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991.
992.
Ralf I. Kaiser Holger F. Bettinger 《Angewandte Chemie (International ed. in English)》2002,41(13):2209-2209
The cover picture shows benzoborirene, the product of the crossed‐molecular‐beam reaction between benzene molecules and boron atoms, displayed above the three‐dimensional plot of the angular‐ and translational‐energy‐dependent flux of the benzoborirene molecules in the center‐of‐mass system. As the reaction conditions preclude secondary collisions, the intermediate initially formed from the reactive collision decays by ejection of a hydrogen atom. The structure of the benzoborirene depicted is based on a DFT computation, which, combined with results of highly accurate coupled‐cluster calculations has been used to assign the reaction product by comparing experimental and theoretical reaction energies. Details are described by R. I. Kaiser and H. F. Bettinger on p. 2350 ff. 相似文献
993.
994.
Ralf Bienert Franziska Emmerling Andreas F. Thünemann 《Analytical and bioanalytical chemistry》2009,395(6):1651-1660
The spherical gold nanoparticle reference materials RM 8011, RM 8012, and RM 8013, with a nominal radius of 5, 15, and 30 nm,
respectively, have been available since 2008 from NIST. These materials are recommended as standards for nanoparticle size
measurements and for the study of the biological effects of nanoparticles, e.g., in pre-clinical biomedical research. We report
on determination of the size distributions of these gold nanoparticles using different small-angle X-ray scattering (SAXS)
instruments. Measurements with a classical Kratky type SAXS instrument are compared with a synchrotron SAXS technique. Samples
were investigated in situ, positioned in capillaries and in levitated droplets. The number-weighted size distributions were
determined applying model scattering functions based on (a) Gaussian, (b) log-normal, and (c) Schulz distributions. The mean
radii are 4.36 ± 0.04 nm (RM 8011), 12.20 ± 0.03 nm (RM 8012), and 25.74 ± 0.27 nm (RM 8013). Low polydispersities, defined
as relative width of the distributions, were detected with values of 0.067 ± 0.006 (RM 8011), 0.103 ± 0.003, (RM 8012), and
0.10 ± 0.01 (RM 8013). The results are in agreement with integral values determined from classical evaluation procedures,
such as the radius of gyration (Guinier) and particle volume (Kratky). No indications of particle aggregation and particle
interactions—repulsive or attractive—were found. We recommend SAXS as a standard method for a fast and precise determination
of size distributions of nanoparticles.
相似文献
995.
996.
Ralf Haiges Juri Skotnitzki Zongtang Fang David A. Dixon Karl O. Christe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(33):9717-9721
Molybdenum(VI) and tungsten(VI) dioxodiazide, MO2(N3)2 (M=Mo, W), were prepared through fluoride–azide exchange reactions between MO2F2 and Me3SiN3 in SO2 solution. In acetonitrile solution, the fluoride–azide exchange resulted in the isolation of the adducts MO2(N3)2⋅2 CH3CN. The subsequent reaction of MO2(N3)2 with 2,2′‐bipyridine (bipy) gave the bipyridine adducts (bipy)MO2(N3)2. The hydrolysis of (bipy)MoO2(N3)2 resulted in the formation and isolation of [(bipy)MoO2N3]2O. The tetraazido anions [MO2(N3)4]2− were obtained by the reaction of MO2(N3)2 with two equivalents of ionic azide. Most molybdenum(VI) and tungsten(VI) dioxoazides were fully characterized by their vibrational spectra, impact, friction, and thermal sensitivity data and, in the case of (bipy)MoO2(N3)2, (bipy)WO2(N3)2, [PPh4]2[MoO2(N3)4], [PPh4]2[WO2(N3)4], and [(bipy)MoO2N3]2O by their X‐ray crystal structures. 相似文献
997.
Dr. Koichi Fumino Anne‐Marie Bonsa Benjamin Golub Dr. Dietmar Paschek Prof. Dr. Ralf Ludwig 《Chemphyschem》2015,16(2):299-304
Ionic liquids (ILs) attract interest in science and technology as a result of their unique properties. Binary and ternary mixtures of ILs significantly increase the number of possible cation/anion combinations, resulting in targeted physical and chemical properties. In this work, we study the mixing behaviour of two protic ILs: triethyl ammonium methylsulfonate [Et3NH][CH3SO3] and triethylammonium triflate [Et3NH][CF3SO3]. We find a characteristic deviation from ideal mixing by means of low‐frequency infrared spectroscopy. By using molecular dynamics simulations, we explain this behaviour as being the result of different strengths of anion/cation hydrogen bonding. This non‐ideality of non‐random H‐bond mixing is also reflected in macroscopic properties such as the viscosity. Mixing suitable ILs may, thus, result in new ILs with targeted physical properties. 相似文献
998.
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
999.
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
1000.
Frontispiece: Dendronized Hyperbranched Macromolecules: Soft Matter with a Novel Type of Segmental Distribution 下载免费PDF全文