全文获取类型
收费全文 | 1783篇 |
免费 | 294篇 |
国内免费 | 142篇 |
专业分类
电工技术 | 90篇 |
综合类 | 133篇 |
化学工业 | 299篇 |
金属工艺 | 26篇 |
机械仪表 | 36篇 |
建筑科学 | 13篇 |
矿业工程 | 7篇 |
能源动力 | 22篇 |
轻工业 | 49篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
武器工业 | 6篇 |
无线电 | 382篇 |
一般工业技术 | 207篇 |
冶金工业 | 21篇 |
原子能技术 | 12篇 |
自动化技术 | 906篇 |
出版年
2024年 | 2篇 |
2023年 | 12篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 15篇 |
2019年 | 21篇 |
2018年 | 25篇 |
2017年 | 23篇 |
2016年 | 38篇 |
2015年 | 45篇 |
2014年 | 102篇 |
2013年 | 156篇 |
2012年 | 240篇 |
2011年 | 316篇 |
2010年 | 248篇 |
2009年 | 220篇 |
2008年 | 183篇 |
2007年 | 214篇 |
2006年 | 118篇 |
2005年 | 53篇 |
2004年 | 34篇 |
2003年 | 21篇 |
2002年 | 24篇 |
2001年 | 11篇 |
2000年 | 16篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1976年 | 1篇 |
排序方式: 共有2219条查询结果,搜索用时 15 毫秒
1.
Wenchao Wang Xueqin Bai Qing Ci Lili Du Xingang Ren David Lee Phillips 《Advanced functional materials》2021,31(35):2103978
Undesired photoelectronic dormancy through active species decay is adverse to photoactivity enhancement. An insufficient extrinsic driving force leads to ultrafast deep charge trapping and photoactive species depopulation in carbon nitride (g-C3N4). Excitation of shallow trapping in g-C3N4 with long-lived excited states opens up the possibility of pursuing high-efficiency photocatalysis. Herein, a near-field-assisted model is constructed consisting of an In2O3-cube/g-C3N4 heterojunction associated with ultrafast photodynamic coupling. This In2O3-cube-induced near-field assistance system provides catalytic “hot areas”, efficiently enhances the lifetimes of excited states and shallow trapping in g-C3N4 and this favors an increased active species density. Optical simulations combined with time-resolved transient absorption spectroscopy shows there is a built-in charge transfer and the active species lifetimes are longer in the In2O3-cube/g-C3N4 hybrid. Besides these properties, the estimated overpotential and interfacial kinetics of the In2O3-cube/g-C3N4 hybrid co-promotes the liquid phase reaction and also helps in boosting the photocatalytic performance. The photocatalytic results exhibit a tremendous improvement (34-fold) for visible-light-driven hydrogen production. Near-field-assisted long-lived active species and the influences of trap states is a novel finding for enhancing (g-C3N4)-based photocatalytic performance. 相似文献
2.
3.
In this article we illustrate a methodology for building cross-language search engine. A synergistic approach between thesaurus-based approach and corpus-based approach is proposed. First, a bilingual ontology thesaurus is designed with respect to two languages: English and Spanish, where a simple bilingual listing of terms, phrases, concepts, and subconcepts is built. Second, term vector translation is used – a statistical multilingual text retrieval techniques that maps statistical information about term use between languages (Ontology co-learning). These techniques map sets of t f id f term weights from one language to another. We also applied a query translation method to retrieve multilingual documents with an expansion technique for phrasal translation. Finally, we present our findings. 相似文献
4.
Massive Open Online Courses (MOOCs) are becoming an essential source of information for both students and teachers. Noticeably, MOOCs have to adapt to the fast development of new technologies; they also have to satisfy the current generation of online students. The current MOOCs’ Management Systems, such as Coursera, Udacity, edX, etc., use content management platforms where content are organized in a hierarchical structure. We envision a new generation of MOOCs that support interpretability with formal semantics by using the SemanticWeb and the online social networks. Semantic technologies support more flexible information management than that offered by the current MOOCs’ platforms. Annotated information about courses, video lectures, assignments, students, teachers, etc., can be composed from heterogeneous sources, including contributions from the communities in the forum space. These annotations, combined with legacy data, build foundations for more efficient information discovery in MOOCs’ platforms. In this article we review various Collaborative Semantic Filtering technologies for building Semantic MOOCs’ management system, then, we present a prototype of a semantic middle-sized platform implemented at Western Kentucky University that answers these aforementioned requirements. 相似文献
5.
