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101.
Henriksson A Friedbacher G Hoffmann H 《Langmuir : the ACS journal of surfaces and colloids》2011,27(12):7345-7348
A two-step process based on copper-free click chemistry is described, by which the surface of silicon nanowires can be functionalized with specific organic substituents. A hydrogen-terminated nanowire surface is first primed with a monolayer of an α,ω-diyne and thereby turned into an alkyne-terminated, clickable platform, which is subsequently coupled with an overlayer of an organic azide carrying the desired terminal functionality. The reactive, electron-deficient character of the employed diyne enabled a quantitative coupling reaction at 50 °C without metal catalysis, which opens up a simple and versatile route for surface functionalization under mild conditions without any potentially harmful additives. 相似文献
102.
Schmidt S Madaboosi N Uhlig K Köhler D Skirtach A Duschl C Möhwald H Volodkin DV 《Langmuir : the ACS journal of surfaces and colloids》2012,28(18):7249-7257
Chemical cross-linking is the standard approach to tune the mechanical properties of polymer coatings for cell culture applications. Here we show that the elastic modulus of highly swollen polyelectrolyte films composed of poly(L-lysine) (PLL) and hyaluronic acid (HA) can be changed by more than 1 order of magnitude by addition of gold nanoparticles (AuNPs) in a one-step procedure. This hydrogel-nanoparticle architecture has great potential as a platform for advanced cell engineering application, for example remote release of drugs. As a first step toward utilization of such films for biomedical applications we identify the most favorable polymer/nanoparticle composition for optimized cell adhesion on the films. Using atomic force microscopy (AFM) we determine the following surface parameters that are relevant for cell adhesion, i.e., stiffness, roughness, and protein interactions. Optimized cell adhesion is observed for films with an elastic modulus of about 1 MPa and a surface roughness on the order of 30 nm. The analysis further shows that AuNPs are not incorporated in the HA/PLL bulk but form clusters on the film surface. Combined studies of the elastic modulus and surface topography indicate a cluster percolation threshold at a critical surface coverage above which the film stiffness drastically increases. In this context we also discuss changes in film thickness, material density and swelling ratio due to nanoparticle treatment. 相似文献
103.
Hollamby MJ Borisova D Möhwald H Shchukin D 《Chemical communications (Cambridge, England)》2012,48(1):115-117
By exploiting spontaneous emulsification to prepare porous SiO(2) particles, we report the formation of porous CeO(2)@SiO(2) hybrid colloids and their incorporation into a silica-zirconia coating to improve the corrosion protection of aluminium. 相似文献
104.
A Brotchie J Schneider R Pflieger D Shchukin H Möhwald 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(36):11201-11204
Single bubble feels the pressure: Sonochemical luminescence has been detected in a single-cavitation bubble within a narrow pressure domain below the sonoluminescence threshold. The parameter space of single-bubble sonochemistry is distinct from that of single-bubble atomic and molecular line emissions. 相似文献
105.
MALONEK Helmuth 《中国科学 数学(英文版)》2012,55(12):2481-2491
Starting from piecewise constant functions, a novel family of generalized symmetric B-splines, with realizable ideal low-pass filters, are constructed. The first order generalized B-spline low-pass filter is closely related to functions analytic in a neighborhood of the unit disc and the generalized sinc functions. The properties of this kind of low-pass filters are investigated. The behavior of the generalized B-spline low-pass filter related to normalized Gaussian distribution is considered. 相似文献
106.
107.
Michelle Prevot Christophe Déjugnat Helmuth M?hwald Gleb B Sukhorukov 《Chemphyschem》2006,7(12):2497-2502
Layer-by-layer assembled polyelectrolyte microcapsules are of great interest because they can possibly be used as microcontainers and they show interesting stimuli-responsive properties, which have been recently investigated. Here, we exploit capsules which are made temperature-sensitive by encapsulating poly(N-isopropylacrylamide) (PNIPAM). PNIPAM has a cloud point in water at about 32 degrees C, above which it collapses and is insoluble in water. Further this temperature responsiveness can be tuned by addition of various ions at various concentrations. Here, we present the encapsulation of PNIPAM inside polyelectrolyte microcapsules, and describe the dependence of the lower critical solution temperature (LCST) on the nature and the amount of different salts added. With this information, we demonstrate the ability to tune and finely control the collapse of encapsulated PNIPAM. In this light, this system could be used as a microsensor or drug- delivery system. 相似文献
108.
