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51.
A stochastic averaging method for strongly non-linear oscillators under external and/or parametric excitation of bounded noise is proposed by using the so-called generalized harmonics functions. The method is then applied to study the primary resonance of Duffing oscillator with hardening spring under external excitation of bounded noise. The stochastic jump and its bifurcation of the system are observed and explained by using the stationary probability density of amplitude and phase. Subsequently, the method is applied to study the dynamical instability and parametric resonance of Duffing oscillator with hardening spring under parametric excitation of bounded noise. The primary unstable region is delineated by evaluating the Lyapunov exponent of linearized system, and the response and jump of non-linear system around the unstable region are examined by using the sample functions and stationary probability density of amplitude and phase. 相似文献
52.
53.
Preparation and Characterization of Antimony and Arsenic Tricyanide and Their 2,2′‐Bipyridine Adducts 下载免费PDF全文
Piyush Deokar Dominik Leitz Trent H. Stein Monica Vasiliu Prof. Dr. David A. Dixon Prof. Dr. Karl O. Christe Prof. Dr. Ralf Haiges 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(37):13251-13257
The arsenic(III) and antimony(III) cyanides M(CN)3 (M=As, Sb) have been prepared in quantitative yields from the corresponding trifluorides through fluoride–cyanide exchange with Me3SiCN in acetonitrile. When the reaction was carried out in the presence of one equivalent of 2,2′‐bipyridine, the adducts [M(CN)3 ? (2,2′‐bipy)] were obtained. The crystal structures of As(CN)3, [As(CN)3 ? (2,2′‐bipy)] and [Sb(CN)3 ? (2,2′‐bipy)] were determined and are surprisingly different. As(CN)3 possesses a polymeric three‐dimensional structure, [As(CN)3 ? (2,2′‐bipy)] exhibits a two‐dimensional sheet structure, and [Sb(CN)3 ? (2,2′‐bipy)] has a chain structure, and none of the structures resembles those found for the corresponding arsenic and antimony triazides. 相似文献
54.
b/a=0.5的椭圆形通道内非牛顿流体的强化传热 总被引:1,自引:0,他引:1
对非牛顿流体在小尺寸椭圆形通道内的层流受迫对流传热进行了实验研究。实验介质为1500Wppm的Carbopol-934中性水溶液。采用直接通电的方法对管壁四周等热流加热。结果表明,椭圆通道内,非牛顿流体Carbopol水溶液的换热强于牛顿流体水,约高出水50%左右,说明粘弹性流体在椭圆形通道内也产生二次流并能强化换热;与同种浓度的Carbopol水溶液在方形通道内的换热结果相比,椭圆通道内的换热高于方形通道。流体的压力降则不受粘弹性的影响,仍符合幂律流体的阻力系数关系式(f=16/Re*)。 相似文献
55.
Thermochemical properties of CHFO and CF 2O and their derivatives were calculated by using coupled-cluster theory (U)CCSD(T) calculations with the aug-cc-pV nZ ( n = D, T, Q, 5) basis sets extrapolated to the complete basis set limit with additional corrections. The predicted properties include the following. Enthalpies of formation (298 K, kcal/mol): Delta H f (CF 2O) = -144.7, Delta H f(CHFO) = -91.1, Delta H f (CFO (*)) = -41.6. Bond dissociation energy (0 K, kcal/mol): BDE(CFO-F) = 120.7, BDE(CHO-F) = 119.1, BDE(CFO-H) = 100.2. Ionization potential (eV): IP 1(CF 2O) = 13.04, IP 2(CF 2O) = 14.09, IP 1(CHFO) = 12.41, IP 2(CHFO) = 13.99, IP 1(CFO (*)) = 9.34. Proton affinity (298 K, kcal/mol), PA O(CF 2O) = 148.8, PA O(CHFO) = 156.7, PA F(CHFO) = 154.5 kcal/mol. Electron affinity: EA(CFO (*)) = 2.38 eV. Triplet-singlet separation gap (eV): Delta E T1-S0(CF 2O) = 4.47, Delta E T1-S0(CHFO) = 4.36. Triplet-triplet transition energy (eV): Delta E T2-T1(CF 2O) = 0.44. The new calculated values contribute to solving some persistent discrepancies in the literature. The effects of F-atoms on thermochemical parameters are not linearly additive, and the changes are largely dominated by the first F-substitution. On the basis of the calculated proton affinities of CF 2O and CF 3OH, the nucleophilicities of the oxygen atoms are, within computational errors, the same in both compounds. 相似文献
56.
