全文获取类型
收费全文 | 1674篇 |
免费 | 49篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 107篇 |
综合类 | 2篇 |
化学工业 | 366篇 |
金属工艺 | 57篇 |
机械仪表 | 37篇 |
建筑科学 | 28篇 |
矿业工程 | 1篇 |
能源动力 | 110篇 |
轻工业 | 105篇 |
水利工程 | 8篇 |
石油天然气 | 6篇 |
无线电 | 153篇 |
一般工业技术 | 390篇 |
冶金工业 | 161篇 |
原子能技术 | 72篇 |
自动化技术 | 127篇 |
出版年
2022年 | 16篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 16篇 |
2018年 | 24篇 |
2017年 | 12篇 |
2016年 | 41篇 |
2015年 | 22篇 |
2014年 | 40篇 |
2013年 | 76篇 |
2012年 | 67篇 |
2011年 | 77篇 |
2010年 | 68篇 |
2009年 | 74篇 |
2008年 | 78篇 |
2007年 | 68篇 |
2006年 | 70篇 |
2005年 | 52篇 |
2004年 | 58篇 |
2003年 | 56篇 |
2002年 | 56篇 |
2001年 | 46篇 |
2000年 | 54篇 |
1999年 | 48篇 |
1998年 | 83篇 |
1997年 | 40篇 |
1996年 | 44篇 |
1995年 | 41篇 |
1994年 | 19篇 |
1993年 | 29篇 |
1992年 | 21篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 23篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 24篇 |
1981年 | 24篇 |
1980年 | 17篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 18篇 |
1976年 | 4篇 |
1975年 | 9篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有1730条查询结果,搜索用时 15 毫秒
81.
Tomoko Okuyama Jun Shirakawa Kazuki Tajima Yoko Ino Heidrun Vethe Yu Togashi Mayu Kyohara Ryota Inoue Daisuke Miyashita Jinghe Li Nozomi Goto Taiga Ichikawa Shingo Yamasaki Haruka Ohnuma Rie Takayanagi Yayoi Kimura Hisashi Hirano Yasuo Terauchi 《International journal of molecular sciences》2020,21(21)
82.
Porous glass-ceramics with a skeleton of the fast-lithium-conducting crystal Li1+ x Ti2− x Al x (PO4 )3 (where x = 0.3–0.5) were prepared by crystallization of glasses in the Li2 O─CaO─TiO2 ─Al2 O3 –P2 O5 system and subsequent acid leaching of the resulting dense glass-ceramics composed of the interlocking of Li1+ x Ti2− x Al x (PO4 )3 and β-Ca3 (PO4 )2 phases. The median pore diameter and surface area of the resulting porous Li1+ x Ti2− x Al x (PO4 )3 glass-ceramics were approximately 0.2 μm and 50 m2 /g, respectively. The electrical conductivity of the porous glass-ceramics after heating in LiNO3 aqueous solution was 8 × 10−5 S/cm at 300 K or 2 × 10−2 S/cm at 600 K. 相似文献
83.
The arabinofuranosidase gene was cloned from the cDNA of Aspergillus sojae. It was found to contain an open reading frame composed of 984 base pairs (bp) and to encode 328 amino acid residues (aa). The cDNA sequence suggested that the mature enzyme is preceded by a 26-aa signal sequence and the molecular mass was predicted to be 32,749 Da. The A. sojae arabinofuranosidase consists of a single catalytic domain; it does not have a specific substrate-binding domain such as the xylan-binding domain reported in an arabinofuranosidase from Streptomyces lividans (Vincent, P. et al.: Biochem. J., 322, 845-852, 1997). The deduced amino acid sequence of the catalytic domain of the mature enzyme exhibits extensive identity with the catalytic domains of Streptomyces coelicolor (74%), Aspergillus niger (75%), S. lividans (74%), and Aspergillus tubingensis (75%), which are enzymes that belong to family 62 of the glycosyl hydrolases. The cloned AFdase gene was expressed in Escherichia coli BL21 (DE3) pLysS as a cellulose-binding domain tag fusion protein. The specific activity of the purified recombinant enzyme was 18.6 units/mg protein, which is one-fourth that of the enzyme purified from a solid-state culture of A. sojae. 相似文献
84.
