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111.
P. G. Oza H. S. Mazumdar A. K. Choudhary K. Gopalan 《Journal of Chemical Sciences》1984,93(2):189-193
A microcomputer system has been designed for semi-automatic operation of a solid source mass spectrometer used for geochronological
studies. It sequentially steps the magnetic field through pre-selected values, reads the digitized ion currents for a given
time and temporarily stores the data which can be transferred to a paper tape or directly to a desk top calculator for further
analysis. The unit is relatively inexpensive, made of readily available components and can be adapted to many laboratory automation
tasks 相似文献
112.
The monoclinic crystal structure of NaH2PO4 at room temperature has been refined from neutron-diffraction measurements on a single-crystal sample and complied with the closely related structure of monoclinic KD2PO4. Attention is paid to the information obtained from these two structures about the geometry of hydrogen (deuterium) bonds ?2.6 A. 相似文献
113.
Choudhary MI Musharraf SG Siddiqui ZA Khan NT Ali RA Ur-Rahman A 《Chemical & pharmaceutical bulletin》2005,53(8):1011-1013
The microbial transformation of an oral contraceptive, mestranol (1) by Cunninghamella elegans yielded two hydroxylated metabolites, 6beta-hydroxymestranol (2) and 6beta,12beta-dihydroxymestranol (3). Metabolite 3 was found to be a new compound. These metabolites were structurally characterized on the basis of spectroscopic techniques. 相似文献
114.
Ahmad I Nawaz SA Afza N Malik A Fatima I Khan SB Ahmad M Choudhary MI 《Chemical & pharmaceutical bulletin》2005,53(8):907-910
Onosmins A (1) and B (2), lipoxygenase inhibitors, have been isolated from Onosma hispida. Their structures were established as 2-[(4-methylbenzyl)amino]benzoic acid (1) and methyl 2-[(4-methylbenzyl)amino]benzoate (2) through spectroscopic studies, including 2D-NMR. The known compounds apigenin (3), 6,4'-dimethoxy-3,5,7-trihydroxyflavone (4), 6,7-dimethoxy-3,5,4'-trihydroxyflavone (5) and apigenin 7-O-beta-D-glucoside (6) are also reported for the first time from this species. Compounds (1) and (2) inhibited lipoxygenase (LOX, EC 1.13.11.12) enzyme in a concentration-dependent fashion with IC50 values of 24.0 and 36.2 microM, respectively. Lineweaver-Burk as well as Dixon plots and their secondary replots indicated that the nature of inhibition was purely a non-competitive type, with K(i) values 22.0 microM and 31.1, respectively. 相似文献
115.
Aziz-Ur-Rehman Malik A Riaz N Ahmad H Nawaz SA Choudhary MI 《Chemical & pharmaceutical bulletin》2005,53(3):263-266
A lignan and two acylphloroglucinols have been isolated from the ethyl acetate soluble fraction of the whole plant of Indigofera hetrantha. Their structures have been assigned on the basis of spectral analysis including 1D and 2D NMR techniques. Compounds 1-3 displayed promising inhibitory potential against enzyme lipoxygenase in concentration-dependent manner. 相似文献
116.
Khan SB Azhar-Ul-Haq Afza N Malik A Khan MT Shah MR Choudhary MI 《Chemical & pharmaceutical bulletin》2005,53(1):86-89
Long-chain esters 1 and 2 have been isolated from the chloroform-soluble fraction of Amberboa ramosa and their structures assigned to be methyl 2beta(2S)-hydroxyl-7(E)-tritriacontenoate (1) and methyl 2beta(2S)-O-beta-D-galactopyranosyl-7(E)-tetratriacontenoate (2). In addition, tricontane (3) and apigenin (4) are also reported for the first time from this species. The structures were assigned on the basis of 1D and 2D NMR techniques. Compounds 1 and 2 showed strong to moderate inhibitory activity against tyrosinase. 相似文献
117.
The ferroelectric lead germanate (Pb5Ge3O11) and its isomorphous compounds are important because of their uses as pyroelectric and electro-optic devices. Comparison
of inter-planar d-spacings of Pb5Ge3−x
Si
x
O11 (x=0, 0.3, 0.7 and 1.00) suggests that there is no change in basic structure of Pb5Ge3−x
Si
x
O11 when Si is substituted for Ge in small quantity (x<1). The dielectric properties of the Si-substituted compounds have been studied as a function of temperature (30 to 200°C).
The ferroelectric-paraelectric phase transition has been observed at 185°C. The Si doping causes (a) Curie point to shift
towards low temperature, (b) peak value of the dielectric constant to decrease and (c) phase transition diffuse. The fast
increase in dielectric constant of pure Pb5Ge3O11 with temperature (beyond transition temperature) may be attributed to the development of space charge polarization in the
system. 相似文献
118.
Michael DG Adamson P Alexopoulos T Allison WW Alner GJ Anderson K Andreopoulos C Andrews M Andrews R Arms KE Armstrong R Arroyo C Auty DJ Avvakumov S Ayres DS Baller B Barish B Barker MA Barnes PD Barr G Barrett WL Beall E Becker BR Belias A Bergfeld T Bernstein RH Bhattacharya D Bishai M Blake A Bocean V Bock B Bock GJ Boehm J Boehnlein DJ Bogert D Border PM Bower C Boyd S Buckley-Geer E Bungau C Byon-Wagner A Cabrera A Chapman JD Chase TR Cherdack D Chernichenko SK Childress S Choudhary BC 《Physical review letters》2006,97(19):191801
This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current nu(mu) interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27 x 10(20) 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336+/-14 events. The data are consistent with nu(mu) disappearance via oscillations with |Delta(m)2/32|=2.74 +0.44/-0.26 x10(-3)eV(2) and sin(2)(2theta(23))>0.87 (68% C.L.). 相似文献
119.
A new cucurbitacin glucoside 2-O-beta-D-glucopyranosyl-16alpha-20R-dihydroxy-cucurbita-1,5,23E,25(26)-tetraen-3,11,22-trione (1) has been isolated from the methanolic extract of the fruits of Citrulluscolocynthis. The structure has been assigned on the basis of spectral analysis including 1D and 2D NMR techniques. In addition 2-O-beta-D-glucopyranosyl-cucurbitacin B (arvenin I) (2) and 2,25-di-O-beta-D-glucopyranosyl-cucurbitacin L (3) are reported for the first time from this species. 相似文献
120.
We develop a theoretical model for quantitative analysis of temperature-dependent thermoelectric power (S) of Zn nanowires. In doing so, we first use the Mott expression to compute the electron diffusive thermoelectric power (Scdiff.) using Fermi energy as electron-free parameter, Scdiff. shows linear temperature dependence. Further, the Scdiff. contribution is subtracted from the experimental data and the difference (Sexperimental-Scdif) is characterized as phonon drag thermoelectric power (Sphdrag) which is obtained within the relaxation time approximation where the thermoelectric power is limited by the scattering of phonons with impurities, grain boundaries, charge careers and phonons in the nanowires. The Sphdrag shows anomalous temperature-dependent behaviour, which is an artifact of various operating scattering mechanisms. The observed anomalies are well accounted in terms of interaction among the phonons-impurity, phonon-grain boundaries, phonon-electron and the umklapp scattering. It is also shown that for phonons the scattering and transport cross-sections are proportional to ω4 in the Rayleigh regime where ω is the frequency of the phonons. Numerical analysis of thermoelectric power from the present model shows similar results as those revealed from experiments. 相似文献