全文获取类型
收费全文 | 1109篇 |
免费 | 66篇 |
国内免费 | 5篇 |
专业分类
化学 | 932篇 |
晶体学 | 1篇 |
力学 | 16篇 |
数学 | 131篇 |
物理学 | 100篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 24篇 |
2021年 | 36篇 |
2020年 | 44篇 |
2019年 | 36篇 |
2018年 | 17篇 |
2017年 | 16篇 |
2016年 | 42篇 |
2015年 | 41篇 |
2014年 | 40篇 |
2013年 | 57篇 |
2012年 | 87篇 |
2011年 | 101篇 |
2010年 | 56篇 |
2009年 | 60篇 |
2008年 | 88篇 |
2007年 | 75篇 |
2006年 | 73篇 |
2005年 | 59篇 |
2004年 | 58篇 |
2003年 | 40篇 |
2002年 | 37篇 |
2001年 | 11篇 |
2000年 | 10篇 |
1999年 | 5篇 |
1998年 | 2篇 |
1997年 | 7篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1989年 | 1篇 |
1982年 | 1篇 |
1948年 | 2篇 |
1946年 | 1篇 |
1945年 | 1篇 |
1939年 | 2篇 |
1938年 | 1篇 |
1936年 | 1篇 |
1935年 | 1篇 |
1933年 | 2篇 |
1929年 | 2篇 |
1927年 | 2篇 |
1917年 | 1篇 |
1891年 | 1篇 |
1890年 | 1篇 |
1889年 | 1篇 |
1885年 | 1篇 |
1884年 | 1篇 |
排序方式: 共有1180条查询结果,搜索用时 31 毫秒
101.
102.
Josiane Courtois Jean-Paul Seguin Sophie Declomesnil Alain Heyraud Philippe Colin-Morel Luciana Dantas 《Journal of carbohydrate chemistry》2013,32(4-5):441-448
Abstract A mutant of the R. meliloti M5N1 strain has been selected. This strain, R. meliloti M5N1 CS (NCIMB 40472), excretes an extracellular material composed of 2-O-Ac-β-GlcpA, 3-O-Ac-β-GlcpA, 2,3-di-O-Ac-β-GlcpA and three species of β-GlcpA residues 1→4 linked. For the culture conditions used, the weight average molecular weight of the polymer varied in the range of 6 × 104 < Mw < 4 × 105. High molecular weight glucuronate forms thermoreversible gels at 5 g L?l. In the presence of divalent cation such as Ca2+ or trivalent cations such as Cr3+ or Fe3 +, cross linking of the polymer occurs. This polysaccharide is the first exocellular (1→4)-β-D-glucuronan produced by a R. meliloti strain. 相似文献
103.
Caterpillar Track Complexes in Template‐Directed Synthesis and Correlated Molecular Motion
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)
Shiqi Liu Dr. Dmitry V. Kondratuk Dr. Sophie A. L. Rousseaux Dr. Guzmán Gil‐Ramírez Dr. Melanie C. O'Sullivan Jonathan Cremers Prof. Tim D. W. Claridge Prof. Harry L. Anderson 《Angewandte Chemie (International ed. in English)》2015,54(18):5355-5359
Small alterations to the structure of a star‐shaped template totally change its mode of operation. The hexapyridyl template directs the conversion of a porphyrin dimer to the cyclic hexamer, but deleting one pyridine site changes the product to the cyclic decamer, while deleting two binding sites changes the product to the cyclic octamer. This surprising switch in selectivity is explained by the formation of 2:1 caterpillar track complexes, in which two template wheels bind inside the nanoring. Caterpillar track complexes can also be prepared by binding the hexapyridyl template inside the 8‐ and 10‐porphyrin nanorings. NMR exchange spectroscopy (EXSY) experiments show that these complexes exhibit correlated motion, in which the conrotatory rotation of the two template wheels is coupled to rotation of the nanoring track. In the case of the 10‐porphyrin system, the correlated motion can be locked by binding palladium(II) dichloride between the two templates. 相似文献
104.
105.
Julien Huser Sophie Bistac Christelle Delaite Didier Dentel Mickaël Derivaz Mohamed Zanouni 《Surface and interface analysis : SIA》2015,47(4):523-528
The grafting of trialkoxysilane molecules should also give rise to the formation of a siloxane network at the substrate's surface when trialkoxysilanes are used. Other candidates that might be able to act as adhesion promoters at metallic surfaces are dimethylalkoxysilanes. The advantage of dimethylalkoxysilanes is that only one silanol group is produced during the hydrolysis step, leading to the formation of a grafted monolayer onto the steel. Moreover, the chemical grafting of stainless steel, which exhibits a low surface reactivity, is of great interest for industrial applications such as adhesive bonding or coatings. The objective of this work was to chemically graft dimethylalkoxysilanes onto AISI 316L stainless steel and to analyze the grafted layer by X‐ray photoelectron spectroscopy (XPS). Investigation of the hydrolysis of these molecules in aqueous solutions was also performed by proton nuclear magnetic resonance spectroscopy (1H NMR). The grafting of 3‐(ethoxydimethylsilyl)propylamine (APDES) and 3‐glycidoxypropyldimethylethoxysilane (GPDES) was achieved onto stainless steel after a controlled hydrolysis reaction. A pH inferior or equal to 5 was necessary to obtain a sufficient hydrolysis of silanes. XPS results have evidenced the grafting of the silanes onto stainless steel. The signal of the Si 2p peak clearly showed the formation of a covalent bond between APDES and the stainless steel surface through the O atoms giving rise to a uniform layer of adsorbed molecules. Moreover, this grafted layer is strongly stable as no removal of the alkoxysilane was observed after immersion in hot water which is very critical for these molecules. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
106.
