全文获取类型
收费全文 | 324792篇 |
免费 | 5294篇 |
国内免费 | 722篇 |
专业分类
电工技术 | 6489篇 |
综合类 | 609篇 |
化学工业 | 50261篇 |
金属工艺 | 10770篇 |
机械仪表 | 9194篇 |
建筑科学 | 8658篇 |
矿业工程 | 970篇 |
能源动力 | 8835篇 |
轻工业 | 33194篇 |
水利工程 | 2650篇 |
石油天然气 | 3692篇 |
武器工业 | 8篇 |
无线电 | 40673篇 |
一般工业技术 | 62577篇 |
冶金工业 | 57294篇 |
原子能技术 | 5577篇 |
自动化技术 | 29357篇 |
出版年
2021年 | 2637篇 |
2019年 | 2426篇 |
2018年 | 4177篇 |
2017年 | 4040篇 |
2016年 | 4197篇 |
2015年 | 3094篇 |
2014年 | 5096篇 |
2013年 | 15587篇 |
2012年 | 8132篇 |
2011年 | 11050篇 |
2010年 | 8709篇 |
2009年 | 9836篇 |
2008年 | 10417篇 |
2007年 | 10359篇 |
2006年 | 9072篇 |
2005年 | 8318篇 |
2004年 | 8120篇 |
2003年 | 7857篇 |
2002年 | 7707篇 |
2001年 | 7839篇 |
2000年 | 7453篇 |
1999年 | 7734篇 |
1998年 | 17878篇 |
1997年 | 13036篇 |
1996年 | 10262篇 |
1995年 | 8033篇 |
1994年 | 7325篇 |
1993年 | 7011篇 |
1992年 | 5377篇 |
1991年 | 5152篇 |
1990年 | 5011篇 |
1989年 | 4847篇 |
1988年 | 4737篇 |
1987年 | 3949篇 |
1986年 | 4063篇 |
1985年 | 4842篇 |
1984年 | 4404篇 |
1983年 | 4109篇 |
1982年 | 3691篇 |
1981年 | 3874篇 |
1980年 | 3548篇 |
1979年 | 3489篇 |
1978年 | 3304篇 |
1977年 | 3877篇 |
1976年 | 4927篇 |
1975年 | 2851篇 |
1974年 | 2709篇 |
1973年 | 2732篇 |
1972年 | 2245篇 |
1971年 | 1988篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Ida-Marie Andersson Björn Bergenståhl Marcela Alexander Marie Paulsson Maria Glantz 《International Journal of Food Science & Technology》2021,56(1):480-492
During whey powder production, the feed is subjected to several heat treatments which can cause lactosylation of proteins. In this study, lactosylation of whey proteins was evaluated in spray-dried powders before and after storage by varying the native protein fraction as well as the serum protein/lactose ratio in the powders. The lactosylation of native α-lactalbumin and β-lactoglobulin in the powders before storage was not affected to a large extent by the protein denaturation or if the feed had been heat treated in a high or low lactose environment. After storage (relative humidity of 23.5%, 30 °C, 25 days), the kinetic of lactosylation tended to increase with increasing native protein fraction and bulk protein content in the powders. An explanation could be that proteins dissolved in the lactose glassy structure might have a lower reactivity, while proteins present in the protein glassy structure with dissolved lactose may display higher lactosylation reactivity. 相似文献
12.
Currently, the efficient detection of fingerprints is essential for the crime investigations. Revealing fingerprints is commonly achieved with fluorescent organic compounds but they are not efficient for fingerprint detection on porous or reflective surfaces. In order to solve the problem of collecting fingerprints on porous/reflective surfaces, inorganic phosphors have been employed, since they have characteristics of variable color emission, afterglow, high chemical stability and nano-size, which allow the fingerprint detection on any porous or non-porous surfaces. Due to these last properties, this review presents a summary about the use of phosphorescent and fluorescent phosphors for the detection of latent fingerprints. First, we discussed the main physical and chemical characteristics of the fingerprints which permit their detection and collection from any surface. After this, we presented the main morphological, structural and luminescent properties of the phosphorescent and fluorescent phosphors that allow their use for fingerprint detection. Later, we demonstrated with pictures of fingerprints (with and without light emission from the phosphors deposited on them) that both, phosphorescent and fluorescent phosphors can be used to visualize fingerprints with high resolution and high contrast without interference of the background surface, which is ideal for its collection and registration in the Automated Fingerprint Identification System (AFIS). We believe that this review could be useful to understand how to select an appropriate phosphorescent or fluorescent material for fingerprint detection depending on the type of surface (porous or non-porous, reflective or not reflective) where the fingerprint is deposited. 相似文献
13.
Automation and Remote Control - We consider multicriteria minimax optimization problems with criteria in the form of the maxima of functionals given by the induced norms of linear operators taking... 相似文献
14.
