全文获取类型
收费全文 | 1261篇 |
免费 | 37篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 91篇 |
综合类 | 2篇 |
化学工业 | 390篇 |
金属工艺 | 23篇 |
机械仪表 | 33篇 |
建筑科学 | 20篇 |
能源动力 | 67篇 |
轻工业 | 101篇 |
无线电 | 119篇 |
一般工业技术 | 208篇 |
冶金工业 | 150篇 |
原子能技术 | 37篇 |
自动化技术 | 60篇 |
出版年
2023年 | 8篇 |
2022年 | 11篇 |
2021年 | 16篇 |
2020年 | 7篇 |
2019年 | 10篇 |
2018年 | 14篇 |
2017年 | 24篇 |
2016年 | 16篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 43篇 |
2012年 | 44篇 |
2011年 | 63篇 |
2010年 | 53篇 |
2009年 | 38篇 |
2008年 | 45篇 |
2007年 | 53篇 |
2006年 | 45篇 |
2005年 | 43篇 |
2004年 | 39篇 |
2003年 | 30篇 |
2002年 | 41篇 |
2001年 | 30篇 |
2000年 | 34篇 |
1999年 | 38篇 |
1998年 | 81篇 |
1997年 | 41篇 |
1996年 | 47篇 |
1995年 | 26篇 |
1994年 | 25篇 |
1993年 | 29篇 |
1992年 | 21篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 15篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 15篇 |
1985年 | 23篇 |
1984年 | 13篇 |
1983年 | 18篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 18篇 |
1975年 | 6篇 |
1974年 | 6篇 |
排序方式: 共有1301条查询结果,搜索用时 31 毫秒
1.
2.
Ichiro Hirosawa Tetsuo Honma Kazuo Kato Naoto Kijima Yasuo Shimomura 《Journal of the Society for Information Display》2004,12(3):269-273
Abstract— We studied the influence of annealing in air on doped europium in BaMgAl10O17 by performing x‐ray absorption fine‐structure measurements. We determined the oxidation of doped divalent europium by annealing in air at over 500°C. The interatomic distance between the europium and the surrounding oxygen atoms was compressed by oxidation. It also appears that the oxidation process of europium is determined by the diffusion of oxygen into BaMgAl10O17. 相似文献
3.
4.
5.
Yasuo Koide T. Kawakami Masanori Murakami N. Teraguchi Y. Tomomura A. Suzuki 《Journal of Electronic Materials》1998,27(6):772-775
Schottky barrier heights (SBHs) of a variety of metals (In, Cd, Nb, Ti, W, Cu, Ag, Au, Ni, Pt, and Se) contacting to p-ZnSe
grown by a molecular beam epitaxy method were determined by analyzing capacitance-voltage (C-V) and/or current density-voltage
(J-V) curves. The SBH values of the Au and Ni contacts were determined from intersections of straight lines of the C−2-V curves to be 1.23 and 1.13 eV, respectively. The J-V calculations provided a large SBH value of 1.2 ± 0.1 eV for a variety
of metals, indicating that the Fermi-level could be pinned at the contact interface. Reduction of the SBH values to a level
lower than 0.4 eV and/or increase of doping concentrations to a level higher than 1020 cm−3 are essential to obtain an ohmic contact with contact resistivity of around 10−3 Ω·cm2. 相似文献
6.
High performance liquid chromatographic separation of a series of mono-, di- and trihydroxylated 5β-cholanic acids which differ
only in position and configuration of hydroxyl groups at positions C-3, C-7 and/or C-12, is reported. The C-24 free acids
were derivatized to four different classes of UV-sensitive esters, i.e.,p-bromophenacyl (BP),m-methoxyphenacyl (MP), 4-nitrophthalimidemethyl (NPM) and 9-anthrylmethyl (AM) esters, and chromatographed on two, variants
of C18 reversed-phase columns (Nova-Pak C18 and Zorbax ODS) with methanol-water systems as mobile phase. Separation efficiency and elution order of some isomeric pairs
were influenced by both the structure of the C-24 ester groups and the nature of the columns used. Excellent chromatographic
properties were found for those derivatives, particularly for the NPM esters. 相似文献
7.
