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61.
Quinoline-2-carboxylic acid (quinaldic acid), C10H7NO2, crystallizes in the monoclinic space group P21/c, a =9.724(1) Å, b = 5.937(1) Å, c = 27.545(2) Å, = 90.15(1)°, z = 4, and occurs in the crystal in two tautomeric forms: the neutral molecule and the zwitterion, with molecular ratio 1:1. The compound can be named quinoline-2-carboxylic acid quinolinium-2-carboxylate. The crystal structure is built up of tautomeric pairs consisting of C9H6NCOOH and C9H6NH+COO– moieties, held up together by hydrogen bonds. 相似文献
62.
Michalska D Bieńko DC Czarnik-Matusewicz B Wierzejewska M Sandorfy C Zeegers-Huyskens T 《The journal of physical chemistry. B》2007,111(42):12228-12238
Theoretical studies are performed on enflurane (CHFCl-CF(2)-O-CHF(2)) to investigate the conformational properties and vibrational spectra. Calculations are carried out at the B3LYP/6-31G(d) level along with a natural bond orbital (NBO) analysis. Experimental infrared spectra are investigated in carbon tetrachloride solution at room temperature and in argon matrix at 12 K. In agreement with previously reported data (Pfeiffer, A.; Mack, H.-G.; Oberhammer, H. J. Am. Chem. Soc. 1998, 120, 6384), it is shown that the four most stable conformers possess a trans configuration of the C-C-O-C skeleton and a gauche orientation of the CHF(2) group (with respect to the central C-O bond). These conformations are favored by electrostatic interaction between the H atom of the CHF(2) group and the F atoms of the central CF(2) group. Hyperconjugation effects from the O lone pairs to the antibonding orbitals of the neighboring C-H and C-F bonds also contribute to the stability of the four conformers. The vibrational frequencies, infrared intensities, and potential energy distributions are calculated at the same level of theory for the most stable conformers. On the basis of the theoretical results, these conformers are identified in an argon matrix. The influence of the concentration on the nu(CH) vibrations suggests the formations of higher aggregates in solution. Theoretical calculations are carried out on the enflurane dimer. The results show that the dimer is formed between two enflurane conformers having the largest stability. The dimer has an asymmetric cyclic structure, the two enflurane molecules being held together by two nonequivalent C-H...F hydrogen bonds, the C-H bond of the CHFCl group acting as a proton donor, and one of the F atoms of the CHF(2) groups acting as a proton acceptor. The theory predicts a contraction of 0.0014-0.0025 A of the two CH bonds involved in the interaction along with a blue shift of 30-38 cm(-1) of the corresponding nu(C-H) bands, in good agreement with the blue shifts of 35-39 cm(-1) observed in an argon matrix. 相似文献
63.
Danuta Gorlo Bogdan Zygmunt Marta Dudek Anna Jaszek Michał Pilarczyk J. Namieśnik 《Analytical and bioanalytical chemistry》1999,363(7):696-699
Practical application of Solid-Phase Microextraction (SPME) for the assessment of the quality of indoor air is presented.
SPME was used to sample selected organic pollutants (carbon tetrachloride, benzene, toluene, chlorobenzene, p-xylene and n-decane). An SPME fiber was coated with a 100 μm film of polydimethylsiloxane. The analytes extracted were analysed with a
gas chromatograph directly coupled with a mass spectrometer (GC-MS). The method was used to assess the indoor air quality
in a few selected flats. The concentrations ranged from below detection limits to 6.9 mg/m3 for benzene depending on the flat; they were relatively high for newly built or freshly renovated flats.
Received: 14 July 1998 / Revised: 17 November 1998 / Accepted: 21 November 1998 相似文献
64.
Thin films containing both the azo-dye disperse red 1 (DR1) and the poly(methylmetacrylate) (PMMA) or the poly(phenylenevinylene) (PPV) are deposited by Langmuir-Blodgett and spin coating techniques on various substrates. The morphology, surface structure and growth pattern of the azo-dye-polymers were studied by atomic force microscopy. Nucleation and growth processes are responsible for the generation of different structures. The spin coated films were additionally oriented using the electric field poling method (corona poling). The film homogeneity is improved by this method in all cases. Due to the polar character of DR1 molecules, rod-like sub-structures are observed after the corona poling process in DR1-MMA films. The indium tin oxide surface enhances reorientation of the azo-dye-polymer molecules during corona poling and results in a significant reduction of the surface roughness. 相似文献
65.
66.
The aim of this work was to investigate the antibacterial properties of geranium oil obtained from Pelargonium graveolens Ait. (family Geraniaceae), against one standard S. aureus strain ATCC 433000 and seventy clinical S. aureus strains. The agar dilution method was used for assessment of bacterial growth inhibition at various concentrations of geranium oil. Susceptibility testing of the clinical strains to antibiotics was carried out using the disk-diffusion and E-test methods. The results of our experiment showed that the oil from P. graveolens has strong activity against all of the clinical S. aureus isolates-including multidrug resistant strains, MRSA strains and MLSB-positive strains-exhibiting MIC values of 0.25-2.50 μL/mL. 相似文献
67.
68.
C-13 and H-1 NMR spectra of some 1-(4′-dimethylaminobenzylideneamino)pyridinium perchlorates show that the angle of twist of the pyridine ring in unsubstituted, 1, and 2-alkyl substituted compounds 2–5 is comparable. However, it is considerably increased in 2,6-dialkyl derivatives. As seen from the spectral data, pyridine and phenyl rings in 2,6-diphenyl derivative 15 are not coplanar. The effect of 4-alkyl substituent is of hyperconjugative chacter. In general, the amount of the positive charge at C-4 in 2,6-dialkyl substituted salts is higher as compared to 2-monosubstituted compounds. 相似文献
69.
70.
Cosper NJ Bienvenue DL Shokes JE Gilner DM Tsukamoto T Scott RA Holz RC 《Journal of the American Chemical Society》2003,125(48):14654-14655
The Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra, of the dapE-encoded N-succinyl-l,l-diaminopimelic acid desuccinylase (DapE) from Haemophilus influenzae have been recorded in the presence of one or two equivalents of Zn(II) (i.e. [Zn_(DapE)] and [ZnZn(DapE)]). The Fourier transforms of the Zn EXAFS are dominated by a peak at ca. 2.0 A, which can be fit for both [Zn_(DapE)] and [ZnZn(DapE)], assuming ca. 5 (N,O) scatterers at 1.96 and 1.98 A, respectively. A second-shell feature at ca. 3.34 A appears in the [ZnZn(DapE)] EXAFS spectrum but is significantly diminished in [Zn_(DapE)]. These data show that DapE contains a dinuclear Zn(II) active site. Since no X-ray crystallographic data are available for any DapE enzyme, these data provide the first glimpse at the active site of DapE enzymes. In addition, the EXAFS data for DapE incubated with two competitive inhibitors, 2-carboxyethylphosphonic acid and 5-mercaptopentanoic acid, are also presented. 相似文献