全文获取类型
收费全文 | 312075篇 |
免费 | 3397篇 |
国内免费 | 1128篇 |
专业分类
电工技术 | 5441篇 |
综合类 | 2429篇 |
化学工业 | 45015篇 |
金属工艺 | 17380篇 |
机械仪表 | 13329篇 |
建筑科学 | 7396篇 |
矿业工程 | 2090篇 |
能源动力 | 6263篇 |
轻工业 | 20067篇 |
水利工程 | 3628篇 |
石油天然气 | 4822篇 |
武器工业 | 2篇 |
无线电 | 33858篇 |
一般工业技术 | 63744篇 |
冶金工业 | 40442篇 |
原子能技术 | 5448篇 |
自动化技术 | 45246篇 |
出版年
2021年 | 1337篇 |
2019年 | 1274篇 |
2018年 | 21935篇 |
2017年 | 21606篇 |
2016年 | 14771篇 |
2015年 | 2572篇 |
2014年 | 3009篇 |
2013年 | 8037篇 |
2012年 | 9397篇 |
2011年 | 21626篇 |
2010年 | 18988篇 |
2009年 | 16685篇 |
2008年 | 17280篇 |
2007年 | 19747篇 |
2006年 | 5184篇 |
2005年 | 9040篇 |
2004年 | 7185篇 |
2003年 | 6583篇 |
2002年 | 5142篇 |
2001年 | 4271篇 |
2000年 | 4186篇 |
1999年 | 4119篇 |
1998年 | 10430篇 |
1997年 | 7417篇 |
1996年 | 5701篇 |
1995年 | 4298篇 |
1994年 | 3657篇 |
1993年 | 3599篇 |
1992年 | 2628篇 |
1991年 | 2580篇 |
1990年 | 2416篇 |
1989年 | 2435篇 |
1988年 | 2385篇 |
1987年 | 2126篇 |
1986年 | 2066篇 |
1985年 | 2368篇 |
1984年 | 2185篇 |
1983年 | 2012篇 |
1982年 | 1880篇 |
1981年 | 1944篇 |
1980年 | 1796篇 |
1979年 | 1816篇 |
1978年 | 1776篇 |
1977年 | 2108篇 |
1976年 | 2687篇 |
1975年 | 1557篇 |
1974年 | 1549篇 |
1973年 | 1607篇 |
1972年 | 1350篇 |
1971年 | 1262篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
101.
Pedro Lavrador Marco R. Esteves Vítor M. Gaspar João F. Mano 《Advanced functional materials》2021,31(8):2005941
The complex tissue-specific physiology that is orchestrated from the nano- to the macroscale, in conjugation with the dynamic biophysical/biochemical stimuli underlying biological processes, has inspired the design of sophisticated hydrogels and nanoparticle systems exhibiting stimuli-responsive features. Recently, hydrogels and nanoparticles have been combined in advanced nanocomposite hybrid platforms expanding their range of biomedical applications. The ease and flexibility of attaining modular nanocomposite hydrogel constructs by selecting different classes of nanomaterials/hydrogels, or tuning nanoparticle-hydrogel physicochemical interactions widely expands the range of attainable properties to levels beyond those of traditional platforms. This review showcases the intrinsic ability of hybrid constructs to react to external or internal/physiological stimuli in the scope of developing sophisticated and intelligent systems with application-oriented features. Moreover, nanoparticle-hydrogel platforms are overviewed in the context of encoding stimuli-responsive cascades that recapitulate signaling interplays present in native biosystems. Collectively, recent breakthroughs in the design of stimuli-responsive nanocomposite hydrogels improve their potential for operating as advanced systems in different biomedical applications that benefit from tailored single or multi-responsiveness. 相似文献
102.
Lisichkin S. E. Rubin O. D. Pashchenko F. A. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(3):373-379
Power Technology and Engineering - The experimental results on retaining reinforced-concrete walls reinforced with anchor ties and carbon composite materials on the face side of hydraulic... 相似文献
103.