We characterized the L-carnitine transport system which is defective in the kidney of juvenile visceral steatosis (JVS) mice by using kidney slices and carnitine-related compounds, and evaluated the influence of the transport defect on the biosynthetic pathway of carnitine. The JVS mouse transport system defect, calculated as the difference in the transport activity between control and JVS mice, was simulated in control by gamma-butyrobetaine (gamma-BB) and acetyl L-carnitine. gamma-BB hydroxylase activity in the liver of JVS mice was double that of control mice, but the hepatic level of gamma-BB in JVS mice was lower than in control mice, suggesting that the conversion of gamma-BB to carnitine is not activated in the liver of JVS mice. JVS mice showed higher fractional excretions not only of L-carnitine but also of gamma-BB and acetyl L-carnitine than control mice, indicating disturbed reabsorption of gamma-BB and acetyl L-carnitine. The disturbed reabsorption of gamma-BB in JVS mice is consistent with the fact that the amount of urinary gamma-BB in JVS mice was four times that of control. The sum of the concentrations of L-carnitine, acetyl L-carnitine and gamma-BB in the urine of JVS mice was not significantly different from that of the control, suggesting no remarkable increase of biosynthesis of gamma-BB and carnitine in JVS mice. All these findings suggest that the carnitine transport system plays a role in the transport of gamma-BB and that carnitine deficiency is aggravated by the disturbed reabsorption of gamma-BB in the kidney. 相似文献
8.
The most serious problem preventing the widespread use of SOI CMOSFETs-the floating body effects-are almost fully suppressed by a new source structure. In an nMOSFET, this new structure can be represented by an equivalent circuit of a bipolar embedded source structure (BESS) just beneath the n+ source junction. In the source region, or p type (or n--type) recombination centers are embedded in a low-impurity-diffusion region (the base) and acts as a collector of the excess body carriers. The low-impurity-source region lowers the diffusion potential barrier for holes at the source junction. The solid-phase epitaxial regrowth mechanism of the Si+ implanted amorphous SOI layer was studied and applied to fabricate a prototype of this device capable of symmetric source-drain operations with the same source-drain breakdown voltage as that of a bulk device 相似文献
9.
Yasuo Suzuki Ryoetsu Yoshino Hisashi Saitoh Kazunori Fukushi Yoshikazu Sonehara 《Journal of Alloys and Compounds》1992,180(1-2):383-389
The mean molal activity coefficients of aqueous scandium chloride, nitrate, bromide and perchlorate solutions were determined at 25.0° for dilute to saturated concentrations, together with the activities of water. In the dilute solutions of scandium halides, the activity coefficients were obtained from electromotive force measurements on galvanic cells, and the osmotic coefficients of all four solutions above 0.1 mol kg−1 were determined from the isopiestic measurements. Least-squares equations were fitted to these coefficients, which were then used to calculate the mean molal activity coefficients and water activities. The relationships between these results and the corresponding activity data for other rare earth salts, and to the cation hydration and ionic interactions, are discussed. The results on scandium perchlorate solutions suggested that the inner-sphere hydration number of tervalent scandium ion may be seven. 相似文献
10.
Enhancing heat transfer ability of drag reducing surfactant solutions with static mixers and honeycombs 总被引:4,自引:0,他引:4
Yunying Qi Yasuo Kawaguchi Richard N. Christensen Jacques L. Zakin 《International Journal of Heat and Mass Transfer》2003,46(26):5161-5173
Solutions containing drag reducing additives also show reduced heat transfer which limits their use in district heating and cooling recirculation systems where heat exchange is critical. In this study, static mixers A and B and honeycombs were installed at the entrance to a heat exchanger to break the solution microstructure temporarily and thereby enhancing their heat transfer ability when passing through the heat exchanger. The effectiveness of the destructive devices in enhancing the heat transfer ability of drag reducing cationic and mixed zwitterionic/anionic surfactant solutions was investigated together with the microstructure recovery time and pressure drop penalty paid for the heat transfer enhancement. 相似文献