全文获取类型
收费全文 | 190篇 |
免费 | 18篇 |
专业分类
化学 | 167篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 22篇 |
物理学 | 16篇 |
出版年
2023年 | 9篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 6篇 |
2013年 | 3篇 |
2012年 | 5篇 |
2011年 | 8篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 12篇 |
2007年 | 13篇 |
2006年 | 6篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 12篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1971年 | 2篇 |
1968年 | 2篇 |
排序方式: 共有208条查询结果,搜索用时 46 毫秒
41.
Polyelectrolyte microcapsules composed by using the LbL technique on stabilized RBC as templates were coated with up to ten layer pairs of trypsin/PSS or trypsin/alginate. The trypsin layer growth was confirmed by particle electrophoresis, confocal laser scanning microscopy, flow cytometry, and protein determination according to Lowry. In the coating series with trypsin/PSS, the amount of immobilized enzyme was larger than that with trypsin/alginate. The enzyme immobilization led to activity reduction of up to 90% compared to that of the same enzyme amount in the solution. No significant differences between the activities of trypsin immobilized in combination with PSS and with alginate were found. 相似文献
42.
43.
44.
Adrian E. Ion Eike T. Spielberg Lorenzo Sorace Axel Buchholz Winfried Plass 《Solid State Sciences》2009,11(4):766-771
Reaction of the copper precursor [Cu(MeOsaltn)(H2O)] (H2MeOsaltn = N,N′-bis(3-methoxysalicylidene)-1,3-diaminopropane) with Ln(NO3)3·6H2O (Ln = Sm and Tb) and pyrazine-2,3-dicarboxylic acid (H2pyrdic) results in the formation of 1D zigzag chains with the general formula of [Cu(MeOsaltn)Ln(NO3)(pyrdic)]n·nDMF. X-ray crystal structures reveal that the samarium and terbium compounds are isostructural and crystalize in the orthorhombic space group Pbcn. The chains are composed of heterodinuclear copper–lanthanide building blocks which are linked by the pyrazine-2,3-dicarboxylate bridging units. Temperature-dependent susceptibility measurements indicate antiferromagnetic exchange interactions for the samarium–copper chain whereas for the terbium–copper compound ferromagnetic interactions are observed. 相似文献
45.
Granitzka M Pöppler AC Schwarze EK Stern D Schulz T John M Herbst-Irmer R Pandey SK Stalke D 《Journal of the American Chemical Society》2012,134(2):1344-1351
Various 2-thienyllithium derivatives were investigated in the solid state by X-ray diffraction and in solution by 2D NMR experiments. The determined structures of [(Et(2)O)Li(C(4)H(3)S)](4) (1), [(THF)(2)Li(C(4)H(3)S)](2) (2), [(DME)Li(C(4)H(3)S)](2) (3), [(TMEDA)Li(C(4)H(3)S)](2) (4), and [(PMDETA)Li(C(4)H(3)S)] (5) (DME = 1,2-dimethoxyethane, TMEDA = N,N,N',N'-tetramethylethylene-1,2-diamine, and PMDETA = N,N,N',N",N"-pentamethyldiethylenetriamine) were solved in nondonating toluene and provide firm ground for diffusion-ordered NMR spectroscopy as well as heteronuclear Overhauser enhancement NMR spectroscopy. The distance relation of nuclear Overhauser effects with a factor of r(-6) is employed to gain further insight into the aggregation degree of 1-5 in solution. Comparison of the slope provided by the linear region of the buildup curves and of the ∑r(-6) calculated distances from the crystal structures offers a handle to judge the structure retention versus conversion in solution. The structures of 3-5 are maintained in toluene solution. The data of 2, however, indicate a partial dissociation or a rapid exchange between the vertices of a tetrameric core and free THF molecules. Auxiliary exchange spectroscopy investigations showed that the signals of the nitrogen donor base containing compounds 4 and 5 exchange with the signals of nonlithiated thiophene. This is explained by exchange of the deuterium by a hydrogen atom via lithiation of toluene molecules. 相似文献
46.
47.
The Scaffold Design of Trivalent Chelator Heads Dictates Affinity and Stability for Labeling His‐tagged Proteins in vitro and in Cells
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Karl Gatterdam Eike F. Joest Dr. Volker Gatterdam Prof. Dr. Robert Tampé 《Angewandte Chemie (International ed. in English)》2018,57(38):12395-12399
Small chemical/biological interaction pairs are at the forefront in tracing protein function and interaction at high signal‐to‐background ratios in cellular pathways. However, the optimal design of scaffold, linker, and chelator head still deserve systematic investigation to achieve the highest affinity and kinetic stability for in vitro and especially cellular applications. We report on a library of N‐nitrilotriacetic acid (NTA)‐based multivalent chelator heads (MCHs) built on linear, cyclic, and dendritic scaffolds and compare these with regard to their binding affinity and stability for the labeling of cellular His‐tagged proteins. Furthermore, we describe a new approach for tracing cellular target proteins at picomolar probe concentrations in cells. Finally, we outline fundamental differences between the MCH scaffolds and define a cyclic trisNTA chelator that displays the highest affinity and kinetic stability of all reported reversible, low‐molecular‐weight interaction pairs. 相似文献
48.
A rigorous and generally applicable method for computing solid-liquid coexistence is presented. The method overcomes some of the technical difficulties associated with other solid-liquid simulation procedures and can be implemented within either a molecular dynamics or Monte Carlo framework. The method consists of three steps: First, relative Gibbs free energy curves are created for the solid and liquid phases using histogram reweighting. Next, the free energy difference between the solid and liquid phases is evaluated at a single state point by integrating along a pseudosupercritical transformation path that connects the two phases. Using this result, the solid and liquid free energy curves are referenced to a common point, allowing a single coexistence point to be determined. Finally, Gibbs-Duhem integration is used to determine the full coexistence curve. To evaluate its utility, this method is applied to the Lennard-Jones and NaCl systems. Results for solid-liquid coexistence agree with previous calculations for these systems. In addition, it is shown that the NaCl model does not correctly describe solid-liquid coexistence at high pressures. An analysis of the accuracy of the method indicates that the results are most sensitive to the transformation free energy calculation. 相似文献
49.
Solid-state 31P NMR spectroscopy was applied to measure the isotropic chemical shifts, chemical shift anisotropies and asymmetry parameters of three phosphorylated amino acids, O-phospho-L-serine, O-phospho-L-threonine and O-phospho-L-tyrosine. The cross-polarization buildup rates and longitudinal relaxation times of 31P and 1H were-determined and compared with the values measured for a triphosphate (GppCH2p) bound to a crystalline protein (Ras). It is shown that the phosphorylated amino acids are well-suited model compounds, e.g. for the optimization of experiments on crystalline proteins. Two-dimensional exchange experiments on O-phospho-L-tyrosine indicate the existence of an exchange between the two different conformations of the molecule. 相似文献
50.
The scope of substrate-controlled diastereoselective hydroborations can be considerably enhanced by a boron-zinc exchange reaction, providing organozinc derivatives that react with a broad range of electrophiles. Even normally unreactive boronic esters, obtained by Rh-catalyzed hydroboration with catecholborane, react readily with iPr2Zn providing the corresponding zinc reagents in high diastereoselectivity. 相似文献