Zeina Al Masry Sophie Mercier Ghislain Verdier 《Methodology and Computing in Applied Probability》2017,19(1):213-235
In reliability theory, many papers use a standard Gamma process to model the evolution of the cumulative deterioration of a system over time. When the variance-to-mean ratio of the system deterioration level varies over time, the standard Gamma process is not convenient any more because it provides a constant ratio. A way to overcome this restriction is to consider the extended version of a Gamma process proposed by Cinlar (J Appl Probab 17:467–480, 1980). However, based on its technicality, the use of such a process for applicative purpose requires the preliminary development of technical tools for simulating its paths and for the numerical assessment of its distribution. This paper is devoted to these two points. 相似文献
107.
Rodolphe Alchaar Houssin Makhlouf Nadine Abboud Sophie Tingry Radhouane Chtourou Matthieu Weber Mikhael Bechelany 《Journal of Solid State Electrochemistry》2017,21(10):2877-2886
A new process enabling the synthesis of zinc oxide (ZnO) and Al-doped ZnO nanowires (NWs) for photosensing applications is reported. By combining atomic layer deposition (ALD) for the seed layer preparation and electrodeposition for the NW growth, high-quality ZnO nanomaterials were prepared and tested as ultraviolet (UV) sensors. The obtained NWs are grown as arrays perpendicular to the substrate surface and present diameters between 70 and 130 nm depending on the Al doping, as seen from scanning electron microscopy (SEM) studies. Their hexagonal microstructure has been determined using X-ray diffraction and Raman spectroscopy. An excellent performance in UV sensing has been observed for the ZnO NWs with low Al doping, and a maximal photoresponse current of 11.1 mA has been measured. In addition, initial studies on the stability have shown that the NW photoresponse currents are stable, even after ten UV on/off cycles. 相似文献
108.
Ta HP Berthelot K Coulary-Salin B Desbat B Géan J Servant L Cullin C Lecomte S 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4797-4807
Many in vitro studies have pointed out the interaction between amyloids and membranes, and their potential involvement in amyloid toxicity. In a previous study, we generated a yeast toxic mutant (M8) of the harmless model amyloid protein HET-s((218-289)). In this study, we compared the self-assembling process of the nontoxic wild-type (WT) and toxic (M8) protein at the air-water interface and in interaction with various phospholipid monolayers (DOPE, DOPC, DOPI, DOPS and DOPG). We first demonstrate using ellipsometry measurements and polarization-modulated infrared reflection absorption spectroscopy (PMIRRAS) that the air-water interface promotes and modifies the assembly of WT since an amyloid-like film was instantaneously formed at the interface with an antiparallel β-sheet structuration instead of the parallel β-sheet commonly observed for amyloid fibers generated in solution. The toxic mutant (M8) behaves in a similar manner at the air-water interface or in bulk, with a fast self-assembling and an antiparallel β-sheet organization. The transmission electron microscopy (TEM) images established the fibrillous morphology of the protein films formed at the air-water interface. Second, we demonstrate for the first time that the main driving force between this particular fungus amyloid and membrane interaction is based on electrostatic interactions with negatively charged phospholipids (DOPG, DOPI, DOPS). Interestingly, the toxic mutant (M8) clearly induces perturbations of the negatively charged phospholipid monolayers, leading to a massive surface aggregation, whereas the nontoxic (WT) exhibits a slight effect on the membrane models. This study allows concluding that the toxicity of the M8 mutant could be due to its high propensity to interact with membranes. 相似文献
109.
Daniela?StoicaEmail author Catherine?Yardin Géraldine?Ebrard Sophie?Vaslin-Reimann Paola?Fisicaro 《Journal of solution chemistry》2011,40(11):1819-1834
This paper deals with the evaluation of the standard potential of the Ag/AgCl electrode in a water–ethanol mixture (50 wt-%).
A potentiometric method was applied using a cell without liquid junction. Mean activity coefficients of HCl in the same mixture
have been also determined. The measurements were performed in the HCl molality range from 0.005 to 0.1 mol⋅kg−1. The Debye–Hückel theory and Pitzer’s model, based on the interactions present in the solution, have been applied. Good agreement
was found between the results obtained with the two approaches. Uncertainties of the Pitzer parameters and interionic forces
are discussed based on the values found. The variation of the standard potential as a function of the temperature was used
to calculate the transfer thermodynamic functions. The effects of the solvent composition on the thermodynamic properties
of HCl allow to highlight structural changes in water–ethanol mixtures. 相似文献
110.
Lubomír Bení?ek Lenka Chvátalová Vincent Verney Sophie Commereuc 《Polymer Degradation and Stability》2011,96(10):1740-1744
The effect of photodegradation in isotactic poly(1-butene) (PB-1) have been investigated using rheology, differential scanning calorimetry and infrared spectroscopy. Two commercially available grades of PB-1 with different average molecular weight were chosen. Specimens prepared by compression moulding were UV irradiated in the interval from 0 to 70 h. UV-induced changes in molecular structure have been followed by evolution of rheological properties, thermal properties and degradation by-products. Thermal analysis showed significant changes in crystallization behaviour influencing morphology and resulting thermal properties. Moreover it has been confirmed that the degradation significantly retards the phase transformation. Rheological measurement has been found as an effective method for determination of early stages of photodegradation of PB-1. 相似文献