全文获取类型
收费全文 | 425篇 |
免费 | 5篇 |
国内免费 | 19篇 |
专业分类
化学 | 413篇 |
晶体学 | 1篇 |
力学 | 1篇 |
物理学 | 34篇 |
出版年
2023年 | 64篇 |
2022年 | 6篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 10篇 |
2016年 | 5篇 |
2015年 | 2篇 |
2014年 | 16篇 |
2013年 | 13篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 18篇 |
2009年 | 16篇 |
2008年 | 29篇 |
2007年 | 24篇 |
2006年 | 27篇 |
2005年 | 18篇 |
2004年 | 23篇 |
2003年 | 5篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 5篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1976年 | 1篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 3篇 |
排序方式: 共有449条查询结果,搜索用时 15 毫秒
1.
Chemiluminescence (CL) is a luminescence phenomenon originated by a “chemical reaction.” CL provides a basis for real-time imaging technology in materials science. In fact, a CL reaction is easily triggered in general and makes it possible to track its progress in a target material by highly sensitive photon detection. Recently, real-time CL imagings became breakthrough techniques for analyzing the molecular mechanisms of failures of polymeric materials and of reactions and phase transitions in soft crystals. In the CL imaging techniques, adamantylideneadamantane 1,2-dioxetane (Adox) has been adopted as a stable core structure of chemiluminophores. That is, Adox is an essential seed compound to design a chemiluminophore with a desired molecular function. To support developments of real-time CL imaging techniques, we review the chemistry of Adox as a representative stable chemiluminophore including scientific history and utilities of Adox and its derivatives. 相似文献
2.
Sulfonylation of alkenes through photoredox‐catalyzed functionalization of alkenes with thiourea dioxide under visible‐light irradiation is achieved. The reaction of alkenes, thiourea dioxide and electrophiles provides a green and efficient access to alkyl sulfones and sulfonamides. A broad reaction scope is presented with good functional group compatibility and excellent regioselectivity. A plausible mechanism involving a radical addition process with sulfur dioxide radical anion (SO2‐) derived from the oxidation of sulfur dioxide anion (SO22–) is proposed, which is supported by fluorescence quenching experiments. 相似文献
3.
Stacey N. Anderson Mark Noble Katarzyna Grubel Brooks Marshall Atta M. Arif 《Journal of Coordination Chemistry》2014,67(23-24):4061-4075
The visible light-induced CO-release reactivity of the zinc flavonolato complex [(6-Ph2TPA)Zn(3-Hfl)]ClO4 (1) has been investigated in 1?:?1 H2O?:?DMSO. Additionally, the effect of ligand secondary microenvironment on the aqueous stability and visible light-induced CO-release reactivity of zinc flavonolato species has been evaluated through the preparation, characterization, and examination of the photochemistry of compounds supported by chelate ligands with differing secondary appendages, [(TPA)Zn(3-Hfl)]ClO4 (3; TPA = tris-2-(pyridylmethyl)amine) and [(bnpapa)Zn(3-Hfl)]ClO4 (4; bnpapa = N,N-bis((6-neopentylamino-2-pyridyl)methyl)-N-((2-pyridyl)methyl)amine)). Compound 3 undergoes reaction in 1?:?1 H2O?:?DMSO resulting in the release of the free neutral flavonol. Irradiation of acetonitrile solutions of 3 and 4 at 419 nm under aerobic conditions results in quantitative, photoinduced CO-release. However, the reaction quantum yields under these conditions are lower than that exhibited by 1, with 4 exhibiting an especially low quantum yield. Overall, the results of this study indicate that positioning a zinc flavonolato moiety within a hydrophobic microenvironment is an important design strategy toward further developing such compounds as CO-release agents for use in biological systems. 相似文献
4.
《Tetrahedron》2019,75(47):130679
An operationally simple method enabling hydrochlorofluoromethylation of unactivated alkenes under visible light activation is reported. The procedure has various benefits. It uses commercially available and inexpensive chlorofluoroacetic acid and phenyliodine(III) diacetate for the generation of the required chlorofluoromethyl radical, it converts feedstock olefins into attractive 1-chloro-1-fluoroalkanes, and it tolerates a broad variety of functional groups. The chlorofluoromethyl radical has a reactivity profile towards alkenes similar to the nucleophilic difluoromethyl radical. 相似文献
5.
