全文获取类型
收费全文 | 2785篇 |
免费 | 126篇 |
国内免费 | 19篇 |
专业分类
化学 | 2011篇 |
晶体学 | 19篇 |
力学 | 58篇 |
数学 | 450篇 |
物理学 | 392篇 |
出版年
2023年 | 21篇 |
2022年 | 23篇 |
2021年 | 37篇 |
2020年 | 49篇 |
2019年 | 45篇 |
2018年 | 43篇 |
2017年 | 36篇 |
2016年 | 95篇 |
2015年 | 81篇 |
2014年 | 85篇 |
2013年 | 155篇 |
2012年 | 179篇 |
2011年 | 197篇 |
2010年 | 104篇 |
2009年 | 111篇 |
2008年 | 189篇 |
2007年 | 196篇 |
2006年 | 200篇 |
2005年 | 152篇 |
2004年 | 136篇 |
2003年 | 89篇 |
2002年 | 115篇 |
2001年 | 66篇 |
2000年 | 63篇 |
1999年 | 38篇 |
1998年 | 34篇 |
1997年 | 31篇 |
1996年 | 39篇 |
1995年 | 26篇 |
1994年 | 30篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 24篇 |
1990年 | 22篇 |
1989年 | 14篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1982年 | 12篇 |
1980年 | 7篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1971年 | 5篇 |
1963年 | 4篇 |
1962年 | 4篇 |
排序方式: 共有2930条查询结果,搜索用时 31 毫秒
121.
A new method for the simultaneous determination of barbital and thiobarbituric acid by derivative spectrophotometry is proposed. The method allows the resolution of mixtures of the two components over the concentration ranges 0.37–4.70 μg/ml (barbital) and 0.40–4.50 μg/ml (thiobarbituric acid) provided the ratio between their concentrations does not exceed 5:1. It was applied to the determination of the two compounds in synthetic samples and blood serum. 相似文献
122.
Sara Bertuzzi Dr. Ana Gimeno Reyes Núñez-Franco Dr. Ganeko Bernardo-Seisdedos Sandra Delgado Dr. Gonzalo Jiménez-Osés Dr. Oscar Millet Prof. Dr. Jesús Jiménez-Barbero Dr. Ana Ardá 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(67):15643-15653
The interaction of human galectin-1 with a variety of oligosaccharides, from di-(N-acetyllactosamine) to tetra-saccharides (blood B type-II antigen) has been scrutinized by using a combined approach of different NMR experiments, molecular dynamics (MD) simulations, and isothermal titration calorimetry. Ligand- and receptor-based NMR experiments assisted by computational methods allowed proposing three-dimensional structures for the different complexes, which explained the lack of enthalpy gain when increasing the chemical complexity of the glycan. Interestingly, and independently of the glycan ligand, the entropy term does not oppose the binding event, a rather unusual feature for protein-sugar interactions. CLEANEX-PM and relaxation dispersion experiments revealed that sugar binding affected residues far from the binding site and described significant changes in the dynamics of the protein. In particular, motions in the microsecond-millisecond timescale in residues at the protein dimer interface were identified in the presence of high affinity ligands. The dynamic process was further explored by extensive MD simulations, which provided additional support for the existence of allostery in glycan recognition by human galectin-1. 相似文献
123.
Juan Amaro-Gahete Prof. Anna M. Kaczmarek Prof. Dolores Esquivel Prof. César Jiménez-Sanchidrián Prof. Pascal Van Der Voort Prof. Francisco J. Romero-Salguero 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(27):6823-6830
Graphene-based materials exhibit outstanding physical properties and so are potentially applicable in a great variety of fields. Unlike their corresponding oxides, graphite and graphene are not prone to functionalization. Diels–Alder reactions are among the scarce reactions that they can occur without disrupting their conjugated sp2 systems. Herein, the reaction between graphite and 3,6-di(2-pyridyl)-1,2,4,5-tetrazine under different conditions affords several graphene-based materials consisting of dipyridylpyridazine-functionalized few-layer graphene, multilayer graphene and graphite, the sheets of which act as ligands for the grafting of a europium complex. These three materials show strong red emission under 365 nm UV radiation. Their emitting particles can be visualized by confocal microscopy. The rich coordination chemistry of dipyridylpyridazine ligands has potential novel properties for similarly functionalized graphene-based materials grafted with other metal complexes. 相似文献
124.
125.
126.
Fabio Drucker David Richeson Jim Wiseman 《Journal of Dynamics and Differential Equations》2016,28(2):301-315
We consider shift spaces in which elements of the alphabet may overlap nontransitively. We define a notion of entropy for such spaces and show that it is equal to a limit of entropies of standard (non-overlapping) shifts when the underlying shift is of finite type. When a shift space with overlaps arises as a model for a discrete dynamical system with a finite set of overlapping neighborhoods, the entropy gives a lower bound for the topological entropy of the dynamical system. 相似文献
127.
David Alonso-Gutiérrez Bernardo González Merino C. Hugo Jiménez Rafael Villa 《Journal of Geometric Analysis》2018,28(2):1182-1201
We extend the notion of John’s ellipsoid to the setting of integrable log-concave functions. This will allow us to define the integral ratio of a log-concave function, which will extend the notion of volume ratio, and we will find the log-concave function maximizing the integral ratio. A reverse functional affine isoperimetric inequality will be given, written in terms of this integral ratio. This can be viewed as a stability version of the functional affine isoperimetric inequality. 相似文献
128.
Ren Y Acuña UM Jiménez F García R Mejía M Chai H Gallucci JC Farnsworth NR Soejarto DD Carcache de Blanco EJ Kinghorn AD 《Tetrahedron》2012,68(12):2671-2678
Six new (1-6) and eight known germacranolide-type sesquiterpene lactones, along with several known phenylpropanol coumarates and methylated flavonoids, were isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. The new compounds were identified by analysis of their spectroscopic data, with the molecular structure of 3 being established by single-crystal X-ray diffraction. The absolute configurations of the sesquiterpene lactones isolated were determined from their CD and NOESY NMR spectra, together with the analysis of Mosher ester reactions. Bioassay screening results showed the majority of the sesquiterpene lactones isolated (1-13) to be highly cytotoxic toward the HT-29 human colon cancer cell line, with the most potent compound being 15-deoxygoyazensolide (10, IC(50), 0.26 μM). In addition, several of the sesquiterpene lactones exhibited NF-κB (p65) inhibitory activity. 相似文献
129.
Inside Cover: Stereoselective Synthesis of 1,3‐Diaminotruxillic Acid Derivatives: An Advantageous Combination of CH‐ortho‐Palladation and On‐Flow [2+2]‐Photocycloaddition in Microreactors (Chem. Eur. J. 1/2016) 下载免费PDF全文
130.