全文获取类型
收费全文 | 1266篇 |
免费 | 56篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
综合类 | 7篇 |
化学工业 | 265篇 |
金属工艺 | 11篇 |
机械仪表 | 7篇 |
建筑科学 | 91篇 |
矿业工程 | 1篇 |
能源动力 | 17篇 |
轻工业 | 147篇 |
水利工程 | 5篇 |
无线电 | 73篇 |
一般工业技术 | 231篇 |
冶金工业 | 136篇 |
原子能技术 | 9篇 |
自动化技术 | 308篇 |
出版年
2023年 | 19篇 |
2022年 | 19篇 |
2021年 | 36篇 |
2020年 | 15篇 |
2019年 | 25篇 |
2018年 | 30篇 |
2017年 | 30篇 |
2016年 | 36篇 |
2015年 | 41篇 |
2014年 | 58篇 |
2013年 | 83篇 |
2012年 | 67篇 |
2011年 | 72篇 |
2010年 | 59篇 |
2009年 | 52篇 |
2008年 | 57篇 |
2007年 | 60篇 |
2006年 | 46篇 |
2005年 | 42篇 |
2004年 | 50篇 |
2003年 | 21篇 |
2002年 | 24篇 |
2001年 | 20篇 |
2000年 | 25篇 |
1999年 | 26篇 |
1998年 | 58篇 |
1997年 | 39篇 |
1996年 | 28篇 |
1995年 | 21篇 |
1994年 | 14篇 |
1993年 | 17篇 |
1992年 | 9篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1983年 | 7篇 |
1982年 | 5篇 |
1980年 | 3篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 12篇 |
1975年 | 3篇 |
1973年 | 4篇 |
1969年 | 6篇 |
1967年 | 3篇 |
1933年 | 2篇 |
排序方式: 共有1323条查询结果,搜索用时 31 毫秒
1.
Seidel A.R. Bisogno F.E. Pinheiro H. do Prado R.N. 《Industrial Electronics, IEEE Transactions on》2003,50(6):1267-1274
This paper presents a simple alternative for an electronic ballast operating in self-sustained oscillating mode with dimming capability for fluorescent lamps. A simple modification in one of the gate drivers side circuit allows the lamp to dim without compromising the simplicity, reliability, and low cost which characterize the self-oscillating electronic ballast (SOEB). A qualitative analysis is presented to explain the behavior of the proposed self-oscillating electronic ballast with dimming feature. In addition, the stability and the key equations for the design are derived using the extended Nyquist criterion and describing function method. Experimental results from two 40-W electronic ballasts are presented to demonstrate the performance and to validate the analysis carried out. 相似文献
2.
Modelling the effects of dam removal on migratory walleye (Sander vitreus) early life‐history stages
Many dams in the USA have outlived their intended purpose and an increasing number are being considered for removal. Yet, quantitative studies of the potential physical, biological and ecological responses are needed to assess dam removal decisions. In this paper, the responses of migratory walleye (Sander vitreus) to increased spawning habitat availability as a result of dam removal was studied by comparing scenarios with and without a high‐head dam in the Sandusky River (Ohio), a major tributary to Lake Erie. A conceptual, ecological model was proposed to define the relationship between hydrodynamics and walleye spawning, egg hatching, larval drift and survival. A mathematical, ecological model of the early life‐history stages was then developed and coupled with time series of depth and velocity predictions over the spawning grounds from a 1‐D hydrodynamic model. Model simulations were run for 1984–1993 for both the with‐ and without‐dam scenarios to assess the potential benefit of dam removal. The simulation results demonstrated that velocity, depth and water temperature are major factors influencing adult walleye spawning success. Without the dam, 10 times the amount of spawning habitat would be available for walleye to spawn. This increase in spawning habitat area resulted in up to five times the total egg deposition and seven times the larval output to the nursing grounds, based on the assumption that 5% of the walleye population of Lake Erie migrated up the Sandusky River to spawn. We concluded that the spawning habitat in the current condition (with the dam) is limiting and additional spawning habitat upstream could significantly increase the number of larval walleye drifting to Lake Erie. The model sensitivity analysis showed that the number of walleye migrating up the river in spring is the dominant factor for larval recruitment to the lake. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
3.
In recent years, a wide range of generalized barycentric coordinates has been suggested. However, all of them lack control over derivatives. We show how the notion of barycentric coordinates can be extended to specify derivatives at control points. This is also known as Hermite interpolation. We introduce a method to modify existing barycentric coordinates to higher order barycentric coordinates and demonstrate, using higher order mean value coordinates, that our method, although conceptually simple and easy to implement, can be used to give easy and intuitive control at interactive frame rates over local space deformations such as rotations. 相似文献
4.
Here, we describe the development of a reacting flow multi-species/combustion methodology, implemented as an extension to the differential reduced ejector analysis (DREA) computer program [Mathematical and computer modeling, vol. 31, 2000, p. 21; Appl. Math. Model. 25 (2001) 427; Comput. Math. Appl. 43(10–11); NASA Contractor Report, 1998]. Use of the single fluid IVP solver framework that was developed for the original DREA model has been directly coupled into the combustion formulation. With these modifications, the analysis has an elementary single step reaction Fuel+Oxidizer→Product combustion capability. Though approximate in nature, the simplicity and efficiency of the DREA formulation make it suitable for its original niche, namely design and preliminary design environments where more complex and expensive models may be inappropriate. 相似文献
5.
