全文获取类型
收费全文 | 205篇 |
免费 | 2篇 |
国内免费 | 13篇 |
专业分类
化学 | 208篇 |
物理学 | 12篇 |
出版年
2023年 | 19篇 |
2021年 | 5篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2014年 | 11篇 |
2013年 | 6篇 |
2012年 | 2篇 |
2011年 | 17篇 |
2010年 | 12篇 |
2009年 | 13篇 |
2008年 | 7篇 |
2007年 | 16篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 19篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1988年 | 1篇 |
1981年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有220条查询结果,搜索用时 15 毫秒
31.
新型氟代三苯胺衍生物的合成和光谱特性研究 总被引:1,自引:0,他引:1
设计和合成了一种新型氟代三苯胺衍生物——N,N,N′,N′-四苯基-[2′,2″,3′,3″,5′,5″,6′,6″-八氟对四联苯]-4,4″′-二胺(OFTPA)。通过元素分析、熔点测定、红外光谱和1 H NMR谱等手段对OFTPA的分子结构进行了表征,并对其主要的红外光谱吸收峰和1 H NMR谱带进行了归属分析。利用紫外-可见吸收光谱、荧光光谱和循环伏安法(CV)对OFTPA的电子能级结构和发光性能进行了研究。紫外-可见吸收光谱测定结果表明,OFTPA薄膜的最大吸收峰波长为355nm,光学带隙(Eg)为3.09eV。荧光光谱测定结果表明,OFTPA薄膜在365nm紫外光的激发下,产生发光峰波长在448nm附近、半峰宽(FWHM)为68nm的蓝光发射,色纯度高,有望成为优良的蓝光发射材料。循环伏安法测定结果表明,OFTPA的最高占有轨道(HOMO)能级为-5.41eV,最低空轨道(LUMO)能级为-2.32eV,具有良好的空穴传输性能。研究结果为进一步研究其在有机光电器件中的应用提供了参考。 相似文献
32.
Takayoshi Fujii Tomoyoshi Takano Hiroyuki Morita Toshiaki Yoshimura 《Tetrahedron》2006,62(41):9622-9627
The fluorination of 10-oxo-10H-5λ4,10λ4-thianthren-5-ylideneamine (2) with Selectfluor™ affords 5-fluoro-10-oxo-5,10-dihydro-5λ6,10λ4-thianthren-5-nitrile (4). The amination of 4 with morpholine gives 5-morpholino-10-oxo-5,10-dihydro-5λ6,10λ4-thianthren-5-nitrile (5). The stereochemical course of both reactions has been studied, while the configurations of their products, cis-isomer 4 and trans-5-morpholino-10-oxo-5,10-dihydro-5λ6,10λ4-thianthren-5-nitrile (trans-5) are elucidated by the use of X-ray crystallographic analyses. 相似文献
33.
Jean-Claude Jacquesy 《Journal of fluorine chemistry》2006,127(11):1484-1487
This is a summary of a lecture presented at the 100th Anniversary, Moissan Symposium in Paris on Friday 10th November 2006.In HF/SbF5, Vinca alkaloids react selectively at the D’ring of the molecule. In the presence of CHCl3 (or CCl4), vinorelbine yields 20′,20′-difluoro-3′,4′-dihydrovinorelbine (vinflunine), presently in phase III experimentation for treatment of bladder cancer and non small cell lung cancer. 相似文献
34.
35.
Formation of ketone acylals bearing trihaloacetoxy groups and their nucleophilic geminal disubstitution by fluoride ions were investigated. Cyclohexanone reacted with trifluoroacetic anhydride without catalyst to give gem-bistrifluoroacetates via a concerted bimolecular reaction. Treatment with hydrogen fluoride under mild conditions efficiently yielded the corresponding gem-difluorides. In this reaction process, trifluoroacetic acid was recovered and converted to trifluoroacetic anhydride using P2O5. Since gem-difluorides were derived from ketones, HF and P2O5, this constitutes a practical synthesis of gem-difluorides. 相似文献
36.
W. Zhang M. Dubois K. Guérin F. Masin A. Hamwi C. Varenne P. Thomas J.L. Mansot 《Journal of fluorine chemistry》2010,131(6):676-3573
Several new synthesis methods of fluorinated carbon nanofibres, such as controlled fluorination using fluorinating agent (TbF4 or XeF2), or assisted fluorination under UV and gamma irradiation, are reviewed and compared with the direct fluorination using undiluted fluorine gas. The results highlight the different fluorination mechanisms for the direct fluorination and the new methods. The other advantage of those alternative fluorination routes is the possibility to provide fine tuning of the fluorination level, i.e. from F/C atomic ratio close to zero, as a functionalization, to the unity (CF1) according to the required application, electrochemical or tribological. Two applications are described in this paper as a function of the fluorine content: protection against ozonation and use as solid lubricants. 相似文献
37.
Gem-difluoroalkenes are an easily accessed fluorinated functional group, and a useful intermediate for elaborating into more complex fluorinated compounds. Currently, most functionalization reactions of gem-difluoroalkenes, with or without a transition metal-based catalyst system, involve the addition or removal of a fluorine atom to generate trifluorinated or monofluorinated products, respectively. In contrast, we present a complementary “fluorine-retentive” reaction that exploits an organocatalytic strategy to add phenols across gem-difluoroalkenes to deliver β,β-difluorophenethyl arylethers. The products are produced in good to moderate yields and selectivities, thus providing a range of compounds that are underrepresented in the synthetic and medicinal chemistry literature. 相似文献
38.
The application of cyclopropenium ion as a phase transfer catalyst for benzylic fluorination in high yields is reported. Integral to the mechanisms of these fluorination reactions was the role of in situ derived cyclopropenium fluoride complexes, the existence of which was supported by 1H, 19F NMR and UV–Vis spectroscopy. Density functional theory calculations were applied to gain insight into the mechanism of these reactions. 相似文献
39.
Ab initio quantum chemical calculation were performed on R2N–O–NR2 type (R=H, F, CH3 and CF3) molecules, using the HF, B3LYP and MP2/6-31G* levels of theory. The equilibrium structures and the internal rotation potentials have been determined. Three stable conformers were found for R=H, F and CH3 while only two in case of R=CF3. The rotation potential energy curves do not change significantly upon fluorination. The calculations suggests that in the ED measurement of the title compound the NC and NO bond length might have been interchanged. 相似文献
40.
Fujio Okino Yukio Kawaguchi Kunitake Momota Toshihiro Ando Mamoru Yoshimoto 《Journal of fluorine chemistry》2004,125(11):1715-1722
Boron-doped semiconducting diamond films were prepared using BF3 by microwave plasma assisted chemical vapor deposition. B-doping was confirmed by SIMS and Raman spectroscopic measurements and the B-doping levels were estimated. Electrochemical behaviors of boron-doped diamond thin-film electrodes prepared using B2H6 and BF3 were studied by measuring cyclic voltammograms for anodic oxidation of 1,4-difluorobenzene in the liquid electrolyte, neat Et4NF·4HF. The results of the direct thermal interaction of elemental fluorine with hydrogenated and oxidized diamond surfaces are also presented. 相似文献