全文获取类型
收费全文 | 2308篇 |
免费 | 48篇 |
国内免费 | 7篇 |
专业分类
化学 | 1345篇 |
晶体学 | 19篇 |
力学 | 53篇 |
数学 | 206篇 |
物理学 | 740篇 |
出版年
2023年 | 18篇 |
2022年 | 55篇 |
2021年 | 39篇 |
2020年 | 45篇 |
2019年 | 62篇 |
2018年 | 49篇 |
2017年 | 59篇 |
2016年 | 86篇 |
2015年 | 49篇 |
2014年 | 94篇 |
2013年 | 167篇 |
2012年 | 125篇 |
2011年 | 137篇 |
2010年 | 101篇 |
2009年 | 97篇 |
2008年 | 133篇 |
2007年 | 114篇 |
2006年 | 78篇 |
2005年 | 63篇 |
2004年 | 58篇 |
2003年 | 37篇 |
2002年 | 43篇 |
2001年 | 35篇 |
2000年 | 27篇 |
1999年 | 13篇 |
1998年 | 15篇 |
1997年 | 11篇 |
1996年 | 23篇 |
1995年 | 29篇 |
1994年 | 31篇 |
1993年 | 41篇 |
1992年 | 40篇 |
1991年 | 30篇 |
1990年 | 30篇 |
1989年 | 28篇 |
1988年 | 15篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 25篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 18篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 22篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1973年 | 9篇 |
1965年 | 7篇 |
排序方式: 共有2363条查询结果,搜索用时 0 毫秒
61.
62.
63.
A. K. Rastogi S. Mishra M. Nigam A. K. Tiwari 《International Journal of Infrared and Millimeter Waves》1994,15(10):1709-1720
Dispersion characteristics and wave impedance of trapped coupled image guides are computed by using mode matching techniques. Dispersion curves for trapped coupled image guide are plotted for various dielectric materials and dimensional parameters. The hybrid directional couplers in the above configuration have been theoretically designed by computing the normalization propagation constant. 相似文献
64.
Dipsikha Bhattacharya Sumanta K. Sahu Indranil Banerjee Manasmita Das Debashish Mishra Tapas K. Maiti Panchanan Pramanik 《Journal of nanoparticle research》2011,13(9):4173-4188
In this article, we report the design and synthesis of a series of well-dispersed superparamagnetic iron oxide nanoparticles
(SPIONs) using chitosan as a surface modifying agent to develop a potential T
2 contrast probe for magnetic resonance imaging (MRI). The amine, carboxyl, hydroxyl, and thiol functionalities were introduced
on chitosan-coated magnetic probe via simple reactions with small reactive organic molecules to afford a series of biofunctionalized
nanoparticles. Physico-chemical characterizations of these functionalized nanoparticles were performed by TEM, XRD, DLS, FTIR,
and VSM. The colloidal stability of these functionalized iron oxide nanoparticles was investigated in presence of phosphate
buffer saline, high salt concentrations and different cell media for 1 week. MRI analysis of human cervical carcinoma (HeLa)
cell lines treated with nanoparticles elucidated that the amine-functionalized nanoparticles exhibited higher amount of signal
darkening and lower T
2 relaxation in comparison to the others. The cellular internalization efficacy of these functionalized SPIONs was also investigated
with HeLa cancer cell line by magnetically activated cell sorting (MACS) and fluorescence microscopy and results established
selectively higher internalization efficacy of amine-functionalized nanoparticles to cancer cells. These positive attributes
demonstrated that these nanoconjugates can be used as a promising platform for further in vitro and in vivo biological evaluations. 相似文献
65.
Venu MankadHimadri R. Soni Sanjeev K. GuptaPrafulla K. Jha 《Physica B: Condensed Matter》2011,406(19):3599-3604
We present results of first principles total energy calculations of the structure, electronic and lattice dynamics for beryllium semiboride and its three ternary alloys using generalized gradient and local density approximations under the framework of density functional theory. The generalized gradient approximation is used for all compounds except MgBeB using the Perdew-Burke-Ernzehorf exchange correlation functional while local density approximations use the Perdew-Zunger ultrasoft exchange correlation functional. The calculated ground state structural parameters are in good agreement with those of experimental and previous theoretical studies. The electronic band structure calculations show that Be2B may transform to a semiconductor after Al substitution. A linear response approach to density functional theory is used to calculate phonon dispersion curves and vibrational density of states. The phonon dispersion curves of Be2B and AlBeB are positive indicating a dynamical stablility of the structure for these compounds. The phonon dispersion curves of NaBeB and MgBeB show the imaginary phonons throughout the Brillouin zone, which confirms dynamical instability as indicated in band structures for these alloys. We also present the partial phonon density of states for different species of Be2B and AlBeB to bring out the details of the participation of different atoms in the total phonon density of state, particularly the role played by Al atom. The first time calculated phonon properties are clearly able to bring out the significant effect of isoelectronic substitution in Be2B. 相似文献
66.
67.
68.
Long distance atomic teleportation (LDAT) is of prime importance in long distance quantum communication. Scheme proposed by Bose et al. (1999) in principle enables us to have LDAT using cavity decay. However it gives message state dependent fidelity and success rate. Here, using interaction of entangled coherent states with atom–cavity systems and a two-step measurement, we show how, LDAT can be achieved with unit fidelity and as good success as desired under ideal conditions. The scheme is unique in that, the first measurement predicts success or failure. If success is predicted then second measurement gives perfect teleportation. If failure is predicted the message-qubit remains conserved therefore a second attempt may be started. We found that even in presence of decoherence due to dissipation of energy our scheme gives message state independent success rate and almost perfect teleportation in single attempt with mean fidelity of teleportation equal to 0.9 at long distances. However if first attempt fails, unlike ideal case where message-qubit remains conserved with unit fidelity, in presence of decoherence the message-qubit remains conserved to some degree, therefore mean fidelity of teleportation can be increased beyond 0.9 by repeating the process. 相似文献
69.
70.
The heavy mesons of the charmonium and upsilon family are described in an alternative static potential model chosen in a combination of Hulthen and linear potential. We find that the quark-confining potential in the form of an equal admixture of vector and scalar parts successfully explains the fine-hyperfine structures of \(c\bar c\) and \(b\bar b\) systems in a flavour-independent manner. The leptonic decay widths of the vector mesons ofψ and γ families are calculated taking into account the Poggio-Schnitzer correction. We obtain some of the bound states of the yet-to-be observed \(t\bar t\) system for thet-quark mass ranging from 50 to 200 GeV. 相似文献