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81.
We report the first successful attempt to generate ultrashort (1-10 ps) relativistic electron bunches characterized by a ramped longitudinal current profile that rises linearly from head to tail and then falls sharply to zero. Bunches with this type of longitudinal shape may be applied to plasma-based accelerator schemes as an optimized drive beam, and to free-electron lasers as a means of reducing asymmetry in microbunching due to slippage. The scheme used to generate the ramped bunches employs an anisochronous dogleg beam line with nonlinear correction elements to compress a beam having an initial positive time-energy chirp. The beam current profile is measured using a deflecting mode cavity, and a pseudoreconstruction of the beam's longitudinal phase space distribution is obtained by using this diagnostic with a residual horizontal dispersion after the dogleg. 相似文献
82.
83.
[reaction: see text]. N-benzoylated quinone imine ketals undergo smooth cycloadditions in a [4 + 2] sense to yield the expected cycloadducts. The crude cycloadducts, when subjected to a short series of simple transformations, produce synthetically useful quantities of 5-methoxyindoles in excellent overall yields. 相似文献
84.
M.E. Cage D.L. Clough A.J. Cole J.B.A. England G.J. Pyle P.M. Rolph L.H. Watson D.H. Worledge 《Nuclear Physics A》1972
Differential cross sections have been measured for the elastic scattering of 33 MeV 3He particles from targets of 58,60,62,64Ni,63,65Cu and 64,66,68Zn over the angular range 5° to 175°. The data have been analysed with the optical model, with particular emphasis on the investigation of the ambiguities in the real potential, the form of the imaginary potential and the use of a spin-orbit term. 相似文献
85.
RM. Sekkappan 《Annals of the Institute of Statistical Mathematics》1982,34(1):605-609
Summary Smith (1976,J. R. Statist. Soc., A,139, 183–204) has argued that survey statisticians should attempt to model finite population structures in the same way that
statisticians in other disciplines have to provide models of finite or infinite populations. Following this argument, we suggest
in this paper that an obvious model for a stratified population when auxiliary information regarding variate values is available,
is the one way analysis of covariance model with unequal variances and we consider the problem of estimating the finite population
mean. Finally a possible extension of this result is discussed. 相似文献
86.
R. Ost N.E. Sanderson S. Mordechai J.B.A. England B.R. Fulton J.M. Nelson G.C. Morrison 《Nuclear Physics A》1976,265(1):142-152
Energy spectra and angular distributions of light particles (Z = 3–8) produced in the reactions 13C+58, 60, 64Ni have been measured at 105 MeV. Coincidence events between light outgoing particles Li, Be, B and α, p have been observed for the first time in the 13C+58Ni and 13C+64Ni reactions. The results show that at least part of the ‘deep-inelastic’ events are due to many-particle reactions. 相似文献
87.
88.
Iron(II)-phenylpyruvate complexes of tetradentate tris(6-methyl-2-pyridylmethyl)amine (6-Me3-TPA) and tridentate benzyl bis(2-quinolinylmethyl)amine (Bn-BQA) were prepared to gain insight into C-C bond cleavage catalyzed by dioxygenase enzymes. The complexes we have prepared and characterized are [Fe(6-Me3-tpa)(prv)][BPh4] (1), [Fe2(6-Me3-tpa)2(pp)][(BPh4)2] (2), and [Fe2(6-Me3-tpa)2(2'-NO2-pp)][(BPh4)2] (3), [Fe(6-Me3-tpa)(pp-Me)][BPh4] (4), [Fe(6-Me3-tpa)(CN-pp-Et)][BPh4] (5), and [Fe(Bn-bqa)(pp)] (8), in which PRV is pyruvate, PP is the enolate form of phenylpyruvate, 2'-NO2-PP is the enolate form of 2'-nitrophenylpyruvate, PP-Me is the enolate form of methyl phenylpyruvate, and CN-PP-Et is the enolate form of ethyl-3-cyanophenylpyruvate. The structures of mononuclear complexes 1 and 5 were determined by single-crystal X-ray diffraction. Both the PRV ligand in 1 and the CN-PP-Et ligand in 5 bind to the iron(II) center in a bidentate manner and form 5-membered chelate rings, but the alpha-keto moiety is in the enolate form in 5 with concomitant loss of a C-H(beta) proton. The PP ligands of 2, 3, 4, and 8 react with dioxygen to form benzaldehyde and oxalate products, which indicates that the C2-C3 PP bond is cleaved, in contrast to cleavage of the C1-C2 bond previously observed for complexes that do not contain alpha-ketocarboxylate ligands in the enolate form. These reactions serve as models for metal-containing dioxygenase enzymes that catalyze the cleavage of aliphatic C-C bonds. 相似文献
89.
RM. Murugappan M. Karthikeyan A. Aravinth MR. Alamelu 《Applied biochemistry and biotechnology》2012,168(8):2170-2183
In the present study, siderophore produced by the marine yeast Aureobasidium pullulans was characterized as hydroxamate by chemical and bioassays. The hydroxamate assignment was supported by the appearance of peaks at 1,647.21?C1,625.99?cm?1 and at 1,435.04?cm?1 in the infrared spectrum. The purified siderophore exhibited specific growth-promoting activity under iron-limited conditions for siderophore auxotrophic probiotic bacteria. Cross-utilization of siderophore indicates a symbiotic relationship between the yeast A. pullulans and the selected probiotic bacterial strains. Statistical optimization of medium components for improved siderophore production in A. pullulans was depicted by response surface methodology. The shift in UV?CVis spectroscopy indicates the photoreactive property and subsequent oxidative cleavage of purified siderophore on exposure to sunlight. 相似文献
90.
K. S. Pramod V. Vijayasundaram N. Krishnakumar PL. RM. Palaniappan 《Journal of Thermal Analysis and Calorimetry》2012,108(1):133-139
This article presents the changes in the thermal properties of the control and titanium dioxide (TiO2), both nano and bulk exposed Zebrafish bones by using thermo analytical techniques. The result shows that the mass loss due
to the thermal decomposition occurs in three distinct steps due to loss of water, organic and inorganic materials. The titanium
dioxide exposed bones present a different thermal behaviour compared to the control bones. The residue masses are found to
be increased due to titanium dioxide exposure. In particular, nano titanium dioxide exposure increases the residue mass level
significantly (three fold) when compared to titanium dioxide bulk exposure. These thermal characteristics can be used as a
qualitative method to check the metal oxide intoxication in biological samples. 相似文献