全文获取类型
收费全文 | 1236篇 |
免费 | 89篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 17篇 |
综合类 | 17篇 |
化学工业 | 267篇 |
金属工艺 | 31篇 |
机械仪表 | 42篇 |
建筑科学 | 35篇 |
矿业工程 | 10篇 |
能源动力 | 39篇 |
轻工业 | 175篇 |
水利工程 | 6篇 |
石油天然气 | 30篇 |
无线电 | 87篇 |
一般工业技术 | 214篇 |
冶金工业 | 97篇 |
原子能技术 | 27篇 |
自动化技术 | 241篇 |
出版年
2024年 | 3篇 |
2023年 | 13篇 |
2022年 | 21篇 |
2021年 | 55篇 |
2020年 | 35篇 |
2019年 | 38篇 |
2018年 | 69篇 |
2017年 | 58篇 |
2016年 | 59篇 |
2015年 | 60篇 |
2014年 | 61篇 |
2013年 | 102篇 |
2012年 | 68篇 |
2011年 | 81篇 |
2010年 | 77篇 |
2009年 | 55篇 |
2008年 | 49篇 |
2007年 | 41篇 |
2006年 | 37篇 |
2005年 | 32篇 |
2004年 | 26篇 |
2003年 | 28篇 |
2002年 | 19篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1998年 | 21篇 |
1997年 | 29篇 |
1996年 | 25篇 |
1995年 | 22篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1984年 | 5篇 |
1983年 | 9篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 13篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1906年 | 5篇 |
排序方式: 共有1335条查询结果,搜索用时 31 毫秒
41.
In this paper, we investigate formulation of non-local memory effect hysteretic loops in presliding domain of friction by examining the dynamic responses of a single-degree-of-freedom friction oscillator. We modify the Maxwell slip model introducing characteristic features of asperities and perform detailed examination of the system from two perspectives. The first one, termed by us as microscale, presents contribution of each individual asperity to the total friction force, whereas the second one, termed by us as macroscale, concerns friction force behaviour of the whole model treated as the unity, with a special emphasis on non-local memory effect hysteretic loops formulation, complemented by time responses. 相似文献
42.
Chenghua Sui Shengjie Wo Pinggen Cai Nan Gao Danyang Xu Yonghao Han 《Journal of Modern Optics》2017,64(21):2413-2419
Corneal topography provides powerful support in the diagnosis and treatment of corneal disease by displaying the corneal surface topography in data or image format. To realize the precise detection of corneal surface topography, an optical system for the corneal topography that is based on a Placido disc is designed, which includes a ring distribution on a Placido disc, an imaging system and a collimating illumination system. First, a mathematical model that is based on the corneal topography working principles is established with MATLAB to determine the distribution of white-and-black rings on the Placido disc, in which the ellipsoid facial rings-target of the Placido disc is utilized. Second, the imaging lens structure is designed and optimized by Zemax software. Last, the collimating illumination lens structure is designed by paraxial ray trace equations. The quality of the corneal topography, which is based on our designed optical system, is evaluated. The high-contrast image of uniformly distributed white-and-black rings is observed through the CCD camera. Our optical system for the corneal topography has high precision, with a measuring region of the cornea with a diameter of approximately 10 mm. Therefore, the creation of this optical system offers guidance for designing and improving the optical system of Placido-disc topography. 相似文献
43.
Krzysztof Dmitruk Marcin Denkowski Michał Mazur Paweł Mikołajczak 《Signal, Image and Video Processing》2017,11(4):613-620
Dual-energy X-ray imaging has a vast range of application in security. Luggage inspection is an essential process for an airplane or court house security as well as securing mass events. An image of a content of some package may help to figure out if there is any dangerous object inside and avoid possibly threatening situation. As the raw X-ray images are not always easy to analyze and interpret, some image processing methods like an object detection, a frequency resolution increase or a pseudocoloring are being used. Since color can be a powerful tool to improve the usefulness of an information display, we propose pseudocoloring improvement by modifying material-based approach with edge detection to fill and sharpen color layers over the image making it easier to read and analyze. We demonstrate the effectiveness of the methods using real data, acquired from a professional dual-energy X-ray scanner. 相似文献
44.
45.
Microbial polyhydroxyalkanoates (PHAs) have been a subject of significant research interest in the past few decades. The recent development of novel functionalized PHAs has opened up new possibilities to combine the good biocompatibility of PHA‐based drug delivery systems to, for example, improve drug loading and release properties, targeting or imaging functionalities. This mini‐review presents some recent scientific developments in the preparation of functionalized PHAs, PHA–drug and PHA–protein conjugates, multifunctional PHA nanoparticles and micelles as well as biosynthetic PHA particles for drug delivery. These developments in combination with the generally excellent biocompatibility of PHA materials are expected to further expand the interest in PHA materials for drug delivery and other therapeutic applications. © 2016 Society of Chemical Industry 相似文献
46.
A sequence S is nonrepetitive if no two adjacent blocks of S are the same. In 1906 Thue proved that there exist arbitrarily long nonrepetitive sequences over 3 symbols. We consider the online variant of this result in which a nonrepetitive sequence is constructed during a play between two players: Bob is choosing a position in a sequence and Alice is inserting a symbol on that position taken from a fixed set A. The goal of Bob is to force Alice to create a repetition, and if he succeeds, then the game stops. The goal of Alice is naturally to avoid that and thereby to construct a nonrepetitive sequence of any given length.We prove that Alice has a strategy to play arbitrarily long provided the size of the set A is at least 12. This is the online version of the theorem of Thue. The proof is based on nonrepetitive colorings of outerplanar graphs. On the other hand, one can prove that even over 4 symbols Alice has no chance to play for too long. The minimum size of the set of symbols needed for the online version of Thue?s theorem remains unknown. 相似文献
47.
Paweł Piszcz Magdalena Woźniak Monika Asztemborska Bronisław K. Głód 《Food Analytical Methods》2014,7(7):1474-1480
The present investigation reports on the application of a new antioxidant activity assay for the examination of flavonoids. It has been shown that the high-performance liquid chromatography with electrochemical detection (HPLC–ED) measurements allow to obtain additional information about the antioxidative properties of pure compounds by measuring their half-wave potential, the chromatographic peak height, and the product of the peak height and exponent of potential. In comparison to the classical electrochemical measurements, the HPLC–ED is characterized by a much smaller detection limit. The results were compared with the standard photometric measurement based on 1,1-diphenyl-2-picrylhydrazyl radicals. The possible antioxidant activity forecasting is also discussed. 相似文献
48.
Maj Justyna Węglewski Witold Bochenek Kamil Rogal Łukasz Woźniacka Stefania Basista Michał 《Metallurgical and Materials Transactions A》2021,52(11):4727-4736
Squeeze casting and powder metallurgy techniques were employed to fabricate AlSi12/Al2O3 composites, which are lightweight structural materials with potential applications in the automotive industry. The impact of the processing route on the material properties was studied. Comparative analyses were conducted for the Vickers hardness, flexural strength, fracture toughness, thermal conductivity, thermal residual stresses, and frictional wear. Our results show that the squeeze cast composite exhibits superior properties to those obtained using powder metallurgy.
相似文献49.
50.