全文获取类型
收费全文 | 84802篇 |
免费 | 10452篇 |
国内免费 | 3993篇 |
专业分类
电工技术 | 5517篇 |
技术理论 | 5篇 |
综合类 | 6873篇 |
化学工业 | 19141篇 |
金属工艺 | 6758篇 |
机械仪表 | 4933篇 |
建筑科学 | 8242篇 |
矿业工程 | 1765篇 |
能源动力 | 10495篇 |
轻工业 | 3566篇 |
水利工程 | 1485篇 |
石油天然气 | 3446篇 |
武器工业 | 699篇 |
无线电 | 5513篇 |
一般工业技术 | 10450篇 |
冶金工业 | 4297篇 |
原子能技术 | 1567篇 |
自动化技术 | 4495篇 |
出版年
2024年 | 475篇 |
2023年 | 1460篇 |
2022年 | 2534篇 |
2021年 | 2903篇 |
2020年 | 3056篇 |
2019年 | 2561篇 |
2018年 | 2341篇 |
2017年 | 2700篇 |
2016年 | 3043篇 |
2015年 | 3175篇 |
2014年 | 4980篇 |
2013年 | 5419篇 |
2012年 | 5995篇 |
2011年 | 6467篇 |
2010年 | 4740篇 |
2009年 | 4847篇 |
2008年 | 4145篇 |
2007年 | 5343篇 |
2006年 | 4848篇 |
2005年 | 4327篇 |
2004年 | 3681篇 |
2003年 | 3276篇 |
2002年 | 2936篇 |
2001年 | 2326篇 |
2000年 | 1980篇 |
1999年 | 1600篇 |
1998年 | 1348篇 |
1997年 | 1186篇 |
1996年 | 992篇 |
1995年 | 854篇 |
1994年 | 692篇 |
1993年 | 568篇 |
1992年 | 508篇 |
1991年 | 357篇 |
1990年 | 305篇 |
1989年 | 288篇 |
1988年 | 202篇 |
1987年 | 141篇 |
1986年 | 116篇 |
1985年 | 84篇 |
1984年 | 116篇 |
1983年 | 81篇 |
1982年 | 75篇 |
1981年 | 22篇 |
1980年 | 23篇 |
1979年 | 15篇 |
1978年 | 7篇 |
1966年 | 7篇 |
1959年 | 31篇 |
1951年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Poly[2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐para‐phenylene vinylene] (MEH‐PPV)/silica nanoparticle hybrid films were prepared and characterised. Three kinds of materials were compared: parent MEH‐PPV, MEH‐PPV/silica (hybrid A films), and MEH‐PPV/coupling agent MSMA/silica (hybrid B films), in which MSMA is 3‐(trimethoxysilyl) propyl methacrylate. It was found that the hybrid B films could significantly prevent macrophase separation, as evidenced by scanning electron and fluorescence microscopy. Furthermore, the thermal characteristics of the hybrid films were largely improved in comparison with the parent MEH‐PPV. The UV‐visible absorption spectra suggested that the incorporation of MSMA‐modified silica into MEH‐PPV could confine the polymer chain between nanoparticles and thus increase the conjugation length. The photoluminescence (PL) studies also indicated enhancement of the PL intensity and quantum efficiency by incorporating just 2 wt% of MSMA‐modified silica into MEH‐PPV. However, hybrid A films did not show such enhancement of optoelectronic properties as the hybrid B films. The present study suggests the importance of the interface between the luminescent organic polymers and the inorganic silica on morphology and optoelectronic properties. Copyright © 2004 Society of Chemical Industry 相似文献
122.
123.
124.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。 相似文献
125.
126.
Technology can take many forms from the development of sophisticated electronics to the application of basic procedural principles. Technology transfer can also take several forms, however, in this case, it is the transfer of technological principles between application domains that is of primary interest. This paper presents a framework (the Five ‘M’s framework) that can be used to consider the likely success of technology transfer. The framework is based upon a sociotechnical system approach. The framework is illustrated with an evaluation of the introduction of intelligent cruise control into motor vehicles. It is argued that this is a technological concept first developed as an aerospace application in the form of the autopilot. In this case, it is argued that the transfer of this technology in its current form may potentially compromise safety. 相似文献
127.
128.
我国风机盘管技术现状分析 总被引:2,自引:2,他引:0
介绍了近年来我国在风机盘管技术领域的最新成果,在结构形式、强化传热、提高室内空气品质、降低噪音和提高自动控制水平等方面的技术进展情况,分析了目前风机盘管中存在的问题,并对今后的发展方向进行了展望。 相似文献
129.
Sirisha Nerella Debendra K. Das Godwin A. Chukwu Abhijit Y. Dandekar Santanu Khataniar Shirish L. Patil 《Petroleum Science and Technology》2003,21(7):1275-1294
Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations. 相似文献
130.
This paper presents the mass transfer results from an impinging liquid jet to a rotating disk. The mass transfer coefficients were measured using the electrochemical limiting diffusion current technique (ELDCT). Rotational Reynolds number (Rer) in the range of 3.4 × 104–1.2 × 105, jet Reynolds number (Rej) 1.7 × 104–5.3 × 104 and non-dimensional jet-to-disk spacing (H/d) 2–8 were taken into consideration as parameters. It was found that the jet impingement resulted in a substantial enhancement in the mass transfer compared to the case of the rotating disk without jet. 相似文献