全文获取类型
收费全文 | 134篇 |
免费 | 2篇 |
专业分类
化学 | 91篇 |
晶体学 | 1篇 |
数学 | 2篇 |
物理学 | 42篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 2篇 |
2017年 | 1篇 |
2016年 | 3篇 |
2015年 | 1篇 |
2014年 | 4篇 |
2013年 | 7篇 |
2012年 | 7篇 |
2011年 | 14篇 |
2010年 | 7篇 |
2009年 | 2篇 |
2008年 | 5篇 |
2007年 | 5篇 |
2006年 | 12篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 6篇 |
1999年 | 4篇 |
1998年 | 3篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1988年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有136条查询结果,搜索用时 31 毫秒
1.
[reaction: see text]. Unified and highly convergent total syntheses of (+)-macrosphelides A and B are described. Key features of the syntheses include (1) concise synthesis of the optically active delta-hydroxy-gamma-keto alpha,beta-unsaturated acid fragment via the direct addition of a trans-vinylogous ester anion equivalent to the readily available Weinreb amide and (2) facile construction of the 16-membered macrolide core of the macrosphelide series via an intramolecular nitrile-oxide cycloaddition (INOC). 相似文献
2.
An unusually stable molecular capsule was formed by heating phenyleneurea-spanned resorcinarene cavitand with 4-methyl-N-p-tolylbenzamide. The molecular capsule behaved as a discrete molecular entity showing a cylindrical D(4d) structure and showed no guest exchange in toluene-d(8) even at 100 degrees C. [structure: see text] 相似文献
3.
Aromatic molecular "clips" bearing two symmetrically bound platinum moieties have been prepared. The molecular "clip" 4 readily self-assembled with linear linkers such as 4,4'-bipyridyl, 1,4-bis[2-(4-isocyano-3,5-diisopropylphenyl)ethynyl]benzene, and nicotinic acid to form molecular rectangles. The overall dimensions of the rectangle 7 were 7.3 Angstroms x 15.3 Angstroms. The molecular "clip" also self-assembled with tritopic pyridyl and isocyanide ligands to form trigonal prismatic frameworks. The characterization of the supramolecules by multinuclear NMR, electrospray mass spectrometry, and X-ray crystal structures is also reported. 相似文献
4.
Primary emphasis is placed on the effects of coating parameters such as coating thickness and tip size, the coating thickness variations due to different draw speeds, and induced maximum shear rate in the applicator. However, in this analysis the flow region is divided into two because of the mixed boundary conditions: non-slip condition (region I) and free shear condition along the meniscus (region II). The surface tension at the edge in region II is balanced with the pressure difference, which becomes a constraint for the flow rate. 相似文献
5.
Gha-Young Kim Tack-Jin Kim Si-Hyung Kim Seungwoo Paek 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(3):1261-1265
The employment of multiple electrode pairs is one of the ways to achieve a high-throughput electrowinner. In order to improve the U/TRU recovery rate and also to obtain economic advantages for a molten salt electrowinning process, which is a major step in pyroprocessing, the development of an electrode module having a compact structure is required. Here, we designed an anode-liquid cathode module (ALCM), where two graphite anodes are symmetrically arranged centering on a liquid Cd cathode with a mesh stirrer to prevent the growth of U dendrites, to be applied to the electrowinning process. As a preliminary study, basic electrochemical characterization of the designed electrode module was conducted and its capability for U recovery was evaluated in the ALCM-employed lab-scale electrowinner including LiCl–KCl-UCl3 at 500 °C. Also, the morphology and component of the recovered U residue by distillation of the cathode product was examined by FE-SEM and EDS analyses. 相似文献
6.
7.
Photonic crystal fiber coupler 总被引:3,自引:0,他引:3
Fiber couplers made with photonic crystal fibers (PCF) are reported. Two types of PCF were fabricated by means of stacking a group of silica tubes around a silica rod and drawing them. The fiber couplers were made by use of the fused biconical tapered method. With a fiber that had five hexagonally stacked layers of air holes, a 33/67 coupling ratio was obtained, and with a one-layer four-hole fiber, a 48/52 coupling ratio was obtained. The fabrication processes and the characteristics of the PCFs and the PCF couplers are presented. 相似文献
8.
We propose the remote multiplexing of holograms with random patterns from a multimode fiber bundle used as the reference beams. The random pattern reference beam is characterized by the superposition and concatenation of propagation modes of multimode fiber and free space. For angle, shift, and wavelength remote multiplexing we compare two methods of laser coupling to the fiber bundle, i.e., direct coupling and lens coupling. A theoretical discussion that uses mode orthogonality is provided to describe multiplexing characteristics, and the theory is verified by experimental results. These remote-multiplexing methods can be applied to general multimode waveguide arrays for construction of compact and integrated optical systems in which multiplexing can be controlled remotely. 相似文献
9.
10.
The retention of polar compounds, the separation of structural isomers and thermal stability make carbonaceous materials very attractive stationary phases for liquid chromatography (LC). Carbon clad zirconia (C/ZrO2), one of the most interesting, exhibits unparalleled chemical and thermal stability, but its characteristically low surface area (20–30 m2/g) limits broader application as a second dimension separation in two-dimensional liquid chromatography (2DLC) where high retentivity and therefore high stationary phase surface area are required. In this work, we used a high surface area commercial HPLC alumina (153 m2/g) as a support material to develop a carbon phase by chemical vapor deposition (CVD) at elevated temperature using hexane vapor as the carbon source. The loading of carbon was varied by changing the CVD time and temperature, and the carbon coated alumina (C/Al2O3) was characterized both physically and chromatographically. The resulting carbon phases behaved as a reversed phase similar to C/ZrO2. At all carbon loadings, C/Al2O3 closely matched the unique chromatographic selectivity of carbon phases, and as expected the retentivity was increased over C/ZrO2. Excess carbon – the amount equivalent to 5 monolayers – was required to fully cover the oxide support in C/Al2O3, but this was less excess than needed with C/ZrO2. Plate counts were 60,000–76,000/m for 5 μm particles. Spectroscopic studies (XPS and FT-IR) were also conducted; they showed that the two materials were chemically very similar. 相似文献