全文获取类型
收费全文 | 769篇 |
免费 | 23篇 |
国内免费 | 6篇 |
专业分类
化学 | 433篇 |
晶体学 | 2篇 |
力学 | 19篇 |
数学 | 86篇 |
物理学 | 258篇 |
出版年
2023年 | 10篇 |
2022年 | 16篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 27篇 |
2015年 | 16篇 |
2014年 | 25篇 |
2013年 | 39篇 |
2012年 | 58篇 |
2011年 | 44篇 |
2010年 | 30篇 |
2009年 | 24篇 |
2008年 | 47篇 |
2007年 | 40篇 |
2006年 | 30篇 |
2005年 | 32篇 |
2004年 | 16篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 18篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 12篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 15篇 |
1985年 | 9篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1971年 | 4篇 |
1970年 | 3篇 |
排序方式: 共有798条查询结果,搜索用时 15 毫秒
91.
A. Sengupta M. J. Kulkarni S. V. Godbole 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(3):961-965
DHOA (Di-n-hexyl-octanamide) is one of the alternative extractants to TBP (tri-n-butyl phosphate) known for the extraction of uranium from moderate nitric acid medium without significant extraction of the fission products. Analytical application of DHOA was explored to develop a methodology for determination of trace metallic constituents in uranium based nuclear materials. This involved the separation of uranium matrix by 1.1 M DHOA-dodecane followed by the analysis of the raffinate for trace constituents by Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). A systematic study showed that four contacts of 1.1 M DHOA-dodecane were required for quantitative extraction of U from 4 M HNO3 feed for the sample size of 1 g in 10 mL. The feasibility of using DHOA for extraction of U from trace metallic constituents in U based fuel materials without losing trace quantities of analytes of interest was studied by using synthetic samples after appropriate spiking of common impurities and critical elements at their required specification limits (common elements—5 ppm, critical elements—1 ppm). A systematic study was carried out to compare the analytical performance of DHOA with TBP, which revealed that DHOA could successfully be employed for the determination of 19 trace constituents with lower estimation limits of 5 ppm for common impurities and 1 ppm for critical elements. 相似文献
92.
Das MR Sarma RK Saikia R Kale VS Shelke MV Sengupta P 《Colloids and surfaces. B, Biointerfaces》2011,83(1):16-22
A solution-based approach to the synthesis of silver (Ag) nanoparticles by chemical reduction of AgNO(3) in a graphene oxide (GrO) suspension is demonstrated. X-ray diffraction and transmission electron microscopy indicate that the Ag nanoparticles, of size range 5-25nm, were decorated on the GrO sheets. The size and shape of the Ag nanoparticles are dependent on the concentration of the AgNO(3) solution. Antimicrobial activity of such hybrids materials is investigated against the Gram negative bacteria Escherichia coli and Pseudomonous aeruginosa. The bacterial growth kinetics was monitored in nutrient broth supplemented with the Ag nanoparticle-GrO suspension at different conditions. It was observed that P. aeruginosa is comparatively more sensitive to the Ag nanoparticle-GrO suspension. 相似文献
93.
94.
In this study, the urea dynamics inside AOT reverse micelle (RM) has been monitored without intervention of water using time-resolved fluorescence techniques from the picosecond to nanosecond time regime. It has been observed that urea dynamics inside the reverse micelle is severely retarded compared to water RM due to the formation of highly networked urea cluster inside the RM. Time-resolved fluorescence anisotropy study also confirms the existence of a confined environment around the dye at higher concentrations of urea inside the reverse micelle. The dynamics of urea-water mixtures inside AOT reverse micelle has also been monitored with increasing urea concentration to get insight about the effect of urea on the overall solvation dynamics feature. It has been observed that with the increase in urea concentration, the overall dynamics becomes slower, and it infers the presence of few water or urea molecules, those strongly associated with surrounding urea and (or) water by hydrogen bonds. 相似文献
95.
