全文获取类型
收费全文 | 769篇 |
免费 | 123篇 |
国内免费 | 129篇 |
专业分类
化学 | 707篇 |
晶体学 | 19篇 |
力学 | 9篇 |
综合类 | 16篇 |
数学 | 79篇 |
物理学 | 191篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 47篇 |
2021年 | 49篇 |
2020年 | 80篇 |
2019年 | 69篇 |
2018年 | 27篇 |
2017年 | 27篇 |
2016年 | 25篇 |
2015年 | 26篇 |
2014年 | 51篇 |
2013年 | 121篇 |
2012年 | 50篇 |
2011年 | 60篇 |
2010年 | 29篇 |
2009年 | 29篇 |
2008年 | 34篇 |
2007年 | 26篇 |
2006年 | 27篇 |
2005年 | 28篇 |
2004年 | 30篇 |
2003年 | 25篇 |
2002年 | 23篇 |
2001年 | 16篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1976年 | 1篇 |
1973年 | 3篇 |
排序方式: 共有1021条查询结果,搜索用时 15 毫秒
51.
Linjing Yang Xizeng Feng Imshik Lee Chunli Bai 《Journal of inclusion phenomena and macrocyclic chemistry》1998,31(3):197-204
Rhodamine B-ethylenediamine--cyclodextrins (RhB--CDen) and rhodamine B--cyclodextrins (RhB--CD) can form inclusive complexes with many guest molecules, a reaction which can be used as a nucleic acid probe. In this paper, the most stable conformations of RhB--CDen and RhB--CD have been determined by fluorescence experiments and analyzed by molecular modeling simulation. The interaction between RhB--CDen and two guest molecules, 1-borneol and cyclohexanol, has also been investigated. The results showed that RhB--CDen has a stronger interaction with 1-borneol than with cyclohexanol. Borneol could push the three aromatic-rings of rhodamine B out of the CD cavity, while the cyclohexanol could not. The interactive sites of host and guest are also presented. 相似文献
52.
Yu S Zhang W Zhu J Yin Y Jin H Zhou L Luo Q Xu J Liu J 《Macromolecular bioscience》2011,11(6):821-827
A HBSP has been designed as a novel bifunctional enzyme model with SOD and GPx activity by host/guest‐directed self‐assembly of MnTPyP‐M‐Ad and 6‐Te‐diCD. The structure of the host/guest complex was elucidated by 1H NMR spectra, and the HBSP was characterized by SEM, DLS and measurement of catalytic properties. In the bifunctional enzyme model, the Mn(III) porphyrins act as efficient SOD active sites and the tellurol moieties endow GPx activity. The SOD‐like activity (IC50) of this new supramolecular catalyst was found to be 1.05 × 10?7 M, which corresponds to 2.82% of the activity of the native SOD enzyme. Besides this, the hyperbranched supramolecular polymer also shows a higher GPx activity (ν0 = 21.7 × 10?6 M · min?1) than other supramolecular enzyme models.
53.
采用四种杯芳烃超分子化合物为吸附涂层物质, 探讨了涂膜石英晶体微天平(QCM)传感方法对环境大气中微量甲醇气体的识别研究, 发现RCT(Resorcinol cyclic tetramer)是对甲醇气体识别最有效的活性涂层材料. 通过RCT-MeOH单晶体的制备并对其进行X-ray衍射结构解析, 发现其识别机制是基于甲醇分子中的甲基与杯芳烃化合物的苯环之间形成了C-H…π键作用. 当RCT涂层质量为28.16 μg时, 涂膜QCM传感器对甲醇的响应最灵敏, 达到0.01245 Hz/ppm. 该传感器对甲醇气体吸附和解吸附的初速度分别为-0.2110 Hz/s和0.09497 Hz/s. 该方法具有响应快、重现性和稳定性好的优点, 对甲醇测定的回收率在97.83%~103.66%之间, 与气相色谱法测定结果一致, 表明该方法可应用于环境大气中甲醇气体含量的检测. 相似文献
54.
