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21.
Summary A new method has been developed for the determination of phenol in urine in which the phenol conjugates are hydrolysed enzymatically and the liberated phenol is analysed by headspace chromatography. The results compare favourably with those obtained by the method of van Haaften and Sie in which acid hydrolysis is carried out in a heated GC precolumn. The enzymatic hydrolysis headspace technique appears to be very reliable and does not suffer from the disadvantages of precolumn acid hydrolysis.Since this paper was submitted, we have found a report on the enzymatic hydrolysis of phenyl glucuronide in urine followed by gas chromatographic analysis which seems to have been overlooked by later workers. The paper is by H. Desoille, T. F. Gandenzi-Britto and M. Philbert in Archives des Maladies Professionelles, de Medecine du Travail et de Securite Sociale (Paris),30 (3), 129 (1969). 相似文献
22.
A scanning Transmission Electron Microscope has been used to investigate the probability of exciting surface modes in MgO cubes when fast electrons pass a certain distance outside the specimen. The experimental results give reasonable agreement with the classical theory of dielectric excitation by a moving charge providing relativistic effects are included. 相似文献
23.
Anirban Chowdhury Jonathan Bould Yifan Zhang Craig James Steven J. Milne 《Journal of nanoparticle research》2010,12(1):209-215
Sodium potassium niobate (NKN) nano-particle powders were synthesised through the thermal decomposition of a sol–gel NKN precursor.
Powders and gels were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric
analysis (TGA) and transmission electron microscopy (TEM). Hydrated carbonate phases formed as a result of reaction with evolved
vapours during organic decomposition, and by reaction of NKN powders with H2O and CO2 on exposure to air. The primary particle size of the powders increased from <50 to <250 nm as decomposition temperatures
were raised from 500 to 950 °C. 相似文献
24.
The major arsenosugar compounds have been reported to be hydride-generation-active, however to a lesser extent in comparison
with the inorganic arsenicals. We report here for the first time the identity and quantity of the volatile arsenicals generated
by As-sugar-SO3, As-sugar-SO4, dimethylarsinoyl acetic acid and dimethylarsinoyl ethanol. Only one major volatile compound was identified for all four
compounds studied: dimethylarsine. This means that the As–C bond to the longer carbon chain was cleaved during the hydride-generation
process. Theoretical calculations at the RHF/6-31G(d,p) ab initio level confirm that this As–C bond is much weaker than the
As–CH3 bonds. Furthermore, it was revealed that the sulphur analogue of dimethylarsinic acid (DMAS ) is hydride-generation-active
at pH 7 in contrast to dimethylarsinic acid, despite the fact that arsenic is also pentavalent. This has been substantiated
by the calculation of the change in susceptibility of the arsenic towards nucleophilic attack when oxygen is replaced by sulphur.
Hence, DMAS can easily be mistaken for a trivalent arsenic species. 相似文献
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The paper reports the results of experimental measurements of the reflection pressures close to spherical charges of TNT. These measurements were made using a pressure bar technique. Charge weights of up to 3.6 kg were used, with the reflecting plane in the range 25 to 300 mm from the charge surface.A possible wave interaction model is discussed, to account for the observed pressure profiles, and its qualitative correctness checked by means of numerical simulation.This article was processed using Springer-Verlag TEX Shock Waves macro package 1.0 and the AMS fonts, developed by the American Mathematical Society. 相似文献
28.
A. Cannizzo C.J. Milne C. Consani W. Gawelda Ch. Bressler F. van Mourik M. Chergui 《Coordination chemistry reviews》2010,254(21-22):2677-2686
The light-induced spin and structure changes upon excitation of the singlet metal-to-ligand charge transfer (1MLCT) state of Fe(II)-polypyridine complexes are investigated in detail in the case of aqueous iron(II)-tris-bipyridine ([FeII(bpy)3]2+) by a combination of ultrafast optical and X-ray spectroscopies. Polychromatic femtosecond fluorescence up-conversion, transient absorption studies in the 290–600 nm region and femtosecond X-ray absorption spectroscopy allow us to retrieve the entire photocycle upon excitation of the 1MLCT state from the singlet low-spin ground state (1GS) as the following sequence: 1,3MLCT → 5T → 1GS, which does not involve intermediate singlet and triplet ligand-field states. The population time of the HS state is found to be ~150 fs, leaving it in a vibrationally hot state that relaxes in 2–3 ps, before decaying to the ground state in 650 ps. We also determine the structure of the high-spin quintet excited state by picosecond X-ray absorption spectroscopy at the K-edge of Fe. We argue that given the many common electronic (ordering of electronic states) and structural (Fe–N bond elongation in the high-spin state, Fe–N mode frequencies, etc.) similarities between all Fe(II)-polypyridine complexes, the results on the electronic relaxation processes reported in the case of [FeII(bpy)3]2+ are of general validity to the entire family of Fe(II)-polypyridine complexes. 相似文献
29.
A new catalyst system for the Pd-catalyzed cross-coupling of organozinc reagents with aryl halides (Negishi coupling) has been developed. This system permits efficient preparation of hindered biaryls (tri- and tetra-ortho-substituted), functions effectively at low levels of catalyst, and tolerates a wide range of functional groups and heterocyclic substrates. A systematic study of ligand structure was performed and was correlated with catalyst activity. 相似文献
30.
Mapping of the Photoinduced Electron Traps in TiO2 by Picosecond X‐ray Absorption Spectroscopy 下载免费PDF全文
Dr. M. Hannelore Rittmann‐Frank Dr. Chris J. Milne Dr. Jochen Rittmann Dr. Marco Reinhard Dr. Thomas J. Penfold Prof. Majed Chergui 《Angewandte Chemie (International ed. in English)》2014,53(23):5858-5862
Titanium dioxide (TiO2) is the most popular material for applications in solar‐energy conversion and photocatalysis, both of which rely on the creation, transport, and trapping of charges (holes and electrons). The nature and lifetime of electron traps at room temperature have so far not been elucidated. Herein, we use picosecond X‐ray absorption spectroscopy at the Ti K‐edge and the Ru L3‐edge to address this issue for photoexcited bare and N719‐dye‐sensitized anatase and amorphous TiO2 nanoparticles. Our results show that 100 ps after photoexcitation, the electrons are trapped deep in the defect‐rich surface shell in the case of anatase TiO2, whereas they are inside the bulk in the case of amorphous TiO2. In the case of dye‐sensitized anatase or amorphous TiO2, the electrons are trapped at the outer surface. Only two traps were identified in all cases, with lifetimes in the range of nanoseconds to tens of nanoseconds. 相似文献