全文获取类型
收费全文 | 24664篇 |
免费 | 2125篇 |
国内免费 | 873篇 |
专业分类
电工技术 | 1006篇 |
技术理论 | 2篇 |
综合类 | 1472篇 |
化学工业 | 4701篇 |
金属工艺 | 984篇 |
机械仪表 | 1112篇 |
建筑科学 | 1534篇 |
矿业工程 | 515篇 |
能源动力 | 587篇 |
轻工业 | 2279篇 |
水利工程 | 382篇 |
石油天然气 | 775篇 |
武器工业 | 131篇 |
无线电 | 2284篇 |
一般工业技术 | 4068篇 |
冶金工业 | 1704篇 |
原子能技术 | 331篇 |
自动化技术 | 3795篇 |
出版年
2024年 | 41篇 |
2023年 | 358篇 |
2022年 | 482篇 |
2021年 | 886篇 |
2020年 | 704篇 |
2019年 | 622篇 |
2018年 | 700篇 |
2017年 | 724篇 |
2016年 | 785篇 |
2015年 | 904篇 |
2014年 | 1286篇 |
2013年 | 1613篇 |
2012年 | 1657篇 |
2011年 | 1876篇 |
2010年 | 1569篇 |
2009年 | 1518篇 |
2008年 | 1566篇 |
2007年 | 1466篇 |
2006年 | 1312篇 |
2005年 | 1080篇 |
2004年 | 866篇 |
2003年 | 750篇 |
2002年 | 767篇 |
2001年 | 593篇 |
2000年 | 477篇 |
1999年 | 420篇 |
1998年 | 366篇 |
1997年 | 304篇 |
1996年 | 250篇 |
1995年 | 210篇 |
1994年 | 182篇 |
1993年 | 157篇 |
1992年 | 124篇 |
1991年 | 98篇 |
1990年 | 85篇 |
1989年 | 65篇 |
1988年 | 69篇 |
1987年 | 54篇 |
1986年 | 47篇 |
1985年 | 58篇 |
1984年 | 47篇 |
1983年 | 37篇 |
1982年 | 32篇 |
1981年 | 33篇 |
1980年 | 28篇 |
1979年 | 26篇 |
1978年 | 31篇 |
1977年 | 28篇 |
1976年 | 67篇 |
1975年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Alexander Tkach Luís Amaral Paula M. Vilarinho Ana M.R. Senos 《Journal of the European Ceramic Society》2018,38(6):2547-2552
Titanium-rich (Sr/Ti?=?0.995) strontium titanate (ST) ceramics, air-sintered in a temperature range of 1400–1625?°C, were reported to possess anomalies in the grain growth and analogous anomalies in the grain boundary (GB) conductivity activation energy. However, these two interface-related phenomena, occurring at GBs, could not be associated with each other using a simple “brick-layer” model. In this work we revise the topic and advocate that the deviation from the model comes from the oxygen vacancies localized at GBs of the rapidly-cooled ST ceramics. To verify this, we annealed the ceramics in oxygen and performed their systematic and comparative analysis using impedance spectroscopy. A levelling-off in the GB conductivity activation energy, which increases for ≤1.24?eV, and a four-fold decrease in the GB permittivity are observed after annealing. Thus, we confirm a key role of oxygen vacancies in relation between the grain growth and GB conductivity anomalies of as-sintered Ti-rich ST ceramics. 相似文献
52.
Matthias Ahlhelm David Werner Johanna Maier Johannes Abel Thomas Behnisch Tassilo Moritz Alexander Michaelis Maik Gude 《Journal of the European Ceramic Society》2018,38(9):3369-3378
The so-called Freeze Foaming method aims at manufacturing ceramic cellular scaffolds for diverse applications. One application is dedicated to potential bone replacement material featuring open, micro and interconnected porosity. However, the main challenges of this foaming method is to achieve a homogeneous pore morphology. In a current project, the authors throw light on the bubble/pore and strut formation of this process by in situ computed tomography. This allows for evaluating varying process parameter’s effects on the growth of the ceramic foam during the foaming process. As first result and basis for CT analysis, a stable and reproducible model suspension was developed which resulted in reproducible foam structures. In dependence of selected process parameters like pressure reduction rate or air content in the ceramic suspension resulting Freeze Foams became adjustable with regard to their pore morphology. Pore size and distribution data as well as the porosity were characterized and evaluated accordingly. 相似文献
53.
