全文获取类型
收费全文 | 662篇 |
免费 | 131篇 |
国内免费 | 105篇 |
专业分类
化学 | 480篇 |
晶体学 | 16篇 |
力学 | 34篇 |
综合类 | 16篇 |
数学 | 65篇 |
物理学 | 287篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 22篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 23篇 |
2015年 | 28篇 |
2014年 | 28篇 |
2013年 | 50篇 |
2012年 | 62篇 |
2011年 | 60篇 |
2010年 | 52篇 |
2009年 | 43篇 |
2008年 | 57篇 |
2007年 | 39篇 |
2006年 | 33篇 |
2005年 | 29篇 |
2004年 | 29篇 |
2003年 | 49篇 |
2002年 | 57篇 |
2001年 | 49篇 |
2000年 | 28篇 |
1999年 | 29篇 |
1998年 | 16篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有898条查询结果,搜索用时 15 毫秒
1.
2.
3.
Dr. Xiaolong Zu Yuan Zhao Dr. Xiaodong Li Runhua Chen Weiwei Shao Li Li Panzhe Qiao Prof. Wensheng Yan Prof. Yang Pan Qian Xu Prof. Junfa Zhu Prof. Yongfu Sun Prof. Yi Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(1):e202215247
Herein, we first design a model of reversible redox-switching metal–organic framework single-unit-cell sheets, where the abundant metal single sites benefit for highly selective CO2 reduction, while the reversible redox-switching metal sites can effectively activate CO2 molecules. Taking the synthetic Cu-MOF single-unit-cell sheets as an example, synchrotron-radiation quasi in situ X-ray photoelectron spectra unravel the reversible switching CuII/CuI single sites initially accept photoexcited electrons and then donate them to CO2 molecules, which favors the rate-liming activation into CO2δ−, verified by in situ FTIR spectra and Gibbs free energy calculations. As an outcome, Cu-MOF single-unit-cell sheets achieve near 100 % selectivity for CO2 photoreduction to CO with a high rate of 860 μmol g−1 h−1 without any sacrifice reagent or photosensitizer, where both the activity and selectivity outperform previously reported photocatalysts evaluated under similar conditions. 相似文献
4.
Yuanyuan Yu Dr. Guang Li Long Jiang Prof. Dr. Liansuo Zu 《Angewandte Chemie (International ed. in English)》2015,54(43):12627-12631
An indoxyl‐based strategy for the synthesis of indolines and indolenines via unprecedented aza‐pinacol and aza‐semipinacol rearrangements was developed. This method provides direct access to the core structures of several classes of indole alkaloids. The synthetic utility was demonstrated by the divergent synthesis of an array of functionalized polycyclic structures from a common intermediate and the formal total synthesis of the indoline natural product minfiensine. The reversed reactivity of indoxyl as a building block compared to that of indole offers a conceptually distinct disconnection strategy for indoline‐ and indolenine‐containing heterocycles and natural products. 相似文献
5.
Meng Wen Zu‐Ping Xiao Chun‐Ya Wang Xi‐He Huang 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(2):136-139
The title compound, {[Zn4(C8H4O4)3(OH)2(C12H6N2O2)2]·2H2O}n, has been prepared hydrothermally by the reaction of Zn(NO3)2·6H2O with benzene‐1,4‐dicarboxylic acid (H2bdc) and 1,10‐phenanthroline‐5,6‐dione (pdon) in H2O. In the crystal structure, a tetranuclear Zn4(OH)2 fragment is located on a crystallographic inversion centre which relates two subunits, each containing a [ZnN2O4] octahedron and a [ZnO4] tetrahedron bridged by a μ3‐OH group. The pdon ligand chelates to zinc through its two N atoms to form part of the [ZnN2O4] octahedron. The two crystallographically independent bdc2− ligands are fully deprotonated and adopt μ3‐κO:κO′:κO′′ and μ4‐κO:κO′:κO′′:κO′′′ coordination modes, bridging three or four ZnII cations, respectively, from two Zn4(OH)2 units. The Zn4(OH)2 fragment connects six neighbouring tetranuclear units through four μ3‐bdc2− and two μ4‐bdc2− ligands, forming a three‐dimensional framework with uninodal 6‐connected α‐Po topology, in which the tetranuclear Zn4(OH)2 units are considered as 6‐connected nodes and the bdc2− ligands act as linkers. The uncoordinated water molecules are located on opposite sides of the Zn4(OH)2 unit and are connected to it through hydrogen‐bonding interactions involving hydroxide and carboxylate groups. The structure is further stabilized by extensive π–π interactions between the pdon and μ4‐bdc2− ligands. 相似文献
6.
本文以量级分析为基础,建立了一般曲线坐标系上的三维旋转边界层方程。对旋转在边界层中的影响进行分析之后,提出了一个能够处理壁面法向压力梯度不为零问题的压力梯度迭代方法。在传统的Box法的基础上发展了一套完整的求解三维旋转边界层的方法和程序,并对螺旋面、压气机转子叶面以及圆柱面上的旋转边界层进行了计算,与他人的计算和实验的对比分析表明,该方法和程序是正确的,可用于求解任意几何物面上的三维旋转边界层。 相似文献
7.
The interactions between potassium perfluorooctanesulfonate (PFOS) and bovine serum albumin (BSA) were studied by fluorescence spectroscopy. The association constants between PFOS and BSA were obtained by fluorescence enhancing and fluorescence quenching respectively. Furthermore, fluorescence quenching was studied at different temperatures, and the binding constant was also determined by the method of fluorescence quenching. According to the thermodynamic parameters, the main binding force could be judged. The experimental results revealed that BSA and PFOS had strong interactions. The mechanism of quenching belonged to dynamic quenching and the main sort of binding force was hydrophobic force. IR-spectra proved the interaction changed the conformation of BSA. 相似文献
8.
Naturally occurring saponins are attractive candidates or lead compounds for new drug design and development and thus have become important synthetic targets. This short account reviews the recent progress in the chemical synthesis and structure-activity relationship (SAR) studies of naturally occurring saponins and their derivatives. 相似文献
9.
Raul Aguayo Felipe Arias Alvaro Cañete Carolina Zuñiga Enrique A. Castro Paulina Pavez José G. Santos 《国际化学动力学杂志》2013,45(3):202-211
The reactions of the title compounds with phenoxides, secondary alicyclic (SA) amines, and pyridines, in 44 wt% ethanol–water, at 25°C and an ionic strength of 0.2 M, were subjected to kinetic and product studies. From analytical techniques (HPLC and NMR), two pathways were detected (nucleophilic attack at the phosphoryl center and at the C‐1 aromatic carbon) for the reactions of all the nucleophiles with the phosphate ( 2 ) and for the pyridinolysis of the thionophosphate ( 1 ). Only aromatic nucleophilic substitution was found for the reactions of 1 with phenoxides and SA amines. For the dual reactions, the nucleophilic rate constants (kN) were separated in two terms: $k_{\rm N}^{\rm P}$ and $k_{\rm N}^{{\rm Ar}}$, which are the rate constants for the corresponding electrophilic centers. The absence of a break in the Brønsted‐type plots for the attack at P is consistent with concerted mechanisms. The Brønsted slopes, βAr 0.32–0.71, for the attack at the aromatic C‐1, are in agreement with stepwise mechanisms where formation of a Meisenheimer complex is the rate‐determining step. © 2013 Wiley Periodicals, Inc. Int J Chem Kinet 45: 202–211, 2013 相似文献
10.