全文获取类型
收费全文 | 320篇 |
免费 | 23篇 |
专业分类
化学 | 278篇 |
晶体学 | 2篇 |
力学 | 12篇 |
数学 | 20篇 |
物理学 | 31篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 7篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 3篇 |
2016年 | 14篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 21篇 |
2012年 | 20篇 |
2011年 | 28篇 |
2010年 | 22篇 |
2009年 | 13篇 |
2008年 | 23篇 |
2007年 | 24篇 |
2006年 | 15篇 |
2005年 | 21篇 |
2004年 | 21篇 |
2003年 | 14篇 |
2002年 | 10篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1998年 | 5篇 |
1995年 | 5篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有343条查询结果,搜索用时 15 毫秒
121.
Thermodynamic and Mechanical Timescales Involved in Foam Film Rupture and Liquid Foam Coalescence
下载免费PDF全文
![点击此处可从《Chemphyschem》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Recent advances in the coalescence in liquid foams are reviewed, with a special focus on the multiscale structure of foams. Studies concerning the stability of isolated foam films, on the one hand, and the coalescence process in macroscopic foams, on the other hand, are not always in good agreement. This discrepancy reveals that two routes can induce coalescence in a foam. The first route is thermodynamic and shows that coalescence is governed by a stochastic rupture of foam films. The second route relies on a mechanically induced rupture of the films, due to the spontaneous evolution of foams. From a literature review, the evaluation of the different timescales involved in these mechanisms allows defining the limiting parameters of foam coalescence. 相似文献
122.
Angular‐Resolved Magnetometry Beyond Triclinic Crystals Part II: Torque Magnetometry of Cp*ErCOT Single‐Molecule Magnets
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mauro Perfetti Giuseppe Cucinotta Dr. Marie‐Emmanuelle Boulon Dr. Fadi El Hallak Prof. Song Gao Prof. Roberta Sessoli 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(43):14051-14056
The experimental investigation of the molecular magnetic anisotropy in crystals in which the magnetic centers are symmetry related, but do not have a parallel orientation has been approached by using torque magnetometry. A single crystal of the orthorhombic organometallic Cp*ErCOT [Cp*=pentamethylcyclopentadiene anion (C5Me5?); COT=cyclooctatetraenedianion (C8H82?)] single‐molecule magnet, characterized by the presence of two nonparallel families of molecules in the crystal, has been investigated above its blocking temperature. The results confirm an Ising‐type anisotropy with the easy direction pointing along the pseudosymmetry axis of the complex, as previously suggested by out‐of‐equilibrium angular‐resolved magnetometry. The use of torque magnetometry, not requiring the presence of magnetic hysteresis, proves to be even more powerful for these purposes than standard single‐crystal magnetometry. Furthermore, exploiting the sensitivity and versatility of this technique, magnetic anisotropy has been investigated up to 150 K, providing additional information on the crystal‐field splitting of the ground J multiplet of the ErIII ion. 相似文献
123.
Emmanuelle Frossard 《Compositio Mathematica》1998,110(2):187-213
We study here the O-dimension Chow group of some particular smooth varieties which are fibrations over curves (i.e. are equipped with a proper, surjective morphism over a smooth curve). We obtain finiteness results for fibrations, whose generic fibres are Severi-Brauer varieties of squarefree index, when the group field is a number field (or in some particular cases a finitely generated field over Q). 相似文献
124.
Moisés Canle López M Isabel Fernández Santiago Rodríguez J Arturo Santaballa Steen Steenken Emmanuelle Vulliet 《Chemphyschem》2005,6(10):2064-2074
Phenylurea herbicides undergo low-yield (phi(PI) <15 %) monophotonic photoionisation upon 193-nm laser flash excitation. The so-formed radical cations (phenylurea.+) are highly acidic (-1.5 < pKa <0.5) and deprotonate readily to yield the corresponding neutral radical (phenylurea.). Pulse radiolysis experiments allowed limitation of the reduction potential of phenylurea.+ within 2.22 V versus the normal hydrogen electrode (NHE) < E degrees (phenylurea.+/phenylurea) < 2.43 V versus NHE. The main photoproducts of UVC (lambda=193 nm) photodegradation of phenylureas correspond to a photo-Fries rearrangement. One-electron reduction with e-(aq) yields the corresponding radical anions (phenylurea.-), for which 4.3< pKa < 5.33. The rate constants for reaction with e-(aq) show that in photocatalysis the generation of phenylurea.- and O2.- on the surface of the photocatalyst may be competitive. High reactivity toward e-(aq) is predicted from linear free-energy relationships (LFER) for phenylureas bearing electron-withdrawing groups. Reaction with HO. takes place mainly via addition to the aromatic ring and/or H. abstraction from a saturated carbon atom (98 %), rather than one-electron oxidation (2 %). High reactivity toward oxidation by HO. is predicted from LFER for phenylureas bearing electron-donating groups. Adsorption studies for TiO2 in its polymorphic forms of rutile and anatase, as well as with the commercial mixture Degussa P-25, show photocatalysis is independent of the specific area of the catalyst. A variety of compounds are generated during the photocatalytic degradation of Diuron, while only two hydroxychloro derivatives are observed upon prolonged direct 365 nm irradiation. The photocatalytic degradation proceeds mainly by oxidation of the Me group of the side chain, hydroxylation of the aromatic ring, and dechlorination. The photoproducts of photocatalytic degradation differ from one polymorphic form of TiO2 to another. 相似文献
125.
