全文获取类型
收费全文 | 75662篇 |
免费 | 8479篇 |
国内免费 | 3969篇 |
专业分类
电工技术 | 4903篇 |
技术理论 | 17篇 |
综合类 | 5485篇 |
化学工业 | 18985篇 |
金属工艺 | 4456篇 |
机械仪表 | 2029篇 |
建筑科学 | 10058篇 |
矿业工程 | 2479篇 |
能源动力 | 3489篇 |
轻工业 | 3968篇 |
水利工程 | 1364篇 |
石油天然气 | 5637篇 |
武器工业 | 392篇 |
无线电 | 6212篇 |
一般工业技术 | 10633篇 |
冶金工业 | 4556篇 |
原子能技术 | 718篇 |
自动化技术 | 2729篇 |
出版年
2024年 | 417篇 |
2023年 | 1469篇 |
2022年 | 2330篇 |
2021年 | 2519篇 |
2020年 | 2831篇 |
2019年 | 2457篇 |
2018年 | 2336篇 |
2017年 | 2755篇 |
2016年 | 2950篇 |
2015年 | 2979篇 |
2014年 | 5122篇 |
2013年 | 4662篇 |
2012年 | 5695篇 |
2011年 | 5968篇 |
2010年 | 4467篇 |
2009年 | 4417篇 |
2008年 | 3861篇 |
2007年 | 4788篇 |
2006年 | 4573篇 |
2005年 | 3806篇 |
2004年 | 3142篇 |
2003年 | 2878篇 |
2002年 | 2300篇 |
2001年 | 1904篇 |
2000年 | 1589篇 |
1999年 | 1177篇 |
1998年 | 930篇 |
1997年 | 693篇 |
1996年 | 585篇 |
1995年 | 476篇 |
1994年 | 417篇 |
1993年 | 310篇 |
1992年 | 262篇 |
1991年 | 210篇 |
1990年 | 182篇 |
1989年 | 108篇 |
1988年 | 74篇 |
1987年 | 71篇 |
1986年 | 51篇 |
1985年 | 89篇 |
1984年 | 74篇 |
1983年 | 62篇 |
1982年 | 31篇 |
1981年 | 9篇 |
1980年 | 23篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1959年 | 9篇 |
1951年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
D. E. Wetzler P. F. Aramendía M. L. Japas R. Fernández-Prini 《International Journal of Thermophysics》1998,19(1):27-42
Thermal diffusivities of supercritical CO2 and C2H6 were determined over a wide density range with a photothermal technique. The thermal lens, formed by the degradation of the absorbed light energy as heat by the sample, allows the employment of a nonequilibrium method in the critical region. Controlling the refractive-index gradient, i.e., a density gradient, perturbations can be maintained at levels where convection is negligible. An easy-to-operate setup allowed us to measure thermal diffusivities in the density ranges 5 to 20 mol·dm–3 for CO2 at 308 and 313 K and 2 to 12 mol·dm–3 for C2H6 at 308 K with a standard precision of 15%. 相似文献
92.
93.
Aggregates of carbon black (CB) in a polymer matrix have a tendency to form a CB network. The dynamic mechanical properties of binary systems of chlorinated polyethylene (CPE) and CB or 3,9‐bis{1,1‐dimethyl‐2[β‐(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyloxy]ethyl}‐2,4,8,10‐tetraoxaspiro[5,5]‐undecane (AO‐80) and their ternary systems were investigated. It was found that the dynamic mechanical properties of those systems depend on the colloidal properties, surface oxides, and surface modification of CB. For binary systems of CPE and CB, oxidized CB gives a high modulus at low strain amplitude and a large Payne effect compared with untreated CB. In contrast, the reverse effect was observed for their ternary systems. Consequently, a good micro‐dispersion is obtainable by surface modification due to physical adsorption of AO‐80 on oxidized CB particles via hydrogen bonds. © 2003 Society of Chemical Industry 相似文献
94.
95.