Jasraj S. Babra Andrew T. Russell Christopher D. Smith Yuxiong Zhang 《Tetrahedron》2018,74(38):5351-5357
C-H Activation/functionalisation and Flow Photochemical Heterocyclic Metamorphosis (FP-HM) have been combined to synthesize a library of benzo [1,3]oxazepines, a rarely described heterocyclic family. This combined protocol allows a range of arylated products to be made from simple starting materials, and the cheap flow photochemical system has proven effective for rapid synthesis of gram-quantities of benzo [1,3]oxazepines. 相似文献
6.
Conventional photocycloaddition of 1,4-dihydropyridines does not afford novel head-to-head 3,6-diazatetraasteranes. Herein, we describe a highly regioselective method to synthesize 3,6-diazatetraasteranes via an intramolecular photodimerization of 1,4-dihydropyridines. First, the 1,4-dihydropyridines were tethered by phthaloyl to direct a proximate parallel arrangement in head-to-head orientation by the rotation of CC single bonds in solution. An intramolecular [2 + 2] photocycloaddition proceeded subsequently to give desired 3,6-diazatetraasteranes in high yield (92–97%) and excellent regioselectivity. Furthermore, two different 1,4-dihydropyridines can also be regiocontrolled by this strategy and produce polysubstituted 3,6-diazatetraasteranes via a cross-photodimerization in a concise and efficient way. In addition, this approach can provide direct access to other polysubstituted polyhedron scaffolds from 1,4-dihydropyridine analogues. 相似文献
7.
Carolina G. Dos Santos Daniela T. Marquez Charles-Oneil L. Crites Jose Carlos Netto-Ferreira Juan C. Scaiano 《Tetrahedron letters》2017,58(5):427-431
Two different hybrid materials composed of gold nanoparticles (AuNPs) supported on either commercial niobium oxide HY 340 or mesoporous niobium oxide catalyzed the Friedel-Crafts alkylation of anisole by benzyl chloride. Excitation of the surface plasmon of the supported AuNPs allowed the reaction to occur at lower temperatures by acting as an alternative heat source. The localized heating produced via plasmon excitation permitted the acid catalyzed reaction to occur - at the Lewis acid sites on the Nb2O5 support - at 80 °C while thermal-dark reactions using a conventional heat source, required temperatures of 120 °C or higher. The catalytic activity of the tested hybrid materials decreased with storage time. However, the deactivation showed to be reversible upon lyophilisation indicating that the nature of the deactivation could be due to water adsorption. 相似文献
8.
Dr. Raphaël Lamare Dr. Romain Ruppert Prof. Corinne Boudon Prof. Laurent Ruhlmann Dr. Jean Weiss 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(65):16071-16081
Polyoxometalates (POMs) can act as unique reservoirs for multiple electron transfers. As POMs display only weak absorption in the visible spectrum, they can be associated with chromophores such as porphyrins and porphyrin antennae. In this Minireview, the research dedicated to the combination of porphyrins and polyoxometalates is put in context and the state of the art identifying the challenges addressed in the optimization of hybrid materials for applications is detailed. 相似文献
9.
针对物理化学教材中有关光化学初级过程和次级过程、初级过程的量子产率、初级过程的反应速率表示以及是否是零级反应等问题发表了看法。 相似文献
10.
Shana Weathersby Brian Dinkelmeyer Robert Pike Scott Huffman 《Tetrahedron letters》2018,59(38):3453-3457
Cinnamylidene malonic acid was synthesized and its crystal structure obtained. The dicarboxylic acid hydrogen-bonding motif of this structure consists of catemer chains that lie along the c- glide plane. A photo induced 2?+?2 cycloaddition occurred upon exposure of the crystals to UV light which resulted in the destruction of the crystal. The structure of the photo products were determined by IR and NMR analysis. The regio- and stereo-chemistry of the photoproduct can be rationalized by examining the relative orientation and symmetry relating reacting molecules within the crystal structure. A kinetic study demonstrated first order reaction kinetics which is consistent with a reaction occurring under topochemical control. 相似文献