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排序方式: 共有165条查询结果,搜索用时 31 毫秒
1.
K. Sreenivasan 《大分子材料与工程》1996,235(1):15-20
A poly(vinyl alcohol)-β-cyclodextrin (PVA-BCD) copolymer was prepared by successive reaction of BCD with toluylene diisocyanate and PVA. Copolymer formation was evidenced by infrared spectroscopy, differential scanning calorimetry and gel permeation chromatography. Scanning electron micrographs show morphological differences between PVA and the copolymer. The copolymer, being almost insoluble in common solvents with an equilibrium swelling in water of 50%, is a potential membrane material. 相似文献
2.
K. Sreenivasan 《应用聚合物科学杂志》1996,59(13):2089-2093
β-Cyclodextrin was blended with poly(vinyl chloride) to study the influence of β-cyclodextrin on the leaching of phthalate ester from PVC. β-Cyclodextrin was found to reduce the migration of phthalate ester. The considerable effect of β-cyclodextrin on the leaching of phthalate ester was traced to the formation of an inclusion complex formation between the two components. © 1996 John Wiley & Sons, Inc. 相似文献
3.
K. Sreenivasan 《应用聚合物科学杂志》1996,60(12):2245-2249
2-Hydroxyethyl methacrylate (HEMA) and β-cyclodextrin are bridged using toluene-2,4-diisocyanate (TDI) by reacting the OH group of HEMA and one of the primary OH groups of β-cyclodextrin. The modified HEMA is grafted to polyurethane by γ-irradiation. The preliminary study showed that the membrane potential of conventional polymers like polyurethane could be enhanced considerably by this type of modification. © 1996 John Wiley & Sons, Inc. 相似文献
4.
Muthuraj Muthaiah Sridharan Jagadeesan Nisha Ayalusamy Manupriya Sreenivasan Sambamurthy Sangamesvara Prabhu Usharani Muthuraj Kamatchiyammal Senthilkumar Saroja Veerappan 《International journal of molecular sciences》2010,11(7):2670-2680
Pyrazinamide (PZA) has been in use for almost 50 years as a first-line drug for short-course chemotherapy against Mycobacterium tuberculosis. In this study, PCR mediated automated DNA sequencing is used to check the prevalence of PZA resistance among treatment failure cases of pulmonary tuberculosis. Out of 50 clinical isolates examined, 39 had mutations in the pncA gene that encodes Pyrazinamidase, an enzyme required to activate PZA. Of these, 31 (79.5%) were localized to three regions of pncA. We found two isolates with hitherto unreported mutation at amino acid 26 (Ala→Gly) of pncA. 相似文献
5.
In this paper, instrumented impact test results obtained using V-notch and precracked Charpy specimens of AISI 308 weld and AISI 316 stainless steels are analysed for determining the plastic -factor for three-point bend specimens used in J-integral evaluation. Tested 316 stainless steel specimens were in various thermal aging/cold-work conditions whereas 308 weld specimens were in the as-welded condition. The results are analysed using the various procedures proposed in the literature and compared with experimental and finite element results reported in the literature. Based on our analysis, two polynomial expressions of a/W for pl are presented: one gives a sort of upper-bound in the a/W range 0.05–1.0 while the other gives conservative values (i.e., use of this results in J-R curves and J sufficiently conservative for engineering purposes). Both provide a smooth variation of pl over the entire a/W range unlike some of the expressions given in the literature which show a discontinuous change at an intermediate a/W. 相似文献
6.
P. R. Sreenivasan S. K. Ray S. L. Mannan P. Rodriguez 《International Journal of Fracture》1992,55(3):273-283
Two kinds of surface cracked specimens are numerically analyzed by the three dimensional elastic-plastic FEM. Near tip regions are divided into fine elements, and the stress and displacement fields at the crack tip are compared with HRR solutions.At first, surface cracked specimens subjected to bending are analyzed by changing the aspect ratio and depth/thickness ratio. The effect of the loading condition, crack shape and the crack depth on the stress and displacement fields are discussed. Then the pipe with surface crack subjected to bending is analyzed and the availability of the J-integral concept to the LBB analysis is discussed.In every specimen, it is shown that in the regions very near to the crack tip, the displacement field is similar to HRR solutions of plane strain. In the outer regions, however, the stress and displacement fields depend strongly on the shape, thickness, and loading conditions. 相似文献
7.
8.
Interesterification of fats 总被引:8,自引:0,他引:8
B. Sreenivasan 《Journal of the American Oil Chemists' Society》1978,55(11):796-805
Interesterification changes the distribution of the fatty acids among the glycerides of fats or mixtures of fats from what
was present originally. This affects the physical nature and behavior of fats. A discussion of this process from the standpoints
of mechanism, catalysts, methods of monitoring the reaction and applications will be presented. 相似文献
9.
J. J. Niemela L. Skrbek K. R. Sreenivasan R. J. Donnelly 《Journal of Low Temperature Physics》2002,126(1-2):297-302
Turbulent convection is studied in a cell filled with cryogenic helium gas. At high Rayleigh numbers a large-scale circulation persists and has a size comparable to the container. Over a wide range of time scales greater than its characteristic turnover time, this mean flow exhibits occasional and irregular reversals of direction without a change in magnitude. We study this feature in an apparatus of aspect ratio unity, in which the highest attainable Rayleigh number is about 10
16. 相似文献
10.
D Li U Sreenivasan N Juranic S Macura FJ Puga PM Frohnert PH Axelsen 《Canadian Metallurgical Quarterly》1997,10(2):73-87
The antimicrobial activity of vancomycin and related glycopeptide antibiotics is due to stereospecific recognition of polypeptide components in bacterial cell walls. To better understand how these antibiotics recognize polypeptide determinants, we have developed dynamic models of the complexes formed by the vancomycin aglycon and two different dipeptide ligands, Ac-D-ala-D-ala and Ac-D-ala-gly. Molecular dynamics simulations of the two complexes, initially conditioned with distance constraints derived from two-dimensional nuclear magnetic resonance (NMR) studies, are conformationally stable and propagate in a manner consistent with the NMR-derived constraints after the constraints are removed. Free energy calculations accurately predict the relative binding affinity of these two complexes and help validate the simulation models for detailed structural analysis. Although the two ligands adopt similar conformations when bound to the antibiotic, there are clear differences in the configuration of intermolecular hydrogen bonds, the overall shape of the antibiotic, and other structural features of the two complexes. This analysis illustrates how complex structural and dynamic factors interrelate and contribute to differences in binding affinity. 相似文献