全文获取类型
收费全文 | 203篇 |
免费 | 19篇 |
国内免费 | 5篇 |
专业分类
化学 | 153篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 42篇 |
物理学 | 25篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 32篇 |
2015年 | 15篇 |
2014年 | 18篇 |
2013年 | 34篇 |
2012年 | 18篇 |
2011年 | 5篇 |
2010年 | 12篇 |
2009年 | 9篇 |
2008年 | 4篇 |
2007年 | 6篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2003年 | 2篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1998年 | 1篇 |
1990年 | 1篇 |
1988年 | 1篇 |
排序方式: 共有227条查询结果,搜索用时 15 毫秒
61.
62.
This paper is devoted to study certain quasi-Gorenstein counterparts to some known properties of Gorenstein rings. 相似文献
63.
64.
65.
The main objective of the present work is the development of a simplified, efficient and easy-to-implement single-phase material model, which is able to describe the essential effects characterising the behaviour of multi-phase saturated materials, such as of intervertebral discs (IVDs). The presented new model mainly focuses on extending a viscoelastic material model in order to not only take the mechanical behaviour of the solid part into account, but also the fluid-flow-dependent behaviour of the material. By applying this model, the complexity and constitutive parameters are reduced, the implementation is more convenient and the experimental investigations can be better supported in comparison to multi-phase material models of IVDs. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
66.
We present a novel source for continuous terahertz (THz) wave generation using an organic ionic salt, 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST). THz waves are generated based on difference frequency generation (DFG) in the device. Phase matching condition and THz generation between 1.3 THz and 2.7 THz, for optical pump around 1.6 μm, are investigated. Our calculations predict that the device produces a relatively high THz output power of 11.07 μW from a 4 cm long waveguide at 2 THz. 相似文献
67.
An bis(2-aminoethyl)-2-(9-fluorenyl)malonamide as fluorophore ligand was immobilized onto mesoporous silica type SBA-15 via post synthesis grafting. The obtained material was characterized by small and wide angle X-ray diffraction, N2 adsorption–desorption, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analysis that indicate the successful immobilization of the ligand on the surface of mesoporous silica. The sensing ability of the obtained material was studied by addition of the cations Fe3+, Mg2+, Cr3+, Co2+, Ni2+, Cu2+, Hg2+ and Zn2+ to water suspensions of the assayed solid. Of all the cations tested addition of Fe3+ ion to a suspension of this material resulted in the largest decrease in the fluorescence intensity. Turn-off photoluminescence of this material was remarkably observed for iron ions in comparing of the other cations. A good linearity between the fluorescence intensity of this material and the concentration of Fe3+ ion is constructed, which enables it as a fluorescence chemosensor for detecting the Fe3+ ion with a suitable detection limit of 1.35?×?10?5. It can be introduced as a novel fluorescent sensor in aqueous solution for a lot of practical applications in chemical, environmental and biological systems. 相似文献
68.
Headspace solid phase microextraction using anodized aluminum fiber in combination with capillary GC–MS was utilized as monitoring technique for the collection and detection of the volatile compounds of Echinophora platyloba DC. Experimental parameters, including the sample weight, extraction temperature, extraction time and humidity effect, desorption time and desorption temperature were examined and optimized. Using HS-SPME followed by GC–MS, 53 compounds were separated and identified in E. platyloba DC, which mainly included E-β ocimene (47.63%), R-D-decalactone (13.28%), α-pinene (7.43%) and nonane (6.71%). Compared with hydrodistillation (HD), HS-SPME, provides the advantages of a small amount of sample, timesaving, simplicity and cheapness. To the best of our knowledge, this is the first report on using anodized aluminum fiber in solid-phase microextraction coupled to headspace for the investigation of volatile fraction of medicinal plant. 相似文献
69.
An efficient synthesis of 2,2-dimethyl-2H-chromenes was accomplished by Pd(II)-catalyzed coupling and SiO2-promoted condensation of o-halophenols with 2-methyl-3-buten-2-ol (1,1-dimethylallyl alcohol) in one pot. The method is very general and can be useful for the synthesis of some natural 2,2-dimethyl-2H-chromenes. 相似文献
70.
Rahman Hosseinzadeh Mahmood Tajbakhsh Farhad Ramzanian-Lehmali Marzieh Sadatshahabi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2279-2283
Deprotection of trimethylsilyl ethers to their parent aldehydes and ketones in high yields has been carried out using 2,6-dicarboxypyridinium fluorochromate under mild conditions. 相似文献