全文获取类型
收费全文 | 161篇 |
免费 | 6篇 |
专业分类
化学 | 115篇 |
晶体学 | 1篇 |
力学 | 9篇 |
数学 | 1篇 |
物理学 | 41篇 |
出版年
2022年 | 1篇 |
2019年 | 3篇 |
2017年 | 1篇 |
2016年 | 2篇 |
2015年 | 2篇 |
2014年 | 8篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 16篇 |
2007年 | 3篇 |
2006年 | 7篇 |
2005年 | 6篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 10篇 |
2000年 | 3篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 7篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有167条查询结果,搜索用时 234 毫秒
61.
Cytotoxicity of Postmodified Zeolitic Imidazolate Framework‐90 (ZIF‐90) Nanocrystals: Correlation between Functionality and Toxicity 下载免费PDF全文
Chia‐I Yen Szu‐Mam Liu Wei‐Shang Lo Jhe‐Wei Wu Yi‐Hsin Liu Prof. Rong‐Jie Chein Prof. Renqiang Yang Prof. Kevin C.‐W. Wu Prof. Jih Ru Hwu Prof. Nianhan Ma Prof. Fa‐Kuen Shieh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):2925-2929
Using a simple method, the aldehyde groups of zeolitic imidazolate framework‐90 (ZIF‐90) nanocrystals were converted into carboxyl, amino, and thiol groups, without affecting the integrity of the framework. Notably, for the first time, correlations between functionality and cytotoxicity are also demonstrated via in vitro cytotoxicity assays. The positive charged aminated‐ZIF‐90 presumably results in either perturbation of cell membrane, more efficient cell uptake, or both. Therefore, the half‐maximal effective (EC50) concentration of aminated‐ZIF‐90 has a higher cytotoxicity of about 30 μg mL?1. 相似文献
62.
Millimeter wave monolithic high electron mobility (HEM) varactor diode-grid frequency tripler arrays
R. J. Hwu L. P. Sadwick D. C. Streit 《International Journal of Infrared and Millimeter Waves》1991,12(12):1409-1423
High Electron Mobility (HEM) varactor structures have been studied for millimeter-wave monolithic diode-grid frequency tripler array applications. The improved HEM varactor diode structures provide a highly nonlinear C-V characteristic (i.e., a steep slope of the C-V curve and a large capacitance ratio) which produces high harmonic generation efficiency and reduce the power requirement for efficiently pumping each device. The effects of the light illumination on the C-V characteristics of the Barrier-Intrinsic-N+ (BIN) varactor diode have also been studied and the results will be discussed in this paper. In the development of a monolithic diode-grid frequency multiplier array, the low-loss quasioptical configuration is used for the construction of the multiplier circuit. The study of the effects of the light illumination on the C-V characteristics of varactor diode is important in understanding the potential applications of the quasi-optical varactor diode-grid frequency multiplier array circuit. 相似文献
63.
Yang Tsung-Yeh Wu Chung-Yi Tsai Meng-Hung Lin Hong-Ming Tsai Wen-Li Hwu Yeukuang 《Journal of nanoparticle research》2004,6(2):171-179
Tungsten oxide nanoparticles are prepared by evaporating and oxidizing the tungsten boat in helium and oxygen atmosphere and then quenched to the liquid nitrogen temperature. The as-prepared tungsten oxide nanoparticles are porous-free with uniform size. The morphology and particle size distribution of the as-prepared and after sinter treatments tungsten oxide nanoparticles are revealed by TEM and AFM. The long-range order of these nanoparticles can be examined by X-ray diffraction technique. The as-prepared nanoparticles exhibit a mixture structure of monoclinic and hexagonal crystals. Preliminary X-ray diffraction results indicate that the hexagonal structure is transformed to monoclinic structure after annealing to above 600°C. In order to better distinguish the structural properties of the tungsten oxide (WO3−
x) nanoparticles before and after annealing, the X-ray absorption spectrum technique is utilized; thus, the detailed local atomic arrangement of oxygen and/or tungsten can be determined. According to the XAS result, the shape of the W L3-edge undergoes no considerable changes. This infers that structural transformation of tungsten oxide nanoparticle may be caused by the migration of oxygen after sintering. From the O K-edge of absorption spectrum, it suggests that a mixture phase structure is obtained when sintered below 300°C. And this result indicates that heat treatment to approximately 600°C produces a stable structure of a monoclinic crystal of WO3. 相似文献
64.
T. S. Argunova L. M. Sorokin B. Z. Pevzner V. S. Balitskii M. A. Gannibal J. H. Je Y. Hwu W. -L. Tsai 《Physics of the Solid State》2003,45(10):1910-1917
The solubility and diffusion of helium in quartz crystals are investigated as functions of the distribution and density of structural defects. The types of defects in the crystals are identified and their distribution over growth sectors is determined by x-ray diffraction topography and phase radiography with a synchrotron radiation source. The effective solubility and effective diffusion coefficients for helium in quartz are estimated from the experimental data on the amount of helium extracted from samples with different contents of defects. It is revealed that the effective diffusion coefficient of helium depends on the number of dislocations. 相似文献
65.
