全文获取类型
收费全文 | 74篇 |
免费 | 3篇 |
专业分类
化学 | 55篇 |
力学 | 2篇 |
数学 | 11篇 |
物理学 | 9篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 1篇 |
2017年 | 1篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 5篇 |
2012年 | 4篇 |
2011年 | 7篇 |
2010年 | 5篇 |
2009年 | 2篇 |
2008年 | 6篇 |
2007年 | 3篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2000年 | 5篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有77条查询结果,搜索用时 31 毫秒
1.
G. Jyothi Chanchal K. Mitra G. Krishnamoorthy 《Journal of Electroanalytical Chemistry》1991,321(3):395-402
The exchange of gramicidin between liposomes made of two different kinds of phospholipids has been studied using a fluorescent probe (pyranine). The experimentally observed rate of exchange is compared with that of nigericin, which is a simple carrier. Possible reasons for the difference in the rate of exchange are discussed and probable mechanisms suggested. It is proposed that gramicidin exchanges between vesicles by a contact mechanism. 相似文献
2.
Abhishek Maurya Arun Kumar Mahato Nikita Chaudhary Neha Kesharwani Payal Kachhap Vivek Kumar Mishra Chanchal Haldar 《应用有机金属化学》2020,34(4):e5508
Two vanadium (IV) complexes [VIVO(Haeae-sal)(MeOH)]+ ( 1 ) and [VIVO(Haeae-hyap)(MeOH)]+ ( 2 ) were prepared by reacting [VO(acac)2] with ligands [H2aeae-sal] ( I ) and [H2aeae-hyap] ( II ) respectively. Condensation of 2-(2-aminoethylamino)ethanol with salicylaldehyde and 2-hydroxyacetophenone produces the ligands ( I ) and ( II ) respectively. Both vanadium complexes 1 and 2 are sensitive towards aerial oxygen in solution and rapidly convert into vanadium(V) dioxido species. Vanadium(V) dioxido species crystalizes as the dimeric form in the solid-state. Single-crystal XRD analysis suggests octahedral geometry around each vanadium center in the solid-state. To access the benefits of heterogeneous catalysis, vanadium(V) dioxido complexes were anchored into the polymeric chain of chloromethylated polystyrene. All the synthesized neat and supported vanadium complexes have been studied by a number of techniques to confirm their structural and functional properties. Bromoperoxidase activity of the synthesized vanadium(V) dioxido complexes 3 and 4 was examined by carrying out oxidative bromination of salicylaldehyde and oxidation of thioanisole. In the presence of hydrogen peroxide, 3 shows 94.4% conversion ( TOF value of 2.739 × 102 h−1) and 4 exhibits 79.0% conversion (TOF value of 2.403 × 102 h−1) for the oxidative bromination of salicylaldehyde where 5-bromosalicylaldehyde appears as the major product. Catalysts 3 and 4 also efficiently catalyze the oxidation of thioanisole in the presence of hydrogen peroxide where sulfoxide is observed as the major product. Covalent attachment of neat catalysts 3 and 4 into the polymer chain enhances substrate conversion (%) and their catalytic efficiency increases many folds, both in the oxidative bromination and oxidation of thioether. Polymer supported catalysts 5 displayed 98.8% conversion with a TOF value of 1.127 × 104 h−1 whereas catalyst 6 showed 95.7% conversion with a TOF value of 4.675 × 103 h−1 for the oxidative bromination of salicylaldehyde. These TOF values are the highest among the supported vanadium catalysts available in the literature for the oxidative bromination of salicylaldehyde. 相似文献
3.
Grainger Reid J. Ko Samuel Koslov Eugene Prokop Ales Tanner Robert D. Loha Veara 《Applied biochemistry and biotechnology》2000,84(1-9):761-768
Human insulin in zinc suspension was used as a model protein to test the effect of shear on the settling rate of proteins,
a possible inference for protein denaturation. The rate of settling was determined directly in a spectropho-tometer. Shear
effects are important in retaining the activity of proteins and are present in bubble, foam, and droplet protein fractionation
processes. A sim pletest, such as that conducted here, mayeven be useful for monitoring changes in protein structure caused
by commercial shipping of the protein. The settling ratefor insulin was continously monitored in theoriginal bottle by spectrophotometric
absorbance changes as a function of time. A settling curve was determined following each shear experiment, which included
shaking the “worked” insulin solution in a vortex mixer for different lengths of time. It was determined, when comparing long
shaking times with short ones, that the initial settling rate was less for the long-term shaking of the insulin samples and
greater for the short-term shaking. The secondary effects of light and heat, along with shaking, a pparently did not produce
differences from shaking alone. 相似文献
4.
