全文获取类型
收费全文 | 6198篇 |
免费 | 434篇 |
国内免费 | 257篇 |
专业分类
电工技术 | 334篇 |
综合类 | 351篇 |
化学工业 | 1093篇 |
金属工艺 | 382篇 |
机械仪表 | 300篇 |
建筑科学 | 469篇 |
矿业工程 | 125篇 |
能源动力 | 222篇 |
轻工业 | 388篇 |
水利工程 | 85篇 |
石油天然气 | 259篇 |
武器工业 | 37篇 |
无线电 | 671篇 |
一般工业技术 | 909篇 |
冶金工业 | 433篇 |
原子能技术 | 76篇 |
自动化技术 | 755篇 |
出版年
2024年 | 21篇 |
2023年 | 88篇 |
2022年 | 140篇 |
2021年 | 227篇 |
2020年 | 184篇 |
2019年 | 173篇 |
2018年 | 151篇 |
2017年 | 171篇 |
2016年 | 169篇 |
2015年 | 171篇 |
2014年 | 252篇 |
2013年 | 353篇 |
2012年 | 318篇 |
2011年 | 396篇 |
2010年 | 320篇 |
2009年 | 306篇 |
2008年 | 338篇 |
2007年 | 315篇 |
2006年 | 343篇 |
2005年 | 310篇 |
2004年 | 207篇 |
2003年 | 212篇 |
2002年 | 169篇 |
2001年 | 167篇 |
2000年 | 138篇 |
1999年 | 188篇 |
1998年 | 179篇 |
1997年 | 132篇 |
1996年 | 137篇 |
1995年 | 112篇 |
1994年 | 92篇 |
1993年 | 82篇 |
1992年 | 51篇 |
1991年 | 52篇 |
1990年 | 37篇 |
1989年 | 35篇 |
1988年 | 29篇 |
1987年 | 21篇 |
1986年 | 24篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 9篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1969年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有6889条查询结果,搜索用时 15 毫秒
991.
尽管对于鄂尔多斯盆地奥陶系马家沟组天然气的来源问题一直都存在着不同的认识,但所有观点均不认为马家沟组自身发育TOC0.5%的规模性烃源岩。通过分析该盆地中东部奥陶系近年来大量新钻井的岩心和岩屑样品,揭示了马家沟组不同岩石类型烃源岩的有机质丰度特征,首次发现并证实马家沟组存在有机质丰度高的规模性有效烃源岩。研究结果表明:1马家沟组有效烃源岩的岩性主要为暗色薄层—厚层状含云泥岩、云质泥岩和泥云岩,其富集分布明显受沉积相的控制,马家沟组沉积期间海退期较海侵期更有利于规模性有效烃源岩的发育,层位上主要集中分布在马五上段,其次为马五中—下段、马三段和马一段;2平面上有效烃源岩围绕米脂盐洼呈双环带状分布,次级洼陷有效烃源岩呈中厚—厚层状,累计厚度大、有机质丰度高;3有效烃源岩在米脂凹陷中心和次级隆起则呈薄层状,累计厚度小、有机质丰度低;4有效烃源岩的有机碳含量变化范围为0.30%~8.45%,其生烃母质为浮游藻类和疑源类,有机质类型为腐泥型或偏腐泥混合型。结论认为:该盆地奥陶系有效烃源岩普遍处于过成熟阶段,以产干气为主,生气量大,是马家沟组天然气的主要贡献者。 相似文献
992.
Au‐Decorated Cracked Carbon Tube Arrays as Binder‐Free Catalytic Cathode Enabling Guided Li2O2 Inner Growth for High‐Performance Li‐O2 Batteries 下载免费PDF全文
Fangfang Tu Junping Hu Jian Xie Gaoshao Cao Shichao Zhang Shengyuan A. Yang Xinbing Zhao Hui Ying Yang 《Advanced functional materials》2016,26(42):7725-7732
Owing to their extremely high energy density, Li‐O2 batteries have attained increasing attention in recent studies. However, deposition of the discharge product, insulating Li2O2, is known to seriously limit the electrochemical performance of Li‐O2 batteries. While extensive studies have focused on relieving electrode deactivation by controlling Li2O2 growth, no permanent or effective mechanism is delivered. Here, a unique design comprising a catalytic cathode constructed by cracked carbon submicron tube (CST) arrays decorated with Au nanoparticles on inner walls is proposed. The introduction of Au nanoparticles not only improves electrode conductivity but also provides catalytic sites, guiding conformal growth of thin‐layered Li2O2 inside the cracked CST. Density functional theory calculations support that Au decoration on CST favors the conformal growth of Li2O2 on inner tubular walls. This growth behavior of Li2O2 renders easy decomposition of Li2O2, prevents carbon tube electrode from full, rapid deactivation, and preserves the free space for reactants transport. Li‐O2 cells with Au@CST exhibit good rate capability (1208 mAh g–1 at a high current density of 1000 mA g–1) and long cycle life (112 cycles at a current density of 400 mA g–1 with a limited capacity of 500 mAh g–1). 相似文献
993.