126.
Rodríguez-Pérez L Teuma E Falqui A Gómez M Serp P 《Chemical communications (Cambridge, England)》2008,(35):4201-4203
Highly active rhodium catalysts have been prepared by immobilization of an ionic liquid film on carbon nanotubes functionalized with imidazolium-based ionic moieties. 相似文献
127.
Bruneaux M Rousselot M Leize E Lallier FH Zal F 《Current protein & peptide science》2008,9(2):150-180
Understanding the function of macromolecular complexes is related to a precise knowledge of their structure. These large complexes are often fragile high molecular mass noncovalent multimeric proteins. Classical biochemical methods for determination of their native mass and subunit composition were used to resolve their quaternary structure, sometimes leading to different models. Recently, the development of mass spectrometry and multi-angle laser light scattering (MALLS) has enabled absolute determination of native masses and subunit masses. Electrospray ionization mass spectrometry (ESI-MS) was used in denaturing and native conditions to probe subunit composition and noncovalent assemblies masses up to 2.25 MDa. In a complementary way, MALLS provides mass and size estimation in various aqueous solvents. ESI-MS method can also give insights into post-translational modifications (glycosylation, disulfide bridges ). By combining native mass and subunit composition data, structural models can be proposed for large edifices such as annelid extracellular hexagonal bilayer hemoglobins (HBL Hb) and crustacean hemocyanins (Hc). Association/dissociation mechanisms, protein-protein interactions, structural diversity among species and environmental adaptations can also be addressed with these methods. With their absolute mass determination, the very high precision of spectrometry and the versatile nature of light scattering, ESI-MS and MALLS have provided a wealth of data helping to resolve parts of controversies for HBL-Hb models and opening access to new fields of investigation in structural diversity and molecular adaptation. In this review we will focus on annelid HBL-Hb and on crustacean Hc and on the original contributions of ESI-MS and MALLS in this field. 相似文献
128.
Herschbach H Brisach F Haddaoui J Saadioui M Leize E Van Dorsselaer A Arnaud-Neu F Böhmer V 《Talanta》2007,74(1):39-46
The binding of lanthanide(III) cations with organophosphorous ligands like CMPO and related calix[4]arene-based derivatives have been investigated using two experimental methods. The stability constants of the lanthanum, europium and ytterbium complexes were first determined in methanol by UV absorption spectrophotometry in the presence of nitrate or chloride anions. The results showed that the stoichiometry and the stability of the complexes formed depend on the position of the CMPO moieties either on the wide or the narrow rim of the calixarene scaffold, the nature of the medium, the conformational mobility of the ligands. Complexation of lanthanum was also followed by ESI-mass spectrometry in the same solvent. This method confirmed the stoichiometry of the complexes, giving also structural information, like coordination of anion or solvent molecules to the complexes, and allowed the calculation of distribution curves in good agreement with those derived from the spectrophotometric results. This is an important result showing that ESI-MS can be used to provide with quantitative information when absorption spectrophotometry is not applicable, i.e. for systems where complexation leads to weak spectral changes. 相似文献
129.
A tricyclic tetraazatriacetic compound, which is a rigidified derivative of PCTA12 ligand with a cyclohexylene bridge replacing an ethylene one, was prepared. Two synthetic routes have been investigated, both of them implying a common functionalized triamine intermediate. Whatever the route, four synthetic steps were necessary to obtain the target tricyclic ligand. The more effective one (Route B) led to the desired compound in 19% overall yield from the triamine intermediate. The corresponding gadolinium complex of 1/1 stoichiometry was then prepared in order to evaluate it as potential contrast agent for MRI. 相似文献
130.
To control protein adsorption on surfaces, low-fouling polymer coatings such as poly(ethylene oxide) (PEG or PEO) and polysaccharides are used. Their ability to resist protein adsorption is related to the layer structure, hence the immobilization mode. A polymer array technology was developed to study the structural diversity of carboxymethyl dextran (CMD) layers, whose immobilization conditions were varied. CMD arrays were analyzed by X-ray photoelectron spectroscopy (XPS) and by atomic force microscopy (AFM) colloidal probe force measurements. Serum protein adsorption was studied directly on the CMD arrays using surface plasmon resonance (SPR) microscopy. Physicochemical characterization revealed that pinning density regulates surface coverage and the amount of adsorbed molecules, and that salt concentration influences the surface structure of the charged polymer, forming extended or short layers. Protein adsorption experiments from serum showed that repulsive CMD layers are dense, with extended flexible chains. The present study underlines the usefulness of polymer arrays to study structural diversity of thin graft layers and to relate their physicochemical properties to their resistance to nonspecific protein adsorption. 相似文献