全文获取类型
收费全文 | 10523篇 |
免费 | 742篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 121篇 |
综合类 | 7篇 |
化学工业 | 3052篇 |
金属工艺 | 168篇 |
机械仪表 | 302篇 |
建筑科学 | 474篇 |
矿业工程 | 32篇 |
能源动力 | 407篇 |
轻工业 | 1462篇 |
水利工程 | 82篇 |
石油天然气 | 46篇 |
无线电 | 681篇 |
一般工业技术 | 1712篇 |
冶金工业 | 430篇 |
原子能技术 | 91篇 |
自动化技术 | 2211篇 |
出版年
2024年 | 28篇 |
2023年 | 133篇 |
2022年 | 446篇 |
2021年 | 514篇 |
2020年 | 300篇 |
2019年 | 342篇 |
2018年 | 412篇 |
2017年 | 415篇 |
2016年 | 459篇 |
2015年 | 341篇 |
2014年 | 473篇 |
2013年 | 859篇 |
2012年 | 705篇 |
2011年 | 862篇 |
2010年 | 579篇 |
2009年 | 638篇 |
2008年 | 557篇 |
2007年 | 493篇 |
2006年 | 450篇 |
2005年 | 345篇 |
2004年 | 249篇 |
2003年 | 257篇 |
2002年 | 208篇 |
2001年 | 133篇 |
2000年 | 138篇 |
1999年 | 118篇 |
1998年 | 89篇 |
1997年 | 88篇 |
1996年 | 82篇 |
1995年 | 79篇 |
1994年 | 49篇 |
1993年 | 51篇 |
1992年 | 25篇 |
1991年 | 36篇 |
1990年 | 22篇 |
1989年 | 30篇 |
1988年 | 18篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 24篇 |
1984年 | 18篇 |
1983年 | 14篇 |
1982年 | 31篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 18篇 |
1978年 | 26篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Marco Mandolini Federico Campi Claudio Favi Michele Germani Roberto Raffaeli 《The International Journal of Advanced Manufacturing Technology》2020,107(3):1131-1151
This paper presents a novel framework for manufacturing and cost-related knowledge formalization. This artefact allows industries to capitalize the knowled 相似文献
23.
Neural Computing and Applications - The goal of this paper is to introduce a novel hybrid model called multi-fuzzy N-soft set, and to design an adjustable decision-making methodology for solving... 相似文献
24.
Roberto C. Dante Pablo Martín-Ramos Pedro Chamorro-Posada Dario Rutto José Vázquez-Cabo Denisse G. Dante 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(7):533-540
AbstractIn this work, a new g-C3N4-based Z-scheme with γ-Fe2O3 and β-Ag2Se both n-type semiconductors, and graphite to favor electron exchange is presented. The composite material was studied by XRD, FTIR, UV-Vis, TEM, XPS, TGA, DSC and TOF-SIMS, and the ability of this photocatalytic system to act as a photo-reductant was assessed using crystal violet (CV+) dye. Solar light driven photo-reduction of CV+ in the presence of tri-sodium citrate evidenced a synergistic enhancement of the activity of the composite toward reduction, with ~20 times higher conversion rates per unit of surface area than those of g-C3N4. Photo-oxidation experiments under Xe lamp irradiation in the presence of H2O2 also showed that the AgFeCN composite featured a higher activity (~8×) than g-C3N4. This Z-scheme may deserve further study as a photo-reductant to obtain hydrogen or hydrogenated compounds. Moreover, the use of CV+ may represent a facile procedure that can aid in the selection of new photocatalysts to be used in hydrogen production. 相似文献
25.
Salehi Maryam Zavarian Ali Asghar Arman Ali Hafezi Fatemeh Rad Ghasem Amraee Mardani Mohsen Hamze Kooros Luna Carlos Naderi Sirvan Ahmadpourian Azin 《SILICON》2018,10(6):2743-2749
Silicon - The characterization of ion beam current density distribution and beam uniformity is crucial for improving broad-beam ion source technologies. The design of the broad ion beam extraction... 相似文献
26.
