全文获取类型
收费全文 | 507篇 |
免费 | 13篇 |
国内免费 | 2篇 |
专业分类
化学 | 377篇 |
晶体学 | 2篇 |
力学 | 12篇 |
数学 | 49篇 |
物理学 | 82篇 |
出版年
2020年 | 7篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 10篇 |
2014年 | 9篇 |
2013年 | 23篇 |
2012年 | 42篇 |
2011年 | 40篇 |
2010年 | 13篇 |
2009年 | 8篇 |
2008年 | 32篇 |
2007年 | 30篇 |
2006年 | 43篇 |
2005年 | 24篇 |
2004年 | 27篇 |
2003年 | 13篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 11篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 7篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 3篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1942年 | 2篇 |
1937年 | 3篇 |
1931年 | 2篇 |
1925年 | 2篇 |
1920年 | 2篇 |
排序方式: 共有522条查询结果,搜索用时 31 毫秒
101.
Campbell CD Duguet N Gallagher KA Thomson JE Lindsay AG O'Donoghue AC Smith AD 《Chemical communications (Cambridge, England)》2008,(30):3528-3530
Cascade reaction sequences incorporating N-heterocyclic carbene-based organocatalysis have been developed that allow the direct preparation of a range of (+/-)-4-phenoxycarbonylazlactones in good isolated yields (66-84%) from the corresponding N-p-anisoyl amino acids. 相似文献
102.
Clayton HJ Harding LP Irvine JP Jeffery JC Riis-Johannessen T Laws AP Rice CR Whitehead M 《Chemical communications (Cambridge, England)》2008,(1):108-110
The reaction of a potentially tetradentate bis(pyridyl-thiazole) ligand with acetone is allosterically activated upon complexation with Cd(II) but deactivated by reaction with Cu(I), demonstrating metal-specific allosteric controlled reactivity. 相似文献
103.
Wang H Obenauer-Kutner L Lin M Huang Y Grace MJ Lindsay SM 《Journal of the American Chemical Society》2008,130(26):8154-8155
The glycosylation state of individual antibodies was imaged using an atomic force microscope with a probe modified with lectins and an image acquisition system that permits simultaneous acquisition of sample topography data along with a map of lectin binding sites. 相似文献
104.
Density Functional calculations have been performed at the uB3LYP and uBP86 levels to calculate the one-electron redox potentials for a series of small models based on the diiron hydrogenase enzymes in the presence of acetonitrile (MeCN). The solvation effects in MeCN are incorporated via a self-consistent reaction field (SCRF) using the polarized continuum model (PCM). The calculated redox potentials reproduce the trends in experimental data with an average error of only 0.12 V using the BP86 functional, whereas comparing results with the B3LYP functional require a systematic shift of -0.82 and -0.53 V for oxidation and reduction, respectively. The bonding orbitals and d-electron populations were examined using Mulliken population analysis, and the results were used to rationalize the calculated and observed redox potentials. These studies demonstrate that the redox potential correlates with the empirical spectrochemical series for the ligands, as well as with the amount of electron density donated by the ligand onto the Fe centers. 相似文献
105.
We report polarized infrared absorption spectra of water isotopologues isolated in solid parahydrogen (pH2) which reveal the crystal field induced splittings of the 1 01<--0 00 R(0) lines in the nu1 HDO, nu3 D2O, nu3 HDO, and nu3 H2O fundamental bands. For annealed pH2 solids, these spectra also reveal a strong alignment of the hexagonal-close-packed crystallites' c axes with the deposition substrate surface normal. This alignment effect explains our failure to detect the parallel-polarized components of these R(0) lines in spectra of pH2 solids produced on a transparent deposition substrate [M. E. Fajardo et al., J. Mol. Struct. 695, 111 (2004)]. This lesson applies more generally to comparison of solid pH2 spectra obtained in different laboratories. The spectra are consistent with water monomers existing in solid pH2 as very slightly hindered rotors. The individual components of the R(0) absorption lines show a Lorentzian lineshape, with vibrational depopulation the most important source of line broadening. 相似文献
106.