Michio Tajima Masatoshi Ikebe Yoshio Ohshita Atsushi Ogura 《Journal of Electronic Materials》2010,39(6):747-750
We investigated the effect of Fe contamination on the electronic properties of dislocation clusters in relation to oxygen
precipitation in multicrystalline silicon (mc-Si). Photoluminescence (PL) spectroscopy and mapping were performed at room
and liquid-He temperatures on mc-Si wafers before and after Fe contamination. PL spectra consisted of the band-edge emission,
the 0.78-eV emission associated with oxygen precipitates, and the dislocation-related D-lines. The Fe contamination increased
the electrically active dislocation clusters. Part of these clusters acted as preferential oxygen precipitation sites, and
their electronic properties were not further influenced by the Fe contamination. 相似文献
85.
Sang Jun Yoon Jae Goo Lee Hideo Tajima Akihiro Yamasaki Fumio Kiyono Tetsuya Nakazato Hiroaki Tao 《Journal of Industrial and Engineering Chemistry》2010,16(3):350-354
Extractions of five kinds of lanthanide metal ions by bis(2-ethylhexyl)phosphoric acid (DEHPA) with [1-Cn-3-methylimidazolium][PF6](Cn = C2, C4) or [1-butyl-4-methylpyridinium][PF6] were carried out under various DEHPA and HNO3 concentrations from 0 to 1 M and under different temperature conditions from 298 to 333 K. These results were compared with those using the conventional organic solvent, hexane, in terms of their distribution coefficient values. Under all of the conditions in this study, the ionic liquid system shows more than three times greater extractability for lanthanide compared to when hexane was used. The distribution coefficient of lanthanide ions decreased as the length of the alkyl chain increased from the ethyl to the butyl. In addition, the imidazolium cation generally shows a higher distribution coefficient compared to the pyridinium cation in an ionic liquid. The concentration ratio of lanthanides and DEHPA resulted in an extraction affinity transition for lanthanides. Also evaluated in this study were issues related to the selectivity associated with the lanthanide mixture and the dependency of the ionic radius during lanthanide extraction. 相似文献
86.
Hideo Tajima Yuta Yoshida Satoko Abiko Kazuaki Yamagiwa 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2010,156(2):479-486
Temperature-sensitive hydrogel beads were prepared by Kenics static mixer technology. The temperature-sensitive monomer N,N-diethylacrylamide and photo-crosslinkable pre-polymer ENT were used as model hydrogel materials. Drop dispersion of high viscosity polymer material in low viscosity hexadecane was made using the static mixer. Drops of a solution of the mixed materials were rapidly photo-crosslinked by UV irradiation after mixing in the static mixer, and spherical hydrogel beads with narrow, normal size distribution were thus prepared. The Kenics static mixer is a useful device for the preparation of spherical beads of temperature-sensitive hydrogels. The Sauter Mean Diameter of the hydrogel beads swollen in deionized water at 293 K was measured. The experimentally determined dimensionless swollen hydrogel bead diameter was well correlated with the Weber number, degree of swelling and viscosity ratio. The effects of gelation and ENT addition on the bead size were evaluated from the degree of swelling. The correlation equation can be used for size adjustment of temperature-sensitive spherical hydrogel beads. 相似文献
87.
88.
89.
This paper presents a construction of timing-error-detecting dual-edge-triggered flip-flops (DET-FFs). The proposed FF is based on a conventional DET-FF and a conventional timing error detection method. While the conventional timing error detection uses a transition detector with relatively large area, the proposed FF uses internal signals in a DET-FF as as an alternative to the transition detector. This paper also shows an evaluation result indicating that the proposed FF has smaller area overhead than the simple combination of the conventional DET-FF and timing error detection methods. 相似文献
90.
Sea urchin gonads are highly priced sushi foodstuff “Uni” in Japanese traditional food, but after removal of them the residual shells with spines are dumped as waste. However, sea urchin shells contain naphthoquinone pigments with several phenolic hydroxyl groups, which were expected to act as potent antioxidant substances by donating hydrogens. Our previous study has evaluated their antioxidant ability to depress lipid peroxidation. This study examined other antioxidant property of the pigments from purple sea urchin shells, which possess larger amount of pigments than those of red and green sea urchins. The pigments as well as known antioxidant, α-tocopherol, exhibited 1,1-diphenyl 2-picryhydrazyl (DPPH) radical scavenging ability. Superoxide anion radical and hydrogen peroxide were also scavenged while hydroxyl radical, one of the most reactive oxygen species, was not significantly inhibited. However, because the pigments had significant activity to scavenge hydrogen peroxide and superoxide anion radical that could be in vivo precursors of hydroxyl radical, sea urchin pigments would be able to depress the generation of its related active oxygen radical species. These results suggested that sea urchin shells, which are still regarded as food waste, would be a new bio-resource for obtaining natural antioxidant. 相似文献