104.
Antti Voss Niko Hänninen Mohammad Pour-Ghaz Marko Vauhkonen Aku Seppänen 《Materials and Structures》2018,51(3):68
The development of visualizing tools to monitor unsaturated moisture flow in cement-based materials is of great importance, as most degradation processes in cement-based materials are connected to and take place in the presence moisture. This paper investigates the ability of electrical capacitance tomography (ECT) to image two-dimensional (2D) unsaturated moisture flow in cement-based materials. In ECT, the electrical permittivity distribution within an object is reconstructed based on measured capacitances between electrodes attached on the object’s surface. In a series of experiments, mortar specimens with and without discrete cracks were imaged with ECT during a 2D moisture ingress. The results show that ECT is able to monitor the evolution of the moisture flow, and to approximate the shape and position of the moisture front. These findings indicate that ECT is a viable method for monitoring and visualizing 2D unsaturated moisture flow in cement-based materials in the presence and absence of discrete cracks. 相似文献
105.
An agriglass composition containing different oxides acts as a slow release for macro and micro nutrients and was chosen to improve maize yield under most important abiotic stresses which affecting agriculture development; salinity and drought. A field experiment was performed in salt affected soil (EC =?7.5 dSm??1) by using different water deficit rates (I1 = 100, I2 = 85 and I3 = 70% of maize water requirements). Irrigation levels were located in main plots. Every main-plot divided into six sub-plots contained glassy fertilizer treatments [F1 = 55 kg fed?1 with 1/2 mm diameter of agriglass (fed. =?4200 m2), F2 = 55 kg fed?1 with 1 mm diameter, F3 = 80 kg fed?1 with 1/2 mm diameter, F4 = 80 kg fed?1 with 1 mm diameter, F5 = Recommendations of Ministry of Agriculture and F6 = control]. The experimental results demonstrated that, ears, straw, grains and biological yields increased with increasing both water and agriglass rates. Application of agriglass as a slow release fertilizer improved yield more than mineral fertilizer. Some growth parameters, water use efficiency (IWUE), macronutrients concentration and their relations were included. Other studies on residual effect of agriglass and the annual application rates to withstand salinity and drought stress by strategic crops are required. 相似文献
106.
107.
Advanced technologies and modern high-production machines for underground mining of thick gently dipping coal demand strict adherence to technological discipline, reduction in operational loss and selection of optimized ventilation modes. The authors analyze ventilation schemes used in working areas in thick gently dipping seams in order to reveal influence exerted by the schemes, methods and parameters of ventilation on distribution of air loss in mined-out areas. 相似文献
108.
Radiochemistry - Azathioprine, an antitumor agent, was labeled with 99mTc using stannous chloride dihydrate as a reducing agent. Factors such as the amounts of the reducing agent and substrate, pH,... 相似文献
109.
110.
Ahmed Obaid M. Alzahrani M. Sh. Abdel-wahab Meshari Alayash M. S. Aida 《Journal of Materials Science: Materials in Electronics》2018,29(19):16317-16324
In this work, p-NiO/n-ZnO heterostructures were successfully prepared at room temperature using RF sputtering technique. The influence of ZnO layer thickness on the performance of the heterojunction was investigated. The deposited ZnO layers have a hexagonal Wurtzite structure with preferable growth orientations along (002) and (103) for thinner films. Increasing the thickness results in more crystallographic orientation randomness. The current–voltage measurements of the realized heterojunctions showed a clear rectifying behavior. The measured ideality factor varies from 2.5 to 1.6 according to the thickness of ZnO layer. The series resistance of the device is enlarged with increasing ZnO thickness. The deduced parameters from the I–V characteristics suggest that 200 nm is the optimal thickness of the ZnO layer according to our experimental conditions. We attribute the relatively better performance of this thickness to achieving reasonable compensation between serial resistance and ideality factor. The best heterojunction was tested and successfully used as a UV detector. 相似文献