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71.
Characterization of high‐aspect‐ratio periodic structures by X‐ray photoelectron spectroscopy 下载免费PDF全文
Kevin McEleney Jared P. Bruce Michael S. Freund 《Surface and interface analysis : SIA》2017,49(6):503-514
X‐ray photoelectron spectroscopy (XPS) is a powerful surface characterization technique often relied on for quantification of surface species and coverages. Investigation of silicon microrods, considered a model for high‐aspect‐ratio structures, at different angles with respect to substrate normal was determined to have a significant impact on the relative sensitivity of surface‐bound species on rods relative to the base substrate. Comparison between planar silicon and microrod arrays demonstrates that the angular dependence is complicated and that careful studies must optimize conditions to differentiate between surfaces. In addition, the use of reverse angle resolved XPS, where the substrate is turned away from the X‐ray source, is shown to assist in simplifying the spectrum by removing underlying signal from the substrate near the base. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
72.
<正>Two new eudesmane derivatives were isolated from the leaves and flowers of Verbesina virginica,along with the known 6-O-β-E -p-coumaroyl-4α-hydroxyeudesmane(1).Their structures were determined as 6-O-β-Z-p-coumaroyl-4α-hydroxyeudesmane(2) and 6-O-α-E-p-coumaroyl-1β-4α-dihydroxyeudesmane(3) by spectroscopic methods. 相似文献
73.
Thermoresponsive copolymer nanofilms for controlling cell adhesion, growth, and detachment 总被引:1,自引:0,他引:1
Yang L Pan F Zhao X Yaseen M Padia F Coffey P Freund A Yang L Liu T Ma X Lu JR 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17304-17314
This study reports the development and use of a novel thermoresponsive polymeric nanofilm for controlling cell adhesion and growth at 37 °C, and then cell detachment for cell recovery by subsequent temperature drop to the ambient temperature, without enzymatic cleavage or mechanical scraping. A copolymer, poly(N-isopropylacrylamide-co-hydroxypropyl methacrylate-co-3-(trimethoxysilyl)propyl methacrylate) (abbreviated PNIPAAm copolymer), was synthesized by free radical polymerization. The thermoresponses of the copolymer in aqueous solution were demonstrated by dynamic light scattering (DLS) through detecting the sensitive changes of copolymer aggregation against temperature. The DLS measurements revealed the lower critical solution temperature (LCST) at approximately 30 °C. The PNIPAAm film stability and robustness was provided through silyl cross-linking within the film and with the hydroxyl groups on the substrate surface. Film thickness, stability, and reversibility with respect to temperature switches were examined by spectroscopic ellipsometry (SE), atomic force microscopy (AFM), and contact angle measurements. The results confirmed the high extent of thermosensitivity and structural restoration based on the alterations of film thickness and surface wettability. The effective control of adhesion, growth, and detachment of HeLa and HEK293 cells demonstrated the physical controllability and cellular compatibility of the copolymer nanofilms. These PNIPAAm copolymer nanofilms could open up a convenient interfacial mediation for cell film production and cell expansion by nonenzymatic and nonmechanical cell recovery. 相似文献
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Strong fluence dependence of photodesorption cross sections is observed in femtosecond laser photodesorption of NO from (NO)2 on silver nanoparticles, in contrast to femtosecond photodesorption on bulk metals. The time scale of excitation buildup is found to be equal or less than the pulse duration of ~100 fs; NO translational energies are independent of fluence and pulse duration. We propose a nanoparticle-specific nonlinear mechanism in which, due to confinement, strongly nonthermal hot-electron distributions are maintained during the femtosecond pulses, enhancing the normal desorption pathway. 相似文献
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Prof. Hans‐Joachim Freund Dr. Niklas Nilius Dr. Thomas Risse Dr. Swetlana Schauermann Dr. Thomas Schmidt 《Chemphyschem》2011,12(1):79-87
We describe four new experimental techniques advanced during the last decade in the authors’ laboratory. The techniques include photon scanning tunneling microscopy; aberration‐corrected low‐energy electron microscopy in combination with photoelectron emission microscopy, microcalorimetry, and electron‐spin resonance spectroscopy. It is demonstrated how those techniques may be applied to solve fundamental problems in surface science with growing demands to tackle complex nanoscopic systems, and, in particular in catalysis science, which, without the availability of those techniques, would be difficult if not impossible to address. 相似文献
80.
We study four measures of problem instance behavior that might account for the observed differences in interior-point method
(IPM) iterations when these methods are used to solve semidefinite programming (SDP) problem instances: (i) an aggregate geometry
measure related to the primal and dual feasible regions (aspect ratios) and norms of the optimal solutions, (ii) the (Renegar-)
condition measure C(d) of the data instance, (iii) a measure of the near-absence of strict complementarity of the optimal solution, and (iv) the
level of degeneracy of the optimal solution. We compute these measures for the SDPLIB suite problem instances and measure
the sample correlation (CORR) between these measures and IPM iteration counts (solved using the software SDPT3) when these
measures have finite values. Our conclusions are roughly as follows: the aggregate geometry measure is highly correlated with
IPM iterations (CORR = 0.901), and provides a very good explanation of IPM iterations, particularly for problem instances
with solutions of small norm and aspect ratio. The condition measure C(d) is also correlated with IPM iterations, but less so than the aggregate geometry measure (CORR = 0.630). The near-absence
of strict complementarity is weakly correlated with IPM iterations (CORR = 0.423). The level of degeneracy of the optimal
solution is essentially uncorrelated with IPM iterations.
This research has been partially supported through the MIT-Singapore Alliance. 相似文献