全文获取类型
收费全文 | 558657篇 |
免费 | 7955篇 |
国内免费 | 1732篇 |
专业分类
电工技术 | 10565篇 |
综合类 | 1528篇 |
化学工业 | 84279篇 |
金属工艺 | 21650篇 |
机械仪表 | 16870篇 |
建筑科学 | 13919篇 |
矿业工程 | 2821篇 |
能源动力 | 14816篇 |
轻工业 | 48607篇 |
水利工程 | 5704篇 |
石油天然气 | 10432篇 |
武器工业 | 49篇 |
无线电 | 64706篇 |
一般工业技术 | 107257篇 |
冶金工业 | 106650篇 |
原子能技术 | 10868篇 |
自动化技术 | 47623篇 |
出版年
2022年 | 5427篇 |
2021年 | 7566篇 |
2020年 | 5512篇 |
2019年 | 7060篇 |
2018年 | 8593篇 |
2017年 | 8124篇 |
2016年 | 8202篇 |
2015年 | 5802篇 |
2014年 | 9509篇 |
2013年 | 24606篇 |
2012年 | 15037篇 |
2011年 | 21512篇 |
2010年 | 16859篇 |
2009年 | 18802篇 |
2008年 | 18623篇 |
2007年 | 18306篇 |
2006年 | 16140篇 |
2005年 | 14916篇 |
2004年 | 15280篇 |
2003年 | 14916篇 |
2002年 | 14215篇 |
2001年 | 14073篇 |
2000年 | 12675篇 |
1999年 | 13243篇 |
1998年 | 33418篇 |
1997年 | 23435篇 |
1996年 | 17826篇 |
1995年 | 13344篇 |
1994年 | 11718篇 |
1993年 | 11312篇 |
1992年 | 8213篇 |
1991年 | 7648篇 |
1990年 | 7481篇 |
1989年 | 7333篇 |
1988年 | 6756篇 |
1987年 | 5978篇 |
1986年 | 5947篇 |
1985年 | 6502篇 |
1984年 | 6067篇 |
1983年 | 5402篇 |
1982年 | 5109篇 |
1981年 | 5114篇 |
1980年 | 4813篇 |
1979年 | 4702篇 |
1978年 | 4580篇 |
1977年 | 5542篇 |
1976年 | 7115篇 |
1975年 | 3957篇 |
1974年 | 3676篇 |
1973年 | 3742篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Kuznetsov Yu. A. Markov M. A. Kravchenko I. N. Krasikov A. V. Bykova A. D. 《Refractories and Industrial Ceramics》2021,62(4):421-425
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized... 相似文献
3.
Chumakov Yu. A. Knyazeva A. G. Pribytkov G. A. 《Theoretical Foundations of Chemical Engineering》2021,55(3):490-503
Theoretical Foundations of Chemical Engineering - On the basis of the classic concepts of the theory of solid-phase combustion, for the first time, a model with a detailed scheme of chemical... 相似文献
4.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a... 相似文献
5.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
6.
To investigate the evolution of the structural and enhanced magnetic properties of GdMnO3 systems induced by the substitution of Mn with Cr, polycrystalline GdMn1-xCrxO3 samples were synthesized via solid-state reactions. XRD characterization shows that all GdMn1-xCrxO3 compounds with single-phase structures crystallize well and that Cr3+ ions entering the lattice sites of GdMnO3 induce structural distortion. SEM results indicate that the grain size of the synthesized samples (a few microns) decreases as the Cr substitution concentration increases. Positron annihilation lifetime spectroscopy reveals that vacancy-type defects occur in GdMn1-xCrxO3 ceramics and that the vacancy size and concentration clearly change with the Cr content. The temperature and field dependence of the magnetization curves show that Cr substitution significantly influences the magnetic ordering of the gadolinium sublattice, improving the weak ferromagnetic transition temperature and magnetization of GdMn1-xCrxO3. The enhanced magnetization of GdMn1-xCrxO3 is closely related to the vacancy defect concentration. 相似文献
7.
In this investigation, low-cement castables were prepared using 70% alumina grog aggregates obtained from crushed alumina brick waste. The aggregates were thermally treated at 1550 °C for 3 h. Four types of low-cement castables were prepared with various types of aggregates (alumina grog with or without thermal treatment) and fillers (with or without zircon addition), and they were evaluated in terms of their physical, thermal, and chemical properties. Microstructural analysis via scanning electron microscopy (SEM) was performed on the castables before and after slag attack. Compared to the other fabricated castables, the thermally treated alumina grog castables with zircon showed better physical properties, such as a higher bulk density, cold crushing strength, and modulus of rupture and a lower apparent porosity and water absorption. In addition, they had a higher positive linear thermal expansion, refractoriness under load, permanent linear change, and hot modulus of rupture. The results of the SEM with energy dispersive X-ray analysis of the prepared castables confirmed that the mullite and anorthite phases were predominant when zircon was not added and the zircon–mullite phase additionally appeared upon the incorporation of zircon. A quantitative elemental analysis via X-ray fluorescence spectroscopy was employed to determine the composition of the castables. X-ray diffraction analysis showed that the alumina grog castables had a high mullite and low anorthite content, and the thermally treated alumina grog had a high anorthite, low mullite, and high zircon content. The improvement in the mechanical and thermo-mechanical properties of the castables with thermally treated alumina grog and added zircon can be attributed to the formation of the zircon–mullite phase with a low mullite phase content. 相似文献
8.
Jiajia Suo Bowen Yang Edoardo Mosconi Hyeon-Seo Choi YeonJu Kim Shaik M. Zakeeruddin Filippo De Angelis Michael Grätzel Hui-Seon Kim Anders Hagfeldt 《Advanced functional materials》2021,31(34):2102902
Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions. 相似文献
9.
Glass and Ceramics - Ceramic bricks based on low-melting clay and ferro-dust from self-disintegrating, low-carbon, ferrochrome slags, graded from M100 to M175, respectively, were obtained in the... 相似文献
10.
Automation and Remote Control - A linear-quadratic positional differential game of three persons is considered. Coefficient criteria are established under which there is no Nash equilibrium... 相似文献