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61.
The vibrations of the stator core of a rotating electrical machine induce acoustic noise. These oscillations of the stator yoke are excited of the force density due to the magnetic field in the air gap. This requires a transient magnetic field analysis coupled with a dynamic mechanical analysis. Coupling these two different physical fields results in a high numerical effort and usually one direction of the interaction is disregarded. This paper presents a method to calculate the vibrations of a stator core under design operating conditions. For this purpose, harmonic electromagnetic excitation forces have been calculated in a linear magnetic field analyses using the finite element method. The resulting forces have been applied to a linear structural dynamic FE model in the frequency domain. The results of the calculations are harmonic velocities specified by amplitude and phase from the structural surface of the stator core. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
62.
63.
Veldboer K Schürmann T Vogel M Wiemhöfer HD Karst U 《Rapid communications in mass spectrometry : RCM》2011,25(1):147-154
Cyclic phosphazenes with different substituents were synthesised and investigated by liquid chromatography (LC) and electrospray ionisation mass spectrometry (ESI-MS). Hexachlorocyclotriphosphazene was functionalised with aliphatic substituents as alcohols and amines, leading to product mixtures, which were subsequently analysed. In contrast to classical methods of structural analysis such as nuclear magnetic resonance (NMR) spectroscopy or X-ray crystallography, which are restricted to pure compounds, these complex mixtures can favourably be analysed by means of LC/ESI-MS. The main products could be separated from by-products and, moreover, all the components of the unknown mixture were unambiguously identified by accurate mass measurements. For all compounds with different side-chain ratios, remaining chlorine atoms or hydroxyl groups and even for spiro or ansa products, molecular structures could be suggested. 相似文献
64.
Katrin?ThümmlerEmail author Steffen?Fischer Alexander?Feldner Viktoria?Weber Marion?Ettenauer Fritz?Loth Dieter?Falkenhagen 《Cellulose (London, England)》2011,18(1):135-142
The aim of this work was to synthesize and characterize cellulose microspheres with a particle size below 5 μm and narrow
size distribution. After activation and functionalization with antibodies, these particles shall be applied as adsorbents
in suspension-based extracorporeal blood purification systems, such as the Microspheres-Based Detoxification System. In the
frame of this work such microspheres were developed and synthesized with reproducible properties. Besides using well-established
methods for characterization of this kind of bead cellulose, additional procedures for the examination of its properties were
developed and applied. 相似文献
65.
Weise K Kapoor S Denter C Nikolaus J Opitz N Koch S Triola G Herrmann A Waldmann H Winter R 《Journal of the American Chemical Society》2011,133(4):880-887
The K-Ras4B GTPase is a major oncoprotein whose signaling activity depends on its correct localization to negatively charged subcellular membranes and nanoclustering in membrane microdomains. Selective localization and clustering are mediated by the polybasic farnesylated C-terminus of K-Ras4B, but the mechanisms and molecular determinants involved are largely unknown. In a combined chemical biological and biophysical approach we investigated the partitioning of semisynthetic fully functional lipidated K-Ras4B proteins into heterogeneous anionic model membranes and membranes composed of viral lipid extracts. Independent of GDP/GTP-loading, K-Ras4B is preferentially localized in liquid-disordered (l(d)) lipid domains and forms new protein-containing fluid domains that are recruiting multivalent acidic lipids by an effective, electrostatic lipid sorting mechanism. In addition, GDP-GTP exchange and, thereby, Ras activation results in a higher concentration of activated K-Ras4B in the nanoscale signaling platforms. Conversely, palmitoylated and farnesylated N-Ras proteins partition into the l(d) phase and concentrate at the l(d)/l(o) phase boundary of heterogeneous membranes. Next to the lipid anchor system, the results reveal an involvement of the G-domain in the membrane interaction process by determining minor but yet significant structural reorientations of the GDP/GTP-K-Ras4B proteins at lipid interfaces. A molecular mechanism for isoform-specific Ras signaling from separate membrane microdomains is postulated from the results of this study. 相似文献
66.
Functional surfaces and especially the control of surface properties depending on external parameters such as light illumination
have gained increasing importance in the last few years. We present the characterization of polymers from the cycloolefin
(co)polymer class (COC/COP) functionalized with an aminosilane as a basis for the further immobilization of compounds. In
a first step, an assay using AlexaFluor?647 fluorescent dye was used to assess surface homogeneity and reproducibility. A
coefficient of variation of less than 15% for dot-to-dot and less than 25% for chip-to-chip could be achieved. The same amino-functionalized
surfaces were then used to immobilize a biotinylated photolabile linker compound, binding AlexaFluor?647-labeled streptavidin.
The linker was photocleaved with high efficiency at λ = 365 nm and P = 0.15 mW/cm2. Fluorescence measurements show that polymers of the COC/COP class can be used as versatile surfaces for the photoinduced
release of compounds immobilized via photolabile linkers. 相似文献
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69.
Since the discovery of the hydrated electron in bulk water in 1962, the species has been the subject of intense research and speculation. For many decades even the basic features of the simplest of all chemical and biological transients and reactants--such as its structure, binding motifs, lifetimes, and binding energies--remained elusive. Recently, another milestone in the research of the hydrated electron was the determination of its vertical binding energy (VBE). Also a long-lived hydrated electron near the surface of liquid water has been discovered. The present Minireview discusses the implications and consequences of this and other new findings in addition to the emerging complex picture of a solvated electron in water. 相似文献
70.
The objective of the study is an analysis of lung ventilation during breathing under rest conditions and for high frequency
ventilation (HFV). The measurements include investigations of the flow using an endotracheal tube. A transparent model of
the upper human lung airways down to the 6th generation was generated, and the oscillatory flow through the branching network
was studied by DPIV. The method of refractive index matching of the fluid (water/glycerin) and the model (silicone) allows
an unobstructed view into the internal flow network. The mass flow rate and the frequency were adapted to the characteristic
flow parameters, the Reynolds- and the Womersley-number. The comparison of the results for normal breathing and HFV shows
that a mass exchange occurs for higher frequencies known as Pendelluft, which could not be seen during normal breathing. This
mass exchange between the daughter tubes is a consequence of the asymmetric impedance in the successive daughter branches.
The lung topology determines the local pressure loss in the model and therefore the local mass flow direction of the Pendelluft.
At higher frequencies we observed an increase in exchange between the daughter branches. The transformation of the velocity
profiles between inspiration and expiration suggests a net mass flow which is created into the model along the centerline
and the inner walls of the bifurcations. This flow is compensated with a net mass outflow to the trachea along the outer walls
of the branches. 相似文献