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101.
Jayaraman Kannappan Aditya N. Khanvilkar Gourav M. Upadhyay Ashutosh V. Bedekar 《Tetrahedron: Asymmetry》2017,28(10):1297-1303
The design and synthesis of a few simple N-benzyl derivatives of isobornyl amine is presented. The derivatives have been assessed as chiral solvating agents for effective discrimination of the signals of some acids in NMR analysis. The single crystal X-ray analysis of the salts of (R)-mandelic acid with two of the title derivatives help to understand the supramolecular interactions and assign the induced chemical shifts in 1H NMR analysis. The title derivative is found to be suitable for quantitative determination of the enantiomeric excess of unknown enantiomeric purity as well as being efficient in resolving racemic mandelic acid. 相似文献
102.
103.
Ranjit Kumar Upadhyay Rashmi Agrawal 《Journal of Applied Mathematics and Computing》2015,49(1-2):13-39
In this paper, we investigate the effect of mutual interference on the dynamics of a predator-prey system with gestation delay. It has been observed that there is stability switches and system becomes unstable due to the combine effect of mutual interference and time delay. We determine the conditions under which the model system becomes globally asymptotically stable around the non-zero equilibria. By applying the normal form theory and the center manifold theorem, the explicit formulae which determine the stability and direction of the bifurcating periodic solutions are determined. Computer simulations have been carried out to illustrate different analytical findings. 相似文献
104.
C. Ruby A. Géhin R. Aissa J. Ghanbaja M. Abdelmoula J.-M. R. Génin 《Hyperfine Interactions》2006,167(1-3):803-807
Hydroxysulphate green rust species were precipitated in the presence of various anions. is stable at ∼pH 7 and is transformed into a mixture of magnetite and ferrous hydroxide when the pH raised at ∼12. In the
presence of carbonate species, is partially transformed into a mixture of magnetite and siderite at ∼pH 8.5. This transformation is stopped when silicate
anions are present in the solution. As already observed for phosphate anions, the adsorption of silicate anions on the lateral
faces of the crystals may explain this stabilization effect. Sulphate anions are easily exchanged by carbonate species at ∼pH 10.5. In
contrast, anionic exchange between sulphate and phosphate anions was not observed. 相似文献
105.
X-ray photoelectron spectroscopy (XPS) was used to investigate chemical bonding and distribution of iron and oxygen species at the surface of Green Rusts (GRs). GRs with variable composition, i.e. FeII6(1−x)FeIII6xO12H2(7−3x) CO3·3H2O where the FeIII molar fraction of the positively charged hydroxide sheets, x=[Fe(III)]/[Fe(total)] belongs to [1/3, 1], were synthesised under an inert atmosphere. The broadened Fe(2p3/2) spectra were fitted using Gupta and Sen multiplets peaks and additional satellite and surface features. The [Fe(III)]/[Fe(total)] surface atomic ratios closely agree with the x ratios expected from the bulk composition, which gives a high degree of confidence on the validity of the proposed fitting procedure. The valence band spectra are also reported and show dependencies on iron speciation. The O(1s) spectra revealed the presence of O2−, OH− species and adsorbed water. The hydroxyl component decreases with increasing x values, i.e. with the amount of ferric iron, while the oxide component increases. This study provides direct spectroscopic evidence of the deprotonation of hydroxyl groups that occurs simultaneously with the oxidation of ferrous iron within the GR structure. 相似文献
106.
Chelates of bidentate ligands, p-dimethylamino and p-diethylaminoanils of 3-benzoylmethylglyoxal with Ir(III), Pt(IV) and Au(III) ions have been studied for their stoichiometry, electrolytic nature, infrared, magnetic, and electronic spectra. In addition to the elucidation of stereochemistry and structures various ligand field parameters have been calculated and unusual paramagnetic behaviour has been accounted for. 相似文献
107.
