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181.
Itoh N Inagaki K Narukawa T Aoyagi Y Narushima I Koguchi M Numata M 《Analytical and bioanalytical chemistry》2011,401(9):2909-2918
The National Metrology Institute of Japan has issued a certified reference material of tunnel dust for polycyclic aromatic
hydrocarbons (PAHs) and toxic element analyses. PAH certification was performed using isotope dilution mass spectrometry with
deuterium-labeled PAHs as internal standards. Three extraction techniques (microwave-assisted extraction with toluene/methanol,
Soxhlet extraction with toluene, and pressurized liquid extraction with toluene) were used, and the extracts were measured
by gas chromatography/mass spectrometry with two different columns. For values of PAHs, 11 PAHs are provided as certified
values between 0.294 and 20.3 mg/kg, and five PAHs are provided as information values. Certified values of five toxic elements
(Cr, Ni, Pb, Mn, and Cd) obtained from microwave-assisted digestions and a combination of measurement techniques are also
provided between 43.4 and 10.71 × 103 mg/kg. 相似文献
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For accurate quantification of polycyclic aromatic hydrocarbons (PAHs) in dust samples, we investigated the use of microwave-assisted solvent extraction (MAE) combined with isotope-dilution mass spectrometry (IDMS) using deuterium-labelled PAHs (D-PAHs). Although MAE with a methanol/toluene mixture (1:3 by volume) at 160 °C for 40 min was best for extracting PAHs from tunnel dust among examined, the recovery yields of D-PAHs decreased with increasing molecular weight (<40% for MW ≥ 264; that of deuterium-labelled indeno[123-cd]pyrene (D-IcdP) was only 7.1%). Although the residues were extracted a second time, the observed concentrations did not change dramatically (<5%), and the recovery yields of heavier D-PAHs (i.e., MW ≥ 264) were approximately half of those of the first extract, including D-IcdP (3.4%). These results suggest that both partitioning and isotopic equilibria of PAHs and D-PAHs between sample and solvent were achieved for extractable heavier PAHs under the condition. Thus, the observed concentrations of PAHs obtained by MAE–IDMS were reasonable, even though recovery yields of D-PAHs were <50%. From the results of carbon analyses and extractable contents, lower recovery yields of D-PAHs from the tunnel dust were due to a large content of char with low extractable contents. 相似文献
184.
We use ultrafast electron crystallography to study structural changes induced in graphite by a femtosecond laser pulse. At moderate fluences of < or =21 mJ/cm2, lattice vibrations are observed to thermalize on a time scale of approximately 8 ps. At higher fluences approaching the damage threshold, lattice vibration amplitudes saturate. Following a marked initial contraction, graphite is driven nonthermally into a transient state with sp3-like character, forming interlayer bonds. Using ab initio density functional calculations, we trace the governing mechanism back to electronic structure changes following the photoexcitation. 相似文献
185.
RbCl和CsCl水溶液结构的X射线散射及经验势结构精修模拟 总被引:1,自引:0,他引:1
采用X射线散射法研究了RbCl和CsCl水溶液的结构,利用基于经验势的结构精修(EPSR)方法获得了溶液中的水合Cl-、Rb+、Cs+、离子缔合及本体水的对径向分布函数、配位数分布及空间密度分布(3D结构)等结构信息。在水溶液中,Cl-具有相对稳定的6水合结构,其水合距离为0.321 nm,外加阳离子对其水合作用的影响不明显。7.3 ± 1.4个水分子与Rb+水合,其特征水合距离为0.297 nm,8.4 ± 1.6个水分子与Cs+水合其水合距离为0.312 nm。Cs+不具有第二水合层,而Rb+表现出了更强的水合能力,具有较明显的第二水合层。Cl-、Rb+及Cs+常被认为是“结构破坏”型离子。从微观角度来看这种所谓的“结构破坏”主要体现在破坏了本体水分子的第二水合层保持四面体构型的趋势。RbCl和CsCl水溶液中部分存在着Rb-Cl和Cs-Cl直接接触离子对,在1.0 mol·dm-3的溶液中Rb-Cl及Cs-Cl的特征距离分别为0.324和0.336 nm,溶剂分割离子对的距离则都在0.6 nm左右。相对于Cs+,Rb+与Cl-离子之间表现出了更强的缔合能力。 相似文献
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Dr. Wataru Kosaka Yoshie Hiwatashi Naoka Amamizu Prof. Dr. Yasutaka Kitagawa Prof. Dr. Jun Zhang Prof. Dr. Hitoshi Miyasaka 《Angewandte Chemie (International ed. in English)》2023,62(48):e202312205
Partial charge fluctuations in the charge-ordered state of a material, often triggered by structural disorders and/or defects, can significantly alter its physical characteristics, such as magnetic long-range ordering. However, it is difficult to post-chemically fix such accidental partial fluctuations to reconstruct a uniform charge-ordered state. Herein, we report CO2-aided charge ordering demonstrated in a CO2-post-captured layered magnet, [{Ru2(o-ClPhCO2)4}2{TCNQ(OMe)2}] ⋅ CO2 ( 1⊃CO2 ; o-ClPhCO2−=ortho-chlorobenzoate; TNCQ(OMe)2=2,5-dimethoxy-7,7,8,8-tetracyanoquinodimethane). Pristine porous layered magnet 1 had a partially charge-fluctuated ordered state, which provided ferrimagnetic ordering at TC=65 K. Upon loading CO2, 1 adsorbed one mole of CO2, forming 1⊃CO2 , and raising TC to 100 K. This was because of the vanishing charge fluctuations without significantly changing the framework structure. This research illustrates the post-accessible host–guest chemistry delicately combined with charge, spin, and lattice ordering in a spongy magnet. Furthermore, it highlights how this innovative approach opens up new possibilities for technology and nanoscale magnetism manipulation. 相似文献
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