RM Bionta G Blewitt CB Bratton D Casper A Ciocio R Claus M Crouch ST Dye S Errede GW Foster W Gajewski KS Ganezer M Goldhaber TJ Haines TW Jones D Kielczewska WR Kropp JG Learned JM LoSecco J Matthews HS Park LR Price F Reines J Schulz S Seidel E Shumard D Sinclair HW Sobel JL Stone L Sulak R Svoboda G Thornton van der Velde JC C Wuest 《Canadian Metallurgical Quarterly》1987,36(1):30-36
6.
7.
S. Brabetz R. Weidl F. Klemm L. Dörrer F. Schmidl P. Seidel 《Journal of Low Temperature Physics》1997,106(3-4):527-532
We investigated different types of high-Tc DC-SQUID gradiometers with the aim to develop an one-channel heart monitoring system for non-invasive measurements in unshielded
environment. This system could be used to obtain information about the patients condition in serial examinations and in emergency
cases fast and stable. Step-edge and bicrystal Josephson junctions were used to prepare planar galvanically coupled thin film
gradiometers and magnetometers. These sensors were used to carry out measurements in well-shielded and non-shielded environment
and we compared the different noise properties and field gradient resolutions. With different types and sizes of high-Tc DC-SQUID sensors magnetocardiograms were measured in a magnetically shielded room. The influence of antenna configurations,
SQUID parameters, and cooling conditions on the measurement of magnetocardiograms will be discussed. We investigated possibilities
to suppress the earth magnetic field (with pairs of Helmholtz coils) and for noise field compensation in unshielded environment. 相似文献
8.
M. A. Weilert D. L. Whitaker H. J. Maris G. M. Seidel 《Journal of Low Temperature Physics》1997,106(1-2):101-131
We report on the stable levitation of liquid helium drops of up to 2 cm diameter in a magnetic trap at temperatures down to
1.5 K in the earth's gravitational field. The production and properties of a magnetic trap for diamagnetic materials is discussed.
The behavior of liquids in such a trap is analyzed, including the deformation of a liquid drop by the trap forces. We frequently
observe two drops in the magnetic trap which are held in apparent contact for up to 3 minutes without coalescing. This non-coalescence
effect was only seen above the superfluid transition temperature. We explain this effect in terms of the existence of a vapor
layer between the drops caused by evaporation of the drops, much like the suspension of a liquid drop above a hot surface
known as the Leidenfrost effect. 相似文献
9.
Lisa Goedtke Heike Sprenger Ute Hofmann Felix F. Schmidt Helen S. Hammer Ulrich M. Zanger Oliver Poetz Albrecht Seidel Albert Braeuning Stefanie Hessel-Pras 《International journal of molecular sciences》2021,22(1)
Polycyclic aromatic hydrocarbons (PAHs) are environmental pollutants produced by incomplete combustion of organic matter. They induce their own metabolism by upregulating xenobiotic-metabolizing enzymes such as cytochrome P450 monooxygenase 1A1 (CYP1A1) by activating the aryl hydrocarbon receptor (AHR). However, previous studies showed that individual PAHs may also interact with the constitutive androstane receptor (CAR). Here, we studied ten PAHs, different in carcinogenicity classification, for their potential to activate AHR- and CAR-dependent luciferase reporter genes in human liver cells. The majority of investigated PAHs activated AHR, while non-carcinogenic PAHs tended to activate CAR. We further characterized gene expression, protein abundancies and activities of the AHR targets CYP1A1 and 1A2, and the CAR target CYP2B6 in human HepaRG hepatoma cells. Enzyme induction patterns strongly resembled the profiles obtained at the receptor level, with AHR-activating PAHs inducing CYP1A1/1A2 and CAR-activating PAHs inducing CYP2B6. In summary, this study provides evidence that beside well-known activation of AHR, some PAHs also activate CAR, followed by subsequent expression of respective target genes. Furthermore, we found that an increased PAH ring number is associated with AHR activation as well as the induction of DNA double-strand breaks, whereas smaller PAHs activated CAR but showed no DNA-damaging potential. 相似文献
10.
Iris Ribitsch Andrea Bileck Alexander D. Aldoshin Maciej M. Kadua Rupert L. Mayer Monika Egerbacher Simone Gabner Ulrike Auer Sinan Gültekin Johann Huber David P. Kreil Christopher Gerner Florien Jenner 《International journal of molecular sciences》2021,22(11)
Tendinopathies are painful, disabling conditions that afflict 25% of the adult human population. Filling an unmet need for realistic large-animal models, we here present an ovine model of tendon injury for the comparative study of adult scarring repair and fetal regeneration. Complete regeneration of the fetal tendon within 28 days is demonstrated, while adult tendon defects remained macroscopically and histologically evident five months post-injury. In addition to a comprehensive histological assessment, proteome analyses of secretomes were performed. Confirming histological data, a specific and pronounced inflammation accompanied by activation of neutrophils in adult tendon defects was observed, corroborated by the significant up-regulation of pro-inflammatory factors, neutrophil attracting chemokines, the release of potentially tissue-damaging antimicrobial and extracellular matrix-degrading enzymes, and a response to oxidative stress. In contrast, secreted proteins of injured fetal tendons included proteins initiating the resolution of inflammation or promoting functional extracellular matrix production. These results demonstrate the power and relevance of our novel ovine fetal tendon regeneration model, which thus promises to accelerate research in the field. First insights from the model already support our molecular understanding of successful fetal tendon healing processes and may guide improved therapeutic strategies. 相似文献