Subhamoy Maitra Goutam Paul Shashwat Raizada Subhabrata Sen Rudradev Sengupta 《Designs, Codes and Cryptography》2011,59(1-3):231-245
In this paper, we study HC-128 in detail from cryptanalytic point of view. First, we use linear approximation of the addition modulo 2 n of three n-bit integers to identify linear approximations of g 1, g 2, the feedback functions of HC-128. This, in turn, shows that the process of keystream output generation of HC-128 can be well approximated by linear functions. In this direction, we show that the ??least significant bit?? based distinguisher (presented by the designer himself) of HC-128 works for the complete 32-bit word. Using the above linear approximations of g 1, g 2, we present a new distinguisher for HC-128 which is slightly weaker than Wu??s distinguisher. Finally, in the line of Dunkelman??s observation, we also study how HC-128 keystream words leak secret state information of the cipher due to the properties of the functions h 1, h 2 and present improved results. 相似文献
96.
Saurav S. Sengupta J. Scott Parent J. Keith McLean 《Journal of polymer science. Part A, Polymer chemistry》2005,43(20):4882-4893
Selective graft modifications of polypropylene (PP) are demonstrated in which desirable functionality is introduced without the degradation that accompanies conventional radical‐mediated processes. A range of modification strategies is presented, each exploiting triallyl trimellitate (TATM) or its derivatives to counteract the effects of macroradical fragmentation on the molecular weight. Model compound studies, as well as examinations of atactic PP reaction products, show that allylic ester activation occurs predominately by a radical‐addition/hydrogen‐transfer sequence, with a limited propensity for telomerization. The cografting of TATM and maleic anhydride leads to maleated PP of a high melt viscosity, whereas the apparent incompatibility of TATM with vinyltrimethoxysilane requires the use of TATM‐assisted thiol–ene addition and/or diallyl silane grafting to produce moisture‐curable PP derivatives. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4882–4893, 2005 相似文献
97.
Dipankar Mishra Subhendu Naskar Shyamal K. Chattopadhyay Milan Maji Parbati Sengupta Rupam Dinda Saktiprasad Ghosh Thomas C. W. Mak 《Transition Metal Chemistry》2005,30(3):352-356
The synthesis, crystal structure, redox and spectroscopic properties of trans-[Ru(bbpH2)(PPh3)2Cl]Cl are reported. In the crystalline solvate trans-[Ru(bbpH2)(PPh3)2cCl]Cl CHCl3 H2O, the molecular components are connected by strong intermolecular hydrogen bonding to form an infinite double column. 相似文献
98.
The spatial stability properties of a mixed convection boundary layer developing over a heated horizontal plate is studied here under linear and quasi-parallel flow assumption. The main aim of the present work is to find out if there is a critical buoyancy parameter that would indicate the importance of heat transfer in destabilizing mixed convection boundary layers, when the buoyancy effect is given by Boussinesq approximation. The undisturbed flow used here is that given by the similarity solution of [ 1 ] that implies the wall temperature to vary as the inverse square root of the distance from the leading edge of the plate. The stability of this flow has been investigated by using the compound matrix method (CMM)—that allows finding all the modes in the chosen range in the complex wave number plane for spatial stability analysis. Presented neutral curves for mixed convection boundary layer show the existence of two types of disturbances present simultaneously, for large buoyancy parameter. One notices very unstable high-frequency mode when the buoyancy parameter exceeds the above-mentioned critical value. This unstable thermal mode is in addition to the hydrodynamic mode of isothermal flow given by corresponding similarity profile. The calculated critical buoyancy parameter is shown to qualitatively match with experimental results. 相似文献
99.
Ambar Sengupta 《Communications in Mathematical Physics》1997,183(3):661-705
The quantum field measure for gauge fields over a compact surface with boundary, with holonomy around the boundary components
specified, is constructed. Loop expectation values for general loop configurations are computed. For a compact oriented surface
with one boundary component, let be the moduli space of flat connections with boundary holonomy lying in a conjugacy class in the gauge group G. We prove that a certain natural closed 2-form on , introduced in an earlier work by C. King and the author, is a symplectic structure on the generic stratum of for generic . We then prove that the quantum Yang-Mills measure, with the boundary holonomy constrained to lie in , converges in a natural sense to the corresponding symplectic volume measure in the classical limit. We conclude with a
detailed treatment of the case , and determine the symplectic volume of this moduli space.
Received: 30 June 1996 / Accepted: 22 July 1996 相似文献
100.
An electron fluid model is proposed for the lattice dynamics of metals which satisfies the requirement of translational invariance
and the lattice is in equilibrium without recourse to external forces. The model is applied to calculate the phonon dispersion
of sodium in the symmetry directions. 相似文献