Luhong Jin Fengqiang Zhao Wanni Lin Xiaoxu Zhou Cuifang Kuang Alexander Nedzved Sergey Ablameyko Xu Liu Yingke Xu 《Microscopy research and technique》2020,83(9):1056-1065
With the development of super‐resolution fluorescence microscopy, complex dynamic processes in living cells can be observed and recorded with unprecedented temporal and spatial resolution. Single particle tracking (SPT) is the most important step to explore the relationship between the spatio‐temporal dynamics of subcellular molecules and their functions. Although previous studies have developed SPT algorithms to quantitatively analyze particle dynamics in cell, traditional tracking methods have poor performance when dealing with intersecting trajectories. This can be attributed to two main reasons: (a) they do not have point compensation process for overlapping objects; (b) they use inefficient motion prediction models. In this paper, we present a novel fan‐shaped tracker (FsT) algorithm to reconstruct the trajectories of subcellular vesicles in living cells. We proposed a customized point compensation method for overlapping objects based on the fan‐shaped motion trend of the particles. Furthermore, we validated the performance of the FsT in both simulated time‐lapse movies with variable imaging quality and in real vesicle moving images. Meanwhile, we compared the performance of FsT with other five state‐of‐the‐art tracking algorithms by using commonly defined measures. The results showed that our FsT achieves better performance in high signal‐to‐noise ratio conditions and in tracking of overlapping objects. We anticipate that our FsT method will have vast applications in tracking of moving objects in cell. 相似文献
54.
Wenyuan Zhou Chasity P. Hankinson Prof. Dr. Alexander Deiters 《Chembiochem : a European journal of chemical biology》2020,21(13):1832-1836
We have developed a new tool for the optical control of cellular ATP concentrations with a photocaged adenylate kinase (Adk). The photocaged Adk is generated by substituting a catalytically essential lysine with a hydroxycoumarin-protected lysine through site-specific unnatural amino acid mutagenesis in both E. coli and mammalian cells. Caging of the critical lysine residue offers complete suppression of Adk's phosphotransferase activity and rapid restoration of its function both in vitro and in vivo upon optical stimulation. Light-activated Adk renders faster rescue of cell growth than chemically inducible expression of wild-type Adk in E. coli as well as rapid ATP depletion in mammalian cells. Thus, caging Adk provides a new tool for direct conditional perturbation of cellular ATP concentrations thereby enabling the investigation of ATP-coupled physiological events in temporally dynamic contexts. 相似文献
55.
56.
57.
58.
59.
Anna A. Fedosova Yury V. Shubin Anna A. Makarova Artem V. Gusel’nikov Alexander V. Okotrub 《Fullerenes, Nanotubes and Carbon Nanostructures》2020,28(4):335-341
AbstractPhosphorus-doped graphene layers have been formed on the surface of nanodiamond (ND) particles by hot pressing of a mixture of purified detonation ND powder and triphenylphosphine (TPP) at 1000?°C and 100?bar. X-ray photoelectron spectroscopy detected about 1.7 at.% of phosphorus in the product, most of which was in the oxidized form. The same treatment conditions of the ND powder without the addition of TPP resulted in the only partial covering of some ND particles by sp2-hybridized carbon layers. The tests in Na-ion half-cells found that the pure carbon sample can reversibly sustain 42 mAh g?1 at a current density of 0.1?A g?1. For the phosphorus-doped sample, this value increases up to 54 mAh g?1 due to mainly accumulation of sodium at various defects created in the graphitic layers as a result of phosphorus incorporation. Taking into account inertness of inner diamond cores, specific capacity values are 417 mAh g?1 for phosphorus-doped graphene layers and 587 mAh g?1 for non-doped ones. 相似文献
60.