全文获取类型
收费全文 | 306篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 234篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 40篇 |
物理学 | 34篇 |
出版年
2023年 | 5篇 |
2022年 | 8篇 |
2021年 | 26篇 |
2020年 | 10篇 |
2019年 | 16篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 13篇 |
2015年 | 16篇 |
2014年 | 11篇 |
2013年 | 14篇 |
2012年 | 21篇 |
2011年 | 16篇 |
2010年 | 14篇 |
2009年 | 18篇 |
2008年 | 24篇 |
2007年 | 14篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 16篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 1篇 |
1999年 | 3篇 |
1997年 | 1篇 |
1994年 | 3篇 |
排序方式: 共有316条查询结果,搜索用时 31 毫秒
71.
Alessia Garavaglia Alessia Moiana Stefano Camnasio Daniele Bolognini Roberto Papait Dorotea Rigamonti Elena Cattaneo 《BMC neuroscience》2010,11(1):7
Background
There is an urgent need of neuronal cell models to be applied to high-throughput screening settings while recapitulating physiological and/or pathological events occurring in the Central Nervous System (CNS). Stem cells offer a great opportunity in this direction since their self renewal capacity allows for large scale expansion. Protocols for directed differentiation also promise to generate populations of biochemically homogenous neuronal progenies. NS (Neural Stem) cells are a novel population of stem cells that undergo symmetric cell division in monolayer and chemically defined media, while remaining highly neurogenic. 相似文献72.
Andreotti A Bonaduce I Colombini MP Ribechini E 《Rapid communications in mass spectrometry : RCM》2004,18(11):1213-1220
Two analytical methods based on mass spectrometry were used in the characterisation of constituents of natural indigo prepared from the leaves of Indigofera tinctoria, and of shellfish purple prepared from the hypobranchial glandular secretions of Murex trunculus, following old recipes. On-line pyrolysis gas chromatography in the presence of hexamethyldisilazane followed by mass spectrometric analysis (Py-silylation/GC/MS), and direct exposure mass spectrometry (DE-MS), were used. Extensive fragmentation of indigoid dyes was obtained by Py-silylation/GC/MS. The following molecular markers were highlighted, which are useful for identification purposes: 1,2-dihydro-3H-indol-3-one for indigoid dyes, 1,3-dihydro-2H-indol-2-one for indirubine, and 6-bromo-1,2-dihydro-3H-indol-3-one for shellfish purple. Using DE-MS, 6,6'dibromoindigotine, monobromoindigotine and indigotine were identified as the main components, and the presence of tyrindoxyl, one of the dye precursors, was also assessed. 相似文献
73.
Isabel M. Gomez-Monterrey Alessia Bertamino Maria V. Diurno Paolo Grieco 《Tetrahedron》2006,62(34):8083-8088
A novel synthetic route of diaza-bridged heterocycles based on natural 3,9-diazabicyclo[3.3.1]non-6-ene scaffold has been accomplished. The synthetic approach consists of a Pictet-Spengler condensation of the l-Dopa-OMe with an appropriate aldehyde, Fmoc-Aa-H, followed by intramolecular lactamization. This approach generated two configurationally distinct products (cis and trans-isomers), increasing the stereochemical diversity of these compounds. The synthesized compounds are potentially useful in the discovery of novel pharmacologically active compounds. 相似文献
74.
The Carlo Alberto Canal connects Bormida and Tanaro rivers in Piedmont (ITALY). It was created for irrigation purposes but since its waters are suspected to be polluted, a sampling campaign was performed by the ARPA of Alessandria. The physico-chemical parameters analysed along 3 years (1998-2000) were investigated by multivariate chemometric methods. PCA showed that the waters situation depends heavily on the sampling period. Also a Kohonen self-organising map confirmed the clustering observed, providing insights into the causes of the clusterisation. New samplings are now being performed and a larger set of environmental variables is determined on each sample. 相似文献
75.
Colombini MP Carmignani A Modugno F Frezzato F Olchini A Brecoulaki H Vassilopoulou V Karkanas P 《Talanta》2004,63(4):839-848
The materials used in the decoration of three painted astragaloi (knucklebones) from the Koroneia cave (Greece) were investigated by means of sequential application of non-destructive and destructive techniques: optical microscopy, environmental scanning electron microscopy coupled with X-ray microanalysis (ESEM-EDX), Fourier transform infrared spectroscopy (FTIR) with micro-attenuated total reflection (μ-ATR) technique, high performance liquid chromatography (HPLC) coupled with UV-fluorescence and gas chromatography-mass spectrometry (GC-MS) were used.The main results highlighted that the three astragaloi were prepared with a ground of ochre or iron clay and painted with a proteinaceous matter such as binder egg tempera. Both FTIR and GC-MS agree in the detection of lipids that can be related to egg. Organic dyestuffs identified as madder lake and shellfish purple were used together with inorganic pigments. 相似文献
76.
Huang Q Fazio A Dai G Campo MA Larock RC 《Journal of the American Chemical Society》2004,126(24):7460-7461
A novel palladium migration methodology for the synthesis of complex fused polycycles has been developed. This process involves 1,4-palladium alkyl to aryl migrations via through-space C-H activation, followed by intramolecular arylation or an intermolecular Heck reaction providing a very efficient way to synthesize fused ring systems. 相似文献
77.
Vesna Radulović Alessia Bacchi Giancarlo Pelizzi Dušan Sladić Ilija Brčeski Katarina Andjelković 《Monatshefte für Chemie / Chemical Monthly》2006,137(6):681-691
Summary. Complexes of Pt(II), Pd(II), and Ni(II) with the condensation derivative of 2-(diphenylphosphino)benzaldehyde and semioxamazide
were synthesized, characterized, and their antimicrobial activity was evaluated. The ligand and the complexes were characterized
by spectroscopic methods with the particular accent on NMR spectral analysis. For the palladium(II) complex, the crystal structure
was determined by X-ray analysis. In all the complexes the ligand is coordinated as a tridentate via a P, N, O donor set. The Pd(II) and Pt(II) complexes have a square planar geometry, whereas the geometry of the Ni(II) complex
is tetrahedral. The ligand showed antibacterial and antifungal activity, which was enhanced upon complexation. 相似文献
78.
79.
80.