全文获取类型
收费全文 | 100238篇 |
免费 | 6028篇 |
国内免费 | 1666篇 |
专业分类
电工技术 | 2456篇 |
技术理论 | 2篇 |
综合类 | 2632篇 |
化学工业 | 15206篇 |
金属工艺 | 2774篇 |
机械仪表 | 3220篇 |
建筑科学 | 3692篇 |
矿业工程 | 1134篇 |
能源动力 | 1881篇 |
轻工业 | 9622篇 |
水利工程 | 1490篇 |
石油天然气 | 1581篇 |
武器工业 | 205篇 |
无线电 | 6198篇 |
一般工业技术 | 12145篇 |
冶金工业 | 29321篇 |
原子能技术 | 641篇 |
自动化技术 | 13732篇 |
出版年
2024年 | 295篇 |
2023年 | 1031篇 |
2022年 | 1324篇 |
2021年 | 2010篇 |
2020年 | 1547篇 |
2019年 | 1612篇 |
2018年 | 2686篇 |
2017年 | 2860篇 |
2016年 | 3324篇 |
2015年 | 2883篇 |
2014年 | 2963篇 |
2013年 | 4501篇 |
2012年 | 5567篇 |
2011年 | 5975篇 |
2010年 | 3656篇 |
2009年 | 3519篇 |
2008年 | 3323篇 |
2007年 | 3225篇 |
2006年 | 2708篇 |
2005年 | 5132篇 |
2004年 | 4019篇 |
2003年 | 3524篇 |
2002年 | 2519篇 |
2001年 | 2158篇 |
2000年 | 1342篇 |
1999年 | 1644篇 |
1998年 | 8561篇 |
1997年 | 5544篇 |
1996年 | 3734篇 |
1995年 | 2303篇 |
1994年 | 1689篇 |
1993年 | 1755篇 |
1992年 | 571篇 |
1991年 | 592篇 |
1990年 | 513篇 |
1989年 | 473篇 |
1988年 | 494篇 |
1987年 | 392篇 |
1986年 | 343篇 |
1985年 | 315篇 |
1984年 | 203篇 |
1983年 | 180篇 |
1982年 | 256篇 |
1981年 | 318篇 |
1980年 | 344篇 |
1979年 | 143篇 |
1978年 | 170篇 |
1977年 | 868篇 |
1976年 | 1893篇 |
1975年 | 145篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Tsuchiya Letícia Diniz Braga Lucas Fiorini de Faria Oliveira Otávio de Bettio Raphael Winckler Greghi Juliana Galvani Freire André Pimenta 《Personal and Ubiquitous Computing》2021,25(2):281-295
Personal and Ubiquitous Computing - This article presents a study concerning the evaluation of a smart home control system for elderly people with a sample of 10 users in a city in the interior of... 相似文献
72.
73.
74.
The fission yeast Schizosaccharomyces pombe is an important model organism for the study of fundamental questions in eukaryotic cell and molecular biology. A plethora of cellular processes are membrane associated and/or dependent on the proper functioning of cellular membranes. Phospholipids are not only the basic building blocks of cellular membranes; they also serve as precursors to numerous signaling molecules. In this review, we describe the biosynthetic pathways leading to major S. pombe phospholipids, how these pathways are regulated, and what is known about degradation and turnover of fission yeast phospholipids. This review also addresses the synthesis, regulation and the role of water-soluble phospholipid precursors. The last chapter of the review is devoted to the use of S. pombe for the biotechnological production of value-added lipid molecules. 相似文献
75.
The in-situ fabrication of an electron-blocking layer between the Ba-containing anode and the ceria-based electrolyte is an effective approach in suppressing the internal electronic leakage in ceria-based solid oxide fuel cell (SOFC). To improve the thickness of the electron-blocking layer and to research the effect of the layer thickness on the improvement of SOFC, a Ba-containing compound (0.6NiO-0.4BaZr0.1Ce0.7Y0.2O3-δ) modified by Y stabilized zirconia (YSZ) was employed as a composite anode in this research. SEM analyses demonstrated that the thickness of the interlayer can be simply controlled by regulating the proportion of YSZ at anode. The in-situ formed interlayer in the cell with the anode modified by 20?mol% YSZ possesses a thickness of 0.9?µm which is more suitable for the cell achieving an enhanced performance. 相似文献
76.
文章介绍了目前旋转式压缩机主要零部件的材料状况,详细论述了金属基复合材料、陶瓷基复合材料在旋转压缩机上的应用情况及前景,为复合材料在压缩机领域的应用提供指导。 相似文献
77.
78.
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
79.
80.
Although Mg alloy attracts great attention for engineering applications because of high specific strength and low density, low corrosion resistance limits its extensive use. In this study, Mg–Al–Zn–Mn alloy was treated via a laser cladding process to generate a dense and compact laser cladding layer with solid metallurgical bonding on the substrate for improving corrosion resistance, effectively hindering the corrosion pervasion into Mg alloy. The corrosion current density declined from 103 μA/cm2 for Mg alloy to 13 μA/cm2 for the laser cladding layer in NaCl aqueous solution. Moreover, the laser cladding layer was slightly corroded in comparison with Mg alloy in NaCl aqueous solution. Besides, the microhardness of the cladding layer reached a mean value of 170.5 HV, 3.1 times of Mg alloy (56.8 HV) due to the in situ formation of hardening intermetallic phases. Wear resistance of laser cladding layer was also obviously improved. These results demonstrated that the laser cladding layer obviously enhanced anticorrosion property of Mg alloy for engineering applications. 相似文献