Ricardo Martínez-Corona Gerardo Vázquez Marrufo Carlos Cortés Penagos Luis Alberto Madrigal-Pérez Juan Carlos González-Hernández 《Yeast (Chichester, England)》2020,37(1):149-162
Lipases are hydrolytic enzymes that break the ester bonds of triglycerides, generating free fatty acids and glycerol. Extracellular lipase activity has been reported for the nonconventional yeast Kluyveromyces marxianus, grown in olive oil as a substrate, and the presence of at least eight putative lipases has been detected in its genome. However, to date, there is no experimental evidence on the physiological role of the putative lipases nor their structural and catalytic properties. In this study, a bioinformatic analysis of the genes of the putative lipases from K. marxianus L-2029 was performed, particularly identifying and characterizing the extracellular expected enzymes, due to their biotechnological relevance. The amino acid sequence of 10 putative lipases, obtained by in silico translation, ranged between 389 and 773 amino acids. Two of the analysed putative proteins showed a signal peptide, 25 and 33 amino acids long for KmYJR107Wp and KmLIP3p, and a molecular weight of 44.53 and 58.23 kDa, respectively. The amino acid alignment of KmLIP3p and KmYJR107Wp with the crystallized lipases from a patatin and the YlLip2 lipase from Yarrowia lipolytica, respectively, revealed the presence of the hydrolase characteristic motifs. From the 3D models of putative extracellular K. marxianus L-2029 lipases, the conserved pentapeptide of each was determined, being GTSMG for KmLIP3p and GHSLG for KmYJR107Wp; besides, the genes of these two enzymes (LIP3 and YJR107W) are apparently regulated by oleate response elements. The phylogenetic analysis of all K. marxianus lipases revealed evolutionary affinities with lipases from abH15.03, abH23.01, and abH23.02 families. 相似文献
27.
Paola Cristina Cajas Daza Rodrigo Arbey Muñoz Meneses Ana Candida Martins Rodrigues Cosme Roberto Moreira da Silva 《Ceramics International》2018,44(12):13699-13705
Doped CeGdO and codoped CeGdOSmO compositions were synthesized, giving rise to nanoparticulate powders. Ionic conductivities at bulk and grain boundaries of the sintered samples were determined, exhibiting increased conductivity in the samaria-codoped samples. Scanning electron microscopy (SEM) showed a significant reduction in the grain size of samaria-codoped electrolytes. This reduced grain size of the codoped samples caused a reduction in Schottky barrier height, increasing oxygen vacancy concentration in the space-charge layer of the grain boundary and culminating in greater ionic conductivity in the boundary region. For the gadolinium doped samples, high resolution transmission electron microscopy images at grains showed the presence of large cluster of defects (nanodomains), hindering the movement of charge carriers and reducing ionic conductivity. However, the samaria-codoped system displayed better homogeneity at atomic level, resulting in reduced oxygen vacancy ordering and, consequently, smaller nanodomains and higher bulk (grain) conductivity. The reduced grain sizes and smaller nanodomains caused by codoping favor the ionic conductivity of ceria-based ceramics, doped with gadolinia and codoped with samaria. 相似文献
28.
Francisco Hernndez-Beltrn Juan Carlos Moreno-Mayorga María de Lourdes Guzmn-Castillo Juan Navarrete-Bolaos Montserrat Gonzlez-Gonzlez Brent E. Handy 《Applied Catalysis A: General》2003,240(1-2):41-51
The evolution of the properties of a REUSY zeolite contained in a fluid cracking catalyst was investigated under laboratory steam deactivation procedures and in age fractions of the corresponding equilibrium catalyst (Ecat). The aging pattern, defined by the evolution of the zeolite surface area (ZSA) related to the decrease of the unit cell size (UCS), was similar between lab-steamed zeolites and Ecat fractions. A sharp drop in ZSA occurred at ca. 2.430 nm UCS. A study done by FT-IR spectroscopy suggested that zeolite dealumination initially took place more extensively on the sodalite cages and double six-member rings (D6R) of the structure and that the final collapse of the zeolite framework occurred through destruction of the 12-member rings (12M). This can be explained by a crystal fracture and break down process and disassembling of the sodalite cages in the faujasite structure. NH3 microcalorimetry showed that strong acid sites in faujasites are destroyed by steam aging, but this effect does not lead to a reduction in the cracking activity of the Ecat form. The microactivity test (MAT) showed that the specific activity declined sharply at 2.430 nm UCS. Differences in product selectivity were related to the extent of damage of the zeolite, extra-framework alumina and mesoporosity. While further aging canceled the effect attributed to extra-framework alumina differences attributed to mesoporosity increased. 相似文献
29.
Ana M. García José M. Villora Diego A. Moreno Carlos Ranninger Pío Callejas M. Flora Barba 《Journal of the American Ceramic Society》2003,86(12):2200-2202
The objective of this research was to study the removal of cadmium and lead from an aqueous solution through a biological treatment. For this purpose a glass-ceramic material was manufactured from industrial and urban wastes. Biofilms of microorganisms found in wastewater were developed on its surface, and continuous tests were conducted in the presence and absence of the biofilm to analyze the glass-ceramic's ability to remove the heavy metals from an aqueous environment. The results suggest that this bioremediation process, developed on an industrial scale, could represent an alternative to the chemical processes currently used. 相似文献