全文获取类型
收费全文 | 135篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学 | 82篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 6篇 |
物理学 | 37篇 |
综合类 | 10篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 17篇 |
2012年 | 13篇 |
2011年 | 6篇 |
2010年 | 4篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1983年 | 1篇 |
1977年 | 2篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1969年 | 2篇 |
1968年 | 1篇 |
排序方式: 共有137条查询结果,搜索用时 46 毫秒
51.
Solvent‐free approach is developed for the rapid synthesis of spiro[azetidine‐indoles] 6a–g on basic alumina supported potassium carbonate (K2CO3–Al2O3) from the cycloaddition reaction of indolylimines 3 and chloroacetyl chloride 4 as synthons using microwaves. The procedure neither required toxic and hazardous base nor volatile solvents. 3 was synthesized in situ by the neat reaction of indole‐2,3‐diones 1 and fluorinated anilines 2 under microwave irradiation. Solvent‐free aminoalkylation of spiro compounds 6a and 6b has been carried out under microwaves. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:468–473, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10180 相似文献
52.
Yasser H. Ochoa-Muoz Ruby Mejía de Gutirrez Jorge E. Rodríguez-Pez Isabel Grcia Stella Vallejos 《Molecules (Basel, Switzerland)》2022,27(9)
In this work, the gas-sensing functionality of porous ceramic bodies formed by the slip casting technique was studied using perovskite nanoparticles of an MSnO3 system (M = Ba, Ca, Zn) synthesized by a chemical route. The performance and reliability of the sensitive materials in the presence of different volatile organic compounds (acetone, ethanol, and toluene), and other gases (CO, H2 and NO2) were analysed. The ZnSnO3, BaSnO3, and CaSnO3 sensors showed sensitivities of 40, 16, and 8% ppm−1 towards acetone, ethanol, and toluene vapours, respectively. Good repeatability and selectivity were also observed for these gaseous analytes, as well as excellent stability for a period of 120 days. The shortest response times were recorded for the ZnSnO3 sensors (e.g., 4 s for 80 ppm acetone) with marked responses to low concentrations of acetone (1000 ppb). These results are attributed to the porosity of the sensitive materials, which favours the diffusion of gases, induces surface defects, and provides greater surface area and good sensitivity to acetone, as is seen in the case of ZnSnO3. 相似文献
53.
54.
Using an hydrodynamical model, analytical investigation of the stimulated Brillouin scattering of an electromagnetic wave
by an acoustic-like mode has been done in a multi-ion species plasma. The acoustic-like mode is a new mode which propagates
in a multi-ion plasma only. The non-linear dispersion relation and the growth rate of the excited modes are derived. The non-linearity
arises through the motion of ions which is introduced through ponderomotive force. It is found that the growth rate can be
controlled by several parameters like charge number, mass, density and temperature of the ions. 相似文献
55.
邓昭镜 《西南师范大学学报(自然科学版)》1988,(4)
一维聚合链可以用一维振子链来模拟.其中联接振子而组装链的键可以分为主键和次键.一维振子链的非线性过程要受主键或次键的非线性过程所控制,本文讨论了在主键或次键的非线性作用下所引起的一维振子链的非线性过程.在一定条件下,我们可以得到解析的孤子解. 相似文献
56.
J.J. Pan FengQing Zhou Haiming Wu Xiangdong Qiu Ruby Chen Yousheng Wu Henry He Eric Zhang Chunmeng Wu 《光学学报》2003,23(Z1)
A compact variable optical attenuator, covering C and L bands with over 50 dB attenuation range, is realized using a single liquid crystal cell with a tilted fused silica coating compensating the cell's small residual birefringence. 相似文献
57.
A rapid one-pot solvent-free procedure has been developed for the synthesis of fluorinated 2,3-disubstituted quinazolin-4(3H)-ones by neat three-component cyclocondensation of anthranilic acid, phenyl acetyl chloride and substituted anilines under microwave irradiation. The experimental methodology and microwave conditions described here are well established, allowing significant rate enhancement and good yields compared to conventional reaction conditions. The reaction is generalized for o-, m- and p-substituted anilines with electron-donating and -withdrawing groups to give quinazolin-4(3H)-ones. Synthesized compounds have been screened for their anti-fungal activity. 相似文献
58.
Howard C. Haas Ruby L. MacDonald 《Journal of polymer science. Part A, Polymer chemistry》1972,10(6):1617-1635
Substitution of several mole per cent of the hydroxyl groups of poly(vinyl alcohol) by fluorine results in marked changes in polymer properties. These fluoro poly(vinyl alcohols) (PVAF) form thermally reversible gels in water at low polymer concentrations. In solution, a helical conformation or a random coil containing helical sequences is more in accord with the experimental observations than the random coil structure of poly(vinyl alcohol). This helical hypothesis is supported by high heats of crosslinking of the aqueous thermally reversible gels, the difficult solubility of PVAF in H2O, the insolubility of the PVAF–iodine complex under conditions where the PVA–iodine complex remains soluble, the temperature-independent high value for the Huggins k ′ slope constant, the greater stability of the PVAF–iodine complex, the shear dependence of the solution viscosity and our inability to form thermally reversible gels by the introduction of fluorine into other water-soluble polymers which are capable of hydrogen bond formation. Infrared dichroism and deuteration measurements do not differentiate between PVA and PVAF. If this conclusion is correct, PVAF is the first vinyl polymer of which we are aware that maintains a helical conformation in solution. 相似文献
59.
60.
Several examples of Mössbauer spectra taken from amorphous materials are presented. The purpose is to help assess whether this technique is likely to be useful in the determination of structure for non-crystalline solids. One conclusion is that, except for iron, the resolution is poor and unique interpretations are unlikely. A second conclusion is that in a glass formed from FeCl2·9H2O the microenvironment is very uniform, as might be expected from a continuous-random-network model. 相似文献