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1.
2.
Hughes RP Meyer MA Tawa MD Ward AJ Williamson A Rheingold AL Zakharov LN 《Inorganic chemistry》2004,43(2):747-756
Reaction of Pd(TMEDA)(CH(3))(2) [TMEDA = tetramethylethylenediamine] with fluoroalkyl iodides R(F)I affords a series of square planar Pd(II) complexes Pd(TMEDA)(CH(3))(R(F)) [R(F) = CF(2)CF(3) (9), CFHCF(3) (10), CH(2)CF(3) (11)], presumably by oxidative addition followed by reductive elimination of CH(3)I. The solid-state structures of each compound have been determined by single crystal X-ray diffraction studies, allowing the effect of increasing alpha-fluorination on the structural trans-influence of alkyl ligands to be examined. In these compounds there is no significant difference observed in the trans-influence of the three fluorinated alkyl ligands toward the trans-N atom, although a significant cis-influence on the neighboring methyl ligand is apparent. Oxidative addition of the same series of fluoroalkyl ligands to the corresponding Pt(TMEDA)(CH(3))(2) affords octahedral Pt(IV) complexes trans-Pt(TMEDA)(CH(3))(2)(R(F))I [R(F) = CF(2)CF(3) (12), CFHCF(3) (13), CH(2)CF(3) (14)] as the kinetic products. In each case, subsequent isomerization to the corresponding all cis-isomers is observed; in the case of 13, the stereocenter at the alpha-carbon results in two diastereomeric cis-isomers, which are formed at different rates. The molecular structures of 13 and its more stable all cis-isomer 16b have been crystallographically determined. Kinetic studies of the trans-cis isomerization reactions show the mechanism to involve a polar transition state, presumably involving iodide dissociation, followed by rearrangement of the cation, and iodide recombination. High dielectric solvents increase the rate, but solvent coordinating ability has no effect. Dissolved salts (LiI, LiOTf) show normal accelerative salt effects, with no inhibition in the case of added iodide, consistent with the formation of an intimate ion pair intermediate. The kinetic parameters show that the trans-effects of fluoroalkyl ligands in these compounds follow the order expected from the relative sigma-donor properties of the ligands, with CF(2)CF(3) < CFHCF(3) < CH(2)CF(3). 相似文献
3.
Nagarajan Shobana Pandurangan Prakash Antony V. Samrot P. J. Jane Cypriyana Purohit Kajal Mahendran Sathiyasree Subramanian Saigeetha T. Stalin Dhas D. Alex Anand Gokul Shankar Sabesan Bala Sundaram Muthuvenkatachalam Basanta Kumar Mohanty Sridevi Visvanathan 《Molecules (Basel, Switzerland)》2022,27(12)
Plant gums are bio-organic substances that are derived from the barks of trees. They are biodegradable and non-adverse complex polysaccharides that have been gaining usage in recent years due to a number of advantages they contribute to various applications. In this study, gum was collected from Moringa oleifera and Azadirachta indica trees, then dried and powdered. Characterizations of gum polysaccharides were performed using TLC, GC-MS, NMR, etc., and sugar molecules such as glucose and xylose were found to be present. Effects of the gums on Abelmoschus esculentus growth were observed through root growth, shoot growth, and biomass content. The exposure of the seeds to the plant gums led to bio stimulation in the growth of the plants. Poor quality soil was exposed to the gum polysaccharide, where the polysaccharide was found to improve soil quality, which was observed through soil analysis and SEM analysis of soil porosity and structure. Furthermore, the plant gums were also found to have bio-pesticidal activity against mealybugs, which showed certain interstitial damage evident through histopathological analysis. 相似文献
4.
5.
Benjamin J. K. Evans Susan M. Scott Antony C. Searle 《General Relativity and Gravitation》2002,34(10):1675-1684
We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time. 相似文献
6.
Using the phenomenological relativistic harmonic model (RHM) for quarks, we have obtained the masses of S wave charmonium and bottomonium states. The full Hamiltonian used in the investigation has Lorentz scalar plus vector confinement potential, along with the confined one gluon exchange potential (COGEP). A good agreement with the experimental masses for the ground and the radially excited states is obtained both for the triplet and singlet S wave mesons. The decay properties of the ground state charmonium and bottomonium are investigated. 相似文献
7.
We have given design of a very small residual dispersion fiber system consisting of a small dispersion fiber(SDF) with flat modal field and a corresponding dual core coaxial dispersion compensating fiber (DCF). 相似文献
8.
Spectral characteristics of 1-(2,4-diamino phenylazo) naphthalene (FBRR, fat brown RR) and 4-aminoazobenzene (AAB) have been
studied in various solvents, varying hydrogen ion concentrations and in β-cyclodextrin (β-CD). The inclusion complex of FBRR
and AAB with β-CD were analysed by UV-visible, fluorometry and CAche-DFT methods. Solvent study reveals that only azo tautomer
is present in both compounds and the large red shifted absorption and emission maxima of FBRR indicate naphthalene ring effectively
increases the π-π* transition. Unusual red shift is observed in acid solutions suggests azonium-ammonium tautomer is present
in both molecules. In β-CD solutions, the large hypsochromic shift is observed in S0 and S1 states indicates ortho amino group of FBRR molecule is entrapped in the β-CD cavity and the large bathochromic shift for AAB in the S1 state indicates 1:1 inclusion complex is formed. 相似文献
9.
K. K. Abdullah K. Karunakaran Nair N. Ramachandran K. M. Varier B. R. S. Babu Antony Joseph Rajive Thomas P. Magudapathy K. G. M. Nair 《Pramana》2010,75(3):459-469
Mass attenuation coefficients (μ/ρ) for Zr, Nb, Mo and Pd elements around their K-edges are measured at 14 energies in the range 15.744–28.564 keV using secondary excitation from thin Zr, Nb, Mo, Rh, Pd,
Cd and Sn foils. The measurements were carried out at the K
α
and K
β
energy values of the target elements by two techniques: (1) Proton-induced X-ray emission (PIXE) and (2) 241Am (300 mCi) source. In PIXE, 2 MeV proton-excited X-rays were detected by a Si(Li) detector. In the second case, X-rays excited
by 59.54 keV photons from the targets were counted by an HPGe detector under a narrow beam good geometry set-up with sufficient
shielding. The results are consistent with theoretical values derived from the XCOM package and indicate that the PIXE data
have better statistical accuracy. 相似文献
10.
K.N. Joshipura M. Vinodkumar B.K. Antony N.J. Mason 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,23(1):81-90
Total ionization cross-sections of electron impact are calculated for the molecular targets CHx, CFx, SiHx, SiFx (x = 1-4) and CCl4 at incident energies 20-3 000 eV. The calculation is based on Complex Scattering Potential approach, as developed by us recently.
This leads to total inelastic cross-sections, from which the total ionization cross-sections are extracted by reasonable physical arguments. Extensive comparisons are made here with the previous theoretical
and experimental data. The present results are satisfactory except for the CFx and SiFx (x = 1-3) radicals, for which the experimental data are lower than most of the theories by more than 50%.
Received 23 May 2002 / Received in final form 24 October 2002 Published online 21 January 2003
RID="a"
ID="a"e-mail: knjoshipura@yahoo.com 相似文献