全文获取类型
收费全文 | 2614篇 |
免费 | 127篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 23篇 |
化学工业 | 424篇 |
金属工艺 | 38篇 |
机械仪表 | 26篇 |
建筑科学 | 74篇 |
矿业工程 | 12篇 |
能源动力 | 33篇 |
轻工业 | 753篇 |
水利工程 | 18篇 |
石油天然气 | 2篇 |
无线电 | 183篇 |
一般工业技术 | 470篇 |
冶金工业 | 294篇 |
原子能技术 | 6篇 |
自动化技术 | 392篇 |
出版年
2023年 | 21篇 |
2022年 | 16篇 |
2021年 | 43篇 |
2020年 | 32篇 |
2019年 | 31篇 |
2018年 | 56篇 |
2017年 | 61篇 |
2016年 | 101篇 |
2015年 | 71篇 |
2014年 | 90篇 |
2013年 | 155篇 |
2012年 | 138篇 |
2011年 | 122篇 |
2010年 | 120篇 |
2009年 | 110篇 |
2008年 | 136篇 |
2007年 | 107篇 |
2006年 | 91篇 |
2005年 | 64篇 |
2004年 | 60篇 |
2003年 | 46篇 |
2002年 | 60篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 32篇 |
1998年 | 96篇 |
1997年 | 54篇 |
1996年 | 54篇 |
1995年 | 18篇 |
1994年 | 16篇 |
1993年 | 21篇 |
1992年 | 13篇 |
1976年 | 19篇 |
1937年 | 11篇 |
1936年 | 29篇 |
1935年 | 32篇 |
1934年 | 21篇 |
1933年 | 21篇 |
1932年 | 16篇 |
1931年 | 25篇 |
1930年 | 24篇 |
1929年 | 20篇 |
1928年 | 46篇 |
1927年 | 36篇 |
1926年 | 14篇 |
1925年 | 23篇 |
1915年 | 16篇 |
1913年 | 49篇 |
1912年 | 28篇 |
1907年 | 13篇 |
排序方式: 共有2748条查询结果,搜索用时 15 毫秒
991.
Matthias Graser Hannes Fröck Michael Lechner Michael Reich Olaf Kessler Marion Merklein 《Production Engineering》2016,10(4-5):391-398
In the automotive industry aluminium and its corresponding semi-finished products contribute an essential part to the aim of weight reduction in car body structures. Aluminium alloys of the 6000 series with Mg and Si contents are preferred because of the possibility to increase strength by ageing processes. However, the cold formability in comparison to other materials like mild steels is quite low and due to this, complex parts are only producible at higher temperatures. Therefore, the so called Tailor Heat Treatment was developed to improve the cold formability of aluminium alloys. In this approach, a short-term heat treatment is conducted to achieve a local softening of the material due to dissolution of Mg and Si clusters (retrogression). This effect is used to improve the material flow, relief critical forming zones and enhance the overall formability of the material. Afterwards, strength can be increased again by ageing processes. However, up till now a holistic process understanding, taking into account all process parameters as well as a microstructural explanation is missing. Therefore, the focus of the fundamental investigations lies on connections between the mechanical properties and short-term heat treatment with industry-relevant heating rates as well as natural and artificial ageing process. Conclusively, the evolution of the mechanical properties with regard to the natural ageing process is compared with findings of DSC analysis, which were discussed in Part A. Based on these results, a process window is derived for the subsequent forming process and the final mechanical properties of the final part in dependency of the forming history as well as the artificial ageing process, are identified. 相似文献
992.
993.
Microstructured Fibers: Instability‐Assisted Direct Writing of Microstructured Fibers Featuring Sacrificial Bonds (Adv. Mater. 24/2015)
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
994.
The deployment of electric taxi fleets is highly desirable from a sustainable point of view. Nevertheless, the weak autonomy of this kind of taxis requires a careful operation. The management of such a fleet looking to prevent possible run out of power is studied in this paper. The related question of locating charging terminals for the taxis is also addressed. Methods for dealing with these tasks are proposed and their efficiency is proved through simulations. 相似文献
995.
Krishnaswamy Hariharan Ngoc-Trung Nguyen Nirupam Chakraborti Frédéric Barlat 《Materials and Manufacturing Processes》2015,30(4):403-413
The texture induced anisotropy of yield strength in cold rolled sheet metals is modeled using anisotropic yield criteria. The classical and other optimization methods used so far to determine the yield coefficients are limited by fixed set of experimental data, initial guess values, and pre-determined weight factors. A robust multiobjective optimization based on evolutionary algorithm proposed in this paper minimizes the error in yield stress and plastic strain ratio simultaneously and thereby overcomes the limitations in the approaches used before. The new approach is tested using Hill48 and Barlat89 yield criteria for five different materials from literature. The new approach is observed to improve the prediction capability of yield coefficients when compared to earlier approaches. The Pareto frontier obtained in the new approach can serve as a comparative tool to evaluate the accuracy of different yield criteria. 相似文献
996.
