全文获取类型
收费全文 | 416篇 |
免费 | 10篇 |
专业分类
化学 | 191篇 |
晶体学 | 2篇 |
力学 | 3篇 |
数学 | 50篇 |
物理学 | 180篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 11篇 |
2012年 | 28篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 14篇 |
2008年 | 35篇 |
2007年 | 50篇 |
2006年 | 31篇 |
2005年 | 40篇 |
2004年 | 29篇 |
2003年 | 18篇 |
2002年 | 27篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1985年 | 2篇 |
1982年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有426条查询结果,搜索用时 31 毫秒
91.
Kim YH Jun YW Jun BH Lee SM Cheon J 《Journal of the American Chemical Society》2002,124(46):13656-13657
We demonstrate a novel synthetic scheme that can be used to control the crystalline phase and shape of GaP semiconductor nanocrystals. Our study shows that steric effects of surfactant ligands can modulate the crystalline phases and control the shapes of nanocrystals. The shape of the nanocrystals obtained varies from zero-dimensional spheres to one-dimensional rods via controlling the ratio between primary and tertiary alkylamines. III-V semiconductors (in our case: GaP) under 10 nm in width are first reported, and unique optical properties due to shape anisotropy are also observed. 相似文献
92.
93.
Stirling numbers and Bessel numbers have a long history, and both have been generalized in a variety of directions. Here, we present a second level generalization that has both as special cases. This generalization often preserves the inverse relation between the first and second kind, and has simple combinatorial interpretations. We also frame the discussion in terms of the exponential Riordan group. Then the inverse relation is just the group inverse, and factoring inside the group leads to many results connecting the various Stirling and Bessel numbers. 相似文献
94.
95.
Keumhan Noh Kwang‐il Kwon Tae Cheon Jeong Wonku Kang 《Biomedical chromatography : BMC》2010,24(11):1199-1202
Sparfloxacin, a fluoroquinolone antibiotic, is used for the treatment of bacterial infection. A quantification method using mass spectrometry was developed for the determination of sparfloxacin in rat plasma. After simple protein precipitation with acetonitrile, the analytes were chromatographed on a reversed‐phase C18 column and detected by liquid chromatography/tandem mass spectrometry with electrospray ionization. The accuracy and precision of the assay were in accordance with FDA regulations for validation of bioanalytical methods. This method was applied to measure the plasma sparfloxacin concentrations after a single oral administration of sparfloxacin in rats. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
96.
Branched poly(1,4‐butylene carbonate‐co‐terephthalate)s: LDPE‐like semicrystalline thermoplastics 下载免费PDF全文
Seong Yeon Park Jiseul Chun Jong Yeob Jeon Pyung Cheon Lee Yongtaek Hwang Bo Geun Song Rafael Ramos Chang Y. Ryu Bun Yeoul Lee 《Journal of polymer science. Part A, Polymer chemistry》2015,53(7):914-923
Branched poly[1,4‐butylene carbonate‐co‐terephthalate]s (PBCTs) have been synthesized by the addition of a small amount of glycerol propoxylate ( 1 ) or pentaerythritol ( 2 ) in the polycondensation of 1,4‐butanediol, dimethyl carbonate, and dimethyl terephthalate. To avoid gel formation, the feed amount of 1 or 2 was carefully controlled at below 0.5 mol % for 1 and below 0.3 mol % for 2 . When feed of 1 or 2 was used, a high‐molecular weight melt state (Mw ~180,000 g/mol) was reached in a total reaction time of 5.5 to 6.5 h with a yield higher than 90%. The generated PBCTs were a semicrystalline polymer (Tg ~5 °C and Tm ~120 °C) when the terephthalate content (F[TPA]) was 45 to 50 mol %. The crystallization rate increased with increasing F[TPA] and branch content (F[ 1 or 2 ]); PBCT composed of F[TPA] = 49 mol % and F[ 1 ] = 0.44 mol % was crystallized completely in a short time, ~3 min, at a crystallization temperature of 50 °C. The branched PBCT exhibited more pronounced toughness in tensile test while providing the advantage of processibility at high shear rates due to the pronounced shear thinning in melt. It was also found that the branched PBCTs were biodegradable. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 914–923 相似文献
97.