Mobile Networks and Applications - Blockchain applications have continuously improved ever since its first debut on cryptocurrency. From then on, its uses have branched out from the financial... 相似文献
15.
Castro Mateus B. Souza Raphael R. N. Junior Agord M. P. Lima Eduardo R. Manera Leandro T. 《Analog Integrated Circuits and Signal Processing》2021,109(3):647-656
Analog Integrated Circuits and Signal Processing - This paper presents the complete design of a phase locked loop-based clock synthesizer for reconfigurable analog-to-digital converters. The... 相似文献
16.
Thomas R. Savage Fernando Almeida-Trasvina Ehecatl A. del-Rio Chanona Robin Smith Dondga Zhang 《American Institute of Chemical Engineers》2021,67(11):e17358
With liquefied natural gas becoming increasingly prevalent as a flexible source of energy, the design and optimization of industrial refrigeration cycles becomes even more important. In this article, we propose an integrated surrogate modeling and optimization framework to model and optimize the complex CryoMan Cascade refrigeration cycle. Dimensionality reduction techniques are used to reduce the large number of process decision variables which are subsequently supplied to an array of Gaussian processes, modeling both the process objective as well as feasibility constraints. Through iterative resampling of the rigorous model, this data-driven surrogate is continually refined and subsequently optimized. This approach was not only able to improve on the results of directly optimizing the process flow sheet but also located the set of optimal operating conditions in only 2 h as opposed to the original 3 weeks, facilitating its use in the operational optimization and enhanced process design of large-scale industrial chemical systems. 相似文献
17.
Bosyakova N. A. Pomortsev S. A. Gizatullin R. G. Klyosov Yu. L. Laptov S. V. Kashcheev I. D. Zemlyanoi K. G. 《Refractories and Industrial Ceramics》2021,62(4):381-383
Refractories and Industrial Ceramics - Technology for producing alumina-periclase-carbon refractories of the brands APUK-D and APU-D is developed and implemented. Use of complex antioxidant and... 相似文献
18.
Khammatova V. V. Gainutdinov R. F. Khammatova E. A. Titova L. V. 《Fibre Chemistry》2021,53(3):204-207
Fibre Chemistry - An analysis of the aramid fiber market including the range of industrial textile materials containing chemical fibers for specialized protective clothing of metallurgical workers,... 相似文献
19.
Reliable prediction of flooding conditions is needed for sizing and operating packed extraction columns. Due to the complex interplay of physicochemical properties, operational parameters and the packing-specific properties, it is challenging to develop accurate semi-empirical or rigorous models with a high validity range. State of the art models may therefore fail to predict flooding accurately. To overcome this problem, a data-driven model based on Gaussian processes is developed to predict flooding for packed liquid-liquid and high-pressure extraction columns. The optimized Gaussian process for the liquid-liquid extraction column results in an average absolute relative error (AARE) of 15.23 %, whereas the algorithm for the high-pressure extraction column results in an AARE of 13.68 %. Both algorithms can predict flooding curves for different packing geometries and chemical systems precisely. 相似文献
20.
N.A. Zhuk M.G. Krzhizhanovskaya N.A. Sekushin V.V. Kharton B.A. Makeev V.A. Belyy R.I. Korolev 《Ceramics International》2021,47(14):19424-19433
The solid solutions based on the pyrochlore-type system Bi2MgNb2-xTaxO9 were formed in the compositional range х = 0–2.0 (Bi1·6Mg0·8Nb1.6-tTatO7.2, t = 0–1.6). The Rietveld method was used to refine the structure for Bi2MgNb2-xTaxO9 (x = 0, 1.0, 2.0). The increasing tantalum content led to the slight decrease in the cubic unit cell parameters from 10.56934 (4) Å for x = 0 and 10.54607 (3) Å for x = 2 (sp.gr. Fd-3m:2). At the same time, tantalum additions suppressed grain growth in the pyrochlore ceramics during sintering and made it possible to obtain materials with an average grain size of 1–2 μm (Bi1·6Mg0·8Ta1·6O7.2). The increase in the Ta5+ concentration led to the decrease in the dielectric permeability from 104 (Bi1·6Mg0·8Nb1·6O7.2) to 20 (Bi1·6Mg0·8Ta1·6O7.2) at room temperature, while the dielectric loss tangent remained lower than 0.002, which is due to the small grain size and the high porosity of the samples. An increase in temperature has practically no effect on the values of the dielectric permittivity in the entire frequency range. The samples have weak through conductivity. The activation energies of electrical conductivity varied in the range of 0.84–1.00 eV, and the less tantalum, the lower the activation energy. The electrical properties of the samples at 200 Hz to 1 MHz are described by the simplest parallel scheme. 相似文献