全文获取类型
收费全文 | 839篇 |
免费 | 57篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 3篇 |
综合类 | 1篇 |
化学工业 | 381篇 |
金属工艺 | 11篇 |
机械仪表 | 19篇 |
建筑科学 | 32篇 |
能源动力 | 24篇 |
轻工业 | 121篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 25篇 |
一般工业技术 | 167篇 |
冶金工业 | 23篇 |
原子能技术 | 5篇 |
自动化技术 | 78篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 118篇 |
2021年 | 75篇 |
2020年 | 36篇 |
2019年 | 40篇 |
2018年 | 21篇 |
2017年 | 37篇 |
2016年 | 27篇 |
2015年 | 18篇 |
2014年 | 34篇 |
2013年 | 54篇 |
2012年 | 46篇 |
2011年 | 64篇 |
2010年 | 36篇 |
2009年 | 42篇 |
2008年 | 44篇 |
2007年 | 29篇 |
2006年 | 44篇 |
2005年 | 12篇 |
2004年 | 20篇 |
2003年 | 17篇 |
2002年 | 18篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有899条查询结果,搜索用时 15 毫秒
51.
Electron holography is a very powerful technique for mapping static electric and magnetic potentials down to atomic resolution. While electron holography is commonly considered synonymous with its off-axis variant in the high energy electron microscopy community, inline electron holography is widely applied in low-energy electron microscopy, where the realization of the off-axis setup is still an experimental challenge. This paper demonstrates that both inline and off-axis holography may be used to recover amplitude and phase shift of the very same object, in our example latex spheres of 90 and 200 nm in diameter, producing very similar results, provided the object does not charge under the electron beam. 相似文献
52.
Stephanie Lansing Jay F. Martin Raúl Botero Botero Tatiana Nogueira da Silva Ederson Dias da Silva 《Biomass & bioenergy》2010,34(12):1711-1720
A nine-month co-digestion investigation was conducted in Costa Rica to optimize animal wastewater treatment, renewable energy production, and fertilizer creation using 12 Taiwanese-model, plug-flow digesters (250 L each) constructed of tubular polyethylene and PVC piping, operating without mechanical or heating components. The experiment tested three replications of four treatment groups: the control (T0), which contained only swine manure, and T2.5, T5, and T10, which contained 2.5%, 5%, and 10% used cooking grease (by volume) combined with swine manure.T2.5 had the greatest methane production (45 L d?1), a 124% increase from the control. No adverse effects were observed from co-digesting 2.5% grease in terms of organic matter removal, pathogen reduction, grease removal, and pH. Chemical oxygen demand (COD) was reduced 94.7% to 1.96 g L?1, fecal coliforms and Escherichia coli were reduced 99.2 and 97.1%, respectively, and grease removal was 99.9%. The average effluent pH (7.05) and alkalinity in T2.5 was within the optimal range for methanogens and increased significantly during the nine-month experiment, likely due to adaptation of the methanogenic organisms to the influent grease concentrations. Total nitrogen concentration decreased 34.0%, and NH4-N increased 97.1% during digestion in T2.5, with no significant differences between T2.5 and T0. There was less phosphorus reduction with co-digestion, with 181 mg g?1 of total phosphorus (TP) in T2.5 and only 90.6 mg g?1 of TP in T0, resulting in lower N:P ratios in the grease treatment groups due to the greater concentration of phosphorus in the effluent. 相似文献
53.
Xavier Chaud Tatiana Prikhna Yaroslav Savchuk Anne Joulain Evert Haanappel Pavel Diko Laureline Porcar Mahmoud Soliman 《Materials Science and Engineering: B》2008,151(1):53
Oxygen high pressure (up to 16 MPa) has been introduced in the oxygen-annealing step necessary to make the YBa2Cu3Ox phase superconducting (change x from 6 to about 7). It enables a displacement in the equilibrium phase diagram towards higher temperatures, which means the possibility to achieve the same final oxygen content as the one at low temperature, but with the benefit of higher diffusion rates. Initial development made on thin bars (1.5–3 mm thick) has confirmed the interest of using a high pressure of oxygen. TEM observations have shown an increase of twin density associated with higher Jc. This is in agreement with other works claiming the possibility of higher Jc by twin engineering, and more precisely by twin refinement while annealing at high temperature. We report the successful application of this process without any adjustment to so-called thin-wall single-domain samples. These samples are obtained by growing a crystal on a pellet already shaped with an array of holes. The advantage is that, as far as diffusion processes are concerned, the typical length is not anymore the diameter of the sample, but the thickness of the walls between holes. The trapped field of 16 mm diameter Y123 thin-wall single-domain samples was doubled (0.6 T vs. 0.3 T at 77 K) in a rather short annealing time (about 3 days). Microstructures as well as magneto-optical observations of plain and thin-wall samples evidenced a reduction of cracks in the thin-wall samples. Improved performances were confirmed by further characterizations performed from 77 down to 20 K using the pulse-field facilities of the LNCMP at Toulouse. 相似文献
54.