Chanchal Das Tanushree Chakraborty Soumen Ghosh Bijan Das 《Colloid and polymer science》2008,286(10):1143-1155
Mixed micellization of binary and ternary mixtures of anionic and nonionic surfactants, such as lithium dodecyl sulfate, polyoxyethylene(23)laurylether,
and polyoxyethylene-tert-octylphenylether, is studied in aqueous solution using tensiometric, conductometric, and spectrophotometric methods. Although
tensiometry and conductometry complement each other closely, the spectroscopic critical micellar concentration (cmc) is far
from agreement with tensiometric study. Several parameters, e.g., cmc, degree of counterion binding, free energies of micellization,
and interfacial adsorption, have been evaluated. Established theories of Clint, Rosen, Rubingh, Motomura, Georgiev, Maeda,
and Blankschtein were applied to evaluate the mole fraction of different components in the self-aggregated phase, the interaction
parameter, free energy contributions, and expected cmc. 相似文献
5.
Veara Loha Aleš Prokop Liping Du Robert D. Tanner 《Applied biochemistry and biotechnology》1999,79(1-3):701-712
Foam fractionation isone of the low operating-cost techniques for removing proteins from a dilute solution. The initial bulk
solution pH and air superficial velocity play an importantrole in the foam-fractionation process. Denaturation of proteins
(enzymes) can occur, however, during the foamfractionation process from the shear forces resulting from bursting air bubbles.
At the extreme bulk solution pHs (lower than 3.0 and higher than 10.0), the en zymatic activity of cellulase in the foamate
phase drops significantly. Within these two pH boundsan increase in the air superficial velocity, Vo, and a decrease in the bulk solution pH leads to a decrease in the separation ratio (SR), defined as theratio of the protein
concentration in the foamate to the protein concentration in the residue. On the other hand, an increase in Vo provides a higher foamate-protein recovery. The process efficiency is defined as the product of foamate-protein recovery
times the SR times the cellulase activity. The optimal operating condition of the cellulase foamfractionation process is taken
into account at the maximum value of the processefficiency. In this study, that optimal condition is atan air superficial
velocity of 32 cm/min and a bulk-solution pH of 10.0. At this condition, the recovered foamate is about 80% of the original
protein mass, the SR is about 12, and the en zymatic activity is about 60% of the original cellulase activity. 相似文献
6.
The present study investigates the utility of composite beads of nano-particles of iron oxide and chitosan for removing Ni (II) ions from aqueous solution by batch and column adsorption techniques. In the batch mode experiment, the influence of pH, concentration, adsorbent dose, temperature, column mode, bed height, flow rate and initial concentration were studied on the adsorption profiles of nickel ions. The maximum uptake of Ni (II) ions was obtained at pH 4.0 in 30 min at room temperature. 相似文献
7.
A series of hetero- and homoleptic tridentate ruthenium(II) and osmium(II) complexes of compositions [(tpy-PhCH(3))Ru(tpy-HImzphen)](ClO(4))(2) (1), [(H(2)pbbzim)Ru(tpy-HImzphen)](ClO(4))(2) (2), and [M(tpy-HImzphen)(2)](ClO(4))(2) [M = Ru(II) (3) and Os(II) (4)], where tpy-PhCH(3) = 4'-(4-methylphenyl)-2,2':6',2"-terpyridine, H(2)pbbzim = 2,6-bis(benzimidazole-2-yl)pyridine and tpy-HImzphen = 2-(4-[2,2':6',2"]terpyridine-4'-yl-phenyl)-1H-phenanthro[9,10-d]imidazole, have been synthesized and characterized by using standard analytical and spectroscopic techniques. X-ray crystal structures of three complexes 2, 3, and 4 have been determined. The absorption spectra, redox behavior, and luminescence properties of the complexes have been thoroughly investigated. All of the complexes display moderately strong luminescence at room temperature with lifetimes in the range of 10-55 ns. The effect of solvents on the absorption and emission spectral behavior of the complexes has also been studied in detail. The anion sensing properties of all the complexes have been studied in solution using absorption, emission, and (1)H NMR spectral studies and by cyclic voltammetric (CV) measurements. It has been observed that the complexes 1, 3, and 4 act as sensors for F(-)only, whereas 2 acts as sensor for F(-), AcO(-), and to some extent for H(2)PO(4)(-). It is evident that in the presence of excess of anions deprotonation of the imidazole N-H fragment(s) occurs in all cases, an event which is signaled by the development of vivid colors visible with the naked eye. The receptor-anion binding/equilibrium constants have been evaluated. 相似文献
8.
Chanchal Singh 《Journal of Mathematical Analysis and Applications》1984,100(2):409-415
Let V ?H be real separable Hilbert spaces. The abstract wave equation u′' + A(t)u = g(u), where u(t) ?V, A(t) maps V to its dual , and g is a nonlinear map from the ball S(R0) = {u?V: ∥u∥ < R0} into H, is considered. It is assumed that g is locally Lipschitz in S(R0) and possibly singular at the boundary. Local existence and continuation theorems are established for the Cauchy problem u(0) = u0?S(R0), u′(0) = u1?H. Global existence is shown for g(u) = εφ(u), where φ has a potential and ε is small. Global nonexistence is shown for g(u) = εφ(u), where φ satisfies an abstract convexity property and ε is large. 相似文献
9.
Saddle-point optimality criteria of Kuhn-Tucker and Fritz Johns are established in the case of continuous time programming problems. The functions involved are not assumed to be differentiable. In the process, an important theorem of the alternative is also proven. 相似文献
10.