全文获取类型
收费全文 | 5578篇 |
免费 | 82篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 277篇 |
综合类 | 3篇 |
化学工业 | 1219篇 |
金属工艺 | 149篇 |
机械仪表 | 108篇 |
建筑科学 | 77篇 |
矿业工程 | 2篇 |
能源动力 | 132篇 |
轻工业 | 391篇 |
水利工程 | 16篇 |
石油天然气 | 2篇 |
无线电 | 593篇 |
一般工业技术 | 933篇 |
冶金工业 | 1281篇 |
原子能技术 | 136篇 |
自动化技术 | 350篇 |
出版年
2022年 | 19篇 |
2021年 | 57篇 |
2020年 | 26篇 |
2019年 | 26篇 |
2018年 | 49篇 |
2017年 | 52篇 |
2016年 | 87篇 |
2015年 | 60篇 |
2014年 | 82篇 |
2013年 | 215篇 |
2012年 | 173篇 |
2011年 | 217篇 |
2010年 | 151篇 |
2009年 | 196篇 |
2008年 | 200篇 |
2007年 | 153篇 |
2006年 | 145篇 |
2005年 | 153篇 |
2004年 | 130篇 |
2003年 | 133篇 |
2002年 | 147篇 |
2001年 | 127篇 |
2000年 | 116篇 |
1999年 | 168篇 |
1998年 | 517篇 |
1997年 | 314篇 |
1996年 | 273篇 |
1995年 | 164篇 |
1994年 | 151篇 |
1993年 | 140篇 |
1992年 | 82篇 |
1991年 | 80篇 |
1990年 | 70篇 |
1989年 | 67篇 |
1988年 | 68篇 |
1987年 | 54篇 |
1986年 | 59篇 |
1985年 | 65篇 |
1984年 | 69篇 |
1983年 | 83篇 |
1982年 | 68篇 |
1981年 | 65篇 |
1980年 | 61篇 |
1979年 | 57篇 |
1978年 | 44篇 |
1977年 | 41篇 |
1976年 | 54篇 |
1975年 | 19篇 |
1974年 | 27篇 |
1973年 | 20篇 |
排序方式: 共有5669条查询结果,搜索用时 15 毫秒
31.
The objective of the present study is to develop multi-functioned coating to the components, which are made of copper with electroplated Ni and are widely used for steel making industry. In this paper, we report the mechanical and thermal properties of Ni based superalloys with carbide sprayed by high velocity oxygen fuel (HVOF), and the detailed effects of sprayed material, spraying conditions, and initial powder structure on these properties. It was found that, among commercial Ni self-fluxing alloys (without fusing treatment), coating with a carbon content of 0.58 mass% had the most preferable properties, with a good balance of the hardness, strength, and thermal shock resistance. The thermal shock resistance depended not only on the strength of the coating but also on the volume contraction when tested at high temperatures. For the several developed Ni based superalloys with carbide, Ni20Cr8Mo5Fe–WC and Ni16Cr15Mo3–WC demonstrated the prominent adhesion strength and thermal shock resistance with high Galvanic corrosion resistance through optimized spraying condition. Also, 20 mass% NiCr–Cr3C2 coating sprayed by using employed relatively small primary particle succeeded in achieving the multi-superior properties; high adhesion strength, high corrosion resistance and thermal shock resistance. 相似文献
32.
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
33.
Takakazu Yamamoto Kouichi ShiraishiMahmut Abla Isao YamaguchiL.“Bert” Groenendaal 《Polymer》2002,43(3):711-719
Neutral and non-doped poly(3,4-ethylenedioxythiophene), PEDOTh(Ni), and its hexyl derivative, PEDOTh-C6(Ni), have been prepared by organometallic dehalogenation polycondensation of 2,5-dichloro-3,4-ethylenedioxythiophene and its hexyl derivative with a zerovalent nickel complex. PEDOTh-C6(Ni) was soluble in organic solvents and 1H NMR data indicated that it had an Mn of 11,000. MALDI-TOF mass analysis of PEDOTh(Ni) gave Mn and Mw of about 1700 and 2400, respectively. PEDOTh-C6(Ni) showed a UV-Vis absorption peak at 546 nm in CHCl3. Electrochemical oxidation of PEDOTh-C6(Ni) started at about −0.40 V vs Ag+/Ag and gave a peak at 0.20 V vs Ag+/Ag. Chemical and electrochemical oxidation (or p-doping) of PEDOTh-C6(Ni), both in solutions and in a solid state, led to weakening of the original π-π∗ peaks and rise of new peak(s) in a region of 800-1500 nm. The p-doping of PEDOTh-C6(Ni) caused not only a decrease in the intensity of 1H NMR signals of the bridging ethylene hydrogens but also a decrease in that of the hexyl side chain, suggesting a strong interaction of the p-dopant with the side chain. NMR data of poly(3-methoxythiophene-2,5-diyl) also supported an assumption that p-doping brings about a severe change in electronic state of the substituent attached to the polythiophene main chain. PEDOTh(Ni) had a density of 1.71 g cm−3; the molecular packing mode of PEDOTh(Ni) is discussed based on the density of the polymer and its XRD data. 相似文献
34.
35.
36.
XIII. Yeast sequencing reports. Cloning and sequencing of the NES24 gene of Saccharomyces cerevisiae
We have cloned NES24 using a temperature-sensitive nes24-1 mutant as a host and sequenced a 3162 bp XhoI-EcoRI DNA fragment containing the NES24 gene. Computer analysis revealed that this segment contains a 1806 bp open reading frame which is needed for complementation of the nes24-1 mutation. We found SUP8 in the region upstream of the NES24 gene, placing the NES24 gene on chromosome XIII. A protein homology search indicated that NES24 encodes a new protein. The disruption of the NES24 gene resulted in temperature-sensitive growth. The sequence has been deposited in DDBJ/EmBL/GenBank data bases under Accession Number D15052. 相似文献
37.
38.
A self-healing algorithm is proposed for a ring network connected as a logical mesh. It offers good performance in terms of protection line capacity, restoration time, and survivability against multiple failures 相似文献
39.
Yasuhiro Kobayashi Toshiyuki Sawa Toshiyuki Furukawa Shigeru Kawamoto 《Electrical Engineering in Japan》2002,138(2):49-58
This paper describes a load dispatch method which minimizes power cost—[fuel cost]/[electric output]—for a power system with thermal plants and energy storage facilities. The proposed method employs fractional programming to convert a minimization problem with fractional objective function to a series of quadratic minimization problems, and semidefinite programming to solve converted problems. The method provides the optimum time‐dependent power output/input and storage level of energy storage facilities as well as time‐dependent power output of thermal plants. The method has been applied to a power system with five thermal plants, two energy storage facilities of various performances, and five load demands. The optimum load scheme of four time mesh points is obtained for the thermal plants and energy storage facilities. The fractional programming successfully converges the optimal scheme through a few iterations. The semidefinite programming deals with a variable matrix of 164 dimensions, and 185 inequality constraints. © 2001 Scripta Technica, Electr Eng Jpn, 138(2): 49–58, 2002 相似文献
40.