全文获取类型
收费全文 | 224篇 |
免费 | 18篇 |
国内免费 | 1篇 |
专业分类
化学 | 130篇 |
力学 | 12篇 |
数学 | 45篇 |
物理学 | 56篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 21篇 |
2015年 | 14篇 |
2014年 | 21篇 |
2013年 | 27篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 19篇 |
2009年 | 11篇 |
2008年 | 9篇 |
2007年 | 11篇 |
2006年 | 5篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1991年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有243条查询结果,搜索用时 15 毫秒
51.
An organic‐inorganic heterogeneous catalyst based on Keplerate polyoxometalates for oxidation of dibenzothiophene derivatives with Hydrogen peroxide 下载免费PDF全文
Reza Fareghi‐Alamdari Negar Zekri Ahmad Jamali Moghadam Khadijeh Tavakoli Hafshajani Mostafa Riahi Farsani 《应用有机金属化学》2018,32(4)
An organic‐inorganic material (NH4)2(MimAM)40[Mo132O372(CH3COO)30(H2O)72] have been synthesized by reacting [(NH4)42[MoVI72 MoV60O372(CH3COO)30(H2O)72] with the ionic liquid 3‐Aminoethyl‐1‐methylimidazolium bromide. The catalyst showed remarkably a high catalytic performance in the oxidation of dibenzothiophene (DBT) derivatives with H2O2 35% as a safe and green oxidant. The main parameters affecting the process including catalyst, acid additive, hydrogen peroxide amounts and temperature have been investigated in detail. Sulfur removal of DBT in n‐heptane reached to 98.3% yield at 40 °C using 2.5 mmol H2O2 and 100 mg of (NH4)2(MimAM)40[Mo132O372(CH3COO)30(H2O)72] after 90 min. Under the optimal conditions, BT (benzothiophene), DBT (dibenzothiophene) and 4,6‐DMDBT (4,6‐dimethyl‐dibenzothiophene) achieved high desulfurization efficiency. Our results showed that the reactivity order of different model sulfur compounds are thiophene <4,6‐dimethyl dibenzothiophene< dibenzothiophene. The catalysts could be easily separated from the reaction solution by simple filtration and recycled for several times without loss of activity. 相似文献
52.
XY5Z2 molecules or ions of D5h symmetry are very rare. For this reason, up to now, little work was done on the interpretation of their vibrational spectra. 相似文献
53.
54.
55.
56.
Seyed Reza Mahmoudi Kazimierz Adamiak Peter Castle Mehdi Ashjaee 《Experimental Thermal and Fluid Science》2010,34(5):528-537
Free convection heat transfer from an isothermal horizontal cylinder in the presence of DC positive corona discharge with a blade edge emitter electrode has been studied experimentally and numerically. A Mach–Zehnder interferometer was used to determine the local Nusselt numbers. The effect of corona discharge on heat transfer from the cylinder was investigated at Rayleigh numbers in the range between 1500 and 5000. To find the details of the flow patterns and to further verify the experimental results, numerical simulations were also performed. It was found that the numerical results are in good agreement with experimental data. By increasing the applied voltage up to 15.5 kV, the corona discharge generates a recirculation zone around the blade and below the lower stagnation point of the cylinder. The effect of the recirculation zone becomes stronger near the breakdown voltage (17 kV) and it is responsible for a local decrease in the cooling of the cylinder around the lower stagnation point. The results indicate that corona discharge has a significant effect on the average Nusselt number at lower Rayleigh numbers whereas it has smaller effect at higher Rayleigh numbers. 相似文献
57.
Fethi Mahmoudi 《Advances in Mathematics》2007,209(2):460-525
We consider the equation −ε2Δu+u=up in Ω⊆RN, where Ω is open, smooth and bounded, and we prove concentration of solutions along k-dimensional minimal submanifolds of ∂Ω, for N?3 and for k∈{1,…,N−2}. We impose Neumann boundary conditions, assuming 1<p<(N−k+2)/(N−k−2) and ε→0+. This result settles in full generality a phenomenon previously considered only in the particular case N=3 and k=1. 相似文献
58.
Majid Montazer Mahbubeh Dastjerdi Maryam Azdaloo Mahnaz Mahmoudi Rad 《Cellulose (London, England)》2015,22(6):4049-4064
59.
60.