Claudio Ferraro Esther Garcia‐Tuñon Victoria G. Rocha Suelen Barg Maria Dolores Fariñas Tomas E. Gomez Alvarez‐Arenas Giorgio Sernicola Finn Giuliani Eduardo Saiz 《Advanced functional materials》2016,26(10):1636-1645
The directional freezing of microfiber suspensions is used to assemble highly porous (porosities ranging between 92% and 98%) SiC networks. These networks exhibit a unique hierarchical architecture in which thin layers with honeycomb‐like structure and internal strut length in the order of 1–10 μm in size are aligned with an interlayer spacing ranging between 15 and 50 μm. The resulting structures exhibit strengths (up to 3 MPa) and stiffness (up to 0.3 GPa) that are higher than aerogels of similar density and comparable to other ceramic microlattices fabricated by vapor deposition. Furthermore, this wet processing technique allows the fabrication of large‐size samples that are stable at high temperature, with acoustic impedance that can be manipulated over one order of magnitude (0.03–0.3 MRayl), electrically conductive and with very low thermal conductivity. The approach can be extended to other ceramic materials and opens new opportunities for the fabrication of ultralight structures with unique mechanical and functional properties in practical dimensions. 相似文献
994.
油气输导体系沟通烃源岩和圈闭,在油气成藏过程中具有关键作用。以黄河口凹陷中央隆起带新近系为研究目的层,基于层序地层发育特征,分析研究区4个油田的实测地层压力系数,进而探讨不同地层压力系数条件下的油气输导体系。研究结果表明,正常地层压力条件下黄河口凹陷中央隆起带新近系发育低地层压力系数—高渗透性储层油气输导体系、高地层压力系数—中等渗透性储层油气输导体系和中等地层压力系数—高渗透性储层油气输导体系。黄河口凹陷中央隆起带的凹陷区—缓坡带的馆陶组与明下段V油组、缓坡带—凸起区的明下段Ⅲ油组以低地层压力系数—高渗透性储层油气输导体系为主,凹陷区—缓坡带的明下段Ⅲ油组以高地层压力系数—中等渗透性储层油气输导体系为主,凸起区以中等地层压力系数—高渗透性储层油气输导体系为主。 相似文献
995.
Liu C Qian Z Jia W Huang M Chao G Gong C Deng H Wen Y Yang J Gou M Tu M 《Journal of materials science. Materials in medicine》2007,18(10):2085-2091
In this paper, a new kind of biodegradable aliphatic polyetheresteramide copolymers (PEEA) based on -caprolactone, 6-aminocaproic acid, and poly(ethylene glycol) (PEG) were synthesized by melt polymerization method. The obtained
copolymers were characterized by 1H-NMR. The thermal properties of PEEA copolymers were studied by DSC and TGA/DTA under nitrogen atmosphere. The water absorption
and hydrolytic degradation behavior was also studied in detail. With the increase in PEG content or the decrease in caprolactone
content, the water absorption of the copolymers increased accordingly. For the hydrolytic degradation behavior, with the increase
in PEG content or caprolactone content, the degradation rate increased then. 相似文献
996.
A new simple approach to effectively detect QRS-T complexes in ECG curve is described,so as to
easily get the P-wave(when AF does not happen)or the f-wave(when AF happens).By means of signal
processing techniques such as the power spectrum function,the auto-correlation function and cross-correlation
function,two kinds of ECG signal when AF does or does not happen were suc cessively analyzed,showing the
evident differences between them. 相似文献
997.
Yun Y Bange A Shanov VN Heineman WR Halsall HB Dong Z Jazieh A Tu Y Wong D Pixley S Behbehani M Schulz MJ 《Journal of nanoscience and nanotechnology》2007,7(7):2293-2300
A carbon nanotube needle biosensor was developed to provide fast, cost effective and highly sensitive electrochemical detection of biomolecules. The sensor was fabricated based on an array of aligned multi-wall carbon nanotubes synthesized by chemical vapor deposition. A bundle of nanotubes in the array was welded onto the tip of a tungsten needle under a microscope. The needle was then encased in glass and a polymer coating leaving only the tip of the needle exposed. Cyclic voltammetry was performed to examine the redox behavior of the nanotube needle. The cyclic voltammetry results showed a steady-state response attributable to radial diffusion with a high steady-state current density. An amperometric sensor was then developed for glucose detection by physically attaching glucose oxidase on the nanotube needle. The amperometric response of these nanotube needles showed a high sensitivity with a low detection limit. It is expected that the nanotube needle can be sharpened to increase the sensitivity to the point where the current is almost too small to measure. The simple manufacturing method should allow commodity level production of highly sensitive electronic biosensors. 相似文献
998.
999.
1000.