全文获取类型
收费全文 | 982篇 |
免费 | 48篇 |
国内免费 | 3篇 |
专业分类
化学 | 596篇 |
晶体学 | 5篇 |
力学 | 43篇 |
数学 | 213篇 |
物理学 | 176篇 |
出版年
2023年 | 11篇 |
2022年 | 10篇 |
2021年 | 18篇 |
2020年 | 24篇 |
2019年 | 13篇 |
2018年 | 18篇 |
2017年 | 20篇 |
2016年 | 27篇 |
2015年 | 34篇 |
2014年 | 34篇 |
2013年 | 59篇 |
2012年 | 83篇 |
2011年 | 90篇 |
2010年 | 54篇 |
2009年 | 41篇 |
2008年 | 83篇 |
2007年 | 58篇 |
2006年 | 54篇 |
2005年 | 51篇 |
2004年 | 40篇 |
2003年 | 38篇 |
2002年 | 38篇 |
2001年 | 14篇 |
2000年 | 13篇 |
1999年 | 6篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1987年 | 2篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 9篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1973年 | 2篇 |
1969年 | 1篇 |
1938年 | 1篇 |
1931年 | 2篇 |
1926年 | 1篇 |
1900年 | 1篇 |
1886年 | 2篇 |
1883年 | 1篇 |
排序方式: 共有1033条查询结果,搜索用时 31 毫秒
951.
Grandeury A Condamine E Hilfert L Gouhier G Petit S Coquerel G 《The journal of physical chemistry. B》2007,111(25):7017-7026
Diastereomeric host-guest associations formed between permethylated-beta-cyclodextrin (TMbeta-Cd) and the two enantiomers of p-bromophenylethanol (pBrPE) were characterized in aqueous solution by NMR spectroscopy, revealing similar inclusion geometries and weak binding constants, whatever the guest configuration. These features were confirmed by hydrogenation experiments, and do not allow to account for the ability of TMbeta-Cd to resolve racemic pBrPE by successive crystallizations [Grandeury, A.; Petit, S.; Gouhier, G.; Agasse, V.; Coquerel, G. Tetrahedron: Asymmetry 2003, 14, 2143-2152]. The analysis, by means of solid-state NMR, oxidation experiments, and solubility measurements, of the two crystalline phases containing known proportions of guest enantiomers revealed identical inclusion geometries in a given phase, irrespective of the enantiomeric composition. The corresponding solid solutions were further characterized by the determination of an isothermal section (40 degrees C) in the relevant ternary phase diagram. It appears from all these data that chiral resolution mechanisms in this system can only be envisaged in terms of nucleation conditions of each crystal form (with its specific inclusion geometry) and enantiomeric recognition at crystal solution interfaces during the growth of each crystal packing. 相似文献
952.
Banchet-Cadeddu A Hénon E Dauchez M Renault JH Monneaux F Haudrechy A 《Organic & biomolecular chemistry》2011,9(9):3080-3104
Associated with the CD1d protein, KRN 7000, a potent synthetic α-galactosylceramide, is known to activate the invariant NKT immune cells. This stimulation then leads to the production of different cytokines modulating a T(H)1/T(H)2 immune response balance involved in protection against several pathologies such as autoimmune diseases and cancers. Various efforts have been made toward the synthesis of simple and more functionalized analogues in order to selectively induce T(H)1 or T(H)2-type cytokine production. Since the discovery of KRN 7000, structure-activity relationships, crystallographic and modelling studies have pointed to the potential of several GalCer analogues in term of selective bioactivity, and have highlighted interesting elements in order to better understand the recognition and activation mechanisms of immune iNKT cells. By presenting an up-to-date library of analogues, collecting recent breakthroughs done in crystallography and molecular modelling, and relating them to the available biological results, we hope that this review will highlight and help the scientific community in their KRN research. 相似文献
953.
In this article, we improve the Strichartz estimates obtained in A. de Bouard, A. Debussche (2010) [12] for the Schrödinger equation with white noise dispersion in one dimension. This allows us to prove global well posedness when a quintic critical nonlinearity is added to the equation. We finally show that the white noise dispersion is the limit of smooth random dispersion. 相似文献
954.
