全文获取类型
收费全文 | 38591篇 |
免费 | 2652篇 |
国内免费 | 2765篇 |
专业分类
电工技术 | 1102篇 |
综合类 | 2134篇 |
化学工业 | 8320篇 |
金属工艺 | 4554篇 |
机械仪表 | 2462篇 |
建筑科学 | 758篇 |
矿业工程 | 758篇 |
能源动力 | 1723篇 |
轻工业 | 1907篇 |
水利工程 | 185篇 |
石油天然气 | 892篇 |
武器工业 | 173篇 |
无线电 | 6175篇 |
一般工业技术 | 9949篇 |
冶金工业 | 1427篇 |
原子能技术 | 494篇 |
自动化技术 | 995篇 |
出版年
2024年 | 110篇 |
2023年 | 568篇 |
2022年 | 735篇 |
2021年 | 933篇 |
2020年 | 1047篇 |
2019年 | 917篇 |
2018年 | 890篇 |
2017年 | 1215篇 |
2016年 | 1124篇 |
2015年 | 1094篇 |
2014年 | 1688篇 |
2013年 | 2064篇 |
2012年 | 2326篇 |
2011年 | 2973篇 |
2010年 | 2100篇 |
2009年 | 2305篇 |
2008年 | 2150篇 |
2007年 | 2588篇 |
2006年 | 2460篇 |
2005年 | 2021篇 |
2004年 | 1881篇 |
2003年 | 1648篇 |
2002年 | 1455篇 |
2001年 | 1306篇 |
2000年 | 1167篇 |
1999年 | 888篇 |
1998年 | 788篇 |
1997年 | 645篇 |
1996年 | 540篇 |
1995年 | 505篇 |
1994年 | 419篇 |
1993年 | 345篇 |
1992年 | 284篇 |
1991年 | 214篇 |
1990年 | 177篇 |
1989年 | 143篇 |
1988年 | 75篇 |
1987年 | 46篇 |
1986年 | 25篇 |
1985年 | 24篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1978年 | 6篇 |
1976年 | 8篇 |
1974年 | 7篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
101.
The dynamics of a thin liquid film falling down a uniformly heated wall is studied. The model introduced by Kalliadasis et al. [J. Fluid Mech. 475 (2003) 377] for the same problem is revisited and its deficiencies, namely the prediction of a critical
Reynolds number with 20% error, cured. For the energy equation a high-order Galerkin projection in terms of polynomial test
functions is developed. It is shown that not only does this more refined formulation correct the critical Reynolds number,
but it also gives, with an appropriate expansion close to criticality, the long-wave theory. Bifurcation diagrams for permanent
solitary waves are constructed and compared with the solution branches obtained from different models. It is shown that, in
all cases, the long-wave theory exhibits limit points and branch multiplicity, while the other models predict the continuing
existence of solitary waves. Time-dependent computations show that the free surface and interfacial temperature approach a
train of coherent structures that resemble the infinite-domain stationary solitary pulses. 相似文献
102.
The switchable optical properties of Pd-protected RCo2-type Ho0.6Mm0.4Co2 alloy thin films have been investigated in a KOH electrolyte. The reversible optical switching has been carried out simultaneously by measuring transmitted light through the thin film during electrochemical charging–discharging of hydrogen. The dependence of switching speed and cyclic durability of the film on the charging and discharging current density as well as concentration of KOH electrolyte has been studied. In addition, cyclic voltammetric measurements have been performed to examine the hydride formation and decomposition reactions. 相似文献
103.
Takayuki Honma Yuichiro Kuroki Tomoichiro Okamoto Masasuke Takata Yukihiro Kanechika Masanobu Azuma Hitofumi Taniguchi 《Ceramics International》2008,34(4):943-946
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density. 相似文献
104.
基体温度对磁控溅射沉积ZAO薄膜性能的影响 总被引:8,自引:2,他引:6
利用中频交流磁控溅射方法 ,采用氧化锌铝陶瓷靶材 [w(ZnO) =98%、w(Al2 O3 ) =2 % ]制备了ZAO(ZnO∶Al)薄膜 ,观察了基体温度对ZAO薄膜的晶体结构、电学和光学性能的影响 ,采用X射线衍射仪对薄膜的结构进行了分析 ,采用光学分度计和电阻测试仪测量了薄膜的光学、电学特性 ,采用霍尔测试仪测量了薄膜的载流子浓度和霍尔迁移率。结果表明 :沉积薄膜时的基体温度对薄膜的结构、结晶状况、可见光透射率以及导电性有较大的影响。当基体温度为 2 5 0℃ ,Ar分压为 0 8Pa时 ,薄膜的最低电阻率为 4 6× 10 -4Ω·cm ,方块电阻为 35Ω时 ,可见光 (λ =5 5 0nm)透射率高达 92 0 %。 相似文献
105.
李彩虹 《南京工业职业技术学院学报》2008,8(2):1-3
根据PET薄膜的特点和高分子熔融态流动理论,分析了挤出回收用螺杆的各段结构,及螺杆参数选择,设计出大长径比、深槽、双排气、高效专用螺杆。 相似文献
106.
文章通过对五口井的现场应用介绍,阐述了快速色谱分析技术在油气层识别和解释方面的准确性,探讨了该技术在薄油气层的发现和评价、快速钻进条件下油气层的发现、对油气层全烃组份变化的统一、水平井的地质导向以及排除钻井液添加荆对油气显示的影响五个方面的优势,从而论证了快速色谱分析技术在油气勘探中的应用价值。 相似文献
107.
The breakdown processes of oil films under quasi-static loading have been investigated by using a newly developed steel-oil-mercury system. The relationship between the thickness and breakdown ratio of a hexadecane film is represented by a single master curve independently of the indentation speed, indentation load, and temperature. The master curve shows that the breakdown process of hexadecane includes two stages; one is the decrement of the thickness without breakdown and the other is the decrement of the thickness with a drastic progress of breakdown. By solving a small amount of fatty acid in hexadecane, the thickness increases and the breakdown ratio decreases noticeably; a multilayer residual film supporting normal load is formed between two metal surfaces. Experiments at different temperatures reveal a negative relationship between the temperature and thickness of residual film, which indicates that the residual film is organized by physical interaction rather than chemical interaction. At least under a lower concentration, the residual film appears to consist of not only fatty acid molecules but also hexadecane molecules. 相似文献
108.
109.
110.