Ulrich Mayer Helmuth Hoffmann Robert Kellner 《Monatshefte für Chemie / Chemical Monthly》1988,119(11):1207-1221
A systematic study has been carried out on the solvent and concentration dependence of the P=O stretching vibrationv(PO) of the model compoundEt
3PO in various aprotic and several CH-acidic solvents. Evidence has been found for the existence of dipole-dipole complexes in concentrated solutions ofEt
3PO in solvents of low acceptor numbers. In dilute solutions, however, the P=O stretching band generally occurs as a single symmetrical peak which shows that only one kind of solvate species is present in solution. In CH-acidic solventsEt
3PO is present in the form of hydrogen bonded complexes. Informations about the structure of these complexes have been obtained by means of spectrophotometric titrations. It has been shown that the wavenumbersv°(PO) obtained by extrapolation ofv(PO) values to zero concentration are linearly related to the acceptor numbers of the solvents, previously derived from31P-chemical shift measurements. The existence of this linear relationships proves that both parameters are linearly related to the strength of the intermolecular interactions and are virtually free from unspecific contributions such as magnetic anisotropy or vibrational coupling effects. The results of the present study show that the P=O stretching vibration ofEt
3PO represents an ideal probe for the investigation of solvent effects and solvation mechanisms.
Infrarotspektroskopische Untersuchungen über Substrat-Lösungsmittel-Wechselwirkungen. Teil 1: Solvatation von Triethylphosphinoxid in aprotischen und CH-aciden Lösungsmitteln
Zusammenfassung Es wurde die Konzentrations- und Lösungsmittelabhängigkeit der P=O-Valenzschwingungv(PO) der ModellverbindungEt 3PO in verschiedenen aprotischen und CH-aciden Lösungsmitteln systematisch untersucht. In hinreichend verdünnten Lösungen tritt die P=O-Valenzschwingung als einzelne symmetrische Bande auf, was beweist, daß nur eine einzige Solvatform vorliegt. In Lösungsmitteln niedriger Akzeptorzahl konnte bei höheren Konzentrationen die Existenz von Dipol-Dipol-Komplexen nachgewiesen werden. In CH-aciden Lösungsmitteln liegtEt 3PO in Form von Wasserstoffbrückenkomplexen vor. Aussagen über die Struktur dieser Komplexe konnten mit Hilfe spektrophotometrischer Titrationen erhalten werden. Die durch Extrapolation auf Konzentration null erhaltenen Wellenzahlenv° (PO) hängen linear von den aus den31P-chemischen Verschiebungen vonEt 3PO bereits früher bestimmten Akzeptorzahlen der Lösungsmittel ab. Die Existenz dieser linearen Beziehung beweist, daß beide Parameter frei von störenden Einflußfaktoren (magnetische Anisotropie- und Schwingungskopp-lungseffekte) sind und tatsächlich linear mit der Stärke der intermolekularen Wechselwirkung variieren. Die Ergebnisse der vorliegenden Studie zeigen, daß die P=O-Valenzschwingung vonEt 3PO eine hervorragende Sonde zur Untersuchung von Lösungsmitteleffekten und Solvatationsmechanismen darstellt.相似文献
109.
Multilayer microcapsules showing unique charge-controlled permeability have been successfully fabricated by employing poly(styrene sulfonate) (PSS)-doped CaCO3 particles as templates. Encapsulation of the PSS molecules is thus achieved after core removal. Scanning force microscopy (SFM), UV-vis, Raman spectroscopy, and zeta-potential confirm the existence of the PSS molecules in the CaCO3 particles and the resultant microcapsules, which are initially incorporated during the core fabrication process. A part of these additionally introduced PSS molecules interacts with PAH molecules residing on the inner surface of the multilayer wall to form a stable complex, while the other part is intertwined in the capsule wall or in a free state. Capsules with this structure possess many special features, such as highly sensitive permeability tuned by probe charge and environmentally controlled gating. They can completely reject negatively charged probes, but attract positively charged species to form a higher concentration in the capsule interior, as evidenced by confocal microscopy. For example, the capsules completely exclude dextran labeled with fluorescein isothiocyanate (FITC-dextran), but are permeable for dextran labeled with tetramethylrhodamine isothiocyanate (TRITC-dextran) having similar molecular mass (from 4 to 70 kDa), although there are only few charged dyes in a dextran chain. By reversing the charge of the probes through pH change, or by suppressing charge repulsion through salt addition, the permeation can be readily switched for proteins such as albumin or small dyes such as fluorescein sodium salt. 相似文献
110.
By reaction of [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) with i-C3H7MgBr in the presence of cyclic dienes, complexes of the type [IrH(COD)L] (L = 1,3-cyclohexadiene, 2-methyl-],3-cyclohexadiene, 5-ethyl-1,3-cyclohexadiene, 1,3-cycloheptadiene) are obtained. The system IrCl3/i-C3H7MgBr/1,3-C6H8 yields [IrH(1,3-C6H8)2]. According to NMR spectroscopic investigations the pure hydrido forms exist in solution only at low temperatures while at room temperature dynamic H-addition—elimination equilibria of the type [IrH(η4-diene)(COD)] ? [Ir(η3-enyl)(COD)] and [IrH(η4-1,3-C6H8)2] ? [Ir(η3-C6H9)-(η4-1,3-C6H8)], respectively, are observed; the hydrogen at the iridium atom is thereby transferred to the endo positions of the diene ligands. 相似文献