Carcinogenic Chromium(VI) Compounds Formed by Intracellular Oxidation of Chromium(III) Dietary Supplements by Adipocytes 下载免费PDF全文
Dr. Lindsay E. Wu Dr. Aviva Levina Prof. Hugh H. Harris Dr. Zhonghou Cai Dr. Barry Lai Dr. Stefan Vogt Prof. David E. James Prof. Peter A. Lay 《Angewandte Chemie (International ed. in English)》2016,55(5):1742-1745
Chromium(III) nutritional supplements are widely consumed for their purported antidiabetic activities. X‐ray fluorescence microscopy (XFM) and X‐ray absorption near‐edge structure (XANES) studies have now shown that non‐toxic doses of [Cr3O(OCOEt)6(OH2)3]+ ( A ), a prospective antidiabetic drug that undergoes similar H2O2 induced oxidation reactions in the blood as other Cr supplements, was also oxidized to carcinogenic CrVI and CrV in living cells. Single adipocytes treated with A had approximately 1 μm large Cr hotspots containing CrIII, CrV, and CrVI (primarily CrVI thiolates) species. These results strongly support the hypothesis that the antidiabetic activity of CrIII and the carcinogenicity of CrVI compounds arise from similar mechanisms involving highly reactive CrVI and CrV intermediates, and highlight concerns over the safety of CrIII nutritional supplements. 相似文献
107.
Synthetic routes for the preparation of O-acetyl-ADP-ribose and two novel non-hydrolyzable analogs containing an N-acetyl are described and shown to interact with the macro domain of histone protein H2A1.1. 相似文献
108.
Ronson TK Adams H Harding LP Pope SJ Sykes D Faulkner S Ward MD 《Dalton transactions (Cambridge, England : 2003)》2007,(10):1006-1022
A set of three potentially bridging ligands containing two tridentate chelating N,N',O-donor (pyrazole-pyridine-amide) donors separated by an o, m, or p-phenylene spacer has been prepared and their coordination chemistry with lanthanide(III) ions investigated. Ligand L(1) (p-phenylene spacer) forms complexes with a 2:3 M:L ratio according to the proportions used in the reaction mixture; the Ln(2)(L(1))(3) complexes contain two 9-coordinate Ln(III) centres with all three bridging ligands spanning both metal ions, and have a cylindrical (non-helical) 'mesocate' architecture. The 1:1 complexes display a range of structural types depending on the conditions used, including a cyclic Ln(4)(L(1))(4) tetranuclear helicate, a Ln(2)(L(1))(2) dinuclear mesocate, and an infinite one-dimensional coordination polymer in which metal ions and bridging ligands alternate along the sequence. ESMS studies indicate that the 1:1 complexes form a mixture of oligonuclear species {Ln(L(1))}(n) in solution (n up to 5) which are likely to be cyclic helicates. In contrast, ligands L(2) and L(3) (with o- and m-phenylene spacers, respectively) generally form dinuclear Ln(2)L(2) Ln(III) complexes in which the two ligands may be arranged in a helical or non-helical architecture about the two metal ions. These complexes also contain an additional exogenous bidentate bridging ligand, either acetate or formate, which has arisen from hydrolysis of solvent molecules promoted by the Lewis-acidity of the Ln(III) ions. Luminescence studies on some of the Nd(III) complexes showed that excitation into ligand-centred pi-pi* transitions result in the characteristic near-infrared luminescence from Nd(III) at 1060 nm. 相似文献
109.
Crystal polymorphism of protein GB1 examined by solid-state NMR spectroscopy and X-ray diffraction 总被引:1,自引:0,他引:1
Schmidt HL Sperling LJ Gao YG Wylie BJ Boettcher JM Wilson SR Rienstra CM 《The journal of physical chemistry. B》2007,111(51):14362-14369
The study of micro- or nanocrystalline proteins by magic-angle spinning (MAS) solid-state NMR (SSNMR) gives atomic-resolution insight into structure in cases when single crystals cannot be obtained for diffraction studies. Subtle differences in the local chemical environment around the protein, including the characteristics of the cosolvent and the buffer, determine whether a protein will form single crystals. The impact of these small changes in formulation is also evident in the SSNMR spectra; however, the changes lead only to correspondingly subtle changes in the spectra. Here, we demonstrate that several formulations of GB1 microcrystals yield very high quality SSNMR spectra, although only a subset of conditions enable growth of single crystals. We have characterized these polymorphs by X-ray powder diffraction and assigned the SSNMR spectra. Assignments of the 13C and 15N SSNMR chemical shifts confirm that the backbone structure is conserved, indicative of a common protein fold, but side chain chemical shifts are changed on the surface of the protein, in a manner dependent upon crystal packing and electrostatic interactions with salt in the mother liquor. Our results demonstrate the ability of SSNMR to reveal minor structural differences among crystal polymorphs. This ability has potential practical utility for studying the formulation chemistry of industrial and therapeutic proteins, as well as for deriving fundamental insights into the phenomenon of single-crystal growth. 相似文献
110.