Arnaud Chéritat 《Mathematische Annalen》2011,349(3):529-542
We construct holomorphic maps f with a Siegel disk whose boundary is not locally connected (and is an indecomposable continuum), yet compactly contained
in the domain of definition of the map. Our examples are injective and defined on a subset of
\mathbb C{\mathbb C}. 相似文献
955.
The constrained adiabatic trajectory method (CATM) allows us to compute solutions of the time-dependent Schro?dinger equation using the Floquet formalism and Fourier decomposition, using matrix manipulation within a non-orthogonal basis set, provided that suitable constraints can be applied to the initial conditions for the Floquet eigenstate. A general form is derived for the inherent absorbing potential, which can reproduce any dispersed boundary conditions. This new artificial potential acting over an additional time interval transforms any wavefunction into a desired state, with an error involving exponentially decreasing factors. Thus, a CATM propagation can be separated into several steps to limit the size of the required Fourier basis. This approach is illustrated by some calculations for the H(2)(+) molecular ion illuminated by a laser pulse. 相似文献
956.
Lebrini M Mbomekallé IM Dolbecq A Marrot J Berthet P Ntienoue J Sécheresse F Vigneron J Etcheberry A 《Inorganic chemistry》2011,50(14):6437-6448
We present the synthesis and structural characterization, assessed by various techniques (FTIR, TGA, UV-vis, elemental analysis, single-crystal X-ray diffraction for three compounds, magnetic susceptibility, and electrochemistry) of five manganese-containing Wells-Dawson sandwich-type (WDST) complexes. The dimanganese(II)-containing complex, [Na(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](18-) (1), was obtained by reaction of MnCl(2) with 1 equiv of [As(2)W(15)O(56)](12-) in acetate medium (pH 4.7). Oxidation of 1 by Na(2)S(2)O(8) in aqueous solution led to the dimanganese(III) complex [Na(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](16-) (2), while its trimanganese(II) homologue, [Na(H(2)O)(2)Mn(II)(H(2)O)Mn(II)(2)(As(2)W(15)O(56))(2)](17-) (3), was obtained by addition of ca. 1 equiv of MnCl(2) to a solution of 1 in 1 M NaCl. The trimanganese(III) and tetramanganese(III) counterparts, [Mn(III)(H(2)O)Mn(III)(2)(As(2)W(15)O(56))(2)](15-) (4) and [Mn(III)(2)(H(2)O)(2)Mn(III)(2)(As(2)W(15)O(56))(2)](12-) (6), are, respectively, obtained by oxidation of aqueous solutions of 3 and [Mn(II)(2)(H(2)O)(2)Mn(II)(2)(As(2)W(15)O(56))(2)](16-) (5) by Na(2)S(2)O(8). Single-crystal X-ray analyses were carried out on 2, 3, and 4. BVS calculations and XPS confirmed that the oxidation state of Mn centers is +II for complexes 1, 3, and 5 and +III for 2, 4, and 6. A complete comparative electrochemical study was carried out on the six compounds cited above, and it was possible to observe the distinct redox steps Mn(IV/III) and Mn(III/II). Magnetization measurements, as a function of temperature, confirm the presence of antiferromagnetic interactions between the Mn ions in these compounds in all cases with the exception of compound 2. 相似文献
957.
Desfougères Y Saint-Jalmes A Salonen A Vié V Beaufils S Pezennec S Desbat B Lechevalier V Nau F 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):14947-14957
Identification of the key physicochemical parameters of proteins that determine their interfacial properties is still incomplete and represents a real stake challenge, especially for food proteins. Many studies have thus consisted in comparing the interfacial behavior of different proteins, but it is difficult to draw clear conclusions when the molecules are completely different on several levels. Here the adsorption process of a model protein, the hen egg-white lysozyme, and the same protein that underwent a thermal treatment in the dry state, was characterized. The consequences of this treatment have been previously studied: net charge and hydrophobicity increase and lesser protein stability, but no secondary and tertiary structure modification (Desfougères, Y.; Jardin, J.; Lechevalier, V.; Pezennec, S.; Nau, F. Biomacromolecules 2011, 12, 156-166). The present study shows that these slight modifications dramatically increase the interfacial properties of the protein, since the adsorption to the air-water interface is much faster and more efficient (higher surface pressure). Moreover, a thick and strongly viscoelastic multilayer film is created, while native lysozyme adsorbs in a fragile monolayer film. Another striking result is that completely different behaviors were observed between two molecular species, i.e., native and native-like lysozyme, even though these species could not be distinguished by usual spectroscopic methods. This suggests that the air-water interface could be considered as a useful tool to reveal very subtle differences between protein molecules. 相似文献
958.
