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41.
M. Djebara M. Asghar J.P. Bocquet R. Brissot M. Maurel H. Nifenecker CH. Ristori 《Nuclear Physics A》1984,425(1):120-140
A gas ΔE ? ER telescope has been used to measure charge yields and their correlations with kinetic energies for 229Th and 232U. Even-charge yields are enhanced compared with odd-charge yields for both fissioning systems; this enhancement increases for events with higher kinetic energy. The mean odd-even effect ; it is . The energy-integrated δp and δp for different energy windows, vary strongly as a function of charge (Z) due to the underlying shells. The δp averaged over Z increases fast with kinetic energy, contrary to the existing results for 233U and 235U, where δp flattens off at low energies. For both systems, the most probable kinetic energy ē shows a strong odd-even stagger; the mean odd-even effect on energy, the latter is about twice the value for . These results are discussed in terms of the existing models. 相似文献
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43.
Maria Bocheńska Robert Banach Anna Zielińska Victor CH. Kravtsov 《Journal of inclusion phenomena and macrocyclic chemistry》2001,39(3-4):219-228
Some di- and tetraamide tert-butylcalix[4]areneswere synthesized and described. Their ionophoric properties were studied in liquid membrane ion-selective electrodes. The correlation between thechemical structure (conformation in solution determined by 1H NMR) and potentiometric ion-selectivity and complex formation constant havebeen studied. The PVC membrane electrodes based on tetraamides 8–11 show high sodium selectivity, are stable and long lasting. Disubstituted amides 1–7 are selective for larger and more lipophilic ions, as for exampleguanidinium ion. The crystal structure of the diamide 4 was determined by single crystal X-ray analysis. Crystals of 4 are triclinic, spacegroup P-1, with: a = 16,669(8), b = 17.795(10), c = 20.984(8) Å, =91.08(4)°, = 91.60(3)°, = 90.73(4)° and Z = 4. Ionophore 4 posseses a distorted cone conformation and is substituted at the proximal phenol rings. 相似文献
44.
45.
Nikolaj S. Troelsen Elena Shanina Diego Gonzalez-Romero Daniela Danková Ida S. A. Jensen Katarzyna J. Śniady Faranak Nami Hengxi Zhang Christoph Rademacher Ana Cuenda Charlotte H. Gotfredsen Mads H. Clausen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(6):2224-2230
Fragment-based drug discovery (FBDD) is a popular method in academia and the pharmaceutical industry for the discovery of early lead candidates. Despite its wide-spread use, the approach still suffers from laborious screening workflows and a limited diversity in the fragments applied. Presented here is the design, synthesis, and biological evaluation of the first fragment library specifically tailored to tackle both these challenges. The 3F library of 115 fluorinated, Fsp3-rich fragments is shape diverse and natural-product-like with desirable physicochemical properties. The library is perfectly suited for rapid and efficient screening by NMR spectroscopy in a two-stage workflow of 19F NMR and subsequent 1H NMR methods. Hits against four diverse protein targets are widely distributed among the fragment scaffolds in the 3F library and a 67 % validation rate was achieved using secondary assays. This collection is the first synthetic fragment library tailor-made for 19F NMR screening and the results demonstrate that the approach should find broad application in the FBDD community. 相似文献
46.
Ming Li Casper Hoeck Dr. Sanne Schoffelen Dr. Charlotte H. Gotfredsen Prof. Morten Meldal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(21):7206-7214
The identification of pairs of small peptides that recognize each other in water exclusively through electrostatic interactions is reported. The target peptide and a structure‐biased combinatorial ligand library consisting of ≈78 125 compounds were synthesized on different sized beads. Peptide–peptide interactions could conveniently be observed by clustering of the small, fluorescently labeled target beads on the surface of larger ligand‐containing beads. Sequences of isolated hits were determined by MS/MS. The interactions of the complex showing the highest affinity were investigated by a novel single‐bead binding assay and by 2D NMR spectroscopy. Molecular dynamics (MD) studies revealed a putative mode of interaction for this unusual electrostatic binding event. High binding specificity occurred through a combination of topological matching and electrostatic and hydrogen‐bond complementarities. From MD simulations binding also seemed to involve three tightly bound water molecules in the interface between the binding partners. Binding constants in the submicromolar range, useful for biomolecular adhesion and in nanostructure design, were measured. 相似文献
47.
