全文获取类型
收费全文 | 6797篇 |
免费 | 130篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 388篇 |
综合类 | 11篇 |
化学工业 | 1223篇 |
金属工艺 | 195篇 |
机械仪表 | 159篇 |
建筑科学 | 104篇 |
矿业工程 | 6篇 |
能源动力 | 181篇 |
轻工业 | 455篇 |
水利工程 | 32篇 |
石油天然气 | 26篇 |
武器工业 | 6篇 |
无线电 | 669篇 |
一般工业技术 | 1184篇 |
冶金工业 | 1781篇 |
原子能技术 | 134篇 |
自动化技术 | 390篇 |
出版年
2023年 | 23篇 |
2022年 | 62篇 |
2021年 | 108篇 |
2020年 | 50篇 |
2019年 | 55篇 |
2018年 | 71篇 |
2017年 | 67篇 |
2016年 | 75篇 |
2015年 | 88篇 |
2014年 | 107篇 |
2013年 | 243篇 |
2012年 | 201篇 |
2011年 | 272篇 |
2010年 | 193篇 |
2009年 | 223篇 |
2008年 | 223篇 |
2007年 | 222篇 |
2006年 | 228篇 |
2005年 | 188篇 |
2004年 | 182篇 |
2003年 | 179篇 |
2002年 | 186篇 |
2001年 | 163篇 |
2000年 | 141篇 |
1999年 | 165篇 |
1998年 | 670篇 |
1997年 | 420篇 |
1996年 | 307篇 |
1995年 | 213篇 |
1994年 | 220篇 |
1993年 | 173篇 |
1992年 | 93篇 |
1991年 | 97篇 |
1990年 | 99篇 |
1989年 | 79篇 |
1988年 | 78篇 |
1987年 | 61篇 |
1986年 | 74篇 |
1985年 | 86篇 |
1984年 | 58篇 |
1983年 | 66篇 |
1982年 | 49篇 |
1981年 | 55篇 |
1980年 | 54篇 |
1979年 | 33篇 |
1978年 | 27篇 |
1977年 | 57篇 |
1976年 | 56篇 |
1975年 | 32篇 |
1973年 | 23篇 |
排序方式: 共有6944条查询结果,搜索用时 0 毫秒
61.
Yasushi Takeuchi Kohjiro Yanagisawa Yuhsuke Tanaka Noriyuki Tsuruoka 《Korean Journal of Chemical Engineering》1997,14(5):377-381
Fixation of nitrogen oxides (NOx) in air onto granular activated carbon impregnated with chemicals was attempted to improve removal efficiency of NOx by activated carbon adsorption. Nitric oxide (NO) and nitrogen dioxide (NO2), were tried to remove by a flow test. Fixed-bed adsorption breakthrough curves were obtained when some kinds of carbon were
used. The amount adsorbed of NO2 changed with the amount and kinds of metallic salts impregnated. Chemicals-impregnated carbons were prepared from a commercial
activated carbon. Among obtained carbons, the one which showed the highest selectivity for NOx was chosen, and its performance with the change in humidity was determined. Removal mechanism of NO2 was estimated, and the carbon impregnated with potassium hydroxide was found to be superior to any other carbon tested. The
amount of the adsorbed NO and that produced by the reduction of NO2 were determined from the breakthrough curves. 相似文献
62.
Effect of Composition on the Oxygen Tracer Diffusion in Transparent Yttrium Aluminium Garnet (YAG) Ceramics 总被引:1,自引:0,他引:1
Isao Sakaguchi Hajime Haneda Junzo Tanaka Takakimi Yanagitani 《Journal of the American Ceramic Society》1996,79(6):1627-1632
The grain boundary structure and oxygen tracer diffusion in transparent yttrium aluminum garnet (YAG) ceramics varying from 2% excess of Y2 O3 to 0.5% excess of Al2 O3 were studied. The characterization of the specimens is as follows: (i) For the Y2 O3 -excess specimen, a second phase (yttrium aluminum perovskite: YAP) containing silicon in the grain boundary was found, (ii) For the Al2 O3 -excess specimen, both aluminum-rich particles (alumina) and a silicon-rich segregant layer were observed in the grain boundary. The volume diffusion of the oxygen tracer is little influenced by the excess composition. In contrast, the grain boundary diffusion of the oxygen tracer is suppressed in the Y2 O3 -excess specimens, compared to Al2 O3 -excess specimens. These differences are thought to result from the chemical reaction between the second phase and the intergranular liquid phase during the sintering. 相似文献
63.
Using a Debye function analysis, the presence of icosahedral and face centered cuboctahedral gold in a 1 1 ratio has been found in freshly prepared Au/Mg(OH)2 catalyst. The results support earlier studies which suggest the icosahedral form to be more stable at small nanometer sizes. Interactions between the gold and the Mg(OH)2 support appear to be weak, with the gold rapidly coagulating over a period of three months. Re-analysis of the aged sample shows the gold to be mainly in the form of truncated decahedra. 相似文献
64.
The feeding and gustatory responses to ecdysone and 20-hydroxyecdysone were investigated in the silkworm,Bombyx mori. 20-Hydroxyecdysone reduced feeding response strongly in fourth- and fifth-instar larvae, whereas ecdysone had no effect on feeding response. 20-Hydroxyecdysone stimulated the R receptor, the receptor to feeding deterrents, to a great degree. By contrast, ecdysone was much less effective for stimulating the R receptor. These results indicate that ecdysone and 20-hydroxyecdysone have different effects on feeding response due to different interactions with mouthpart chemoreceptors. 相似文献
65.