Eva Frühwald 《Holz als Roh- und Werkstoff》2007,65(6):411-418
In timber drying, mechanical properties may be changed due to treatment temperature and treatment duration. In general, when increasing the kiln temperature, drying time is decreased and some timber properties are negatively affected. In this study, the effect of different drying temperatures (80, 120 and 170 °C) on equilibrium moisture content and sorption rate, on bending strength and stiffness was investigated for Norway spruce and larch from four proveniences and the results were compared to those obtained for heat-treated wood (Thermowood ®). The experiments confirm earlier research that both treatment temperature and treatment duration affect the properties. High-temperature drying or treatment can be optimized for several applications, yielding strong but not so durable timber or vice versa. 相似文献
997.
Maria N. Criado Francisco J. Barba Ana Frígola Dolores Rodrigo 《Food and Bioprocess Technology》2014,7(5):1518-1525
The effect of different concentrations of Stevia rebaudiana Bertoni (Stevia) on polyphenoloxidase and peroxidase activities, antioxidant capacity and other bioactive compounds of a mixture of fruits, during 10 days of incubation at 10 and 37 °C, was studied. A significant decrease (p?<?0.05) in both enzyme activities was observed when Stevia was added, showing an inhibitory effect. Samples with a high Stevia concentration showed the highest total phenolic content and antioxidant capacity, whereas non-significant changes were found in the ascorbic acid and carotenoid contents of the samples with Stevia added. A negative significant dependence (p?<?0.05) during incubation was obtained between enzyme activity and antioxidant capacity, so that antioxidant capacity increases as enzyme activity decreases. Therefore, enzyme activity could be used as an indirect index of antioxidant capacity. The results clearly showed that Stevia had significant potential for use not only as a sweetener but also as a natural preservative agent. 相似文献
998.
Abstract: Addition of wheat bran to flours modifies their expansion properties after cooking extrusion. This can be attributed to changes in the melt shear viscosity at the die. The effect of wheat bran concentration added to achieve 2 levels of dietary fibers of 12. 6% and 24.4%, and process conditions on the shear viscosity of wheat flour was therefore assessed using an online twin‐slit rheometer. The shear viscosity measured at 30 s?1 ranged from 9.5 × 103 to 53.4 × 103 Pa s. Regardless of the process conditions and bran concentration, the extruded melts showed a pseudoplastic behavior with a power law index n ranging from 0.05 to 0.27. Increasing the barrel temperature of the extruder from 120 to 180 °C, the water content from 18% to 22% or the screw speed from 400 to 800 rpm significantly decreased the melt shear viscosity at the extruder exit. The addition of bran significantly increased the melt shear viscosity only at the highest bran concentration. The effect was process condition dependant. Mathematical interpretations, based upon observations, of the experimental data were carried out. They can be used to predict the effect of the process conditions on the melt shear viscosity at the die of extruded wheat flour with increasing bran concentration. The viscosity data will be applied in future works to study the expansion properties of extruded wheat flour supplemented with bran. Practical Application: Incorporation of wheat bran, a readily available and low cost by‐product, in extruded puffed foods is constrained due to its negative effect on the product texture. Understanding the effect of wheat bran on rheological properties of extruded melts, driving the final product properties, is essential to provide solutions to the food industry and enhance its use. 相似文献
999.
Capuano F Bond NJ Gatto L Beaudoin F Napier JA Benvenuto E Lilley KS Baschieri S 《Analytical chemistry》2011,83(24):9267-9272
Oil bodies (OBs) are plant cell organelles that consist of a lipid core surrounded by a phospholipid monolayer embedded with specialized proteins such as oleosins. Recombinant proteins expressed in plants can be targeted to OBs as fusions with oleosin. This expression strategy is attractive because OBs are easily enriched and purified from other cellular components, based on their unique physicochemical properties. For recombinant OBs to be a potential therapeutic agent in biomedical applications, it is necessary to comprehensively analyze and quantify both endogenous and heterologously expressed OB proteins. In this study, a mass spectrometry (MS)-based method was developed to accurately quantify an OB-targeted heterologously expressed fusion protein that has potential as a therapeutic agent. The effect of the chimeric oleosin expression upon the OB proteome in transgenic plants was also investigated, and the identification of new potential OB residents was pursued through a variety of liquid chromatography (LC)-MS/MS approaches. The results showed that the accumulation of the fusion protein on OBs was low. Moreover, no significant differences in the accumulation of OB proteins were revealed between transgenic and wild-type seeds. The identification of five new putative components of OB proteome was also reported. 相似文献
1000.
In situ tracking of enzymatic breakdown of starch granules by synchrotron UV fluorescence microscopy
Tawil G Jamme F Réfrégiers M Viksø-Nielsen A Colonna P Buléon A 《Analytical chemistry》2011,83(3):989-993
Synchrotron UV fluorescence microscopy was used for the first time to visualize the adsorption and diffusion of an enzyme while degrading a solid substrate. The degradation pathway of single starch granules by two amylases, optimized for biofuel production and industrial starch hydrolysis, was followed by tryptophan fluorescence (excitation at 280 nm, emission filter at 300-400 nm) and visible light imaging. Thus, both the adsorption of enzyme onto starch granules at 283 nm resolution and the resulting morphological changes were recorded at different stages of hydrolysis. It is the first time that amylases were localized on starch without staining or adding a fluorescent probe at such high resolution. This technique presents a very high potential for imaging proteins in complex systems. Its sensitivity was demonstrated by the detection of GBSS (the granular bound starch synthase) at high recording times, GBSS being present at very low levels in maize starch granules. 相似文献