全文获取类型
收费全文 | 265篇 |
免费 | 13篇 |
专业分类
化学 | 222篇 |
力学 | 2篇 |
数学 | 7篇 |
物理学 | 47篇 |
出版年
2023年 | 2篇 |
2021年 | 1篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 10篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 7篇 |
2009年 | 4篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 16篇 |
2005年 | 19篇 |
2004年 | 14篇 |
2003年 | 7篇 |
2002年 | 11篇 |
2001年 | 3篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 5篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1979年 | 7篇 |
1976年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有278条查询结果,搜索用时 140 毫秒
1.
2.
3.
Limiting the Number of Potential Binding Modes by Introducing Symmetry into Ligands: Structure‐Based Design of Inhibitors for Trypsin‐Like Serine Proteases 下载免费PDF全文
Norbert Furtmann Daniela Häußler Tamara Scheidt Dr. Marit Stirnberg Prof. Dr. Torsten Steinmetzer Prof. Dr. Jürgen Bajorath Prof. Dr. Michael Gütschow 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(2):610-625
In the absence of X‐ray data, the exploration of compound binding modes continues to be a challenging task. For structure‐based design, specific features of active sites in different targets play a major role in rationalizing ligand binding characteristics. For example, dibasic compounds have been reported as potent inhibitors of various trypsin‐like serine proteases, the active sites of which contain several binding pockets that can be targeted by cationic moieties. This results in several possible orientations within the active site, complicating the binding mode prediction of such compounds by docking tools. Therefore, we introduced symmetry in bi‐ and tribasic compounds to reduce conformational space in docking calculations and to simplify binding mode selection by limiting the number of possible pocket occupations. Asymmetric bisbenzamidines were used as starting points for a multistage and structure‐guided optimization. A series of 24 final compounds with either two or three benzamidine substructures was ultimately synthesized and evaluated as inhibitors of five serine proteases, leading to potent symmetric inhibitors for the pharmaceutical drug targets matriptase, matriptase‐2, thrombin and factor Xa. This study underlines the relevance of ligand symmetry for chemical biology. 相似文献
4.
Anna V. Davies Keegan P. Fitzpatrick Rick C. Betori Karl A. Scheidt 《Angewandte Chemie (International ed. in English)》2020,59(23):9143-9148
As a key element in the construction of complex organic scaffolds, the formation of C?C bonds remains a challenge in the field of synthetic organic chemistry. Recent advancements in single‐electron chemistry have enabled new methods for the formation of various C?C bonds. Disclosed herein is the development of a novel single‐electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium in situ followed by a radical–radical coupling was made possible merging N‐heterocyclic carbene (NHC) and photoredox catalysis. The utility of this protocol in synthesis was showcased in the late‐stage functionalization of a variety of pharmaceutical compounds. Preliminary investigations using chiral NHCs demonstrate that enantioselectivity can be achieved, showcasing the advantages of this protocol over alternative methodologies. 相似文献
5.
Dipl.‐Chem. Hilke Wolf Dr. Dirk Leusser Dr. Mads R. V. Jørgensen Dr. Regine Herbst‐Irmer Dr. Yu‐Sheng Chen Dr. Ernst‐Wilhelm Scheidt Prof. Dr. Wolfgang Scherer Prof. Dr. Bo B. Iversen Prof. Dr. Dietmar Stalke 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):7048-7053
In this contribution, the solid‐state low‐temperature phase structure of [2,2]‐paracyclophane is unambiguously characterised by single‐crystal X‐ray analysis. Additionally, a heat capacity measurement was undertaken, which proves the existence of a λ‐type phase transition at 45 K, a transition that is connected with the formation of a secondary Cp/T feature at 60 K. The low‐temperature phase (<45 K) crystallises in the lower symmetry space group P$\bar 4$ n2, whereas the high‐temperature phase (>60 K) crystallises in space group P42/mnm. This proves what has been postulated both by experimental and theoretical chemists but has repeatedly been dismissed as speculation many times. 相似文献
6.
7.
8.
Wolfgang Scherer Prof. Dr. Christoph Hauf Dipl.‐Phys. Manuel Presnitz Dipl.‐Phys. Ernst‐Wilhelm Scheidt Dr. Georg Eickerling Dr. Volker Eyert Dr. Rolf‐Dieter Hoffmann Dr. Ute C. Rodewald Dipl.‐Ing. Adrienne Hammerschmidt Dr. Christian Vogt Dr. Rainer Pöttgen Prof. Dr. 《Angewandte Chemie (International ed. in English)》2010,49(9):1578-1582
9.
Rick C. Betori Catherine M. May Karl A. Scheidt 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16642-16646
Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value‐added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single‐flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations. 相似文献
10.
Low pressure steam turbine blades are subjected to high static and dynamic loads during operation. These loads strongly depend on the turbine's rotational speed, leading to entirely new load conditions. To avoid high dynamic stresses due to the forced vibrations, a coupling of the blades, such as shrouds or snubber coupling, is applied to reinforce the structure. In this work the influence of the rotational speed on the vibration behavior of shrouded blades is investigated. Two fundamental phenomena are considered: the stress stiffening and the spin softening effect. Both effects are caused by centrifugal forces and affect the structural mechanical properties, i.e. the stiffness matrix K , of the rotating system. Since the rotational speed Ω appears quadratically, it is possible to derive the stiffness matrix as a second order matrix polynomial in Ω2 [3]. In the case of shrouded blades, contact forces between neighboring blades must be taken into account. The contact status and the pressure distribution in particular is strongly influenced by the rotational speed, respectively, centrifugal forces, caused by the untwisting and radial deformation of the blades. For the calculation, a three dimensional structural mechanical model including a spatial contact model is considered. The solution of the nonlinear equations of motion is based on the well known Multiharmonic Balance Method [2]. Here, the nonlinear forces are computed in the time domain and transferred in the frequency domain by the use of the Fast Fourier Transformation (FFT), also known as the Alternating Frequency Time method (AFT) [1]. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献