In order to examine the effect of iodide ions on reaction catalyzed by phase-transfer technique, we made kinetic studies, under the influence of added Na1, on the synthesis of benzyl esters from benzyl chloride and sodium carboxylate. These carboxylates include sodium acetate, sodium benzoate, sodium salicylate and sodium formate; the catalyst was a quaternary ammonium salt. The results reveal that iodide ions at a suitable concentration accelerate the reaction, whereas iodide ions in excess poison the catalyst. The optimum concentration varies with the reaction system. This critical concentration depends upon the distribution coefficient of the intermediates formed in the reactions. 相似文献
66.
Fang-Yuan Lee Yu-Ju Chen Gene-Hsiang Lee Jih Ru Hwu 《Journal of organometallic chemistry》2005,690(2):441-449
The reaction of Os3(CO)12 with an excess of 1-hydroxypyridine-2-thione and Me3NO gives three mononuclear osmium complexes Os(CO)2(η2-SC5H4N(O))2 (1), Os(CO)2(η2-SC5H4N(O))(η2-SC5H4N) (2), and Os(CO)2(η2-SC5H4N)2 (3). The results of single-crystal X-ray analyses reveal that complex 1 contains two O,S-chelate pyridine-2-thione N-oxide (PyOS) ligands, whereas complex 2 contains one O,S-chelate PyOS and one N,S-chelate pyridine-2-thiolate group. The unique structure of 2 provides evidence of the pathway for this transformation. When this reaction was monitored by 1H NMR spectroscopy the triosmium complexes Os3(CO)10(μ-H)(μ-η1-S-C5H4N(O)) (4) and Os3(CO)9(μ-H)(μ-η1:η2-SC5H4N(O)) (5) were identified as intermediates in the formation of the mononuclear final products 1-3. The proposed pathway is further supported by the observation of several dinuclear osmium intermediates by electrospray ionization mass spectrometry. In addition, the reaction of Os3(CO)12 with 1-hydroxypyridine-2-thione in the absence of Me3NO at 90 °C generated mononuclear complex 2 as the major product along with smaller amounts of complexes 1 and 3. These results suggest that the N-oxide facilitates the decarbonylation reaction. Crystal data for 1: monoclinic, space group C2/c, a = 26.9990(5) Å, b = 7.6230(7) Å, c = 14.2980(13) Å, β = 101.620(2)°, V = 2882.4(4) Å3, Z = 8. Crystal data for 2: monoclinic, space group C2/c, a = 5.7884(3) Å, b = 13.9667(7) Å, c = 17.2575(9) Å, β = 96.686(1)°, V = 1385.69(12) Å3, Z = 4. 相似文献
67.
Henry H Hwu Joseph Eng Jingguang G Chen 《Journal of the American Chemical Society》2002,124(4):702-709
We have utilized the dehydrogenation and hydrogenation of cyclohexene as probe reactions to compare the chemical reactivity of Ni overlayers that are grown epitaxially on a Pt(111) surface. The reaction pathways of cyclohexene were investigated using temperature-programmed desorption, high-resolution electron energy loss (HREELS), and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Our results provide conclusive spectroscopic evidence that the adsorption and subsequent reactions of cyclohexene are unique on the monolayer Ni surface as compared to those on the clean Pt(111) surface or the thick Ni(111) film. HREELS and NEXAFS studies show that cyclohexene is weakly pi-bonded on monolayer Ni/Pt(111) but di-sigma-bonded to Pt(111) and Ni(111). In addition, a new hydrogenation pathway is detected on the monolayer Ni surface at temperatures as low as 245 K. By exposing the monolayer Ni/Pt(111) surface to D2 prior to the adsorption of cyclohexene, the total yield of the normal and deuterated cyclohexanes increases by approximately 5-fold. Furthermore, the reaction pathway for the complete decomposition of cyclohexene to atomic carbon and hydrogen, which has a selectivity of 69% on the thick Ni(111) film, is nearly negligible (<2%) on the monolayer Ni surface. Overall, the unique chemistry of the monolayer Ni/Pt(111) surface can be explained by the weaker interaction between adsorbates and the monolayer Ni film. These results also point out the possibility of manipulating the chemical properties of metals by controlling the overlayer thickness. 相似文献
68.
The addition of reactive carbanions to tricarbonyl(η4-1,3-diene)iron(0) complexes proceeded at 23°C to give putative tricarbonyl(η3-allyl)iron(0) anion complexes. Trapping of the reactive intermediates with bromine produced nucleophilic-substituted tricarbonyl(η4-1,3-diene)iron(0) complexes. 相似文献
69.
70.