全文获取类型
收费全文 | 10162篇 |
免费 | 2631篇 |
国内免费 | 476篇 |
专业分类
电工技术 | 245篇 |
综合类 | 371篇 |
化学工业 | 3646篇 |
金属工艺 | 481篇 |
机械仪表 | 146篇 |
建筑科学 | 194篇 |
矿业工程 | 108篇 |
能源动力 | 840篇 |
轻工业 | 422篇 |
水利工程 | 44篇 |
石油天然气 | 169篇 |
武器工业 | 38篇 |
无线电 | 1633篇 |
一般工业技术 | 4089篇 |
冶金工业 | 380篇 |
原子能技术 | 177篇 |
自动化技术 | 286篇 |
出版年
2024年 | 94篇 |
2023年 | 470篇 |
2022年 | 472篇 |
2021年 | 743篇 |
2020年 | 842篇 |
2019年 | 900篇 |
2018年 | 859篇 |
2017年 | 988篇 |
2016年 | 852篇 |
2015年 | 779篇 |
2014年 | 902篇 |
2013年 | 914篇 |
2012年 | 638篇 |
2011年 | 543篇 |
2010年 | 341篇 |
2009年 | 323篇 |
2008年 | 309篇 |
2007年 | 339篇 |
2006年 | 270篇 |
2005年 | 208篇 |
2004年 | 194篇 |
2003年 | 165篇 |
2002年 | 163篇 |
2001年 | 132篇 |
2000年 | 141篇 |
1999年 | 115篇 |
1998年 | 85篇 |
1997年 | 62篇 |
1996年 | 77篇 |
1995年 | 54篇 |
1994年 | 48篇 |
1993年 | 31篇 |
1992年 | 45篇 |
1991年 | 30篇 |
1990年 | 34篇 |
1989年 | 25篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1955年 | 1篇 |
1951年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
Thermochemical analyses of interfacial reactions in titanium, zirconium, and hafnium diboride reinforced oxidematrix composites have been carried out to evaluate the chemical compatibility. The chemical reactivity of these diborides with oxygen and the high volatility of B2 O3 ( l ) at reduced oxygen pressures are concerns during processing and operating conditions. The thermochemical stability and the vaporization behavior of B2 O3 ( l ) are discussed in terms of partial pressures of dominant gaseous species of the boron-oxygen system at 1700 and 2300 K. The TiB2 /ZrO2 and TiB2 /HfO2 systems are thermodynamically stable in a limited oxygen pressure range. The TiB2 /Al2 O3 system is stable, but the reactions in this system may apparently be accompanied by formation of gaseous products (B2 O3 , AlO, Al2 O, and lower boron oxides) in the presence of elemental oxygen. These thermochemical considerations are very useful in evaluating the effectiveness of oxides as diffusion barrier coatings on diboride reinforcements. 相似文献
22.
X. Liang X. Wang J. Zhuang Y. Chen D. Wang Y. Li 《Advanced functional materials》2006,16(14):1805-1813
Uniform magnetite, hematite, and goethite nanocrystals were prepared through an attractive method based on an oleic acid/alcohol/water system. By adjusting the synthetic parameters (base concentration, alcohol content, categories of alcohols, etc.), the controlled synthesis of uniform magnetite, hematite, and goethite nanocrystals can be easily achieved. Detailed investigations on the effect of the experimental parameters on the morphology of the final products and the phase transitions among the magnetite, hematite, and goethite phases were carried out. Finally, a method of doping other metal ions into magnetite was developed and the magnetic properties of magnetite doped with different metal elements were studied. 相似文献
23.
Auguste Commeyras Hlne Collet Laurent Boiteau Jacques Taillades Odile Vandenabeele‐Trambouze Herv Cottet Jean‐Philippe Biron Raphaël Plasson Louis Mion Olivier Lagrille Herv Martin Franck Selsis Michel Dobrijevic 《Polymer International》2002,51(7):661-665
Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry. 相似文献
24.
The effect of reducing the reactor air pressure on the morphology of spray dried magnesium sulphate powders is investigated, experimentally. A reactor, capable of drying and pyrolyzing solution sprays at low pressures, is designed and manufactured. A vibrating mesh nebulizer is employed to generate the spray. Four different pressures, starting from 60 Torr to the atmospheric pressure, and two different reactor air temperatures of 130°C and 420°C, are considered. In addition, two different concentrations of magnesium sulphate solutions are tested. The results are explained based on the effect of reactor air pressure on the droplet evaporation rate. 相似文献
25.
26.
27.
介绍了福建炼油化工有限公司重整装置CB -60 /CB -70重整催化剂 (还原态 )分段组合装填的应用情况 ,列出了还原态催化剂和氧化态催化剂开工的不同特点。通过开工初期标定的数据与CB -6/CB -7催化剂的对比 ,说明CB -60 /CB -70催化剂有良好的活性和选择性 ,尤其是选择性、产氢率优于CB -6/CB -7,且使开工步骤得到了简化 相似文献
28.
The equilibrium reaction 3'(Fe, Co)O'( ss ) +1/2O2 ( g ) ⇄ (Fe, Co)3 O4 ( ss ) was studied in the temperature range 970 to 1370 K for seven different total compositions of molar ratios 0.5 < Fe/(Fe + Co) ≤ 1.0. The equilibrium pressures of oxygen were determined by using galvanic cells incorporating calcia stabilized zirconia as solid electrolyte and the Fe/Co ratios in the solid-solution phases by wavelength dispersive spectrometry microprobe analyses. The activities of 'FeO' in the cobaltowüstite phase were then derived from the experimental results obtained. 相似文献
29.
Solomon Sundar Manoharan Swati Sigamani John Prasanna Manju Lata Rao Ranjan Kumar Sahu 《Journal of the American Ceramic Society》2002,85(10):2469-2471
Interaction of electromagnetic radiation with a physical mixture of metal nitrates and amides/hydrazides is observed to initiate high-temperature reactions, useful for realizing several high-temperature ceramic materials. A judicious choice of such redox mixtures undergoes exothermic reactions when they couple with microwave radiation. The coupling of electromagnetic radiation with metal salts and amides/hydrazides depends on the dielectric properties of the individual components in the reaction mixture. The approach has been used to prepare γ-Fe2 O3 , Fe3 O4 , MgCr2 O4 , α-CaCr2 O4 , and La0.7 Ba0.3 MnO3 . 相似文献
30.