高速气流冲击式粉体表面改性装置——HYBRIDIZATION系统及应用 总被引:4,自引:0,他引:4
利用高速气流冲击法进行粉体/粉体系表面改性技术,是迄今为止各种粉体材料开发中最为引人注目的技术之一。HYBRIDIZATION(下称HYB)系统是利用高速气流冲击法对微粉体进行干式/机械化处理,是使材料复合化的最实用的装置,可对各类有机物、无机物、金属等进行广泛组合,通用性很强,适用于许多行业领域。从本文所述的系统构成、型式,有关的典型球形化处理的运转特性,利用复合化高温粉体测定被处理粉体表面温度,利用颜料改变色调等的处理特点及该系统的适用性等(一部分是从已发表的学术论文及专利上摘录的),可以说明HYB系统的概况。 相似文献
66.
67.
The diamond-like carbon (DLC) multilayer films have been deposited by plasma CVD deposition onSi wafer substrate. The deposited films have then been post-annealed in vacuum at 250 °C for 2 h. Changes in internal stress, hardness, critical load, friction coefficient and wear have been investigated toassess the influence of annealing on mechanical and tribological properties of DLC multilayer films. At the same time, DLC single layerfilms are also deposited and annealed in the same method for a comparison.The results show that there is 28–33% decrease in internal stress and 10–13% decrease in hardness of theDLC single layer films after the anneal treatment. However, for the DLC multilayer films, there is 41–43% decreasein internal stress and less than 2% decrease in hardness. In addition, the annealed DLC multilayer filmhas the same friction and wear properties as that un-annealed film. This result indicates that the anneal treatment isan effective method for the DLC multilayer films to reduce the internal stress and to increase the critical load.The by-effect of the annealing, decrease of hardness and wear resistance of the multilayer film, can be restrictedby the multilayer structure. 相似文献
68.
Hui Gu Rowland M. Cannon Hans J. Seifert Michael J. Hoffmann Isao Tanaka 《Journal of the American Ceramic Society》2002,85(1):25-32
The nitrogen solubility in the SiO2 -rich liquid in the metastable binary SiO2 -Si3 N4 system has been determined by analytical TEM to be 1%–4% of N/(O + N) at 1973–2223 K. Analysis of the near edge structure of the electron energy loss peak indicates that nitrogen is incorporated into the silicate network rather than being present as molecular N2 . A regular solution model with a positive enthalpy of mixing for the liquid was used to match the data for the metastable solubility of N in the presence of crystalline Si3 N4 and to adjust the computed phase diagram. The solubility of Si3 N4 in fused SiO2 is far less than reported in liquid silicates also containing Al, Mg, and/or Y. Apparently, these cations act as modifiers that break anion bridges in the silicate network and, thereby, allow further incorporation of Si3 N4 without prohibitive amounts of network cross-linking. Finally, indications emerged regarding the diffuse nature of the Si3 N4 -SiO2 interface that leads to amorphous regions of higher N content. 相似文献
69.
Composite sheets composed of biodegradable polymers (BP) and paper were prepared, and their physical and biodegradable properties were investigated. The paper sheets were soaked in BP emulsions and cured at 100°C for 20 min. The wet strength of composite sheets with the same basis weight increased significantly with increasing BP content, although dry strength increased only moderately. A 0.5% addition of a common wet paper‐strengthening agent, poly(amidoamine‐epichlorohydrin) (PAE) resin, enhanced the wet strength, which reached 9.3 MPa, of composite sheets consisting of a BP : paper ratio of 20 : 80. Further enhancement was achieved by the addition of polyvinylamines (PVAm). The wet tensile strength of composite sheets consisting of BP and paper (20 : 80) increased by 27% with the addition of 0.2% PVAm and 0.5% PAE, whereas it was enhanced by only 3–4% with the addition of 0.7% PAE. The biodegradability of the composite sheets was somewhat retarded by the addition of PAE and PVAm. However, a 90% weight loss was observed 60 days after placing composite sheet samples in soil. A similar weight loss was observed after 45 days for composites without additives and after 30 days for base paper alone. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 861–866, 2005 相似文献
70.
Isao Tanaka Ken'ichiro Igashira Taira Okamoto Koichi Niihara Rowland M. Cannon 《Journal of the American Ceramic Society》1995,78(3):673-679
High-purity Si3 N4 (with 2.5 wt% glassy SiO2 ) doped with 0 to 450 at.ppm of Ca was prepared as a model system to investigate the effects of grain-boundary segregants on fracture phenomenology at 1400°C. Subcritical crack-growth (SCG) resistance as well as creep resistance was degraded significantly by the presence of a small amount of Ca. The internal friction of the doped materials exhibited the superposition of a grain-boundary relaxation peak and a high-temperature background, and the apparent viscosity of the grain-boundary film was determined from the peak. Based on these experimental data, the fracture mechanism at 1400°C was divided into three regions: "brittle," SCG, and creep failure as a function of both external strain rate and Ca concentration, C Ca . From the investigation of the C Ca dependence of the critical strain rate for the transition from "brittle" to SCG fractures, the SCG phenomenon is suggested to be triggered by small-scale, grain-boundary sliding. The C Ca dependence of "steady-state" creep rate was far from the theoretical dependence of diffusional creep via a solution-precipitation mechanism. The discrepancy was interpreted to be due to the presence of an impurity-insensitive creep component. This component may correspond to the lowest limit of the tensile creep rate in Si3 N4 polycrystalline materials containing intergranular glassy-SiO2 film. 相似文献