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排序方式: 共有405条查询结果,搜索用时 406 毫秒
1.
M. Mayr K. -H. Speidel M. Knopp W. Karle T. Faestermann F. Hagelberg H. -J. Simonis P. N. Tandon J. Gerber 《Zeitschrift für Physik A Hadrons and Nuclei》1987,327(2):157-161
[Theg-factor ratio of the first excited 3? and 5? states in40Ca was measured to beg 3/g 5=1.01(10) employing the implantation perturbed angular correlation technique. The static hyperfine fields (SF) in Fe and Gd hosts were used. In addition the lifetime of the 5? state was measured to be τ=426(7)ps. The values of the SF in Gd and Fe hosts were deduced and compared with systematics in this element region. 相似文献
2.
CV Tomy D Pal SS Banerjee S Ramakrishnan AK Grover S Bhattacharya MJ Higgins G Balakrishnan McK Paul 《Pramana》2002,58(5-6):925-935
The weakly pinned single crystals of the hexagonal 2H-NbSe2 compound have emerged as prototypes for determining and characterizing the phase boundaries of the possible order-disorder
transformations in the vortex matter. We present here a status report based on the ac and dc magnetization measurements of
the peak effect phenomenon in three crystals of 2H-NbSe2, in which the critical current densities vary over two orders of magnitude. We sketch the generic vortex phase diagram of
a weakly pinned superconductor, which also utilizes theoretical proposals. We also establish the connection between the metastability
effects and pinning. 相似文献
3.
Praveen K. Tandon Gayatri Sumita Sahgal Manish Srivastava Santosh B. Singh 《应用有机金属化学》2007,21(3):135-138
Catalytic activities of three transition metals, as iridium (III) chloride, rhodium (III) chloride and palladium (II) chloride, were compared in the oxidation of six aromatic aldehydes (benzaldehyde, p‐chloro benzaldehyde, p‐nitro benzaldehyde, m‐nitro benzaldehyde, p‐methoxy benzaldehyde and cinnamaldehyde), two hydrocarbons (viz. (anthracene and phenanthrene)) and one aromatic and one cyclic alcohol (cyclohexanol and benzyl alcohol) by 50% H2O2. The presence of traces (substrate: catalyst ratio equal to 1:62500 to 1:1961) of the chlorides of iridium(III), rhodium(III) and palladium(II) catalyze these oxidations, resulting in good to excellent yields. It was observed that in most of the cases palladium(II) chloride is the most efficient catalyst. Conditions for the highest and most economical yields were obtained. Deviation from the optimum conditions decreases the yields. Oxidation in aromatic aldehydes is selective at the aldehydeic group only and other groups remain unaffected. This new, simple and economical method, which is environmentally safe, also requires less time. Reactive species of catalysts, existing in the reaction mixture are also discussed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
Triorganotin(IV) and triorganolead(IV) derivatives of the types Me3Sn(SCZ) and Ph3Pb(SCZ) (where SCZ? is the anion of a semicarbanzone ligand) have been synthesized by substitution reactions of trimethyltin chloride and triphenyl-lead chloride with semicarbazones derived from heterocyclic ketones. The resulting complexes have been characterized by elemental analyses, molecualr weight determinations and conductivity measurements. The mode of bonding has been established on the basis of infrared and 1H, 13C and 119Sn NMR spectroscopic studies. Some respresentative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria; the results of these investigations have been reported in the present paper. 相似文献
5.
H. -J. Simonis S. Kremeyer F. Hagelberg U. Reuter M. Knopp K. -H. Speidel J. Cub W. Karle P. N. Tandon J. Gerber 《Hyperfine Interactions》1990,61(1-4):1351-1354
From hyperfine interaction studles on free single electron16O(3−) ions. in a time differential mode using the recoil distance technique. It is shown that these ions are polarized when emerging
from magnetized thin layers of Fe. The observed degree of polarization
, however, is smaller than expected from transient field measurements. 相似文献
6.
7.
M. Knopp K. -H. Speidel F. Hagelberg H. -J. Simonis J. Gerber P. N. Tandon 《Hyperfine Interactions》1987,34(1-4):183-186
A new method to detect polarization pick-up by ions emerging from thin polarized ferromagnetic layers has been tested. The applied technique consists in the observation of attenuated-angular correlations and atomic spin precessions for single-electron ions recoiling through vacuum in weak transverse magnetic fields. The Coulomb-excited19F(5/2+) state at 197 keV was used as probe. The experimental concept is described and the expected effects are discussed using the perturbed angular correlation formalism for polarized hyperfine interactions. 相似文献
8.
S. N. Mishra D. Rambabu A. K. Grover R. G. Pillay P. N. Tandon H. G. Devare R. Vijayaraghavan 《Hyperfine Interactions》1986,28(1-4):471-474
57Fe Mössbauer and magnetization studies on a new series Fe4–2xRuxSix (1.0x1.7) are reported. The system is seen to transform from a collinear ferromagnet for x1.2 to a cluster spin glass for x>=1.54 In the intermediate region the magnetic behaviour of the system, as probed by the Mössbauer effect, is dominated by the presence of clusters and their dynamics. The alloys have large ordering temperatures ( 750 K) throughout the series except for x>1.54 where they drop sharply. The moment values, in contrast, fall sharply from 4.8B at x=1 to 0.5B at x=1.6C. The average value of the HF at57Fe measured at 15 K does not change significantly throughout the series. 相似文献
9.
Thermodynamic association constants of benzohydroxamic acid and several ortho-substituted N-phenylbenzohydroxamic acids have been determined by pH titration in aqueous dioxan media at 25 degrees and 35 degrees . Empirical pH corrections for mixed aqueous media have been applied. The pK(a) values do not vary linearly with the reciprocal of dielectric constant of the medium, but a plot of pK(a) vs. the mole fraction of dioxan is linear at a given temperature. Values of DeltaG degrees , DeltaH degrees and DeltaS degrees are tabulated. 相似文献
10.
The formation constants, log K(mab), for the reactions MA + B right harpoon over left harpoon MAB [where M = Cu(II), Ni, Zn or Cd, A = terdentate ligand and B = bidentate or terdentate ligand] have been determined. Potentiometric evidence is presented for the stepwise addition of the secondary ligand B to the 1:1 metal iminodiacetate (MA). The formation constants and the free energies of formation (DeltaG) have been calculated at 25 +/- 1 degrees and mu = 0.10. The order in terms of secondary ligands has been found to be ASPA > Gly > Aln and Gly > Aln > ASPA with iminodiacetic and nitrilotriacetic acid as primary ligands respectively (ASPA = aspartic acid, Gly = glycine, Aln = dl-alanine). The plot of log K(mab) against log k(mb)(2) shows a linear relationship between the formation constants of the ternary and 1:2 M(II)secondary ligand complexes. 相似文献