Calcium Carbonate Mineralized Nanoparticles as an Intracellular Transporter of Cytochrome c for Cancer Therapy 下载免费PDF全文
Ahn Na Koo Kyung Hyun Min Hong Jae Lee Jun Ho Jegal Jae Won Lee Prof. Dr. Sang Cheon Lee 《化学:亚洲杂志》2015,10(11):2380-2387
A new intracellular delivery system based on an apoptotic protein‐loaded calcium carbonate (CaCO3) mineralized nanoparticle (MNP) is described. Apoptosis‐inducing cytochrome c (Cyt c) loaded CaCO3 MNPs (Cyt c MNPs) were prepared by block copolymer mediated in situ CaCO3 mineralization in the presence of Cyt c. The resulting Cyt c MNPs had a vaterite polymorph of CaCO3 with a mean hydrodynamic diameter of 360.5 nm and exhibited 60 % efficiency for Cyt c loading. The Cyt c MNPs were stable at physiological pH (pH 7.4) and effectively prohibited the release of Cyt c, whereas, at intracellular endosomal pH (pH 5.0), Cyt c release was facilitated. The MNPs enable the endosomal escape of Cyt c for effective localization of Cyt c in the cytosols of MCF‐7 cells. Flow cytometry showed that the Cyt c MNPs effectively induced apoptosis of MCF‐7 cells. These findings indicate that the CaCO3 MNPs can meet the prerequisites for delivery of cell‐impermeable therapeutic proteins for cancer therapy. 相似文献
98.
Hye Jeong Park Young Eun Cheon Prof. Myunghyun Paik Suh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(38):11662-11669
The porous metal–organic framework (MOF) {[Zn2(TCPBDA)(H2O)2]?30 DMF?6 H2O}n ( SNU‐30 ; DMF=N,N‐dimethylformamide) has been prepared by the solvothermal reaction of N,N,N′,N′‐tetrakis(4‐carboxyphenyl)biphenyl‐4,4′‐diamine (H4TCPBDA) and Zn(NO3)2?6 H2O in DMF/tBuOH. The post‐synthetic modification of SNU‐30 by the insertion of 3,6‐di(4‐pyridyl)‐1,2,4,5‐tetrazine (bpta) affords single‐crystalline {[Zn2(TCPBDA)(bpta)]?23 DMF?4 H2O}n ( SNU‐31 SC ), in which channels are divided by the bpta linkers. Interestingly, unlike its pristine form, the bridging bpta ligand in the MOF is bent due to steric constraints. SNU‐31 can be also prepared through a one‐pot solvothermal synthesis from ZnII, TCPBDA4?, and bpta. The bpta linker can be liberated from this MOF by immersion in N,N‐diethylformamide (DEF) to afford the single‐crystalline SNU‐30 SC , which is structurally similar to SNU‐30 . This phenomenon of reversible insertion and removal of the bridging ligand while preserving the single crystallinity is unprecedented in MOFs. Desolvated solid SNU‐30′ adsorbs N2, O2, H2, CO2, and CH4 gases, whereas desolvated SNU‐31′ exhibits selective adsorption of CO2 over N2, O2, H2, and CH4, thus demonstrating that the gas adsorption properties of MOF can be modified by post‐synthetic insertion/removal of a bridging ligand. 相似文献
99.
Jung‐tak Jang Hyunsoo Nah Jae‐Hyun Lee Seung Ho Moon Min Gyu Kim Dr. Jinwoo Cheon Prof. 《Angewandte Chemie (International ed. in English)》2009,48(7):1234-1238
Doped up : The incorporation of Zn2+ dopants in tetrahedral sites leads to the successful magnetism tuning of spinel metal ferrite nanoparticles (see picture). (Zn0.4Mn0.6)Fe2O4 nanoparticles exhibit the highest magnetization value among the metal ferrite nanoparticles. Such high magnetism results in the largest MRI contrast effects (r2=860 mm?1 s?1) reported to date and also huge hyperthermic effects.
100.
Tyrosine ammonia-lyase (TAL) is a recently described member of the aromatic amino acid lyase family, which also includes phenylalanine (PAL) and histidine ammonia-lyases (HAL). TAL is highly selective for L-tyrosine, and synthesizes 4-coumaric acid as a protein cofactor or antibiotic precursor in microorganisms. In this report, we identify a single active site residue important for substrate selection in this enzyme family. Replacing the active site residue His89 with Phe in TAL completely switched its substrate selectivity from tyrosine to phenylalanine, thereby converting it into a highly active PAL. When a corresponding mutation was made in PAL, the enzyme lost PAL activity and gained TAL activity. The discovered substrate selectivity switch is a rare example of a complete alteration of substrate specificity by a single point mutation. We also show that the identity of the amino acid at the switch position can serve as a guide to predict substrate specificities of annotated aromatic amino acid lyases in genome sequences. 相似文献