Yi‐Hong Chiu Jui‐Hsiang Liu 《Journal of polymer science. Part A, Polymer chemistry》2010,48(15):3368-3374
A novel achiral monomer end‐capped with a phenyl‐[1,3,4]oxadiazolyl group and threaded through β‐cyclodextrin was synthesized to investigate the host‐guest interactions in the inclusion complex. 1H NMR studies revealed that one or two cyclodextrin molecules were threaded onto the synthesized achiral monomer, leading to the formation of a fibrous construction of self‐assembled inclusion complexes. The formation of a self‐assembled inclusion complex was identified using SEM and TEM. The highly ordered alignment of self‐assembled supramolecules was confirmed using polarized optical microscopy. We demonstrate an easy process for the fabrication of nano‐structured self‐assembled inclusion complexes in pyridine/ethanol (1 mL/10 mL) as well as the enhancement of photo‐induced fluorescence via monomers end‐capped with a phenyl‐[1,3,4]oxadiazolyl moiety threaded with β‐cyclodextrins. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3368–3374, 2010 相似文献
55.
Shijun Li Bo Zheng Jianzhuang Chen Shengyi Dong Zhi Ma Feihe Huang Harry W. Gibson 《Journal of polymer science. Part A, Polymer chemistry》2010,48(18):4067-4073
Based on the dibenzo‐24‐crown‐8/1,2‐bis(pyridinium)ethane recognition motif, a hyperbranched mechanically interlocked polymer was prepared by polyesterification of an easily available dynamic trifunctional AB2 pseudorotaxane monomer. It was characterized by various techniques including 1H NMR, COSY, NOESY, GPC, viscosity, TGA, dynamic laser light scattering, AFM, and SEM. Its GPC Mn was determined to be 191 kDa with polydispersity 1.7 and its hydrodynamic diameter in a dilute solution in acetone was about 70 nm. This measured Mn value corresponds to about 93 repeating units. The study reported here presents not only a new polymer topology but also a novel and convenient way to prepare mechanically interlocked polymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4067–4073, 2010 相似文献
56.
In this communication, β‐cyclodextrin modified quantum dots were used as a water‐soluble “supramolecular” cross‐linker (SCL) because of its surface's supramolecular activity. The guest monomer‐loaded SCL (mSCL) can be used to copolymerize with water‐soluble monomers leading to transparent hybrid supramolecular hydrogels. This simple and versatile method opens new venues for the preparation of hybrid supramolecular hydrogels and the host–guest chemistry of cyclodextrins.
57.
58.
Ju Wang Zuo Yin Yang Xiu Li Wang Jing Chang Zhang Wei Liang Cao State Key Laboratory of Chemical Resource Engineering Faculty of Science Beijing University of Chemical Technology Beijing China 《中国化学快报》2007,18(2):244-246
The conformational conversion of 1,3-dioxane guest encapsulated inside a cylindrical capsular host was investigated with PM3 method and single point energies were evaluated by B3LYP method. When entrapped in the capsule, the guest tumbles were slower than that in the free condition. The influences of the inner phase of the capsule on the guest conformational conversion were discussed in detail. 相似文献
59.
Yoshitane Imai Kensaku Kamon Nobuo Tajima Reiko Kuroda Yoshio Matsubara 《Tetrahedron》2007,63(48):11928-11932
Chiral charge-transfer (CT) complexes composed of a chiral 1,1′-bi-2-naphthol cluster as the electron donor and 1,1′-dibenzyl-4,4′-bipyridinium dichloride as the electron acceptor serve as a host system for molecular recognition. CT complexes that include guest alcohols show different diffuse reflectance spectra (DRS) depending on the included guest. 相似文献
60.
The synthesis and anion recognition properties of four novel [2]rotaxane host architectures containing additional alkyl functionality integrated within macrocyclic and axle components to shield the binding cavity from the solvent are described. The rotaxane species containing a tetra(methyl)-functionalised macrocycle component is found to be a weaker anion complexant than the equivalent unfunctionalised receptor, which is likely due to steric hindrance restricting the anion's access to the interlocked cavity. Rotaxane molecules containing tetra(methyl)-functionalised axle components are also investigated, and the additional alkyl functionality serves to enhance anion binding affinity and selectivity when incorporated within the axle's flexible ethylene linkages. Moreover, the equivalent unfunctionalised rotaxane displays a rare preference for oxoanions over chloride guest species. 相似文献