全文获取类型
收费全文 | 243篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
化学 | 171篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 30篇 |
物理学 | 50篇 |
出版年
2024年 | 1篇 |
2023年 | 4篇 |
2022年 | 8篇 |
2021年 | 21篇 |
2020年 | 9篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 14篇 |
2016年 | 21篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 19篇 |
2011年 | 18篇 |
2010年 | 11篇 |
2009年 | 17篇 |
2008年 | 10篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2000年 | 1篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 3篇 |
1974年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有258条查询结果,搜索用时 599 毫秒
41.
Stefan Schippers Ticia Buhr Alexander Borovik Jr. Kristof Holste Alexander Perry-Sassmannshausen Karolin Mertens Simon Reinwardt Michael Martins Stephan Klumpp Kaja Schubert Sadia Bari Randolf Beerwerth Stephan Fritzsche Sandor Ricz Jonas Hellhund Alfred Müller 《X射线光谱测定》2020,49(1):11-20
The Photon-Ion Spectrometer at PETRA III—in short, PIPE—is a permanently installed user facility at the "Variable Polarization XUV Beamline" P04 of the synchrotron light source PETRA III operated by DESY in Hamburg, Germany. The careful design of the PIPE ion-optics in combination with the record-high photon flux at P04 has lead to a breakthrough in experimental studies of photon interactions with ionized small quantum systems. This short review provides an overview over the published scientific results from photon-ion merged-beams experiments at PIPE that were obtained since the start of P04 operations in 2013. The topics covered comprise photoionization of ions of astrophysical relevance, quantitative studies of multi-electron processes upon inner-shell photoexcitation and photoionization of negative and positive atomic ions, precision spectroscopy of photoionization resonances, photoionization and photofragmentation of molecular ions, and of endohedral fullerene ions. 相似文献
42.
43.
Ivan Scodeller Samir Mansouri Dr. Didier Morvan Dr. Eric Muller Dr. Karine de Oliveira Vigier Dr. Raphael Wischert Dr. François Jérôme 《Angewandte Chemie (International ed. in English)》2018,57(33):10510-10514
We report the synthesis of biomass‐derived functionalized aromatic chemicals from furfural, a building block nowadays available in large scale from low‐cost biomass. The scientific strategy relies on a Diels–Alder/aromatization sequence. By controlling the rate of each step, it was possible to produce exclusively the meta aromatic isomer. In particular, through this route, we describe the synthesis of renewably sourced meta‐xylylenediamine (MXD). Transposition of this work to other furfural‐derived chemicals is also discussed and reveals that functionalized biomass‐derived aromatics (benzaldehyde, benzylamine, etc.) can be potentially produced, according to this route. 相似文献
44.
Inside Cover: Synthesis of Renewable meta‐Xylylenediamine from Biomass‐Derived Furfural (Angew. Chem. Int. Ed. 33/2018)
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
45.
Partial oxidation of methane to formaldehyde and methanol was studied at atmospheric pressure in the temperature range of 700-750 °C using heteropolycompound catalysts (NH4)6HSiMo11FeO40, (NH4)4PMo11FeO39, and H4PMo11VO40, which were prepared and characterized by various analysis techniques such as infrared, visible UV, XRD and DTA. O2 or N2O was used as the oxidizing agent, and the principal products of the reaction were CH3OH, CH2O, CO, CO2, and water. The conversion and the selectivity of products depend strongly on the reaction temperature, the nature of oxidizing agent, and the composition of catalyst. 相似文献
46.
B. Mansouri N. Manamanni K. Guelton M. Djemai 《Nonlinear Analysis: Hybrid Systems》2008,2(4):1136-1143
This paper concerns the state feedback control for continuous-time, disturbed and uncertain linear switched systems with arbitrary switching rules. The main result of this work consists in getting a LMI (Linear Matrix Inequalities) condition guaranteeing a robust pole placement according to some desired specifications. Then, external disturbance attenuation with a fixed rate according to the H∞ criterion is ensured. This is obtained thanks to the existence of a common quadratic Lyapunov function for all sub-systems. Finally, an academic example illustrates the efficiency of the developed approach. 相似文献
47.
