全文获取类型
收费全文 | 1315篇 |
免费 | 35篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 56篇 |
综合类 | 1篇 |
化学工业 | 323篇 |
金属工艺 | 25篇 |
机械仪表 | 30篇 |
建筑科学 | 25篇 |
能源动力 | 30篇 |
轻工业 | 69篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 161篇 |
一般工业技术 | 236篇 |
冶金工业 | 274篇 |
原子能技术 | 33篇 |
自动化技术 | 87篇 |
出版年
2023年 | 9篇 |
2022年 | 23篇 |
2021年 | 22篇 |
2020年 | 15篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 15篇 |
2016年 | 37篇 |
2015年 | 25篇 |
2014年 | 24篇 |
2013年 | 56篇 |
2012年 | 36篇 |
2011年 | 43篇 |
2010年 | 41篇 |
2009年 | 52篇 |
2008年 | 55篇 |
2007年 | 47篇 |
2006年 | 35篇 |
2005年 | 45篇 |
2004年 | 32篇 |
2003年 | 38篇 |
2002年 | 35篇 |
2001年 | 33篇 |
2000年 | 37篇 |
1999年 | 32篇 |
1998年 | 97篇 |
1997年 | 64篇 |
1996年 | 41篇 |
1995年 | 30篇 |
1994年 | 31篇 |
1993年 | 30篇 |
1992年 | 25篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 11篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 12篇 |
1976年 | 10篇 |
1974年 | 5篇 |
1973年 | 2篇 |
排序方式: 共有1354条查询结果,搜索用时 15 毫秒
41.
Heat-moisture treatment of high-amylose corn starch increases dietary fiber content and lowers plasma cholesterol in ovariectomized rats 总被引:1,自引:0,他引:1
ABSTRACT: The effect of dietary high-amylose corn starch (HACS) of varying dietary fiber (DF) content on plasma cholesterol was examined in ovariectomized (OVX) rats. Gelatinized normal corn starch (G-CS) was used as a reference. OVX rats were fed a fiber-free purified diet containing G-CS, HACS, gelatinized high-amylose corn starch (G-HACS), or heat-moisture treated HACS (HM-HACS) at 400 g starch/kg diet for 21 d. The DF content of G-CS, HACS, G-HACS, and HM-HACS measured by the AOAC method was 0.1, 19.3, 2.4, and 64.5 g/100 g, respectively. The dry weight of cecal contents, cecal wall weight, the amount of short chain fatty acids in cecal contents, the amount of bile acids in small intestinal contents, and fecal excretion of neutral sterols increased logarithmically with increasing DF, while total plasma cholesterol concentration decreased. On the other hand, hepatic CYP7A1 activity, fecal dry weight, and fecal excretion of bile acids increased linearly with increasing DF, while body weight gain decreased. The hypocholesterolemic effect of HACS in OVX-rats appeared to be more effective by heat-moisture treatment. 相似文献
42.
Crack-Healing Behavior of Si3 N4 /SiC Ceramics under Cyclic Stress and Resultant Fatigue Strength at the Healing Temperature 总被引:1,自引:0,他引:1
Kotoji Ando Koji Takahashi Shin Nakayama Shinji Saito 《Journal of the American Ceramic Society》2002,85(9):2268-2272
Si3 N4 /SiC composite ceramics were sintered and subjected to three-point bending. A semi-elliptical surface crack of 100 μm surface length was made on each specimen. The crack-healing behavior under cyclic stress of 5 Hz, and resultant cyclic fatigue strengths at healing temperatures of 1100° and 1200°C, were systematically investigated. The main conclusions are as follows: (1) Si3 N4 /SiC composite ceramics have an excellent ability to heal a crack at 1100° and 1200°C. (2) This sample could heal a crack even under cyclic stress at a frequency of 5 Hz. (3) The crack-healed sample exhibited quite high cyclic fatigue strength at each crack-healing temperature, 1100° and 1200°C. 相似文献
43.
Ken Ando Masataka Momoda Takeshi Azumi Sadakichi Kitajima 《Journal of the American Ceramic Society》1987,70(11):309-C
Solubility of NiO in Al2 O3 was determined by electron probe microanalysisy A diffusion couple method was used by coupling an NiO-doped Al2 O3 polycrystal to a pure single crystal of Al2 O3 . The solubility of NiO in Al2 O3 in air was 230 wt ppm (157 at. ppm of cations) and 170 wt ppm (116 at. ppm) at 2073 and 1973 K, respectively. The solubility of NiO in Al2 O3 obtained in this work was compared with our previous work of the solubility of MgO in Al2 o3 . 相似文献
44.
45.
46.
We have investigated an optimal annealing process in order to enhance 1.55 μm light emission from semiconducting β-FeSi2 and found that two steps annealing at 600 °C and 800 °C is effective to its enhancement. Rutherford backscattering spectroscopy and SEM observations revealed that pronounced surface segregation of Fe atoms during annealing at 600 °C caused surface precipitate of β-FeSi2. The enhancement of light emission is attributed spatial isolation of the surface β-FeSi2 (light emitting layer) from damaged and defective layers with nonradiative recombination centers. 相似文献
47.