Schneider S Gerken M Haiges R Schroer T Boatz JA Dixon DA Grant DJ Christe KO 《Inorganic chemistry》2007,46(1):93-102
Only two silyldichloramines, (C6H5)3SiNCl2 and (CH3)3SiNCl2, have been reported in the literature. The synthesis of the former was successfully repeated, and its structure was established by single-crystal X-ray diffraction and vibrational spectroscopy. Attempts to prepare (CH3)3SiNCl2 were unsuccessful; however, a new trialkylsilyldichloramine, t-BuMe2Si-NCl2, was prepared and characterized by Raman and multinuclear NMR spectroscopy. The reaction of t-BuMe2SiNCl2 with (CH3)4NF in CHF3 solution at -78 degrees C, followed by removal of all volatile products at -30 degrees C, produced the expected t-BuMe2SiF byproduct and a white solid consisting of NCl3 absorbed on Me4NCl. The NCl3 could be reversibly desorbed from the substrate and was identified as a neat liquid at room temperature by Raman spectroscopy. The observed final reaction products are consistent with the formation of an unstable N(CH3)4+NCl2- intermediate which decomposes to N(CH3)4+Cl- and NCl molecules which can dimerize to N2Cl2. Theoretical calculations confirm that NCl2- can readily lose Cl- and that N2Cl2 also possesses a low barrier toward loss of N2 to give chlorine atoms and, thus, can account for the formation of NCl3. 相似文献
57.
The Molybdenum(V) and Tungsten(VI) Oxoazides [MoO(N3)3], [MoO(N3)3⋅2 CH3CN], [(bipy)MoO(N3)3], [MoO(N3)5]2−, [WO(N3)4], and [WO(N3)4⋅CH3CN] 下载免费PDF全文
Prof. Dr. Ralf Haiges Juri Skotnitzki Zongtang Fang Prof. Dr. David A. Dixon Prof. Dr. Karl O. Christe 《Angewandte Chemie (International ed. in English)》2015,54(51):15550-15555
A series of novel molybdenum(V) and tungsten(VI) oxoazides was prepared starting from [MOF4] (M=Mo, W) and Me3SiN3. While [WO(N3)4] was formed through fluoride–azide exchange in the reaction of Me3SiN3 with WOF4 in SO2 solution, the reaction with MoOF4 resulted in a reduction of MoVI to MoV and formation of [MoO(N3)3]. Carried out in acetonitrile solution, these reactions resulted in the isolation of the corresponding adducts [MoO(N3)3?2 CH3CN] and [WO(N3)4?CH3CN]. Subsequent reactions of [MoO(N3)3] with 2,2′‐bipyridine and [PPh4][N3] resulted in the formation and isolation of [(bipy)MoO(N3)3] and [PPh4]2[MoO(N3)5], respectively. Most molybdenum(V) and tungsten(VI) oxoazides were fully characterized by their vibrational spectra, impact, friction and thermal sensitivity data and, in the case of [WO(N3)4?CH3CN], [(bipy)MoO(N3)3], and [PPh4]2[MoO(N3)5], by their X‐ray crystal structures. 相似文献
58.
Amanda F. Baxter Prof. Dr. Karl O. Christe Prof. Dr. Ralf Haiges 《Angewandte Chemie (International ed. in English)》2015,54(48):14535-14538
A series of novel α‐fluoroalkyl ammonium salts was obtained from the corresponding cyano compounds or nitriles by reaction with anhydrous HF. Room‐temperature stable trifluoromethyl ammonium salts were obtained in quantitative yield in a one‐step reaction at ambient temperature from the commercially available starting materials BrCN or ClCN. The novel cations [CF3CF2NH3]+, [HCF2CF2NH3]+, and [(NH3CF2)2]2+ were obtained from CF3CN, HCF2CN, and (CN)2, respectively, and anhydrous HF. The aforementioned fluorinated ammonium cations were isolated as room temperature stable [AsF6]? and/or [SbF6]? salts, and characterized by multi‐nuclear NMR and vibrational spectroscopy. The salts [HCF2NH3][AsF6] and [CF3NH3][Sb2F11] were characterized by their X‐ray crystal structure. 相似文献
59.
波长对Ag/TiO2催化剂上二氧化碳光催化还原的影响 总被引:1,自引:0,他引:1
K.KOí K.ZATLOUKALOV L.OBALOV S.KREJíKOV Z.LACNY L.APEK A.HOSPODKOV O.OLCOV 《催化学报》2011,32(5):812-815
Photocatalytic reduction of CO2 by water was performed in the presence of a Ag/TiO2 catalyst under illumination by lamps with different wavelengths(254,365,and 400 nm).The yields of the main products(methane and methanol)were higher with the 254 nm lamp than with the 365 lamp while no products were observed with the 400 nm lamp.This was because the electron-hole generation rate increased with increasing energy of irradiation(decreasing wavelength)and there were higher densities of electron states at higher energies in TiO2. The increased efficiency of electron-hole generation with a shorter wavelength irradiation increased the efficiency of the catalyst.The energy of the electrons excited by visible light(400 nm)was too low for CO2 photocatalytic reduction. 相似文献