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951.
The reaction of Cp2Sm(THF) with 1,2-dibromoethane or 1,2-diiodoethane leads to an equimolar mixture of Cp3Sm(THF) and CpSmX2(THF)3 (X = Br, I). CpSmBr2(THF)3 crystallizes in the monoclinic system (P21, Z = 2, a = 804.6(1), b = 1507.6(2), c = 913.8(1) pm, β = 107.36(1)°, R1 = 0.0327, wR2 = 0.0578), while CpSmI2(THF)3 is orthorhombic (Pna21, Z = 4, a = 1950.6(3), b = 1377.1(2), c = 831.93(9) pm, R1 = 0.0438, wR2 = 0.0412). The ligand arrangement around the formally eight coordinate Sm atom is a distorted octahedron with the centroid of the Cp-ring and one THF-molecule in the apical positions, whilst the halides are transoid in the equatorial plane. 相似文献
952.
Synthesis and Crystal Structures of the Samarium Complexes [SmI2(DME)3] and [Sm2I(NPPh3)5(DME)] When treated with ultrasound, the reaction of samarium metal with N-iodine-triphenylphosphaneimine in 1,2-dimethoxyethane (DME) leads to the two samarium complexes [SmI2(DME)3] ( 1 ) and [Sm2I(NPPh3)5(DME)] ( 2 ), which are separated from each other by fractional crystallization. 1 could be isolated in two different crystallographic forms, namely as brownish black crystals ( 1 a ) and as violet-black crystals ( 1 b ), both of them are characterized by crystal structure analyses. 1 a : Space group P21/c, Z = 4, lattice dimensions at –80 °C: a = 1459.4(1), b = 1314.4(1), c = 2293.6(2) pm, β = 99.245(8)°, R = 0.0344. The structure of 1 a holds two crystallographically independent molecules [SmI2(DME)3], in which the samarium atoms have coordination number eight. The two individuals differ from each other particularly in their I–Sm–I bond angles, which are 157.94 and 178.45°. 1 b : Space group P21, Z = 2, lattice dimensions at –80 °C: a = 849.4(3), b = 1060.1(3), c = 1235.1(6) pm, b = 93.86(5)°, R = 0.0251. 1 b has a molecular structure similar to that of 1a with a bond angle I–Sm–I of 158.40°. The phosphoraneiminato complex [Sm2I(NPPh3)5(DME)] ( 2 ) forms colourless, moisture sensitive crystals which contain two molecules DME per formula unit. 2 · 2 DME: Space group P1, Z = 2, lattice dimensions at –80 °C: a = 1405.0(4), b = 1656.5(3), c = 2208.3(7) pm, α = 89.60(3)°, β = 72.96(4)°, γ = 78.70(3)°, R = 0.0408. In 2 the two samarium atoms are linked via the μ-N atoms of two phosphoraneiminato ligands to form a planar Sm2N2 four-membered ring. One of the Sm atoms is terminally coordinated by the N atoms of two (NPPh3)– groups, thus achieving a distorted tetrahedral surrounding. The second Sm atom is coordinated by the N atom of one (NPPh3)– group, by the terminally bonded iodine atom, and by the O atoms of the DME chelate, thus achieving a distorted octahedral surrounding. 相似文献
953.
Action of Ammonium Fluoride on Scandium: Synthesis and Crystal Structures of (NH4)3[ScF6] and [Cu(NH3)4]3[ScF6]2 The action of (NH4)F on scandium in copper ampoules yields either (NH4)3[ScF6] or ScF3 and a small quantity of [Cu(NH3)4]3[ScF6]2, respectively, depending upon the molar ratio of the educts (NH4)F : Sc (6 : 1 and 4 : 1, respectively) and temperature. (NH4)3[ScF6] crystallizes with the cryolite type of structure: monoclinic, P21/n, Z = 2; a = 650.0(2); b = 651.4(2); c = 949.0(2) pm; β = 90.40(2)°, [Cu(NH3)4]3[ScF6]2 is triclinic, P‐1, Z = 1; a = 821.1(2); b = 821.2(2); c = 822.7(2) pm; α = 90.04(3); β = 90.00(3); γ = 90.16(3)°. In its chemical behaviour against (NH4)F, scandium parallels aluminium rather than gallium. 相似文献
954.
955.
956.
Gerd Mannebach Ruth Bieringer Roman Morschhuser Reimund Stadler 《Macromolecular Symposia》1998,132(1):245-248
The anionic copolymerization of 5-(N,N-dialkylamino)isoprenes and 1,3 -butadiene was investigated in hexane. We found that basicity and increasing amount of the polar monomer has a strong influence on the microstructure of polybutadiene. All tested 5-(N,N-dialkylamino)isoprenes were incorporated much faster into the copolymer than butadiene. Depending on the alkyl substituents the resulting copolymer is either a nearly perfect diblock or shows a considerable tapered structure. 相似文献
957.
Crystal Structure of BaGdCl5 Colourless single crystals of BaGdCl5 are obtained from a 1 : 2 molar mixture of BaCl2 and GdCl3. It crystallizes with the monoclinic space group C2/c with a = 552.1(2), b = 1925.7(5), c = 687.4(2) pm, β = 93.25(4)° in a new structure. Ba2+ and Gd3+ have coordination numbers of 8 + 2 and 8, respectively. 相似文献
958.
Transverse deuterium (2H) nuclear spin relaxation experiments have been performed on a 2H labelled main chain liquid crystal polymer. Relaxation rates are determined as a function of temperature and pulse frequency using a modified Carr-Purcell-Meiboom-Gill pulse train. The results are analysed in terms of a hydrodynamic model for fluctuations of the liquid crystal director. Analytic expressions are employed which relate the transverse spin relaxation rate to the anisotropic viscoelastic parameters of the polymer and allow estimates to be obtained for the effective viscosity and average elastic constant of the polymer. The molecular weight dependence of the viscoelastic parameters has been investigated and is found to be consistent with theoretical predictions for highly extended liquid crystal polymers. 相似文献
959.
Metal Ampoules as Mini‐Autoclaves: Syntheses and Crystal Structures of [Al(NH3)4Cl2][Al(NH3)2Cl4] and (NH4)2[Al(NH3)4Cl2][Al(NH3)2Cl4]Cl2 The salts [Al(NH3)4Cl2]+[Al(NH3)2Cl4]–≡AlCl3 · 3 NH3 ( 1 ) and (NH4+)2[Al(NH3)4Cl2]+[Al(NH3)2Cl4]–(Cl–)2≡ AlCl3 · 3 NH3 · (NH4)Cl ( 2 ) have been obtained as single crystals during the reactions of aluminum and aluminum trichloride, respectively, with ammonium chloride in sealed Monel metal containers. The crystal structure of 1 was determined again [triclinic, P‐1; a = 574.16(10); b = 655.67(12); c = 954.80(16) pm; α = 86.41(2); β = 87.16(2); γ = 84.89(2)°], that of 2 for the first time [monoclinic, I2/m; a = 657.74(12); b = 1103.01(14); c = 1358.1(3) pm; β = 103.24(2)°]. 相似文献
960.