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31.
Street A. M. Stavrinou P. N. O'brien D. C. Edwards D. J. 《Optical and Quantum Electronics》1997,29(3):349-378
This paper reviews the research effort to date into optical wireless communication systems, both in academic and industrial
contexts. The idea of using the optical medium for wireless communications is not new, having been proposed as a means for
indoor communications almost two decades ago. However, the last few years have seen an explosive interest in the potential
for free space optical systems to provide portable data communications. One of the prime motivators for reconsidering the
use of an optical carrier in the wireless context is the demand for greater transmission bandwidths. The radio frequency spectrum
is already exceedingly congested and frequency allocations of sufficient bandwidths are extremely hard to obtain. Further,
for the high bandwidth services envisaged, the use of microwave or mm-wave systems will be required, where device technology
is currently either expensive or immature. Proponents of optical wireless systems argue that the optical medium is the only
cost-effective way to provide high bit-rate mobile services to volume markets. This paper identifies the technical obstacles
and limitations of indoor optical wireless delivery in addition to techniques for mitigating these effects and shows that
infrared is a viable alternative to radio for certain applications.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
32.
The two-dimensional, laminar boundary-layer equations of heat, mass and momentum at a smooth, phase-changing, gas-liquid interface are solved numerically by the Keller Box method. The gas and liquid regimes are embedded in a single marching scheme which computes interfacial parameters implicitly. Results of both self-similar and non-similar boundary-layer computations are presented and effects of mild pressure gradient, a mean current in the liquid, and free-stream vapour concentration on the interfacial parameters are analysed. In order to assess the accuracy of the method, several self-similar problems are solved by Runge-Kutta integration and results are compared to those obtained by the finite-difference scheme. Agreement is excellent in all cases. 相似文献
33.
A new method for the extraction of bile acids from human plasma using acetonitrile precipitation of plasma protein and subsequent use of Bond-Elut C18 cartridges is described. After extraction the bile acids can be separated into three fractions: unconjugated, glycine-, and taurine-conjugated, using Sep-Pak SIL cartridges at 4 degrees C, eluting with ethanol--chloroform--water--glacial acetic acid mixtures. These extraction and fractionation procedures were evaluated in terms of recovery, reproducibility and resolution between the fractions. All these parameters were found to be satisfactory. Although the reproducibility of fractionation on Sep-Pak SIL cartridges was found to vary between batches, this did not give rise to significant difficulties. Plasmas from normals and patients with hepatobiliary disease were analysed by capillary gas-liquid chromatography after extraction and fractionation using the procedure described. 相似文献
34.
Ross Street 《Applied Categorical Structures》1995,3(2):139-149
Simple and semisimple additive categories are studied. We prove, for example, that an artinian additive category is (semi)simple iff it is Morita equivalent to a division ring(oid). Semiprimitive additive categories (that is, those with zero radical) are those which admit anoether full, faithful functor into a category of modules over a division ringoid. 相似文献
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Adam D. Darwish Anthony G. Avent Joan M. Street 《Journal of fluorine chemistry》2004,125(9):1383-1391
Pyrolytic trifluoromethylation of [70]fullerene with CF3CO2Ag at 300 °C results in the addition of up to 12 CF3 groups to the fullerene cage. Forty-six C70(CF3)n derivatives (numbers in parentheses) were separated by two-stage high pressure liquid chromatography (HPLC) as follows: n = 2(2), 4(16), 6(9), 8(14) 10(5), some being characterised by NMR. The range of derivatives is much greater than for other [70]fullerene reactions, and as with [60]fullerene trifluoromethylation, no single derivative is dominant, indicating that kinetic stability mainly controls product formation. NMR spectra show most derivatives to be unsymmetrical, with combinations of quartets and septets (overlapping quartets) due to contiguous (‘linear’) addend arrays, having significantly different coupling constants of the ‘terminal’ quartets of between 9.1 and 17.7 Hz. These differences, together with those observed previously in trifluoromethylation of [60]fullerene are consistent with addition across both 6:6- and 5:6-ring junctions. Of the two C70(CF3)2 isomers, one has either Cs or C2 symmetry, the other has C1 symmetry, whilst the C70(CF3)4 derivatives fall into four categories: (i) symmetrical compounds (one gives only two singlets in the NMR); (ii) unsymmetrical compounds that show a ‘linear’ coupling sequence; (iii) unsymmetrical compounds having a remote pairs of adjacent groups; (iv) compounds having a coupled array of three CF3 groups, together with a remote group suggesting sterically-driven migration. The first evaluation of differential NMR couplings across 6:6- and 5:6-bonds in a fullerene has been made using C60F6 as a model. 相似文献
39.
Steven T. G. Street Yunxiang He Xu-Hui Jin Lorna Hodgson Paul Verkade Ian Manners 《Chemical science》2020,11(32):8394
Polymer-based nanoparticles show substantial promise in the treatment and diagnosis of cancer and other diseases. Herein we report an exploration of the cellular uptake of tailored, low dispersity segmented 1D nanoparticles which were prepared from an amphiphilic block copolymer, poly(dihexylfluorene)-b-poly(ethyleneglycol) (PDHF13-b-PEG227), with a crystallizable PDHF core-forming block and a ‘stealth’ PEG corona-forming block with different end-group functionalities. Segmented C–B–A–B–C pentablock 1D nanofibers with varied spatially-defined coronal chemistries and a selected length (95 nm) were prepared using the living crystallization-driven self-assembly (CDSA) seeded-growth method. As the blue fluorescence of PDHF is often subject to environment-related quenching, a far-red BODIPY (BD) fluorophore was attached to the PEG end-group of the coronal B segments to provide additional tracking capability. Folic acid (FA) was also incorporated as a targeting group in the terminal C segments. These dual-emissive pentablock nanofibers exhibited uptake into >97% of folate receptor positive HeLa cells by flow cytometry. In the absence of FA, no significant uptake was detected and nanofibers with either FA or BD coronal groups showed no significant toxicity. Correlative light and electron microscopy (CLEM) studies revealed receptor-mediated endocytosis as an uptake pathway, with subsequent localization to the perinuclear region. A significant proportion of the nanofibers also appeared to interact with the cell membrane in an end-on fashion, which was coupled with fluorescence quenching of the PDHF core. These results provide new insights into the cellular uptake of polymer-based nanofibers and suggest their potential use in targeted therapies and diagnostics.The cellular uptake of tailored, modular, and segmented low dispersity nanofibers with a crystalline π-conjugated core has been studied. 相似文献
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