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111.
The use of organofunctional silane chemistry is a flexible and general method for immobilizing biomolecules on silicon oxide surfaces, including fabricating DNA, small-molecule, and protein microarrays. The biggest hurdle in employing dip-pen nanolithography (DPN) for extending this general approach to the nanoscopic domain is the tendency of trialkoxy- and trichlorosilanes to rapidly polymerize due to hydrolysis reactions. The control of the local water concentration between the substrate surface and the scanning AFM tip is critical, both to the physical and chemical processes involved in DPN writing and to the ability to form well-defined thin layers of reactive silanes without extensive polymerization induced disorder. We found that we could control the degree of polymerization through careful choice of the alkoxysilane used as the "ink" for DPN and through control of the relative humidity during inking and writing with the coated AFM tip. As a proof-of-principle, we demonstrate that areas patterned with an alkoxysilane on glass with DPN are functional for subsequent immobilization of fluorescently labeled streptavidin via covalent attachment of biotin. This preliminary result sets the stage for the ability to capture proteins in their fully hydrated state from buffered solution, by molecular recognition onto previously written reactive nanoscopic regions on oxidized silicon and glass. 相似文献
112.
Yip VL Varrot A Davies GJ Rajan SS Yang X Thompson J Anderson WF Withers SG 《Journal of the American Chemical Society》2004,126(27):8354-8355
Among the numerous well-characterized families of glycosidases, family 4 appears to be the anomaly, requiring both catalytic NAD+ and a divalent metal for activity. The unusual cofactor requirement prompted the proposal of a mechanism involving key NAD+-mediated redox steps as well as elimination of the glycosidic oxygen. Primary kinetic isotope effects for the 2- and 3-deutero substrate analogues, isotopic exchange with solvent, and structural analysis of a 6-phospho-beta-glucosidase, BglT (E.C. 3.2.1.6), provided evidence in support of the proposed mechanism, which has striking resemblances to that of the sugar dehydratases. Furthermore, analysis of the stereochemical outcome indicated that family 4 enzymes are retaining glycosidases. 相似文献
113.
In order to overcome the hydrolysis of monomer when polymerisation of N-vinylpyrrolidone is attempted in aqueous solution in the presence of polyacrylic acid and potassium per sulphate, the reaction was carried out in dimethylformamide. Two distinct regions in the polymerisation were observed, corresponding to the first five minutes of the reaction and to the later stages. In both, a template effect could be observed, a maximum in rate occurring as the concentration of the polyacrylic acid was increased. The reaction appeared to be very much faster in the initial stages. The orders with respect to monomer and initiator were found. 相似文献
114.
V. Kabaleeswaran S. S. Rajan Geetha Gopalakrishnan G. Suresh T. R. Govindachari 《Journal of chemical crystallography》1997,27(12):731-733
The crystal structure of nimbin has been determined. The crystals are orthorhombic, space groupP212121 witha=6.790(2),b=14.875(4),c=27.160(8) Å andZ=4. The packing of the molecules in the lattice is due to C?H…O type of hydrogen bonds. 相似文献
115.
Mediterranean Journal of Mathematics - In the present paper, we introduce screen generic lightlike submanifold of golden semi-Riemannian manifolds and give non-trivial examples of such... 相似文献
116.
T. G. Gopakumar S. Ponrathnam C. R. Rajan A. Fradet 《Journal of polymer science. Part A, Polymer chemistry》1998,36(15):2707-2713
We report the synthesis and characterization of copolymers comprising poly(phenyl sulfide) (PPS) blocks and semiaromatic thermotropic liquid crystalline polymer (TLCP) blocks. The copolymers, synthesized by melt-transesterification of dicarboxy-terminated poly(phenylene sulfide) with poly(ethylene terephthalate-co-oxybenzoate) (PET/OB), were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized light optical microscopy (PLOM). The crystallizability and liquid crystalline properties of the copolymers are greatly influenced by the extent of interchange reactions, the mole percent of oxybenzoate with respect to the PET, the PPS : PET/OB weight ratio, and the reaction time. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2707–2713, 1998 相似文献
117.
Sunita Omprakash Yemul Omprakash Shrinivas Yemul Surendra Ponrathnam C. R. Rajan Alain Fradet 《Macromolecular rapid communications》1998,19(12):635-639
The synthesis of poly(thio- 1,4-phenylene) (PPS) at room temperature by the reaction of diphenyl disulfide with potassium persulfate (K2S2O8) in non-basic solvents, in the presence of trifluoromethanesulfonic acid, is reported. The reaction in chlorinated solvents, such as dichloromethane and tetrachloroethane, resulted in partial oxidation of sulfide to sulfoxide and sulfone. On the other hand, the polymerization proceeded well in nitrobenzene and the PPS formed was free of branches, crosslinks and thianthrene units. The molecular weight of the polymers formed in different solvents were in the range 2000–8000. The reaction proceeded under identical conditions with bis(2,6-dimethylphenyl) disulfide as well, but the polymer yield was lower. 相似文献
118.
S.K. Katoch S.L. Gupta S.C. Pancholi D. Mehta S. Malik G. Shanker L. Chaturvedi R.K. Bhowmik 《The European Physical Journal A - Hadrons and Nuclei》1999,4(4):307-309
High-spin states in the odd-odd 168Lu nucleus, populated in the 154Sm(19F,5n) reaction at a beam energy of 96 MeV, were investigated using in-beam γ-ray spectroscopy techniques. The BC neutron crossing
in the yrast band, based on πg
7/2[404]7/2+⊗νi
13/2[642]5/2+ configuration, occurs at ħω= 0.31 MeV. The two side bands, based on πh
11/2[514]9/2−⊗νi
13/2[642]5/2+ and πh
9/2[541]1/2−⊗νi
13/2[642]5/2+ configurations, show anomalous signature-splitting and signature-inversion in the first one, to occur at ħω= 0.24 MeV. A
moderately delayed BC-crossing is anticipated in the second one.
Received: 15 June 1998 / Revised version: 11 January 1999 相似文献
119.
120.
Ashich V. Naik Alok Baveja Rajan Batta Jonathan P. Caulkins 《European Journal of Operational Research》1996
This paper presents an analytical approach for scheduling crackdowns on street-corner drug markets. The crackdown scheduling problem is shown to be NP-complete. We then provide efficient optimal algorithms for several special cases and approximation algorithms for the general case. These results show that the optimal strategy is to give priority to markets that take longer to bring down and which require low levels of post-crackdown maintenance. The results are then extended to incorporate dealer displacement between drug markets. 相似文献