全文获取类型
收费全文 | 718篇 |
免费 | 16篇 |
国内免费 | 6篇 |
专业分类
化学 | 475篇 |
晶体学 | 4篇 |
力学 | 36篇 |
数学 | 136篇 |
物理学 | 89篇 |
出版年
2018年 | 9篇 |
2017年 | 16篇 |
2016年 | 14篇 |
2015年 | 13篇 |
2014年 | 19篇 |
2013年 | 32篇 |
2012年 | 28篇 |
2011年 | 41篇 |
2010年 | 18篇 |
2009年 | 25篇 |
2008年 | 14篇 |
2007年 | 26篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 9篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1985年 | 16篇 |
1984年 | 7篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1939年 | 6篇 |
1938年 | 10篇 |
1937年 | 10篇 |
1934年 | 10篇 |
1932年 | 9篇 |
1931年 | 7篇 |
1930年 | 6篇 |
1929年 | 9篇 |
1928年 | 7篇 |
1927年 | 9篇 |
1926年 | 11篇 |
1923年 | 7篇 |
1922年 | 6篇 |
1919年 | 6篇 |
1916年 | 8篇 |
1913年 | 7篇 |
1912年 | 7篇 |
1911年 | 6篇 |
1909年 | 8篇 |
1908年 | 9篇 |
排序方式: 共有740条查询结果,搜索用时 17 毫秒
1.
Zenon Moszner 《Aequationes Mathematicae》2018,92(4):617-625
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form. 相似文献
2.
3.
On the Total-Neighbor-Distinguishing Index by Sums 总被引:2,自引:0,他引:2
4.
Michał Dąbrowski Dr. Przemysław Wyrębek Dr. Damian Trzybiński Prof. Krzysztof Woźniak Prof. Karol Grela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(17):3782-3794
Robust, selective, and stable in the presence of ethylene, ruthenium olefin metathesis pre-catalyst, {[3-benzyl-1-(10-phenyl-9-phenanthryl)]-2-imidazolidinylidene}dichloro(o-isopropoxyphenylmethylene)ruthenium(II), Ru-3 , bearing an unsymetrical N-heterocyclic carbene (uNHC) ligand, has been synthesized. The initiation rate of Ru-3 was examined by ring-closing metathesis and cross-metathesis reactions with a broad spectrum of olefins, showing an unprecendented selectivity. It was also tested in industrially relevant ethenolysis reactions of olefinic substrates from renewable feedstock with very good yields and selectivities. 相似文献
5.
Tuuli A. Hakala Sarah Davies Dr. Zenon Toprakcioglu Dr. Barbara Bernardim Dr. Gonçalo J. L. Bernardes Prof. Tuomas P. J. Knowles 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(27):5965-5969
Nanoparticles are widely studied as carrier vehicles in biological systems because their size readily allows access through cellular membranes. Moreover, they have the potential to carry cargo molecules and as such, these factors make them especially attractive for intravenous drug delivery purposes. Interest in protein-based nanoparticles has recently gained attraction due to particle biocompatibility and lack of toxicity. However, the production of homogeneous protein nanoparticles with high encapsulation efficiencies, without the need for additional cross-linking or further engineering of the molecule, remains challenging. Herein, we present a microfluidic 3D co-flow device to generate human serum albumin/celastrol nanoparticles by co-flowing an aqueous protein solution with celastrol in ethanol. This microscale co-flow method resulted in the formation of nanoparticles with a homogeneous size distribution and an average size, which could be tuned from ≈100 nm to 1 μm by modulating the flow rates used. We show that the high stability of the particles stems from the covalent cross-linking of the naturally present cysteine residues within the particles formed during the assembly step. By choosing optimal flow rates during synthesis an encapsulation efficiency of 75±24 % was achieved. Finally, we show that this approach achieves significantly enhanced solubility of celastrol in the aqueous phase and, crucially, reduced cellular toxicity. 相似文献
6.
Michal Bartoš Radovan Jiřík Jiří Kratochvíla Michal Standara Zenon Starčuk jr. Torfinn Taxt 《Magnetic resonance imaging》2014
The present trend in dynamic contrast-enhanced MRI is to increase the number of estimated perfusion parameters using complex pharmacokinetic models. However, less attention is given to the precision analysis of the parameter estimates. In this paper, the distributed capillary adiabatic tissue homogeneity pharmacokinetic model is extended by the bolus arrival time formulated as a free continuous parameter. With the continuous formulation of all perfusion parameters, it is possible to use standard gradient-based optimization algorithms in the approximation of the tissue concentration time sequences. This new six-parameter model is investigated by comparing Monte-Carlo simulations with theoretically derived covariance matrices. The covariance-matrix approach is extended from the usual analysis of the primary perfusion parameters of the pharmacokinetic model to the analysis of the perfusion parameters derived from the primary ones. The results indicate that the precision of the estimated perfusion parameters can be described by the covariance matrix for signal-to-noise ratio higher than ~ 20 dB. The application of the new analysis model on a real DCE-MRI data set is also presented. 相似文献
7.
A discrete group G is amenable if there exists a finitely additive probability measure on G which is invariant under left translations and is defined on all subsets of G. It is proved that if the group is generated by two elements and is amenable then there are words being relators whose most of the consecutive pairs of the letters belong to a certain four-element set of pairs. This fact is applied to reproving non-amenability of a braid group. The same group provides an example showing that such type of condition is not su?cient for amenabilty. 相似文献
8.
9.
10.
Dr. Joice Thomas Dr. Liliana Dobrzańska Prof. Luc Van Meervelt Prof. Mario Alfredo Quevedo Prof. Krzysztof Woźniak Marcin Stachowicz Prof. Mario Smet Prof. Wouter Maes Prof. Wim Dehaen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(3):979-987
A synthetic route towards homodiselenacalix[4]arene macrocycles is presented, based on the dynamic covalent chemistry of diselenides. The calixarene inner rim is decorated with either alkoxy or tert‐butyl ester groups. Single‐crystal X‐ray analysis of two THF solvates with methoxy and ethoxy substituents reveals the high similarity of their molecular structures and alterations on the supramolecular level. In both crystal structures, solvent channels are present and differ in both shape and capacity. Furthermore, the methoxy‐substituted macrocycle undergoes a single‐crystal‐to‐single‐crystal transformation during which the molecular structure changes its conformation from 1,3‐alternate (loaded with THF/water) to 1,2‐alternate (apohost form). Molecular modelling techniques were applied to explore the conformational and energetic behaviour of the macrocycles. 相似文献