Min Zhao Fengjiao Shang Jianguo Lv Ying Song Feng Wang Zhitao Zhou Gang He Miao Zhang Xueping Song Zhaoqi Sun Yiyong Wei Xiaoshuang Chen 《Nanoscale research letters》2014,9(1):485
ZnO thin films have been synthesized by means of a simple hydrothermal method with different solvents. The effect of deionized water content in the mixed solvents on the surface morphology, crystal structure, and optical property has been investigated by scanning electron microscopy, X-ray diffraction, and UV-Vis spectrophotometer. A large number of compact and well-aligned hexagonal ZnO nanorods and the maximal texture coefficient have been observed in the thin film, which is grown in the mixed solvent with x = 40%. A lot of sparse, diagonal, and pointed nanorods can be seen in the ZnO thin film, which is grown in the 40-mL DI water solution. The optical band gap decreases firstly and then increases with the increase of x. Reversible wettability of ZnO thin films were studied by home-made water contact angle apparatus. Reversible transition between hydrophobicity and hydrophilicity may be attributed to the change of surface chemical composition, surface roughness and the proportion of nonpolar planes on the surface of ZnO thin films. Photocurrent response of ZnO thin films grown at different solvents were measured in air. The response duration of the thin film, which is grown in the solvent with x = 40%, exhibits a fast growth in the beginning but cannot approach the saturate current value within 100 s. The theoretical mechanism for the slower growth or decay duration of the photocurrent has been discussed in detail. 相似文献
6.
Journal of Signal Processing Systems - The existing researches of fast parallel algorithms for DCT-based real-valued discrete Gabor transform and expansion are limited to theoretical analysis. In... 相似文献
7.
硅基液晶(LCOS)是最适合用于全息视频显示的空间光调制器之一,但是受限于小衍射角和低分辨率的特性,当前市场上的LCOS并不完全适用。近年来出现的超常表面(例如,间隙表面等离子体激元)具有独特的特性,提供了一种新的对光传播进行控制的方法。文中采用数值方法研究了在LCOS中插入超常表面结构,旨在解决小衍射角和低分辨率的问题。为了实用化,使用铝作为金属层、三氧化二铝层作为电介质层,生成GSP结构。首先,研究了铝在可见光频率的光学特性以及相应的法布里珀罗共振子模型。然后将初始GSP结构插入到LCOS中,得到液晶中的电场分布,进一步观察液晶中指向矢分布的变化。数值模拟的结果表明,所提出的结构对远场衍射光具有一定的影响,并且全息显示的视场角也发生一些改变。因此,这里提出的在LCOS装置中插入GSP的方案在技术上是可行的。 相似文献
8.
Four sputtered oxide films (SiO2, Al2O3, Y2O3 and TiO2) along with their passivating amorphous InGaZnO thin film transistors (a-IGZO TFTs) were comparatively studied in this paper. The device passivated by an Al2O3 thin film showed both satisfactory performance (μFE=5.3 cm2/V s, Ion/Ioff>107) and stability, as was probably related to smooth surface of Al2O3 thin films. Although the performance of the a-IGZO TFTs with a TiO2 passivation layer was also good enough (μFE=3.5 cm2/V s, Ion/Ioff>107), apparent Vth shift occurred in positive bias-stress tests due to the abnormal interface state between IGZO and TiO2 thin films. Sputtered Y2O3 was proved no potential for passivation layers of a-IGZO TFTs in this study. Despite unsatisfactory performance of the corresponding a-IGZO TFT devices, sputtered SiO2 passivation layer might still be preferred for its high deposition rate and excellent transparency which benefit the mass production of flat panel displays, especially active-matrix liquid crystal displays. 相似文献
9.
This study aims to design and implement new learning methodologies and resources that seek to advance the development and assessment of one of the fundamental students’ competencies from any Business Administration Degree, such as critical thinking, that is, this is an exploratory study on computing for human learning, specifically, learning of key competencies for business. We are going to use audiovisual case methodology through the use of short film clips, usually real stories, to help students understand the practical implications of theoretical concepts explained in the classroom. A theoretical model test uses data from 32 business students from the Open University of Catalonia. The first results show positive attitudes toward a new technological resource ‘audio-visual cases’. They indicate that the use of this tool can improve the comprehension of a problem and its origins and, at the same time, stimulate learning. In addition, this tool helps to develop critical thinking competency. This study offers important contributions to an e-learning environment and their applicability to the workplace, since it is the first type of research about the impact of audiovisual cases in the acquisition of critical thinking competency. Furthermore, this methodology promotes collaborative learning. 相似文献
10.
In this study, an integrated multi-objective production-distribution flow-shop scheduling problem will be taken into consideration with respect to two objective functions. The first objective function aims to minimize total weighted tardiness and make-span and the second objective function aims to minimize the summation of total weighted earliness, total weighted number of tardy jobs, inventory costs and total delivery costs. Firstly, a mathematical model is proposed for this problem. After that, two new meta-heuristic algorithms are developed in order to solve the problem. The first algorithm (HCMOPSO), is a multi-objective particle swarm optimization combined with a heuristic mutation operator, Gaussian membership function and a chaotic sequence and the second algorithm (HBNSGA-II), is a non-dominated sorting genetic algorithm II with a heuristic criterion for generation of initial population and a heuristic crossover operator. The proposed HCMOPSO and HBNSGA-II are tested and compared with a Non-dominated Sorting Genetic Algorithm II (NSGA-II), a Multi-Objective Particle Swarm Optimization (MOPSO) and two state-of-the-art algorithms from recent researches, by means of several comparing criteria. The computational experiments demonstrate the outperformance of the proposed HCMOPSO and HBNSGA-II. 相似文献