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91.
92.
Edward A. Karakhanov Anton L. Maximov Anna V. Zolotukhina Nadezhda Yatmanova Edward Rosenberg 《应用有机金属化学》2015,29(11):777-784
A series of Pd–Ag mixed‐metal nanocatalysts were prepared by reduction of Pd–Ag salts in the presence of poly(propylene imine) dendrimers, which were covalently bound to the surface of a silica polyamine composite, BP‐1 (polyallylamine covalently bound to a silanized amorphous silica gel). Three different Pd‐to‐Ag ratios were evaluated (50:50, catalyst 1 ; 40:60, catalyst 2 ; 60:40, catalyst 3 ) with the goal of determining how the amount of Ag effects selectivity, rate and conversion in the selective reduction of alkynes, such as phenylacetylene and 1‐ or 4‐octyne, to the corresponding alkenes. Conditions for the catalysis are reported where there is improved selectivity without a serious reduction in rate when compared with the analogous Pd‐only catalysts. Catalyst 2 worked best for phenylacetylene and catalyst 3 worked best for the octynes. The catalysts could be reused seven times without loss of activity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
93.
94.
95.
The helicoid and plane are the only known complete embedded minimal surfaces inR
3 that are simply connected. We prove the helicoid and plane are the only surfaces of this type that have bounded curvature
and meet each plane x3 = constant in (at most) one smooth connected curve. 相似文献
96.
97.
Arun K. Raha Mohammad R. Hassan Shariff E. Kabir Md. Manzurul Karim Brian K. Nicholson Ayesha Sharmin Luca Salassa Edward Rosenberg 《Journal of Cluster Science》2008,19(1):47-62
Reaction of [Os3(CO)10(CH3CN)2] with thianthrene at 80 °C leads to the nonacarbonyl dihydride compound [Os3(CO)9(μ-3,4-η2-C12H6S2)(μ-H)2] (1) and the 46-electron monohydride compound [Os3(CO)9(μ3-η2-C12H7S2)(μ-H)] (2). Compound 2 reacts reversibly with CO to give the CO adduct [Os3(CO)10(μ-η2-C12H7S2)(μ-H)] (3) whereas with PPh3 it gives the addition product [Os3(CO)9)(PPh3)(μ-η2-C12H7S2)(μ-H)] (4) as well as the substitution product 1,2-[Os3(CO)10((PPh3)2] (5) Compound 2 represents a unique example of an electron-deficient triosmium cluster in which the thianthrene ring is bound to cluster
by coordination of the sulfur lone pair and a three-center-two-electron bond with the C(2) carbon which bridges the same edge
of the triangle as the hydride. Electrochemical and DFT studies which elucidate the electronic properties of 2 are reported.
Dedicated to the memory of a great scientist, F. Albert Cotton. 相似文献
98.
The kinetic and mechanism of thermal decay of transition metal acrylates or its cocrystallites are studied. At 200–300°C the rate of thermal decay can be described by first-order rate equations. The thermal transformations of the metal-containing monomers under study involve dehydration, solid-phase polymerization and thermolysis processes. The composition of products of the thermal transformations are studied. The products of the decay are analyzed by optical and electron microscopy as well as by magnetic measurements, IR and mass spectroscopy. The main solid-state products of decomposition are nanometer-sized particles of metal or its oxide and ferrites with a narrow size distribution stabilized by the polymeric matrix. The average particle sizes, Lav, are 6.0–13.0 nm in the case of FeAcr3 and 6.0 nm for cocrystallites FeCoAcr and Fe2CoAcr. © 1998 John Wiley & Sons, Ltd. 相似文献
99.
Sara Rosenberg 《Tetrahedron letters》2009,50(38):5305-6240
The preparation of chiral spirocyclic ethers via allylic etherification/olefin metathesis of homoallylic alcohols is investigated. This reaction sequence transforms the enantiopure substrate alcohols, synthesized by a one-pot asymmetric rhodium-catalyzed conjugate addition/metal-mediated allylation procedure, into the desired spiro ethers with full conversions and in excellent isolated yields. The synthetic sequence provides an efficient means for a rapid construction of functionalized spiro ethers in a stereoselective manner. 相似文献
100.
Ivana Kiov Zdenk To
ík Milo Budínský Ondej imk Radek Liboska Dominik Rejman Ondej Pa
es Ivan Rosenberg 《Tetrahedron letters》2009,50(49):6745-6747
A straightforward procedure leading to the new phosphonylating reagent, methyl 4-toluenesulfonyloxymethylphosphonate, requiring no chromatographic purification is described. This stable reagent works with the same efficiency as dimethyl and other dialkyl esters for the introduction of an O-phosphonomethyl moiety while, in contrast to dimethyl ester, it does not cause any unwanted methylation of sensitive functionalities. Its utility for the alkylation of protected nucleosides in high yield is exemplified. 相似文献