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111.
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113.
Syntheses and Crystal Structures of New Selenido-bridged Ruthenium Clusters The reaction of Se(SiMe3)2 with [RuCl2(PPh3)3], or a mixture of [RuCl2(PPh3)3] and alkylphosphines leads to the formation of selenido-bridged ruthenium clusters. In this publication the compounds [Ru6Se8(PPh3)6] ( 1 ), [Ru6Se8(PEt3)6] ( 2 ) und[Ru6Se8(PnPr3)6] ( 3 ) are described.The compounds 1-3 contain Ru616+ cluster cores with Ru2+ and Ru3+ centers. The structures of these compounds were elucidated by single crystal X-ray structural analyses. 相似文献
114.
Synthesis and Crystal Structure of [(n‐Bu)4N][W6Cl18] Single‐crystals of [(n‐Bu)4N][W6Cl18] were obtained as thin needles by adding methanol to a solution of W6Cl18 and [(n‐Bu)4N]Cl in tetrahydrofuran. The structure was determined by single‐crystal X‐ray diffraction at 210 K. [(n‐Bu)4N][W6Cl18] crystallizes in the monoclinic space group C 2/c with Z = 8 and the lattice parameters a = 2175.6(1) pm, b = 1738.0(1) pm, c = 2160.36(9) pm, and β = 91.680(5) °. The crystal structure contains isolated [(W6Cl12i)Cl6a]— clusters and [(n‐Bu)4N]+ ions. 相似文献
115.
Markus Håkansson Johanna Suomi Mauri Nauma Jouko Kankare Jarkko U. Eskola 《Analytica chimica acta》2006,556(2):450-454
Double insulating barrier tunnel emission electrodes were fabricated by adding a new pure aluminum layer upon oxidized aluminum electrodes by vacuum evaporation and thermally oxidizing the new aluminum layer in air at room temperature. Resulting Al/Al2O3/Al/Al2O3 electrodes allow the use of various aluminum alloys in the electrode body necessary for hardness or shaping ability of the electrode while obtaining the luminescence properties of pure aluminum oxide. During electrical excitation of luminescent labels by cathodic hot electron injection into aqueous electrolyte solution, the background noise is mainly based on high-field-induced solid-state electroluminescence and F-center luminescence of the outer aluminum oxide film. The more defect states and/or impurity centers the outer oxide film contains, the higher is the background emission intensity. The present electrode fabrication method provides a considerable improvement in signal-to-noise ratio for time-resolved electrochemiluminescence (TR-ECL) measurements when the original native oxide film of the electrode body contains luminescence centers displaying long-lived luminescence. The excellent performance of the present electrodes is demonstrated by extremely low-level detection of Tb(III) chelates, luminol, Pt(II) coproporphyrin and Tb(III) labels in an immunometric immunoassay by time-resolved electrochemiluminescence. 相似文献
116.
Small-angle neutron scattering study of structural changes in temperature sensitive microgel colloids 总被引:3,自引:0,他引:3
Stieger M Richtering W Pedersen JS Lindner P 《The Journal of chemical physics》2004,120(13):6197-6206
The structure of temperature-sensitive poly(N-isopropylacrylamide) microgels in dilute suspension was investigated by means of small-angle neutron scattering. A direct modeling expression for the scattering intensity distribution was derived which describes very well the experimental data at all temperatures over an extensive q range. The overall particle form as well as the internal structure of the microgel network is described by the model. The influence of temperature, cross-linking density, and particle size on the structure was revealed by radial density profiles and clearly showed that the segment density in the swollen state is not homogeneous, but gradually decays at the surface. The density profile reveals a box profile only when the particles are collapsed at elevated temperatures. An increase of the cross-linking density resulted in both an increase of the polymer volume fraction in the inner region of the particle and a reduction of the smearing of the surface. The polymer volume fraction inside the colloid decreased with increasing particle size. The structural changes are in good agreement with the kinetics of the emulsion copolymerization used to prepare the microgel colloids. 相似文献
117.
Hans Bock Claudia Arad Christian Nther Zdenek Havlas Ilka Gbel Andreas John Markus Kleine 《Helvetica chimica acta》1995,78(4):866-878
Electron Transfer and Ion Pair Formation Single Crystal Structure of Bis(sodium 1,1′-biphenyl-2-thiolate-diglyme): An Intermediate in the Reductive Ring Opening of Dibenzothiophene On Na-metal reduction of dibenzothiophene, the five-membered sulfur ring opens to form a colorless 1,1′-biphenyl-2-thiolate sodium salt, which, according to its single-crystal structure determination, is a dimer containing a four-membered, twice diglyme-solvated ring (diglyme···Na⊕?SR)2. Additional measurements provide the following information: cyclic voltammetry in aprotic MeCN solution shows one quasi-reversible electron transfer at E = ?2.58 V. The dibenzothiophene radical anion can be generated in aprotic THF solution at a K mirror and characterized by an 81-line ESR spectrum and its simulation. This blue species is also the first UV/VIS detectable one before the solution changes via green (due to blue + yellow color mixing) to yellow, yielding across an isosbestic point a second and diamagnetic compound. All of the above results suggest a consecutive two-electron reduction followed by an intersystem protonation, M + (e?) → M.? (blue) + (e?) → (M??, yellow?) + (H⊕) → MH? (colorless), to yield the crystallized and structurally characterized reaction intermediate. The diglyme-solvated sodium-salt dimer provides a basis for a quantum-chemical discussion of some facets of the most likely microscopic reduction pathway. 相似文献
118.
Avula B Ganzera M Warnick JE Feltenstein MW Sufka KJ Khan IA 《Journal of chromatographic science》2004,42(7):378-382
Xanthohumol (XN) is the major prenylated flavonoid in hop plants and as such a constituent of beer. Pharmacological studies have shown that XN possesses marked antioxidant and antiproliferative effects. In order to study the resorption and metabolism of this compound, reversed-phase high-performance liquid chromatography is used for the determination of XN in rat plasma, urine, and feces. In session one, rats receive either oral or intravenous (iv) administration (20 mg/kg body weight) of XN. In session two, rats receive oral administration of 50, 100, 200, 400, and 500 mg/kg body weight XN for bioavailability studies at various dose levels. Plasma, urine, and feces are collected at varying time points and assayed for their XN content. Plasma levels of XN fell rapidly within 60 min after iv administration; no XN is detected in plasma after oral administration in either session. XN and its metabolites are excreted mainly in feces within 24 h of administration. The method is a reliable tool for performing studies of XN in different biological material. 相似文献
119.
120.
Travaille AM Kaptijn L Verwer P Hulsken B Elemans JA Nolte RJ van Kempen H 《Journal of the American Chemical Society》2003,125(38):11571-11577
The lateral alignment of [012] habit-modified calcite crystals with respect to a carboxylic acid terminated self-assembled monolayer (SAM) of thiols has been determined. The crystals were grown from a Kitano solution (pH 5.6-6.0), and the samples were investigated with scanning electron microscopy, X-ray diffraction, and polarization microscopy. For the first time, a lattice match in one direction, which is the nearest neighbor direction of the SAM and the calcite <100> direction, has been experimentally shown. The experimental results are in good agreement with the theoretical models proposed in previous work, and it is expected that this method can be applied to similar systems where inorganic crystals nucleate with a preferred orientation to a SAM. 相似文献