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排序方式: 共有300条查询结果,搜索用时 171 毫秒
61.
Mutyala R Reddy RN Sumakanth M Reddanna P Reddy MR 《Journal of computational chemistry》2007,28(5):932-937
The free energy perturbation (FEP) methodology is the most accurate means of estimating relative binding affinities between inhibitors and protein variants. In this article, the importance of hydrophobic and hydrophilic residues to the binding of adenosine monophosphate (AMP) to the fructose 1,6-bisphosphatase (FBPase), a target enzyme for type-II diabetes, was examined by FEP method. Five mutations were made to the FBPase enzyme with AMP inhibitor bound: 113Tyr --> 113Phe, 31Thr --> 31Ala, 31Thr --> 31Ser, 177Met --> 177Ala, and 30Leu --> 30Phe. These mutations test the strength of hydrogen bonds and van der Waals interactions between the ligand and enzyme. The calculated relative free energies indicated that: 113Tyr and 31Thr play an important role, each via two hydrogen bonds affecting the binding affinity of inhibitor AMP to FBPase, and any changes in these hydrogen bonds due to mutations on the protein will have significant effect on the binding affinity of AMP to FBPase, consistent to experimental results. Also, the free energy calculations clearly show that the hydrophilic interactions are more important than the hydrophobic interactions of the binding pocket of FBPase. 相似文献
62.
Biswajita Baruah 《Tetrahedron letters》2009,50(2):243-245
5-Formyl-6-tertiaryamino uracils 3 prepared from 6-chloro-5-formyl uracil derivative 1 react with barbituric acids 4 in the presence of base catalyst to afford a novel class of spirosubstituted pyrido[2,3-d]pyrimidines 5 via 1,6-electro-cyclisation in excellent yields. 相似文献
63.
M. López-Sánchez M. J. Ayora-Cañada A. Molina-Díaz M. Siam W. Huber G. Quintás S. Armenta B. Lendl 《Analytical and bioanalytical chemistry》2009,394(8):2137-2144
A mid-infrared enzymatic assay for label-free monitoring of the enzymatic reaction of fructose-1,6-bisphosphatase with fructose
1,6-bisphosphate has been proposed. The whole procedure was done in an automated way operating in the stopped flow mode by
incorporating a temperature-controlled flow cell in a sequential injection manifold. Fourier transform infrared difference
spectra were evaluated for kinetic parameters, like the Michaelis–Menten constant (K
M) of the enzyme and V
max of the reaction. The obtained K
M of the reaction was 14 ± 3 g L−1 (41 μM). Furthermore, inhibition by adenosine 5′-monophosphate (AMP) was evaluated, and the K
MApp value was determined to be 12 ± 2 g L−1 (35 μM) for 7.5 and 15 μM AMP, respectively, with V
max decreasing from 0.1 ± 0.03 to 0.05 ± 0.01 g L−1 min−1. Therefore, AMP exerted a non-competitive inhibition. 相似文献
64.
Sedat Ture 《Phosphorus, sulfur, and silicon and the related elements》2016,191(8):1174-1182
Reactions of hexachlorocyclotriphosphazene N3P3Cl6 (1) with 1,4-butane-(2) and 1,6-hexane-diols (3) in (1:1:2, 1:2:4, and 1:3:6) stoichiometries in THF solution at room temperature (r.t.) and under refluxing conditions yield a total of 15 products: two open chain, N3P3Cl5[O(CH2)nOH] (n = 4, 6) (4, 5), two mono-spiro, N3P3Cl4[O(CH2)nO] (n = 4, 6) (6, 7), two mono-ansa, N3P3Cl4[O(CH2)nO] (n = 4,6) (8, 9), two dispiro, N3P3Cl2[O(CH2)nO]2 (n = 4, 6) (10, 11), two spiro-ansa, N3P3Cl2[O(CH2)nO]2 (n = 4, 6) (12, 13), one tri-spiro, N3P3[O(CH2)4O]3 (14), two single-bridged, N3P3Cl5[O(CH2)nO]N3P3Cl5 (n = 4, 6) (15, 16), one double-bridged, N3P3Cl4[O(CH2)6O]2N3P3Cl4 (17), and one tri-bridged, N3P3Cl3[O(CH2)6O]3N3P3Cl3 (18) derivatives. Their structures have been elucidated by MS, 31P, and 1H NMR spectroscopy. The results obtained, based on the synthesis, characterization, product types, and the relative yields, are compared with those of previous studies on the reactions of 1 with 1,2-ethane-, 1,3-propane-, 1,4-butane-, 1,5-pentane-, and 1,6-hexane-diols. 相似文献
65.
