全文获取类型
收费全文 | 243篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
化学 | 147篇 |
晶体学 | 3篇 |
力学 | 5篇 |
数学 | 12篇 |
物理学 | 96篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 7篇 |
2020年 | 14篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 16篇 |
2016年 | 12篇 |
2015年 | 12篇 |
2014年 | 10篇 |
2013年 | 19篇 |
2012年 | 12篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 12篇 |
2006年 | 13篇 |
2005年 | 7篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 3篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1982年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有263条查询结果,搜索用时 15 毫秒
81.
Reactions of carbonate radical (Co3
−) generated by photolysis or by radiolysis of a carbonate solution, with Cu(II) complexes of aminopolycarboxylic acids viz.,
Cu(II)ethylenediamine tetraacetate [CuIIEDTA]2− and Cu(II)-iminodiacetate [CuIIIDA] were studied at pH 10. 5 and ionic strength 0.2 mol·dm−3. Time-resolved spectroscopy and kinetics for the transients were studied using flash photolysis and stable products arising
from the ligand degradation of the complex were ascertained by steady-state radiolysis experiments. From the kinetic data
it is observed that CO3
−, radical reacts initially with CuII-complex to form a transient intermediate having maximum absorption at 335 nm and 430 nm. From the subsequent reactions of
this intermediate it was assigned to be CuIII. species. This Cu(III) species undergoes intermolecular electron transfer with the CuII-complex to give a radical intermediate which again slowly reacts with CuII-complex to give a long lived species containing Cu−C bond. This long lived species, however, slowly decomposed to give glyoxalic
reaction between CuIII-complex and a suitable donor, the one electron reduction potential for [CuIIIEDTA]1−/[CuIIEDTA]2− and [CuIIIIDA]+1/CuIIIDA was determined. 相似文献
82.
The phase separation kinetics of a binary fluid is studied analytically through an effective one-fluid model with a random force spectrum determined self-consistently: the rate of kinetic energy injection by the random force is consistent with the droplet coalescence rate. Our detailed results for the rates of energy dissipation and kinetic energy decay are consistent with previous numerical studies. We find that simple nontrivial scaling, if any, is associated with a new universality class where the velocity length scale follows . 相似文献
83.
K.K. Bardhan 《Solid State Communications》1982,44(5):583-586
Results of a x-ray scattering study of the inplane ordering in dilute graphite-bromine in the temperature range from 300 to 400K are presented. Evidence is obtained for a commensurate-incommensurate transition which is found to behave differently from those observed in the case of adsorbed monolayers. The bromine layers undergo continuous order-disorder transition from the incommensurate phase at 374K. Implications of this result and the large value of the measured exponent (β=0.32) are discussed. 相似文献
84.
Debajyoti Choudhury Rahul Sinha S Arunagiri Gautam Bhattacharyya Debrupa Chakraverty Debajyoti Choudhury Amitava Datta Anindya Datta Aseskrishna Datta Amol Dighe Dilip Kumar Ghosh Anjan Giri Stephen King Anirban Kundu Rukmani Mohanta Biswarup Mukhopadhyaya Sreerup Raychaudhuri Saurabh Rindani Probir Roy DP Roy Sourov Roy AI Sanda Nita Sinha Rahul Sinha K Sridhar H Yamamoto 《Pramana》2000,55(1-2):335-345
This report summarises the work done during WHEPP-6 (Institute of Mathematical Sciences, Chennai, India, Jan 3–15, 2000) in
Working group on ‘B and collider physics’. 相似文献
85.
86.
Debi Banerjee Anirban Ghosh Pradipta Ghosh Rajat K. Chaudhuri 《Molecular physics》2014,112(24):3206-3224
The relative stabilities of cis- and trans- isomers of 1,2-difluoroethylene and 1,2-difluorodiazene have been studied via the state-specific multireference coupled cluster (SS-MRCC) method and its perturbative counterpart through the computation of the optimised structures and corresponding energies. Despite the existence of several cis-destabilising mechanisms, present calculations reveal the energetic preference of the cis- isomer (the cis-effect) for the systems considered here. Differences in structural parameters and vibrational frequencies among cis- and trans- isomers have been discussed. Very good agreement of our estimates has been found with the benchmark theoretical and experimental results. The SS-MRCC methods produce a smooth and consistent behaviour across the entire torsional surface for the cis–trans isomerisation indicating that the method has sufficient flexibility to model large changes in electronic structure that accompany chemical changes. 相似文献
87.
