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A theoretical framework is presented to treat both imaging and diffraction experiments performed with point-focus and line-focus X-ray sources, with particular emphasis on two-dimensional and planar X-ray waveguides. In particular, point-projection and line-projection microscopy has been approached within the Huygens-Fresnel formalism; point-projection and line-projection diffraction, such as spatially-resolved Bragg/Laue diffraction of crystalline samples in a regime of dynamical scattering, has been treated both by means of the Huygens-Fresnel formalism and of the Takagi-Taupin dynamical theory. Both in point- and line- projection geometry, simply rotating the investigated crystalline samples, it is possible to switch from Fresnel self-imaging to Bragg/Laue diffraction conditions. This means to image, within the same experiment, either morphological features, with a sub-micrometric resolution, out of the exact diffraction condition, or the structure order on an atomic scale if placing the sample in diffraction. 相似文献
63.
Figuerola A Fiore A Di Corato R Falqui A Giannini C Micotti E Lascialfari A Corti M Cingolani R Pellegrino T Cozzoli PD Manna L 《Journal of the American Chemical Society》2008,130(4):1477-1487
A one-pot, two-step colloidal strategy to prepare bimagnetic hybrid nanocrystals (HNCs), comprising size-tuned fcc FePt and inverse spinel cubic iron oxide domains epitaxially arranged in a heterodimer configuration, is described. The HNCs have been synthesized in a unique surfactant environment by temperature-driven sequential reactions, involving the homogeneous nucleation of FePt seeds and the subsequent heterogeneous growth of iron oxide. This self-regulated mechanism offers high versatility in the control of the geometric features of the resulting heterostructures, circumventing the use of more elaborate seeded growth techniques. It has been found that, as a consequence of the exchange coupling between the two materials, the HNCs exhibit tunable single-phase-like magnetic behavior, distinct from that of their individual components. In addition, the potential of the heterodimers as effective contrast agents for magnetic resonance imaging techniques has been examined. 相似文献
64.
Liberato Cardellini 《Foundations of Chemistry》2008,10(2):129-134
Research into learners' ideas about science suggests that students often have alternative conceptions about important science
concepts. Because of this dissatisfaction, constructivism has been adopted as a theoretical framework by many teachers and
researchers, and it has had a curricular influence in many countries. Constructivism is much more than an educational doctrine
and we are aware that a ‘science war’ about the possibility of objectivity is in progress. ‘Constructivism’ cannot necessary
be a package deal: it must be possible to accept educational suggestions deemed useful without buying all the epistemology
or the metaphysical implications. The claim that cognitive agents understand the world by constructing mental representations
of it can be a shared suggestion for changing science instruction. Many teachers are much more concerned in finding productive
teaching methods than about philosophical questions as if knowledge must be considered an objective representation of the
real world or not. We have to ponder if some ideas from the constructivist theory of instruction can help instructors to become
better teachers. The pragmatic suggestions that come from the constructivist theory of instruction developed by von Glasersfeld,
the leading proponent of radical constructivism, could be a good start in this␣search. 相似文献
65.
Ippolito Antonini Mario Cardellini Francesco Claudi Palmarisa Franchetti Franco Micheletti Moracci 《合成通讯》2013,43(14):1229-1232
Stereoselective one-step synthesis of 4-alkoxy-1-ethoxycarbonylmethylazetidin-2-ones from acid chlorides and N-ethoxycarbonylmethylimidates. 相似文献
66.
Luigi Carbone Dr. Liberato Manna Dr. Carsten Sönnichsen Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(24):4282-4283
Amphiphilic hybrid materials are formed from polymer‐coated semiconductor nanoparticles that simulate a surfactant‐like response (see picture). The strength and density of the surface coating are the key assembling forces driving a transition from single particles to cylindrical or vesicular superstructures.
67.
Riccardo Di Corato Philomena Piacenza Mariarosaria Musarò Raffaella Buonsanti Pantaleo Davide Cozzoli Massimo Zambianchi Giovanna Barbarella Roberto Cingolani Liberato Manna Teresa Pellegrino 《Macromolecular bioscience》2009,9(10):952-958
Nanostructures displaying fluorescence and magnetic properties at the same time are potentially useful for achieving simultaneous bio‐separation and bio‐sensing (e.g., magnetic separation coupled with multiplexing optical detection of different tumour cell populations). Spherical nanobeads that display both fluorescent and magnetic features are reported; they are fabricated by grafting fluorescent oligothiophene molecules to an amphiphilic polymer that is then used to enwrap iron oxide nanoparticles, which acts as the magnetic domain. By tuning experimental conditions, control over the number of magnetic nanoparticles per bead and over the bead diameter (30–400 nm) was achieved. A cell separation efficiency of the level required for cell sorting applications is also reported.
68.
Current efforts and success of nanoscale science and technology are related to the fabrication of functional materials and devices in which the individual units and their spatial arrangement are engineered down to the nanometer level. One promising way of achieving this goal is by assembling colloidal inorganic nanocrystals as the novel building blocks of matter. This trend has been stimulated by significant advances in the wet-chemical syntheses of robust and easily processable nanocrystals in a wide range of sizes and shapes. The increase in the degree of structural complexity of solution-grown nanostructures appears to be one of the natural directions towards which nanoscience will increasingly orient. Recently, several groups have indeed devised innovative syntheses of nanocrystals through which they have been able to group inorganic materials with different properties in the same particle. These approaches are paving the way to the development of nanosized objects able to perform multiple technological tasks. In this critical review (165 references), we will summarize the recent advances in the synthesis of colloidal nanocrystals, with emphasis on the strategies followed for the fabrication of nano-heterostructures, as well as on their properties and the perspectives in this field. 相似文献
69.
Dalmora SL da Silva Sangoi M Barth T Brum L Vaccari SF 《Journal of AOAC International》2006,89(1):58-64
The low-molecular weight heparin nadroparin calcium is used clinically for the prevention and treatment of venous and arterial thrombosis. The antifactor Xa and antifactor IIa assays were validated by investigating the parameters of range, linearity (r2 = 0.9905 and r2 = 0.9914, respectively) precision, accuracy, and robustness. The 2 methods incorporated a chromogenic endpoint and detection at 405 nm, yielding good results with detection limits of 0.004 and 0.01 IU/mL and quantitation limits of 0.01 and 0.03 IU/mL, respectively, for the antifactor Xa and antifactor IIa assays. Nadroparin calcium pharmaceutical products were evaluated by the antifactor Xa assay and the antifactor IIa assay, giving potencies between 93.86 and 109.88%, with an antifactor Xa/antifactor IIa ratio between 3.2 and 3.7. The results demonstrated the validity of the assays that are useful methodologies for the routine quality control of nadroparin in pharmaceutical formulations. 相似文献