Study of the factors determining the outcome of cycloaddition of isocyanurato-substituted azides to [60]fullerene 总被引:2,自引:0,他引:2
Sinyashin O. G. Romanova I. P. Yusupova G. G. Nafikova A. A. Kovalenko V. I. Azancheev N. M. Fattakhov S. G. Reznik V. S. 《Russian Chemical Bulletin》2001,50(11):2162-2171
The final outcome of cycloaddition of isocyanuratoalkyl azides to C60 depends on the temperature, the thermal stability of azides, the substituents in the isocyanurate ring, and the number of methylene groups in the alkyl radical. The thermal transformations of the monoadducts obtained were studied. 相似文献
66.
An efficient synthesis of 1,2,3,4,6‐penta‐O‐acetyl‐L ‐idopyranose 2 from 3,5‐O‐benzylidene‐1,2‐O‐isopropylidene‐α‐D ‐glucofuranose in five steps in 45% overall yield via hydroboration of enol ether, hydrolysis of L ‐idofuranosyl sugar and acetolysis of 1,6‐anhydro‐β‐L ‐idopyranose as key steps is described here. 相似文献
67.
Tobias S. Halbach Jens O. Krause Oskar Nuyken Michael R. Buchmeiser 《Macromolecular rapid communications》2005,26(10):784-790
Summary: The cyclopolymerization of 4,4‐bis(hydroxymethyl)‐1,6‐heptadiyne ( M1 ), 4‐(carboxyethyl)‐1,6‐heptadiyne ( M2 ), 4‐(hydroxymethyl)‐1,6‐heptadiyne ( M3 ), and 4‐carboxy‐1,6‐heptadiyne ( M4 ) using five different well‐defined metathesis initiators was investigated. Control of molar mass was achieved with catalysts bearing trifluoroacetate ligands. 13C NMR experiments showed that poly‐ M2 , prepared by the action of any catalyst consisted solely of five‐membered ring structures, i.e., 1,2‐(cyclopent‐1‐enylene)vinylene units. Effective conjugation lengths of all polymers were calculated from the corresponding UV‐Vis absorption maxima, which varied reversibly with temperature.
68.
María L. Cerrada Rosario Benavente Ernesto Prez Jorge Moniz‐Santos M. Rosrio Ribeiro 《Journal of Polymer Science.Polymer Physics》2004,42(20):3797-3808
The relationship between the structure and mechanical properties has been established for several copolymers of ethylene and 5,7‐dimethylocta‐1,6‐diene synthesized with a metallocene catalyst. A dependence on the composition and polymerization temperature has been found. The branches cannot be incorporated into the orthorhombic crystal lattice, and consequently, structural parameters such as the crystallinity and crystal size are considerably affected as the 5,7‐dimethylocta‐1,6‐diene content increases in the copolymers. The viscoelastic relaxations have been analyzed and compared with those exhibited by high‐density polyethylene (HDPE). The β relaxation does not appear in HDPE and is exclusively seen in the copolymers. As the 5,7‐dimethylocta‐1,6‐diene content rises, the intensity of this process is increased, and its location is shifted to a lower temperature up to comonomer contents of approximately 6–8 mol % in the copolymers. On the other hand, the α mechanism associated with motion within the crystalline regions is also moved to a lower temperature and its intensity is diminished as the 5,7‐dimethylocta‐1,6‐diene molar fraction increases in the copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3797–3808, 2004 相似文献
69.
Takushi Azemi 《Tetrahedron》2004,60(6):1339-1344
Cyclopentane and cyclohexane derivatives are prepared from 1,5- and 1,6-dienes in a one pot procedure by hydrozirconation, then oxidation of the generated 5- and 6-alkenylzirconocene chlorides with ammonium hexanitratocerate. 相似文献
70.
Junhua Tong Liang Zhao Huihui Li Chenglin Wu Xu Han Jiang Wang Hong Liu 《Tetrahedron》2018,74(27):3755-3760
Asymmetric construction of β,β-diaryl substituted glycine bearing two contiguous chiral centers remains a significant challenge. Herein, the application of the para-quinone methides (p-QMs) and Ni(II)- complex of glycine via 1,6-conjugate addition to achieve asymmetric synthesis of β,β-diaryl substituted glycine has been explored successfully. This protocol features operational simplicity, high diastereoselectivity, and recyclable chiral ligand, which provides a versatile approach to the synthesis of highly enantiopure β,β-diaryl substituted glycine. 相似文献