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31.
Pentafluorethyl Sulfurtrifluoride: Synthesis and Reactions By oxidation of (C2F5S?)2 ( 1 ) with AgF2 at 0°C a mixture of C2F5SF3 ( 2 ) and C2F5SF5 ( 3 ) besides C2F5S(O)F ( 4 ) is formed. With elemental fluorine only 3 is isolated, an intermediate in this reaction is (C2F5SF4?)2 ( 5 ). At ?40 to ?30°C the mixture of 2, 3 and 4 was reacted with TASF and AsF5, to give TAS+ C2F5SF4? ( 6 ), TAS+ C2F5S(O)F2? ( 7 ) and C2F5SF2+AsF6? ( 8 ), respectively. While 6 and 7 decompose rapidly in solution even at low temperatures, of thermally stable 8 the solid state structure was determined by x-ray diffraction. 相似文献
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Laurent De Windt Detlef W. M. Hofman Lorenzo Pisani Enrico Clementi 《International journal of quantum chemistry》1995,53(2):131-147
The Coulomb–Hole–Hartree–Fock method introduced by E. Clementi in the early 1960s and reparametrized more recently by S. Chakraworty and E. Clementi to compute the correlated electronic energy in atomic systems, is here extended to compute molecules. The new parametrization is obtained empirically by fitting first and second atomic ionization potentials from He to Ca and a few diatomic molecules. The present formulation makes use of either one or more determinants in order to ensure proper dissociation products, following the early proposal of G.C. Lie and E. Clementi in the context of density functional computations for molecular systems. The new formulation is tested against the dissociation energies of a large number of molecules and it is found satisfactory. © 1995 John Wiley & Sons, Inc. 相似文献
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Joseph Schwarz Detlef Schrder Helmut Schwarz Christoph Heinemann Jan Hruk 《Helvetica chimica acta》1996,79(4):1110-1120
State-of-the-art ab initio studies demonstrate that the reaction Pd+ + CH3I → PdCH2I+ + H. is endothermic by ca. 20 kcal/mol, which translates into a bond dissociation energy (BDE) of ca. 83 kcal/mol for the Pd+? CH2I bond. This figure is in agreement with an experimental bracket of 68 kcal/mol < BDE(Pd+? CH2I) < 92 kcal/mol. Based on these findings, the previously studied Pd+/CH3I system was re-investigated, and double-resonance experiments demonstrate that the formation of PdCH2I+ occurs stepwise via PdCH as a reactive intermediate. Further, ion/molecule reactions of PdCH2I+ with unsaturated hydrocarbons are studied, which reveal the formation of carbon–carbon bonds in the gas phase. 相似文献
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Bis(dimethylamino)trifluoro sulfonium Salts: [CF3S(NMe2)2]+[Me3SiF2]‐, [CF3S(NMe2)2]+ [HF2]‐ and [CF3S(NMe2)2]+[CF3S]‐ From the reaction of CF3SF3 with an excess of Me2NSiMe3 [CF3(NMe2)2]+[Me3SiF2]‐ (CF3‐BAS‐fluoride) ( 5 ), from CF3SF3/CF3SSCF3 and Me2NSiMe3 [CF3S(NMe2)2]+‐ [CF3S]‐ ( 7 ) are isolated. Thermal decomposition of 5 gives [CF3S(NMe2)2]+ [HF2]‐ ( 6 ). Reaction pathways are discussed, the structures of 5 ‐ 7 are reported. 相似文献
36.
Size-related vaporisation and ionisation of laser-induced glass particles in the inductively coupled plasma 总被引:1,自引:0,他引:1
Ongoing discussions about the origin of elemental fractionation occurring during LA-ICP-MS analysis show that this problem is still far from being well understood. It is becoming accepted that all three possible sources (ablation, transport, excitation) contribute to elemental fractionation. However, experimental data about the vaporisation size limit of different particles in the ICP, as produced in laser ablation, have not been available until now. This information should allow one to determine the signal contributing mass within the ICP and would further clarify demands on suitable laser ablation systems and gas atmospheres in terms of their particle size distribution.The results presented here show a vaporisation size limit of laser induced particles, which was found at particle sizes between 90 nm and 150 nm using an Elan 6000 ICP-MS. Due to the fact that the ICP-MS response was used as evaluation parameter, vaporisation and ionisation limits are not distinguishable.The upper limit was determined by successively removing the larger particles from the aerosol, which was created by ablation of a NIST 610 glass standard at a wavelength of 266 nm, using a recently developed particle separation device. Various particle fractions were separated from the aerosol entering the ICP. The decrease in signal intensity is not proportional to the decrease in volume, indicating that particles above 150 nm in diameter are not completely ionised in the ICP. Due to the limited removal range of the particle separation device, which cannot remove particles smaller than 150 nm, single hole ablations were used to determine the lower vaporisation limit. This is based on measurements showing that larger particles occur dominantly during the first 100 laser pulses only. After this period, the ratio of ICP-MS counts and total particle volume was found to be constant while most of the particles are smaller than 90 nm, indicating complete vaporisation and ionisation of these particles.To describe the influence of different plasma forward powers on the vaporisation limit, the range 1000–1600 W was studied. Results indicate that optimum vaporisation and ionisation occurs at 1300 W. However, an increase of the particle ionisation limit towards larger particles was not observed within the accuracy of this study using the full range of parameters available for optimisation on commonly used ICP-MS instruments. 相似文献
37.