Larisa I. Nasibulina Tatiana S. Koltsova Tuomo Joentakanen Albert G. Nasibulin Oleg V. Tolochko Jari E.M. Malm Maarit J. Karppinen Esko I. Kauppinen 《Carbon》2010,48(15):4559-4562
A novel approach to synthesize carbon nanofibers (CNFs) directly on the surface of metal μm-sized particles to evenly disperse the carbon nanomaterials in a composite material was proposed. As a metal matrix, 5–10 μm copper particles were utilized. As a carbon source, C2H2, CH4 and CO were examined. The best conditions were found to be in C2H2 (30 cm3/min) and H2 (260 cm3/min) atmosphere at the temperature of 750 °C. The composites based on copper and CNFs prepared by vacuum hot pressing showed the increase in hardness from 35 to 60 kg/mm2 almost retaining pure copper electrical properties. 相似文献
55.
Tatiana A. Kolesnikova Dmitry A. Gorin Paulo Fernandes Stefanie Kessel Gennady B. Khomutov Andreas Fery Dmitry G. Shchukin Helmuth Möhwald 《Advanced functional materials》2010,20(7):1189-1195
A water suspension of nanocomposite microcapsules with embedded ZnO nanoparticles in the capsule shell is reported. The microcapsule morphology is characterized by confocal microscopy, TEM, SEM, and AFM before and after ultrasound treatment. A remarkably high capsule sensitivity to ultrasound is evidenced, and it is observed to grow with increasing number of ZnO nanoparticle layers in the nanocomposite shell. This effect is correlated with the mechanical properties of microcapsules measured with AFM. 相似文献
56.
Counter-clustering for Training Pattern Selection 总被引:2,自引:0,他引:2
57.
Daniel Errandonea David Santamaria-Perez Tatiana Bondarenko 《Materials Research Bulletin》2010,45(11):1732-1735
We studied the high-pressure effects on the crystalline structure of monoclinic HfTiO4 and ZrTiO4. We found that the compressibility of these ceramics is highly non-isotropic, being the b-axis the most compressible one. In addition, the a-axis is found to have a small and negative compressibility. At 2.7 GPa (10.7 GPa) we discovered the onset of a structural phase transition in HfTiO4 (ZrTiO4), coexisting the low- and high-pressure phases in a broad pressure range. The new high-pressure phase has a monoclinic structure which involves an increase in the Ti-O coordination and a collapse of the cell volume. The equation of state for the low-pressure phase is also determined. 相似文献
58.
Electrochemical studies were carried out to estimate the risks of perchlorate formation in drinking water disinfected by direct electrolysis. Boron Doped Diamond (BDD) anodes were used in laboratory and commercially available cells at 20 °C. The current density was changed between 50 and 500 A m−2. For comparison, other anode materials such as platinum and mixed oxide were also tested. It was found that BDD anodes have a thousandfold higher perchlorate formation potential compared with the other electrode materials that were tested. In long-term discontinuous experiments all the chloride finally reacted to form perchlorate. The same result was obtained when probable oxychlorine intermediates (OCl−, ClO2−, ClO3−) were electrolysed in synthetic waters in the ppm range of concentrations. The tendency to form perchlorate was confirmed when the flow rate of drinking water was varied between 100 and 300 L h−1 and the temperature increased to 30 °C. In a continuous flow mode of operation a higher chloride concentration in the water resulted in a lower perchlorate formation. This can be explained by reaction competition of species near and on the anode surface for experiments both with synthetic and local drinking waters. It is concluded that the use of electrodes producing highly reactive species must be more carefully controlled in hygienically and environmentally oriented applications. 相似文献
59.
Kinetics and mechanism of low-temperature ozone decomposition by Co-ions adsorbed on silica 总被引:3,自引:0,他引:3
Tatiana L. Rakitskaya Alim A. Ennan Irina V. Granatyuk Alexander Yu. Bandurko Gilbert G. A. Balavoine Yurii V. Geletii V. Ya. Paina 《Catalysis Today》1999,53(4):616-723
Kinetics and mechanism of low-temperature ozone ((5–50) × 10−3 mol/m3 in the gas–air mixture) decomposition by Co-catalysts supported on silica have been studied. Co-ions adsorbed on silica react with surface oxygen species, thus resulting in an active catalyst. Low concentrations of Co-ions form a monolayer on the surface. Their specific catalytic activity remained constant, but sharply decreased at higher concentrations due to a formation of polynuclear Co-complexes. Ozone decomposition may occur either as a stoichiometric or catalytic process, depending on the ozone and catalyst concentrations. The turnover number increases with ozone concentration reaching a saturation point. It also increases with Co-concentration in the beginning, but drops at a concentration >1 × 10−4 mol/g. The mechanism of the reaction is discussed. 相似文献
60.