全文获取类型
收费全文 | 375篇 |
免费 | 53篇 |
国内免费 | 134篇 |
专业分类
化学 | 530篇 |
力学 | 1篇 |
综合类 | 2篇 |
数学 | 2篇 |
物理学 | 27篇 |
出版年
2024年 | 4篇 |
2023年 | 14篇 |
2022年 | 32篇 |
2021年 | 50篇 |
2020年 | 58篇 |
2019年 | 33篇 |
2018年 | 31篇 |
2017年 | 22篇 |
2016年 | 31篇 |
2015年 | 20篇 |
2014年 | 22篇 |
2013年 | 22篇 |
2012年 | 22篇 |
2011年 | 18篇 |
2010年 | 20篇 |
2009年 | 27篇 |
2008年 | 23篇 |
2007年 | 12篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 15篇 |
2003年 | 10篇 |
2002年 | 7篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 1篇 |
1987年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有562条查询结果,搜索用时 106 毫秒
41.
工业化的快速发展导致含有六价铬(Cr(Ⅵ))的废水排放量日益增加,Cr(Ⅵ)的毒性和高流动性造成极大的环境污染问题。将Cr(Ⅵ)还原成低毒性和低流动性三价铬(Cr(Ⅲ))是当前的有效处理方式之一。与传统方法相比,利用太阳光、电和微波等驱动氧化还原反应进行Cr(Ⅵ)降解,无催化剂消耗,还原剂用量少,且不会造成二次污染和有限资源损耗,成为处理Cr(Ⅵ)污染的有效解决方案。基于此,本文综述了光催化剂、电催化剂及微波催化剂等在还原Cr(Ⅵ)领域的应用现状,在总结分析前人研究成果的基础上,对今后Cr(Ⅵ) 催化还原技术的研究方向和重点进行了展望。 相似文献
42.
催化剂的性能与其表面结构及组成密切相关,高指数晶面纳米晶的表面含有高密度的台阶原子等活性位点而表现出较高的催化活性. 本文综述了电化学方波电位方法用于Pt、Pd、Rh等贵金属高指数晶面结构纳米晶催化剂的制备、形成机理及其电催化性能的研究. 针对贵金属利用率问题,还着重介绍了具有较高质量活性的小粒径Pt二十四面体的制备. 在此基础上,还介绍了电化学方波电位方法用于低共熔溶剂中制备高指数晶面纳米晶,以及高指数晶面纳米催化剂的表面修饰及应用;最后对高指数晶面纳米催化剂的发展做出了展望. 相似文献
43.
Kangjae Lee Seojin Lee Namhoon Kim Seonyul Kim Sungwoo Hong 《Angewandte Chemie (International ed. in English)》2020,59(32):13379-13384
A general strategy for visible‐light‐enabled site‐selective trifluoromethylative pyridylation of unactivated alkenes has been developed using pyridines and triflic anhydride (Tf2O). Intriguingly, the N‐triflylpyridinium salts, generated in situ from pyridines and Tf2O, serve as effective modular bifunctional reagents to install both CF3 and pyridyl groups to various olefins while controlling C4‐selectivity in radical addition to the pyridine core. This synthetic route exhibited broad substrate scope under metal‐free and mild photocatalytic conditions, granting efficient access to valuable C4‐alkylated pyridines and quinolines without requiring prefunctionalization of the reaction site. 相似文献
44.
Jonathan C. Golec Eve M. Carter John W. Ward William G. Whittingham Luis Simn Robert S. Paton Darren J. Dixon 《Angewandte Chemie (International ed. in English)》2020,59(40):17417-17422
A bifunctional iminophosphorane (BIMP)‐catalysed enantioselective synthesis of α,β‐unsaturated cyclohexenones through a facially selective 1,3‐prototropic shift of β,γ‐unsaturated prochiral isomers, under mild reaction conditions and in short reaction times, on a range of structurally diverse substrates, is reported. α,β‐Unsaturated cyclohexenone products primed for downstream derivatisation were obtained in high yields (up to 99 %) and consistently high enantioselectivity (up to 99 % ee). Computational studies into the reaction mechanism and origins of enantioselectivity, including multivariate linear regression of TS energy, were carried out and the obtained data were found to be in good agreement with experimental findings. 相似文献
45.
Electrocatalytic water splitting to produce hydrogen and oxygen is regarded as one of the most promising methods to generate clean and sustainable energy for replacing fossil fuels. However, the design and development of an efficient bifunctional catalyst for simultaneous generation of hydrogen and oxygen remains extremely challenging yet is critical for the practical implementation of water electrolysis. Here, we report a facile method to fabricate novel N‐doped carbon nanotube frameworks (NCNTFs) by the pyrolysis of a bimetallic metal organic framework (MIL‐88‐Fe/Co). The resultant electrocatalyst, Co3Fe7@NCNTFs, exhibits excellent oxygen evolution reaction (OER) activity, achieving 10 mA/cm2 at a low overpotential of just 264 mV in 1 M KOH solution, and 197 mV for the hydrogen evolution reaction. The high electrocatalytic activity arises from the synergistic effect between the chemistry of the Co3Fe7 and the NCNTs coupled to the novel framework structure. The remarkable electrocatalytic performance of our bifunctional electrocatalyst provides a promising pathway to high‐performance overall water splitting and electrochemical energy devices. 相似文献
46.
Here, based on self-assembly of carbon quantum dots (CDs), an innovative method to prepare nanomaterials under the action of a metal catalyst was presented. CDs were synthesized by a one-step hydrothermal method with citric acid (CA) as the carbon source, ethylenediamine (EDA) as the passivator and FeSO4•7H2O as the pre-catalyst. In the experiment, it was found that the nano-carbon films with a graphene-like structure were formed on the surface of the solution. The structure of the films was studied by high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR), etc. The results demonstrated that the films were formed by the self-assembly of CDs under the action of the gas–liquid interface template and the metal catalyst. Meanwhile, the electrochemical performance of the films was evaluated by linear cyclic voltammetry (CV) and galvanostatic charge discharge (GOD) tests. In addition, the bulk solution could be further reacted and self-assembled by reflux to form a bifunctional magnetic–fluorescent composite material. Characterizations such as X-ray diffractometer (XRD), fluorescence spectra (FL), vibrating sample magnetometer (VSM), etc. revealed that it was a composite of superparamagnetic γ-Fe2O3 and CDs. The results showed that self-assembly of CDs is a novel and effective method for preparing new carbon nanomaterials. 相似文献
47.
48.
49.
50.