Enjalbert Q Simon R Salvador A Antoine R Redon S Ayhan MM Darbour F Chambert S Bretonnière Y Dugourd P Lemoine J 《Rapid communications in mass spectrometry : RCM》2011,25(22):3375-3381
Selected Reaction Monitoring (SRM) carried out on triple‐quadrupole mass spectrometers coupled to liquid chromatography has been a reference method to develop quantitative analysis of small molecules in biological or environmental matrices for years and is currently emerging as a promising tool in clinical proteomic. However, sensitive assays in complex matrices are often hampered by the presence of co‐eluted compounds that share redundant transitions with the target species. On‐the‐fly better selection of the precursor ion by high‐field asymmetric waveform ion mobility spectrometry (FAIMS) or increased quadrupole resolution is one way to escape from interferences. In the present work we document the potential interest of substituting classical gas‐collision activation mode by laser‐induced dissociation in the visible wavelength range to improve the specificity of the fragmentation step. Optimization of the laser beam pathway across the different quadrupoles to ensure high photo‐dissociation yield in Q2 without detectable fragmentation in Q1 was assessed with sucrose tagged with a push‐pull chromophore. Next, the proof of concept that photo‐SRM ensures more specific detection than does conventional collision‐induced dissociation (CID)‐based SRM was carried out with oxytocin peptide. Oxytocin was derivatized by the thiol‐reactive QSY® 7 C5‐maleimide quencher on cysteine residues to shift its absorption property into the visible range. Photo‐SRM chromatograms of tagged oxytocin spiked in whole human plasma digest showed better detection specificity and sensitivity than CID, that resulted in extended calibration curve linearity. We anticipate that photo‐SRM might significantly improve the limit of quantification of classical SRM‐based assays targeting cysteine‐containing peptides. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
959.
Vrlinic T Debarnot D Mozetic M Vesel A Kovac J Coudreuse A Legeay G Poncin-Epaillard F 《Journal of colloid and interface science》2011,362(2):300-310
The surface grafting of multi-polymeric materials can be achieved by grafting as components such as polymers poly(N-isopropylacrylamide) and/or surfactant molecules (hexatrimethylammonium bromide, polyoxyethylene sorbitan monolaurate). The chosen grafting techniques, i.e. plasma activation followed by coating, allow a large spectrum of functional groups that can be inserted on the surface controlling the surface properties like adhesion, wettability and biocompatibility. The grafted polypropylene surfaces were characterized by contact angle analyses, XPS and AFM analyses. The influence of He plasma activation, of the coating parameters such as concentrations of the various reactive agents are discussed in terms of hydrophilic character, chemical composition and morphologic surface heterogeneity. The plasma pre-activation was shown inevitable for a permanent polymeric grafting. PNIPAM was grafted alone or with a mixture of the surfactant molecules. Depending on the individual proportion of each component, the grafted surfaces are shown homogeneous or composed of small domains of one component leading to a nano-structuration of the grafted surface. 相似文献
960.
Unusual partially crystalline ordered mesoporous zirconosilicate doughnuts with Si/Zr ratio as low as 1.5 were synthesized from the aqueous polymerisation of a single source molecular precursor Zr[OSi(Ot-BuO)(3)](4) without the use of any templating agent. A radial homogenous mesoporosity (4 nm) was observed inside these very regular sub-micrometric (600 nm) doughnuts. These structures were partially crystallized in hydrothermal conditions (100°C) into an analogous zircon (ZrSiO(4)) framework. The formation mechanism has been investigated. It is evidenced that chlorine anions Cl(-) concentration and pH value are essential to achieve the process, even if their role is still a matter of investigations. The obtained materials demonstrated even higher catalytic activity, selectivity and stability in the liquid oxidative dehydrogenation of hydroquinone to 1,4-benzoquinone compared to TS-1 zeolite catalysts and amorphous highly ordered mesoporous zirconosilicate materials. 相似文献