随着苏丹1/2/4区块的深入开发,为了加快开发主力油层,提高原油产量,降低钻井成本,GNPOC在此区块布置水平井开发任务。所开发的区域主要分布于Heglig,Munga,Simbir,Bamboo区块,油层所在是Zaqar和Bentiue地层。此层位具有高渗透,地层温度高,易塌、气窜等复杂问题,尤其是Heglig和Munga地区井壁坍塌严重。为此,根据地质资料、井身结构和对水平井注水泥的技术要求,科学合理设计施工工艺,优选出适合此地区固井施工的冲洗液和隔离液,特别是经过努力实践,开发出了新型膨胀水泥浆体系,此体系具有高强度、低失水、无析水、防气窜之功效。结合使用哈里伯顿CPT—Y4大功率固井车,精确计量和自动密度控制,该体系水泥浆目前已在7口水平井施工中得以应用,均为优质井。现正在被大量使用,此体系的开发,解决了该固井技术难题,创造了中国固井在海外首次水平井作业一次成功的历史记录,具有较高的经济和社会效益。 相似文献
96.
Works of adhesion at the carbon fiber-liquid interface determined using a modified wetting technique
Works of adhesion WSL between aqueous solutions with pH values in the range from 1 to 14 and carbon fibers from different sources, which were additionally treated in an inert atmosphere or in oxygen, were measured by use of a microbalance. These works of adhesion WSL were found to show distinct stepwise dependencies on the pH value. The works of adhesion WSL are attributed to dispersion interactions WSL1 and various acid-base interactions wslab—in the latter case between the acidic and basic surface groups of carbon and the various basic and acidic aqueous solutions. 相似文献
97.
活性炭单柱提取肌苷新技术研究 总被引:1,自引:0,他引:1
活性炭单柱提取肌苷新技术研究李永泉,张进,姚恕,郑莲英,俞峰(杭州大学生物系杭州310028)(浙江大学化工系杭州310027)关键词:肌苷,提取技术,活性炭单柱1前言目前,国内肌苷发酵后处理工艺落后,在分离提取工序中肌苷损失严重,收率一般只有50%... 相似文献
98.
Asbestos fibres, of the chrysotile variety, and chopped carbon fibres were pretreated by an in-situ polycondensation technique eventually resulting in a polyamide coating on the fibre surface. Ionomer based composites containing either carbon or asbestos fibres in random in plane fibre orientation were prepared, and the influence of this coating process on the tensile properties was investigated. It was found that for the asbestos-filled composites the presence of the nylon 6,6 interlayer improves the tensile performance, especially at moderate polyamide depositions. This is not the case with the pretreated carbon-filled composites for which carbon fibres with higher polyamide contents are preferred. Combinations of the treated asbestos fibres with carbon and/or aramid fibres may be used to reduce the asbestos content in asbestos-only based engineering plastics. 相似文献
99.
The effect of heat treatment on microstructure of a plain-weave carbon fabric reinforced carbon-carbon composite with phenolformaldehyde-derived carbon matrix was investigated by X-ray diffraction. The diffraction patterns were analysed by the least-square fitting program Carbonxs. After heat treatment from 1000 to 2800 °C the interplanar distance of (002) planes decreased from 3.488 to 3.420 Å and the lattice parameter in basal plane increased from 2.440 to 2.464 Å, respectively. Simultaneously, the coherent block size in the basal plane directions increased from 18 to 54 Å, which was accompanied by an increase of the fraction of organised carbon atoms from 0.50 to 0.85. The 002 diffraction profile of the composite was much narrower than the sum of peaks of the matrix and fabric alone. This can probably be caused by a better crystallographic ordering (or by a partial graphitisation) of the matrix in the composite. On the other hand, the composite Young’s modulus slightly decreased with the treatment temperature increasing from 2200 to 2800 °C in spite of the established strong improvement of fibre crystallinity and, therefore, fibre modulus. The mechanisms diminishing the modulus of composite (e.g. partial matrix graphitisation at the fibre/matrix interface and decreasing fibre/matrix contact area) probably prevailed over the increasing contribution of the fibre modulus. 相似文献
100.
Activated nanostructured-carbon cloths with a high ratio of surface area to volume are used as electrode for capacitive deionization. The electrochemical properties on capacitive deionization for NaCl solution have been investigated to improve efficiency of capacitive deionization properties from aqueous solution, employing chemical surface-modification by etching in alkaline and acidic solution. The removal efficiency of inorganic salts of activated carbon cloths by chemical modification significantly increased. Specially the carbon cloth surface modified in HNO3 showed an effect of improvement in the CDI efficiency due to not only ion adsorption by an electric double layer, but also electron transfer by Faradaic reaction. 相似文献