Mostafaie A Bidmeshkipour A Shirvani Z Mansouri K Chalabi M 《Applied biochemistry and biotechnology》2008,144(2):123-131
Actinidin is a cysteine protease abundant in Kiwifruit. This enzyme is known as a meat-tenderizing protease. In this project,
actinidin was purified from kiwifruit by salt precipitation and ion exchange chromatography. Collagenolytic effect of the
purified enzyme was tested in four different buffer systems. Thereafter, the enzyme was used for isolation and culture of
cells from three different tissues: endothelial cells from human umbilical vein, hepatocytes from rat liver, and thymic epithelial
cells from rat thymus. Our results revealed that actinidin can hydrolyze collagen types I and II at neutral and alkaline buffers.
Furthermore, actinidin compared with type II or IV collagenase isolated intact human umbilical vein endothelial cells, hepatocytes,
and thymic epithelial cells with viability more than 90%. These results address a novel and valuable collagenase, which can
be used efficiently for hydrolysis of collagen and isolation of different cell populations from various solid tissues. 相似文献
48.
Ahmad VU Arshad S Bader S Iqbal S Khan A Khan SS Hussain J Tareen RB Ahmed A 《Magnetic resonance in chemistry : MRC》2008,46(10):986-989
Two new triterpenoidal saponins were isolated from the n-butanolic extract of Stachys parviflora (Lamiaceae). Their structures were elucidated on the basis of spectral data as stachyssaponin A; 3beta, 15alpha, 19alpha, 21beta, 22alpha-pentahydroxyolean-12-ene-28-oic acid 3-O-{alpha-L-rhamnopyranosyl-(1 --> 3)-beta-D-glucopyranoside}-22-O-{alpha-L-arabinofuranosyl-(1 --> 3)-beta-D-glucopyranoside} (1) and stachyssaponin B; 2beta, 3beta, 15alpha, 21beta-tetrahydroxyolean-12-ene-28-oic acid 2-O-[alpha-L-arabinofuranoside]-3, 21-bis-O-[beta-D-glucopyranoside] (2). 相似文献
49.
Isothermal Cyclic Conversion of Methane into Methanol over Copper‐Exchanged Zeolite at Low Temperature
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Patrick Tomkins Ali Mansouri Dr. Selmi E. Bozbag Dr. Frank Krumeich Dr. Min Bum Park Dr. Evalyn Mae C. Alayon Dr. Marco Ranocchiari Prof. Dr. Jeroen A. van Bokhoven 《Angewandte Chemie (International ed. in English)》2016,55(18):5467-5471
Direct partial oxidation of methane into methanol is a cornerstone of catalysis. The stepped conversion of methane into methanol currently involves activation at high temperature and reaction with methane at decreased temperature, which limits applicability of the technique. The first implementation of copper‐containing zeolites in the production of methanol directly from methane is reported, using molecular oxygen under isothermal conditions at 200 °C. Copper‐exchanged zeolite is activated with oxygen, reacts with methane, and is subsequently extracted with steam in a repeated cyclic process. Methanol yield increases with methane pressure, enabling reactivity with less reactive oxidized copper species. It is possible to produce methanol over catalysts that were inactive in prior state of the art systems. Characterization of the activated catalyst at low temperature revealed that the active sites are small clusters of copper, and not necessarily di‐ or tricopper sites, indicating that catalysts can be designed with greater flexibility than formerly proposed. 相似文献
50.
Ce(IV) salophen encapsulated into dealuminated Y zeolite was prepared by the flexible ligand method. Incorporation of TiO2 into nanocages of dealuminated Y zeolite was performed by the impregnation method. The obtained photocatalyst was characterized by FT-IR, XRD, DRS, SEM, EDS and ICP techniques. The amount of Ce(salophen) in the zeolite supercages was 0.07 mg/g of encapsulated zeolite. This catalytic system was investigated in the photodegradation of 4-nitrophenol. In this work, the effect of dark conditions, and visible and UV illumination was investigated for the degradation of 4-nitrophenol. In addition, the effect of other parameters including catalyst loading, H2O2 and TiO2 was studied in the degradation of 4-nitrophenol. The obtained results reveal that the photocatalyst performance depends on catalyst loading, the presence of H2O2, and UV illumination. 相似文献