Anirban Pal Dnyaneshwar Umrao Bawankule Mahendra Pandurang Darokar Subhash Chandra Gupta Jai Shankar Arya Karuna Shanker Madan Mohan Gupta Narayan Prasad Yadav Suman Preet Singh Khanuja 《Biomedical chromatography : BMC》2011,25(6):641-645
The influence of active fraction isolated from pods of an indigenous plant, Moringa oleifera (MoAF) was studied on the pharmacokinetic profile of the orally administered frontline anti‐tuberculosis drug rifampicin (20 mg/kg b.w.) in Swiss albino mice. The antibiotic rifampicin alone and in combination with MoAF (0.1 mg/kg b.w.) was administered orally and heparanized blood samples were collected from the orbital plexus of mice for plasma separation at 0, 1, 2, 3, 4 and 5 h, post treatment. Plasma rifampicin concentration, pharmacokinetic parameters and drug metabolizing enzyme (cytochrome P‐450) activity were determined. The pharmacokinetic data revealed that MoAF‐treated animals had significantly increased rifampicin plasma concentration, Cmax, Kel, t½(a), t½(el), Ka and AUC as well as inhibited rifampicin‐induced cytochrome P‐450 activity. In conclusion, the result of this study suggested that the bioavailability‐enhancing property of MoAF may help to lower the dosage level and shorten the treatment course of rifampicin. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
88.
This paper analyses the nonlinear transverse vibrations of a rotating, clamped-free, flexible disc coupled to a precompressed spring. This is representative of a large class of loadings in rotating disc systems such as air jet and electromagnetic excitation commonly used in experiments. Such a loading induces a simultaneous critical speed resonance and parametric instability. The disc is modelled as a Von Kármán plate, and the equations of motion are discretised by a Galerkin projection onto a pair of 1:1 internally resonant modes. The large amplitude wave motions and their stabilities are studied using the averaging method and via numerical continuation techniques. The analysis is carried out in a co-rotating as well as a ground-fixed frame. Numerical simulations are used to verify the above analyses. The response predicted by these analyses is substantially different from that arising from a critical speed resonance or of a parametric instability alone. As many as five equilibrium solutions can coexist at supercritical speed. Two distinct regimes of large amplitude response appear to exist depending on the relationship between the strength of the parametric excitation and the damping. The existence of these regimes underscores the subtle competition between critical speed resonance and parametric instability that is likely to be observed in experiments near critical speed in such systems.Contributed by Prof. A.K. Bajaj. 相似文献
89.
Bardhan JP 《The Journal of chemical physics》2011,135(10):104113
We study the energetics of burying charges, ion pairs, and ionizable groups in a simple protein model using nonlocal continuum electrostatics. Our primary finding is that the nonlocal response leads to markedly reduced solvent screening, comparable to the use of application-specific protein dielectric constants. Employing the same parameters as used in other nonlocal studies, we find that for a sphere of radius 13.4 ? containing a single +1e charge, the nonlocal solvation free energy varies less than 18 kcal/mol as the charge moves from the surface to the center, whereas the difference in the local Poisson model is ~35 kcal/mol. Because an ion pair (salt bridge) generates a comparatively more rapidly varying Coulomb potential, energetics for salt bridges are even more significantly reduced in the nonlocal model. By varying the central parameter in nonlocal theory, which is an effective length scale associated with correlations between solvent molecules, nonlocal-model energetics can be varied from the standard local results to essentially zero; however, the existence of the reduction in charge-burial penalties is quite robust to variations in the protein dielectric constant and the correlation length. Finally, as a simple exploratory test of the implications of nonlocal response, we calculate glutamate pK(a) shifts and find that using standard protein parameters (ε(protein) = 2-4), nonlocal results match local-model predictions with much higher dielectric constants. Nonlocality may, therefore, be one factor in resolving discrepancies between measured protein dielectric constants and the model parameters often used to match titration experiments. Nonlocal models may hold significant promise to deepen our understanding of macromolecular electrostatics without substantially increasing computational complexity. 相似文献
90.
Regiocontrolled nitration of 4-quinolone, the highly privileged scaffold, has been developed at ambient conditions. The nitro group can selectively be introduced at diverse positions simply by tuning the reactivity of the moiety. Discrimination is being achieved through the selective functionalization of the free N-H group. The functional group has been screened theoretically with the help of Fukui function and local softness calculation. Theoretical predictions are synchronized well with the experimental findings. Finally, this nitration technique allows quick access to the structurally diverse 4-quinolones. 相似文献