全文获取类型
收费全文 | 269篇 |
免费 | 11篇 |
专业分类
化学 | 196篇 |
力学 | 1篇 |
数学 | 11篇 |
物理学 | 72篇 |
出版年
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2018年 | 8篇 |
2017年 | 1篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 13篇 |
2012年 | 15篇 |
2011年 | 17篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 18篇 |
2007年 | 8篇 |
2006年 | 20篇 |
2005年 | 30篇 |
2004年 | 16篇 |
2003年 | 15篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 12篇 |
1998年 | 2篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有280条查询结果,搜索用时 306 毫秒
131.
A novel palladium- and copper-catalyzed one-pot multicomponent synthesis of hetero α,α'-dimers of heterocycles via Sonogashira coupling and double cyclization cascade involving imine formation has been developed. This reaction cascade proceeded under mild conditions, providing a powerful synthetic tool for the assembly of π-conjugated systems with a combination of palladium-catalyzed post-direct C-H bond arylations. 相似文献
132.
Okamoto K Mashida A Watanabe M Ohe K 《Chemical communications (Cambridge, England)》2012,48(29):3554-3556
An unprecedented nickel-catalysed disproportional reaction of 2,3-diaryl-2H-azirines forming azabutadienes and aromatic nitriles was discovered. This reaction involves the cleavage of two bonds of the 2H-azirine framework, which provides a novel type of transformation of 2H-azirines. 相似文献
133.
Okamoto K Watanabe M Murai M Hatano R Ohe K 《Chemical communications (Cambridge, England)》2012,48(25):3127-3129
A gallium-catalysed, direct cyanation reaction of aromatic and heteroaromatic C-H bonds with cyanogen bromide was developed as a practical synthetic method for the preparation of aromatic nitriles. 相似文献
134.
Crystalline sucrose irradiated with C and Si ions is investigated with EPR and UV spectroscopy. Samples are treated at different doses of radiation in the region 20–300 Gy and linear energy transfer (LET) values of 39.6, 49 and 58 keV μm?1 for C ions and 60 keV μm?1 for Si ions. All samples exhibit identical EPR spectra due to radiation-induced stable sucrose radicals. At given constant LET the EPR signal responses are linear to the absorbed doses of Si and C ions. Water solutions of irradiated sucrose exhibit UV absorption maximum at 267 nm due to the product of radical recombination. The intensity of this band is stronger at irradiation with Si than with C ions. UV absorption is more sensitive to heavy-ion species irradiation than the EPR signals. 相似文献
135.
Solid/liquid interfaces are important locations for various chemical reactions, such as electrode chemical reactions and metal corrosions. Conventional surface analytical methods, such as XPS and SEM-EDS, have been applied to solid materials after being removed from the liquid phase. These methods do not involve direct observation, although useful information is available. It is important to directly observe surface reactions on solid materials in the liquid phase in order to understand the details of these reactions. One feasible method of doing this is 3D micro-XRF analysis. The confocal 3D micro XRF method enables nondestructive x-ray elemental analysis of localized microspace. We have applied a confocal 3D micro-XRF instrument for solid/liquid interface analysis. This technique was applied for direct observation of the chemical deposition of Cu on an Fe plate and the dissolution of Fe in a CuSO4 solution. 相似文献
136.
Sentaro Okamoto Kouichi Takano Tomohiro Ishikawa Satoshi Ishigami Akiko Tsuhako 《Tetrahedron letters》2006,47(46):8055-8058
The structure-activity relationship and behavior of N,N′-dialkylimidazolium salts as a phase transfer and/or ion-exchange catalyst in a liquid-liquid phase system were investigated for the reactions such as β-elimination reaction of alkyl halides, nucleophilic epoxidation of α,β-unsaturated carbonyl compounds, alkylation of active methylenes, and nucleophilic substitution reaction. 相似文献
137.
138.
139.
Stereoselective Construction of 1,3‐Disilylcyclopentane Derivatives by Scandium‐Catalyzed [3+2] Cycloaddition of Allylsilanes to β‐Silylenones
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)
Dr. Kazuhiro Okamoto Eisuke Tamura Prof. Dr. Kouichi Ohe 《Angewandte Chemie (International ed. in English)》2014,53(38):10195-10199
The Sc(OTf)3‐catalyzed [3+2] cycloaddition of allylsilanes to β‐silyl‐α,β‐unsaturated ketones (β‐silylenones) has been developed to form five‐membered syn‐1,3‐disilylketones diastereoselectively through the rearrangement of the silicon substituents on the allylsilane. Stabilization of the carbocation intermediates by a double silicon effect plays a key role in directing the course of the reaction to favor the [3+2] cycloaddition pathway over simple allylation. 相似文献
140.
Toshihiro Kobayashi Yuriko Matsumura Toshihiko Ozawa Hiroyuki Yanai Atsuo Iwasawa Toshiaki Kamachi Kouichi Fujiwara Noriaki Tanaka Masahiro Kohno 《Analytical and bioanalytical chemistry》2014,406(5):1365-1376
To identify blood markers for early stages of chronic kidney disease (CKD), blood samples were collected from rats with adenine-induced CKD over 28 days. Plasma samples were subjected to metabolomic profiling by liquid chromatography-mass spectrometry, followed by multivariate analyses. In addition to already-identified uremic toxins, we found that plasma concentrations of N6-succinyl adenosine, lysophosphatidylethanolamine 20:4, and glycocholic acid were altered, and that these changes during early CKD were more sensitive markers than creatinine concentration, a universal indicator of renal dysfunction. Moreover, the increase in plasma indoxyl sulfate concentration occurred earlier than increases in phenyl sulfate and p-cresol sulfate. These novel metabolites may serve as biomarkers in identifying early stage CKD. 相似文献