Jalpa C. Trivedi Kuldip D. Upadhyay Sudhir K. Joshi Erik De Clercq 《Tetrahedron letters》2007,48(48):8472-8474
Two closely structurally related coumarins, 4-hydroxy-8-isopropyl-5-methylcoumarin and 4-hydroxy-6-chloro-7-methylcoumarin were acylated at C-3 and further converted to the respective chalcones and two series of eighteen new compounds, which were evaluated for possible antiviral activity. 相似文献
108.
Buglyó P Crans DC Nagy EM Lindo RL Yang L Smee JJ Jin W Chi LH Godzala Iii ME Willsky GR 《Inorganic chemistry》2005,44(15):5416-5427
The aqueous vanadium(III) (V(III)) speciation chemistry of two dipicolinate-type complexes and the insulin-enhancing effects of V-dipicolinate (V-dipic) complexes in three different oxidation states (V(III), V(IV), and V(V)) have been studied in a chronic animal model system. The characterization of the V(III) species was carried out at low ionic strength to reflect physiological conditions and required an evaluation of the hydrolysis of V(III) at 0.20 M KCl. The aqueous V(III)-dipic and V(III)-dipic-OH systems were characterized, and complexes were observed from pH 2 to 7 at 0.2 M KCl. The V(III)-dipic system forms stable 1:2 complexes, whereas the V(III)-dipic-OH system forms stable 1:1 complexes. A comparison of these complexes with the V-pic system demonstrates that a second ligand has lower affinity for the V(III), presumably reflecting bidentate coordination of the second dipic(2)(-) to the V(III). The thermodynamic stability of the [V(III)(dipic)(2)](-) complex was compared to the stability of the corresponding V(IV) and V(V) complexes, and surprisingly, the V(III) complexes were found to be more stable than anticipated. Oral administration of three V-dipicolinate compounds in different oxidation states {H[V(III)(dipic)(2)H(2)O].3H(2)O, [V(IV)Odipic(H(2)O)(2)].2H(2)O, and NH(4)[V(V)O(2)dipic]} and the positive control, VOSO(4), significantly lowered diabetic hyperglycemia in rats with streptozotocin-induced diabetes. The diabetic animals treated with the V(III)- or V(IV)-dipic complexes had blood glucose levels that were statistically different from those of the diabetic group. The animals treated with the V(V)-dipic complex had the lowest blood glucose levels of the treated diabetic animals, which were statistically different from those of the diabetic group at all time points. Among the diabetic animals, complexation to dipic increased the serum levels of V after the administration of the V(V) and V(IV) complexes but not after the administration of the V(III) complex when data are normalized to the ingested dose of V. Because V compounds differing only in oxidation state have different biological properties, it is implied that redox processes must be important factors for the biological action of V compounds. We observe that the V(V)-dipic complex is the most effective insulin-enhancing agent, in contrast to previous studies in which the V(IV)-maltol complex is the most effective. We conclude that the effectiveness of complexed V is both ligand and oxidation state dependent. 相似文献
109.
Pradeep K Pandey Neerja Kaushik Kamalendra Singh Bechan Sharma Alok K Upadhyay Suriender Kumar Dylan Harris Virendra N Pandey 《BMC biochemistry》2002,3(1):18-14
Background
HIV-1 RT is a heterodimeric enzyme, comprising of the p66 and p51 subunits. Earlier, we have shown that the β7-β8 loop of p51 is a key structural element for RT dimerization (Pandey et al., Biochemistry 40: 9505, 2001). Deletion or alanine substitution of four amino acid residues of this loop in the p51 subunit severely impaired DNA binding and catalytic activities of the enzyme. To further examine the role of this loop in HIV-1 RT, we have increased its size such that the six amino acids loop sequences are repeated in tandem and examined its impact on the dimerization process and catalytic function of the enzyme. 相似文献110.
Spectrophotometric studies support the formation of { PtIV–S} (where S = glucose, galactose and fructose) complexes in an alkaline medium. The resistance of these complexes to reaction with N-bromosuccinimide (NBS) has been observed. The kinetic data also support the formation of { PtIV –S} complexes. 相似文献