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991.
The magnesium transition metal stannides MgRuSn4 and MgxRh3Sn7—x (x = 0.98—1.55) were synthesized from the elements in glassy carbon crucibles in a water‐cooled sample chamber of a high‐frequency furnace. They were characterized by X‐ray diffraction on powders and single crystals. MgRuSn4 adopts an ordered PdGa5 type structure: I4/mcm, a = 674.7(1), c = 1118.1(2) pm, wR2 = 0.0506, 515 F2 values and 12 variable parameters. The ruthenium atoms have a square‐antiprismatic tin coordination with Ru—Sn distances of 284 pm. These [RuSn8/2] antiprisms are condensed via common faces forming two‐dimensional networks. The magnesium atoms fill square‐prismatic cavities between adjacent [RuSn4] layers with Mg—Sn distances of 299 pm. The rhodium based stannides MgxRh3Sn7—x crystallize with the cubic Ir3Ge7 type structure, space groupe Im3m. The structures of four single crystals with x = 0.98, 1.17, 1.36, and 1.55 have been refined from X‐ray diffractometer data. With increasing tin substitution the a lattice parameter decreases from 932.3(1) pm for x = 0.98 to 929.49(6) pm for x = 1.55. The rhodium atoms have a square antiprismatic tin/magnesium coordination. Mixed Sn/Mg occupancies have been observed for both tin sites but to a larger extend for the 12d Sn2 site. Chemical bonding in MgRuSn4 and MgxRh3Sn7—x is briefly discussed. 相似文献
992.
993.
Anton Hammerl Gerhard Holl Manfred Kaiser Thomas M. Klaptke Rainer Krnzle Martin Vogt 《无机化学与普通化学杂志》2002,628(1):322-325
1,2‐Diorganylsubstituted derivatives of hydrazinium azide were examined in order to investigate their higher volatility and higher sensitivity to initiation compared to 1,1‐diorganylsubstituted hydrazinium azide derivatives. The compounds were synthesized from the respective hydrazines by reaction with HN3 and characterized by elemental analysis, vibrational (IR, Raman) and multinuclear NMR spectroscopy (1H, 13C, 14N). Their sensitivity to friction, shock, electrostatic impact and heat was examined and the explosion products were investigated. The crystal structure of pyrazolidinium azide was determined. 相似文献
994.
995.
996.
Ralf Goretzki Gerhard Fink Bernd Tesche Bernd Steinmetz Rainer Rieger Wolfram Uzick 《Journal of polymer science. Part A, Polymer chemistry》1999,37(5):677-682
With the development of methods to support metallocenes and methylaluminoxane cocatalysts on suitable carriers, it became possible to combine the specific advantages of homogeneous metallocene catalysis with those of heterogeneous Ziegler catalysts in olefin polymerization. By means of ethylene polymerization it could be shown that the method of supporting methylaluminoxane and metallocene on porous silica has a substantial influence on the progress of polymerization. In particular, fragmentation of catalyst particles during polymerization can be circumvented, maintaining the catalyst activity, if active catalyst sites are being generated on the particle surface only. A method of preparation for such newly designed supported metallocene catalysts is presented, where the active catalyst sites are located exclusively on the particle surface. Furthermore, the kinetics of ethylene polymerization and morphology properties prior to and after polymerization are discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 677–682, 1999 相似文献
997.
998.
Pure polycrystalline Li2C2 could be obtained by the reaction of lithium and graphite flakes in an arc-melting furnace. X-ray powder investigations on these samples confirm the crystal structure given by Juza, Wehle, and Schuster (Immm, No. 71, Z = 2) which is isotypic to Rb2O2 and Cs2O2. At about 500 °C a reversible phase transition (1st order) to a cubic modification (Fm 3 m, No. 225, Z = 4) has been observed. This high temperature modification can be described as an antifluorite-structure with disordered C22– dumbbells. 相似文献
999.
1-Ethoxycarbonyl-3-ferrocenyl-propane-1,3-dion and Ferrocene-1,1′bis(2,4-dioxobutanoic acid ethylester) as Ligands for Transition Metal Ions. Crystal Structure of Bis(1-ethoxycarbonyl-3-ferrocenyl-propane-1,3dionato)copper(II) The ligands 1-ethoxycarbonyl-3-ferrocenyl-propane-1,3-dion and ferrocene-1,1′-bis(2,4-dioxo-butanoic acid ethylester) have been prepared by reaction of acetylferrocene or 1,1′-diacetylferrocene and diethyl oxalate. They yield neutral chelates with CuII, NiII, ZnII, CoII, and MnII. The acid dissociation constants of the ligands and the stability constants of their metal complexes including FeII complexes are reported. The structure of bis(1-ethoxycarbonyl-3-ferrocenyl-propane-1,3-dionato)copper(II) was determined by X-ray structure analysis. A cis arrangement with a nearly square planar coordination sphere at the Cu atom is found. 相似文献
1000.
Martin Stork Matthias Koch Markus Klapper Klaus Müllen Heike Gregorius Ursula Rief 《Macromolecular rapid communications》1999,20(4):210-213
In this paper we report on a zirconocene dichloride/methylaluminoxane catalyst system supported on a crosslinked polystyrene in order to provide ethylene polymerization catalysts for gas phase or slurry processes. Our novel approach uses the Diels‐Alder reaction of cyclopentadiene functions as the final, cross‐linking synthetic step. This provides polymer supported zirconocene catalysts with a homogeneous distribution of active sites. The catalysts were shown to be highly active and to form spherical beads as proven by scanning electron microscopy. 相似文献