The syntheses, solid state structures, and spectral properties of O-alkyl and O-acyl derivatives of hydroxoundecahydro-closo-dodecaborate(2-), 1, are described. Alkylation of 1 with ethyl iodide was achieved in dimethyl sulfoxide using potassium hydroxide as a base, leading to [N(n-C(4)H(9))(4)](2)[CH(3)CH(2)O-B(12)H(11)(2-)], 2, bis(tetrabutylammonium) ethoxyundecahydro-closo-dodecaborate(2-) [monoclinic P2(1)/n, a = 1192.4(9) pm, b = 1253.9(4) pm, c = 3049.1(10) pm, beta = 92.69(4) degrees, Z = 4, R1 = 0.0693, wR(2) = 0.1517]. Alkylation with 1,5-dibromopentane afforded the cyclic oxonium salt [PPN][C(5)H(10)O-B(12)H(11)(1-)], 3, (&mgr;-nitrido)bis(triphenylphosphorus)(1+) tetrahydropyrane-undecahydro-closo-dodecaborate(1-) [monoclinic P2(1)/c, a = 1938.1(2) pm, b = 1329.7(10) pm, c = 1944.0(2) pm, beta = 108.82(10) degrees, Z = 4, R1 = 0.0484, wR(2) = 0.0833]. Acylation of 1 in acetonitrile with acyl chlorides in the presence of pyridine yielded [N(n-C(4)H(9))(4)](2)[C(6)H(5)CO(2)-B(12)H(11)(2-)], 4, bis(tetrabutylammonium) undecahydrobenzoyl-closo-dodecaborate(2-) [monoclinic P2(1)/c, a = 1812.0(4) pm, b = 1711.9(3) pm, c = 1685.0(3) pm, beta = 114.03(3) degrees, Z = 4, R1 = 0.0915, wR(2) = 0.2093], and [N(n-C(4)H(9))(4)](2)[CH(3)CO(2)-B(12)H(11)(2-)], 5, bis(tetrabutylammonium) acetoxyundecahydro-closo-dodecaborate(2-) [monoclinic P2(1)/n, a = 1190.5(2) pm, b = 1243.0(10) pm, c = 3078.4(4) pm, beta = 92.76(10) degrees, Z = 4, R1 = 0.0642, wR(2) = 0.1462]. All crystal structures showed distortion of the pseudoicosahedral geometry of the boron cluster. The boron-oxygen distances varied from 144.2(5) pm for 2, 148.5(3) pm for 5, 149.4(12) pm for 4, to 152.8(4) pm for 3. The 3-fold coordinated oxygen of oxonium salt 3 is nearly planar. 相似文献
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Alain Chaintreau Wolfgang Fieber Horst Sommer Alexis Gilbert Keita Yamada Naohiro Yoshida Alain Pagelot Detlef Moskau Aitor Moreno Jürgen Schleucher Fabiano Reniero Margaret Holland Claude Guillou Virginie Silvestre Serge Akoka Gérald S. Remaud 《Analytica chimica acta》2013
Isotopic 13C NMR spectrometry, which is able to measure intra-molecular 13C composition, is of emerging demand because of the new information provided by the 13C site-specific content of a given molecule. A systematic evaluation of instrumental behaviour is of importance to envisage isotopic 13C NMR as a routine tool. This paper describes the first collaborative study of intra-molecular 13C composition by NMR. The main goals of the ring test were to establish intra- and inter-variability of the spectrometer response. Eight instruments with different configuration were retained for the exercise on the basis of a qualification test. Reproducibility at the natural abundance of isotopic 13C NMR was then assessed on vanillin from three different origins associated with specific δ13Ci profiles. The standard deviation was, on average, between 0.9 and 1.2‰ for intra-variability. The highest standard deviation for inter-variability was 2.1‰. This is significantly higher than the internal precision but could be considered good in respect of a first ring test on a new analytical method. The standard deviation of δ13Ci in vanillin was not homogeneous over the eight carbons, with no trend either for the carbon position or for the configuration of the spectrometer. However, since the repeatability for each instrument was satisfactory, correction factors for each carbon in vanillin could be calculated to harmonize the results. 相似文献