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21.
To harness the full spectrum of solar energy, Fresnel reflection at the surface of a solar cell must be eliminated over the entire solar spectrum and at all angles. Here, we show that a multilayer nanostructure having a graded-index profile, as predicted by theory [J. Opt. Soc. Am. 66, 515 (1976); Appl. Opt. 46, 6533 (2007)], can accomplish a near-perfect transmission of all-color of sunlight. An ultralow total reflectance of 1%-6% has been achieved over a broad spectrum, lambda = 400 to 1600 nm, and a wide range of angles of incidence, theta = 0 degrees-60 degrees . The measured angle- and wavelength-averaged total reflectance of 3.79% is the smallest ever reported in the literature, to our knowledge. 相似文献
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Mont N Mehta VP Appukkuttan P Beryozkina T Toppet S Van Hecke K Van Meervelt L Voet A DeMaeyer M Van der Eycken E 《The Journal of organic chemistry》2008,73(19):7509-7516
A novel microwave-assisted, highly efficient protocol for the synthesis of hitherto unknown aza-analogues of (-)-Steganacin, a naturally occurring bisbenzocyclooctadiene lignan lactone with potent antileukemic and tubulin polymerization inhibitory activity, has been developed. Focused microwave irradiation is demonstrated to be highly beneficial in promoting the three crucial steps of the sequence to effect the final ring closure: the Suzuki-Miyaura reaction, Cu-mediated A3-coupling, as well as the intramolecular Huisgen 1,3-dipolar cycloaddition. 相似文献
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Jens Mahnke Andreas Zanin Wolf-Walther du
Mont Frank Ruthe Peter G. Jones 《无机化学与普通化学杂志》1998,624(9):1447-1454
The New P -Phosphanylphosphaalkene 1-Bis(trimethylsilyl)methylidene-2,2-diisopropyldiphosphane: First Reactions at its P=C and P–P Bonds (Me3Si)2C=PCl ( 1 ) reacts with the trichlorosilylphosphanes RR′PSiCl3 (R and R′ = t-Bu or i-Pr) providing the new P-dialkylphosphanylphosphaalkenes (Me3Si)2C=P–P-i-Pr2 ( 2 ) and (Me3Si)2C=P–P(t-Bu)(i-Pr) ( 3 ) as well as the known (Me3Si)2C=P–P-t-Bu2 ( 4 ). The P=C double bond of 2 can be protected reversibly by a [2 + 4]-cycloaddition with cyclopentadiene resulting in the formation of a P-phosphanyl-phosphanorbornene derivative 5 . The [2 + 4]-cycloaddition of 2 with 2,3-dimethylbutadiene provides the cyclic diphosphane 6 . Reactions of 2 with sulfur and selenium were followed by 31P and 77Se nmr: Chalcogen insertion into the P–P bond leads to the products (Me3Si)2C=P–X–P-i-Pr2 9 a (X = S) and 9 b (X = Se). Subsequent σ3λ3 → σ4λ5 oxidation steps of 9 a with S and of 9 b with Se lead to compounds (Me3Si)2C=P–X–P(=X)-i-Pr2 10 a (X = S) and 10 b (X = Se), which contain phosphinic acid functions with the phosphaalkene moieties attached to S or Se. 10 a and 10 b were not isolated in a pure state. However, trapping 10 b from an enriched solution by [2 + 4]-cycloaddition with cyclopentadiene allowed the isolation of the P-diseleno-phosphinato-phosphanorbornene 12 . The constitution of new compounds 2 , 3 , 5 , 6 and 12 was confirmed by elemental analyses, nmr and mass spectra. The structures of cycloadducts 5 and 6 were determined by X-ray diffraction analysis. 相似文献
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Burck S Gudat D Nieger M Du Mont WW 《Journal of the American Chemical Society》2006,128(12):3946-3955
P-Hydrogen-substituted 1,3,2-diazaphospholenes 1 were prepared by an improved procedure from diazadienes and were characterized by spectroscopy and in one case by X-ray diffraction. A unique hydride-type reactivity of the P-H bonds was documented by extensive reactivity studies. Aldehydes and ketones were readily reduced to diazaphospholene derivatives of the corresponding alcohols, with alkyl-substituted ketones being converted at much lower rates than aldehydes or diaryl ketones. Reactions with the tetrachlorides of group 14 elements proceeded via hydride/chloride metathesis to give either partially chlorinated derivatives EH(n)Cl(4-n) (n = 0-3 for E = C, Si) or HCl and phosphenium salts 16c[ECl3] (for E = Ge, Sn) which were characterized by spectroscopic and X-ray diffraction studies. Tin dichloride was readily reduced to the element. Reactions of 1c with the P-chloro-diazaphospholene 3c and the salt 16c[OTf] allowed the first experimental detection of intermolecular exchange of a hydride, rather than a proton, between phosphine derivatives. Computational studies indicated that the hydride transfer between 1c and the cation 16c involves a transient H-bridged species with bonding properties similar to those of B2H7-. The preference for the formation of these bridged intermediates over P-P bonded phosphenium-phosphine adducts is attributed to the low electrophilicity of the diazaphospholenium cations and characterizes a novel reaction mode for phosphenium ions. 相似文献
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The complex PtClMe(2,2′-bipy)(MeO2CCCCO2Me) decomposes to PtClMe(2,2′bipy) and MeO2 CCCCO2 Me by a complex mechanism involving preliminary ionisation of the chloride ligand, but the dissociation of CF3CCCF3 from PtlMe(2,2′-bipy)(CF3CCCF3) takes place without ionisation of iodide. 相似文献
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