P. A. Kumar Swathi Pisupati V. G. K. M. Pisipati CH. Srinivasu P. Narayana Murty 《Liquid crystals》2013,40(7):967-977
A systematic kinetic study leading to the crystallization process from the kinetophases (which occur prior to crystal phase) smectic B, crystal G and smectic F is performed on representative compounds of the homologous series p -phenylbenzylidene-p′-alkylanilines (PBnA) and p-n -alkoxybenzylidene-p′-alkylanilines (nO.m) these compounds are p-phenylbenzylidene-p′-nonylaniline (PB9A), p -phenylbenzylidene-p′-tetradecylaniline (PB14A), p-n -pentadecyloxybenzylidene p′-tetradecylaniline (15O.14) and p-n -octadecyloxybenzylidene-p′-nonylaniline (18O.9). The molecular mechanism and dimensionality in crystal growth from the kineto phases are computed from the Avrami equation, while the characteristic crystalline time (t *) at each crystallization temperature is deduced from the individual plots of log t vs. Δ H. The low magnitudes of the dimensionality parameter n infers the occurrence of diffusion-controlled transformations leading to the formation of plates or needles of finite size possessing impinged edges. The degree of variation in the value of n at each crystallization temperature also reveals the existence of an independent nucleation mechanism for any individual member of the series. The influence of the terminal alkyl chain lengths on the rate of crystallization is determined from a comparative study with the reported analogous compounds. 相似文献
48.
Mössbauer spectroscopy, X-ray diffractometry and chemical fractionation have been used to study the clay smaples in sediments of Charhan playa and Qinghai lake. The spectral components of the Mossbauer spectra of the samples are attributed to Fe2+ ions in chlorite and siderite, Fe3+ ions in clay minerals and hematite, and partly in amorphous ferric hydroxides. The essential difference in the mineral composition of the sediments of both lakes is the presence of siderite in the samples of Char han playa, whereas it is absent in the samples of Qinghai lake. The fraction of the amorphous ferric hydroxides is higher in the sediments of Qinghai lake. Total Fe2+/Fe3+ ratios increase with sediment depth of Charhan playa, whereas these ratios are altogether smaller and run through a maximum at a certain depth for Qinghai lake. 相似文献
49.
C.R. Ottermann CH. Schmitt G.G. Simon F. Borkowski V.H. Walther 《Nuclear Physics A》1982,379(3):396-406
Cross sections for elastic electron scattering from 40Ar have been measured for the momentum transfer range from 0.59 to 1.31 fm?1. We have analyzed with the Fourier-Bessel ansatz our data as well as the data of former experiments. The rms charge radius we have found is 3.423(14) fm. The results are in excellent agreement with latest muonic data. Furthermore, we have reanalyzed former 40Ca data and have discussed the 40Ca- 40Ar charge distribution. 相似文献
50.
H. Zarschizky CH. Gerndt M. Honsberg H. W. Schneider A. Stemmer 《Optical and Quantum Electronics》1994,26(5):S471-S481
Optical clock signal distribution has been widely discussed to be an attractive way to reduce the clock skew in high-speed digital systems. For short interconnect lengths, especially for chip level clock distribution, free space systems using diffractive optical elements (DOEs) have specific advantages. The optoelectronic pathway described in this paper consists of a GaAs laser diode, a microetched silicon mirror, a faceted diffractive element and four silicon photodiodes hybridized to a (dummy) silicon chip. The key element of the clock distribution demonstrator is the diffractive element which matches setup requirements like compactness, off-axis geometry and use of an unshaped laser beam. The whole setup meets the demands of alignment accuracy in an excellent way. This is achieved by the very good imaging characteristic of the DOE and by an alignment technique based on precision mounting of micromachined silicon components. The system was tested with clock rates up to 2.5 GHz, the cut-off frequency is 350 MHz. 相似文献