Nitroarene concentrations and direct-acting mutagenicity of diesel exhaust particulates fractionated by silica-gel column chromatography 总被引:2,自引:0,他引:2
Diesel exhaust particulates were extracted with benzene-ethanol (3:1, v/v) and separated into five fractions by silica-gel column chromatography. Direct-acting mutagenic activity was assayed by the Ames test using the Salmonella typhimurium YG1024 strain. The total activity of five fractions was about four times greater than that of the crude extract, suggesting that the activities in the fractions were suppressed in the crude extract. Strong activity was observed in fraction 4 which was eluted with dichloromethane (61.5% of the total activity) and fraction 5 which was eluted with ethanol (35.3%). Nitropolycyclic aromatic hydrocarbons (NPAHs) were determined by high-performance liquid chromatography with chemiluminescence detection. They were found mainly in fraction 4, although one NPAH was in fraction 3 which was eluted with n-hexane-dichloromethane (3:1, v/v). Based on these results, 53.1% of the activity in fraction 4 was attributed to NPAHs. The contribution of 1-nitropyrene and 1,3-, 1,6- and 1,8-dinitropyrenes was great and that of the other NPAHs was small. The mutagenic compound in fraction 5 was not identified. Fractions 1 and 2, which were eluted with n-hexane, and fraction 3 suppressed the activity of fraction 4. Polycyclic aromatic hydrocarbons in fractions 2 and 3 were considered as possible suppressors of NPAHs. 相似文献
48.
Koji Takahashi Kenichi Uchiide Yoshitaka Kimura Wataru Nakao Kotoji Ando Masahiro Yokouchi 《Journal of the American Ceramic Society》2007,90(7):2159-2164
A mullite/SiC whisker/SiC particle multi-composite, having excellent crack-healing ability and mechanical properties, was hot pressed in order to investigate the crack-healing behavior under stress and the resultant fatigue strength at the temperature of healing. A semi-elliptical surface crack 100 μm in surface length was introduced on each specimen. The pre-cracked specimens were crack healed under cyclic or constant stress by using a three-point bending stress at 1473 K, and the resultant bending strength and cyclic fatigue strength were measured at 1473 K. The pre-crack on the surface of the specimens could be healed even under stress. The threshold stresses for crack healing, as determined by evaluating the strengths of crack-healed specimens at a healing temperature of 1473 K, were 170 MPa for both constant and cyclic stresses, corresponding to 77% of the bending strength of the pre-cracked specimens. The static and cyclic fatigue behaviors of crack-healed specimens were also investigated at a healing temperature of 1473 K. 相似文献
49.
Natural graphite particles with high crystallinity sieved to obtain a particle size range of under 63 μm were ground with a ball mill, under various well-controlled grinding atmospheres such as N2, O2, He, H2, and vacuum. The ratio, Xdif50/Xst50, i.e. between the 50 wt.% Stokes diameter and the 50 wt.% laser diffraction diameter, of the ground particles, was used as an index of the flakiness of the particles. The specific resistance of films composed of the ground graphite particles was systematically measured. The rate of reduction in the size of the particles by grinding was slow under an O2-rich atmosphere such as 100% O2 and dry air. On the other hand, it was relatively fast in vacuum, or under an N2 or He atmosphere, and a gas mixture of 99% N2 and 1% O2. The rate of size reduction by grinding under a H2 atmosphere was intermediate. In our experimental conditions, the flakiness of the ground particles increased with the decrease in the particles’ sizes. The electrical conductivity of the ground particles, however, tended to decrease with the decrease in their sizes. Under the condition that the Stokes diameter of the ground particles remains constant, the electrical conductivity of films made from the ground particles increases with the increase in the flakiness of the particles. It was finally determined from our systematic grinding experiments that small flaky particles, which had a size, Xst of ∼1 μm, with a high electrical conductivity can be produced by grinding in a gas mixture of 99% N2 and 1% O2. In this case, the flaky shape of the ground particles was visually confirmed by scanning electron microscopy. 相似文献
50.
K. Nishio M. Fujimoto O. Ando H. Ono T. Murayama 《Journal of Applied Electrochemistry》1996,26(4):425-429
Polypyrrole was chemically synthesized using various oxidizing reagents and examined as a positive electrode material. Physical properties, morphologies and electrochemical characteristics of polypyrrole were greatly influenced by the oxidizing reagent used for polymerization. In general, polypyrrole with a smaller particle size and a larger specific surface area showed better discharge performance than that with a larger particle size and a smaller specific surface area. Polypyrrole was also synthesized on various conducting and nonconducting substrates using Fe(C104)3 as an oxidizing reagent. By using PP nonwoven fabric as a substrate material, a high discharge capacity of 72 mA h g–1 was obtained. Polypyrrole synthesized on only one side of PP nonwoven fabric was able to be used as an electrode. 相似文献