全文获取类型
收费全文 | 202篇 |
免费 | 2篇 |
专业分类
化学 | 162篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 22篇 |
物理学 | 18篇 |
出版年
2023年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2013年 | 5篇 |
2012年 | 5篇 |
2011年 | 9篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 7篇 |
2006年 | 8篇 |
2005年 | 11篇 |
2004年 | 12篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1966年 | 1篇 |
1909年 | 1篇 |
1905年 | 2篇 |
1903年 | 1篇 |
1902年 | 1篇 |
1899年 | 3篇 |
1897年 | 1篇 |
1896年 | 3篇 |
1894年 | 6篇 |
1892年 | 2篇 |
1891年 | 1篇 |
1890年 | 1篇 |
1889年 | 4篇 |
1886年 | 2篇 |
1885年 | 3篇 |
1883年 | 2篇 |
1882年 | 2篇 |
排序方式: 共有204条查询结果,搜索用时 15 毫秒
51.
Kristof Seubert Dominik Böhme Jutta Kösters Wei‐Zheng Shen Eva Freisinger Prof. Dr. Jens Müller 《无机化学与普通化学杂志》2012,638(11):1761-1767
Metal‐mediated base pairs can be used to insert metal ions into nucleic acids at precisely defined positions. As structural data on the resulting metal‐modified DNA are scarce, appropriate model complexes need to be synthesized and structurally characterized. Accordingly, the molecular structures of nine transition metal complexes of N‐methyl‐2, 2'‐dipicolylamine (dipic) are reported. In combination with an azole‐containing artificial nucleoside, this tridentate ligand had recently been used to generate metal‐mediated base pairs (Chem. Commun. 2011 , 47, 11041–11043). The PdII and PtII complexes reported here confirm that the formation of planar complexes (as required for a metal‐mediated base pair) comprising N‐methyl‐2, 2'‐dipicolylamine is possible. Two HgII complexes with differing stoichiometry indicate that a planar structure might also be formed with this metal ion, even though it is not favored. In the complex [Ag2(dipic)2](ClO4)2, the two AgI ions are located close to one another with an Ag ··· Ag distance of 2.9152(3) Å, suggesting the presence of a strong argentophilic interaction. 相似文献
52.
Jurgen Sleven Thomas Cardinaels Koen Binnemans Daniel Guillon Bertrand Donnio 《Liquid crystals》2013,40(11):1425-1433
This paper deals with the synthesis of vanadyl phthalocyanines substituted with eight alkoxy chains in the peripheral (2, 3, 9, 10, 16, 17, 23, 24) positions. The alkoxy chain length was varied, and octa-octyloxy (C8H17O), octa-dodecyloxy (C12H25O) and octa-hexadecyloxy (C16H33O) substituted vanadyl phthalocyanine complexes were prepared. Studies by polarizing optical microscopy and small angle X-ray diffraction (XRD) revealed that all the complexes are liquid crystalline and that these metallomesogens exhibit a columnar phase. The symmetry of the 2D lattice is rectangular, with a c 2 mm space group, as determined by the indexation of the XRD reflections; hence a rectangular columnar phase (Colr) was assigned. A double periodicity, although weak, along the axis of the columns was found, which indicates some degree of pairing or dimerization. A tentative explanation based on an antiferroelectric stacking is given. Transition enthalpies were determined by differential scanning calorimetry. The compounds start to decompose above 250°C before reaching the clearing temperatures. A significant bathochromic shift of the Q-band in the UV/Vis spectra of the vanadyl complexes compared with the metal-free ligands and other metallophthalocyanines (M=CoII, NiII, CuII, ZnII) was also observed. 相似文献
53.
Jurgen Sleven Thomas Cardinaels Koen Binnemans Daniël Nelis Jules Mullens Dirk Hinz-Hübner 《Liquid crystals》2013,40(2):143-148
Cobalt (II) phthalocyanines substituted with eight alkoxy chains in the peripheral (2, 3, 9, 10, 16, 17, 23, 24) positions were prepared. The alkoxy chain length was varied between n-butyloxy (C4H9O) and n-octadecyloxy (C18H37O). Studies by polarizing optical microscopy and high temperature X-ray diffraction revealed that all the complexes are liquid crystalline and that they exhibit a hexagonal columnar mesophase (Colh). Transition enthalpies were determined by differential scanning calorimetry. The clearing point could only be observed for compounds with a chain length longer than C13H27O. Both the melting and clearing points decrease with increasing chain length. The transition temperatures of these discotic metallomesogens are higher than those of the corresponding metal-free phthalocyanines, but are comparable with those of the corresponding copper (II) compounds. The thermal decomposition of the compounds was studied by thermogravimetry. 相似文献
54.
55.
56.
The on-line-coupling of ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) is a powerful tool for the determination of bromate in drinking waters. The use of a high-capacity and high-performance anion-exchanger combined with an NH4NO3-based elution system allows the determination of bromate in almost every water sample without any sample pretreatment. The method detection limits in the water samples investigated are 50 to 65 ng/L or 44 to 58 pg bromate, respectively. Considering sensivity as well as imprecision (5% at 500 ng/L bromate) and short analysis times (8 to 15 min per sample including sample uptake), the described IC-ICP-MS coupling is well suited for precise routine analyses of bromate in drinking waters at the sub μg/L level. 相似文献
57.
This paper demonstrates the special potential of vibrational NIR FT Raman microspectroscopy for the study of fennel fruits, chamomile inflorescence and curcuma roots to obtain detailed information about their microstructure and chemical composition. Microscopic Raman maps of fennel fruits demonstrate that anethole, which is the main essential oil component, is present in the whole mericarp with highest concentration at the top of the fruit. In situ measurements obtained of the essential oil cells are dominated by two bands observed at 1657 cm(-1) and 1609 cm(-1) which are characteristic for anethole. Raman images of chamomile inflorescence show that spiroethers, identified by significant bands between 2150 and 2250 cm(-1), are accumulated in the middle part of the flower head. Due to the intense curcumin bands in the Raman spectrum of curcuma root, the distribution of this dyeing substance can be clearly determined; highest concentration of curcumin was observed on the core of the root. 相似文献
58.
MA Smith M Coinçon A Paschos B Jolicoeur P Lavallée J Sygusch C Baron 《Chemistry & biology》2012,19(8):1041-1048
Secretion systems translocate virulence factors of many bacterial pathogens, enabling their survival inside the host organism. Consequently, inhibition strongly attenuates pathogenicity and can be considered a target for novel antimicrobial drugs. The type IV secretion system (T4SS) of the intracellular pathogen Brucella is a prerequisite for its virulence, and in this work we targeted the interactions of the?essential assembly factor protein, VirB8, using small-molecule inhibitors. High-throughput screening identified several potent and specific inhibitors, and the target-binding site of these inhibitors was identified by X-ray crystallography, in?silico docking, and analysis of the derivates of the inhibitor B8I-2. VirB8 interaction inhibitors bind to a surface groove opposite to the dimerization interface, and by varying the binding-site residues, we were able to determine which residues are required for inhibitor activity. E115 and K182 were found to be especially important, and changes at R114, Y229, and L151 also reduced inhibitor efficiency. 相似文献
59.
The authors consider the stationary relativistic coupled system consisting of Vlasov’s equation for the distribution function of charged particles and Maxwell''s equations for the electric and magnetic fields of a plasma. With different tools of nonlinear functional analysis the existence of solutions is proved, in which, according to different geometries and symmetries, the distribution function depends on one, two or three independent integrals of the motion. 相似文献
60.