glass‐Ceramics
Go Kawamura Ryota Yoshimura Kazunari Ota Song‐Yul Oh Norio Hakiri Hiroyuki Muto Tomokatsu Hayakawa Atsunori Matsuda 《Journal of the American Ceramic Society》2013,96(2):476-480
Using the sol‐gel route Nd3+‐doped oxyfluoride glass‐ceramics were prepared. LiYF4 and YF3 crystals were deposited in the glass‐ceramics and their size, distribution, and amount ratio were varied by changing the compositions and heating temperatures. The incorporation of Nd3+ ions into both the fluoride crystals was confirmed by the high‐resolution elemental mapping of the glass‐ceramics. The incorporated Nd3+ ions showed up and down conversion photoluminescence whose properties were obviously different among the samples. The preliminary site analysis for Nd3+ ions was carried out using a unique approach associated with the Prony series approximation. Finally, the approach was found to be useful for the analysis of materials that are structurally complicating. 相似文献
108.
Takeshi Kobayashi Yuki Imade Daisuke Shishihara Kenji Homma Miki Nagao Ryota Watanabe Toshiyuki Yokoi Atsuo Yamada Ryoji Kanno Takashi Tatsumi 《Journal of power sources》2008
A high-capacity type of all solid-state battery was developed using sulfur electrode and the thio-LISICON electrolyte. New nano-composite of sulfur and acetylene black (AB) with an average particle size of 1–10 nm was fabricated by gas-phase mixing and showed a reversible capacity of 900 mAh g−1 at a current density of 0.013 mA cm−2. 相似文献
109.
110.
Ryota NAKANISHI Koji SUEOKA Seiji SHIBA Makoto HINO Koji MURAKAMI Ken MURAOKA 《中国有色金属学会会刊》2009,19(4):988-991
A study the with first principles calculation of the interfaces of the Ni layer or Cu layer on the Fe(100) surface formed with metal plating was performed. Ni or Cu atoms were shown to adopt the corresponding position to the bcc structure of the Fe(100) substrate. Other calculations showed that the interfaces of Ni (5 atomic layers)/Fe(100) (5 layers) or Cu (5 atomic layers)/Fe(100) (5 layers) had square lattices. The orientation relationship of Ni/Fe(100) interface corresponds to fcc-Ni(100)//bcc-Fe(100), Ni[011]//Fe[010], and Ni[01]//Fe[001]. Similar results were obtained for Cu/Fe(100) interfaces. This structure was supported by TEM analysis of plated Ni layer on Fe(100) surfaces. The adhesion strength of the Ni/Fe(100) interface evaluated by first principles calculation was higher than that of the Cu/Fe(100) interface. The experimental results of Hull cell iron plated with Ni or Cu supported the results of the calculation. These results indicate that the first principles calculation, which deals with the ideal interface at the atomic scale, has the potential to evaluate the adhesion strength of metallic material interfaces. 相似文献