全文获取类型
收费全文 | 25871篇 |
免费 | 6601篇 |
国内免费 | 2255篇 |
专业分类
化学 | 4992篇 |
晶体学 | 352篇 |
力学 | 1806篇 |
综合类 | 276篇 |
数学 | 3974篇 |
物理学 | 23327篇 |
出版年
2024年 | 48篇 |
2023年 | 212篇 |
2022年 | 482篇 |
2021年 | 602篇 |
2020年 | 675篇 |
2019年 | 533篇 |
2018年 | 604篇 |
2017年 | 835篇 |
2016年 | 999篇 |
2015年 | 942篇 |
2014年 | 1484篇 |
2013年 | 1815篇 |
2012年 | 1655篇 |
2011年 | 2029篇 |
2010年 | 1610篇 |
2009年 | 1711篇 |
2008年 | 1810篇 |
2007年 | 1887篇 |
2006年 | 1746篇 |
2005年 | 1528篇 |
2004年 | 1530篇 |
2003年 | 1267篇 |
2002年 | 1220篇 |
2001年 | 997篇 |
2000年 | 1027篇 |
1999年 | 892篇 |
1998年 | 756篇 |
1997年 | 636篇 |
1996年 | 575篇 |
1995年 | 416篇 |
1994年 | 371篇 |
1993年 | 287篇 |
1992年 | 270篇 |
1991年 | 215篇 |
1990年 | 194篇 |
1989年 | 170篇 |
1988年 | 116篇 |
1987年 | 110篇 |
1986年 | 90篇 |
1985年 | 68篇 |
1984年 | 64篇 |
1983年 | 23篇 |
1982年 | 40篇 |
1981年 | 45篇 |
1980年 | 30篇 |
1979年 | 25篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1973年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
Knowledge of the vibrational properties of nanoparticles is of fundamental interest since it is a signature of their morphology, and it can be utilized to characterize their physical properties. In addition, the vibration characteristics of the nanoparticles coupled with surrounding media and subjected to magnetic field are of recent interest. This paper develops an analytical approach to study the radial breathing-mode frequency of elastically confined spherical nanoparticles subjected to magnetic field. Based on Maxwell's equations, the nonlocal differential equation of radial motion is derived in terms of radial displacement and Lorentz's force. Bessel functions are used to obtain a frequency equation. The model is justified by a good agreement between the results given by the present model and available experimental and atomic simulation data. Furthermore, the model is used to elucidate the effect of nanoparticle size, the magnetic field and the stiffness of the elastic medium on the radial breathing-mode frequencies of several nanoparticles. Our results reveal that the effects of the magnetic field and the elastic medium are significant for nanoparticle with small size. 相似文献
4.
就标准厚度卡片在霍尔传感器的定标方面的应用作了有益的探讨。在纵向测量微小长度时,霍尔片处于磁场边缘位置,其对磁场的梯度更大,即灵敏度更高,且靠中心位置的线性更好。 相似文献
5.
Naoto Takase Junpei Kuwabara Seong Jib Choi Takeshi Yasuda Liyuan Han Takaki Kanbara 《Journal of polymer science. Part A, Polymer chemistry》2015,53(4):536-542
The Pd‐catalyzed polycondensation of 4‐octylaniline with various dibromoarylenes was carried out under microwave heating. Microwave heating led to a decrease in the reaction time and an increase in the molecular weight of the polymers as compared to conventional heating. Microwave heating also allowed the catalyst loading to be reduced to 1 mol %, yielding polymerization results that were comparable to those under conventional heating and 5 mol % catalyst. Investigations regarding field‐effect transistors and organic photovoltaic cells using the obtained poly(arylamine) with azobenzene units revealed that increasing the molecular weight of the polymer led to improved device performance, including hole mobility and power conversion efficiency. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 536–542 相似文献
6.
We give a sheaf theoretic interpretation of Potts models with external magnetic field, in terms of constructible sheaves and their Euler characteristics. We show that the polynomial countability question for the hypersurfaces defined by the vanishing of the partition function is affected by changes in the magnetic field: elementary examples suffice to see non-polynomially countable cases that become polynomially countable after a perturbation of the magnetic field. The same recursive formula for the Grothendieck classes, under edge-doubling operations, holds as in the case without magnetic field, but the closed formulae for specific examples like banana graphs differ in the presence of magnetic field. We give examples of computation of the Euler characteristic with compact support, for the set of real zeros, and find a similar exponential growth with the size of the graph. This can be viewed as a measure of topological and algorithmic complexity. We also consider the computational complexity question for evaluations of the polynomial, and show both tractable and NP-hard examples, using dynamic programming. 相似文献
7.
The dependence of the beam propagation factor (M
2 parameter) with the absorbed pump power in the case of monolithic microchip laser under face-cooled configuration is extensively
studied. Our investigations show that the M
2 parameter is related to the absorbed pump power through two parameters (α and β) whose values depend on the laser material properties and laser configuration. We have shown that one parameter arises due
to the oscillation of higher order modes in the microchip cavity and the other parameter accounts for the spherical aberration
associated with the thermal lens induced by the pump beam. Such dependency of M
2 parameter with the absorbed pump power is experimentally verified for a face-cooled monolithic microchip laser based on Nd3+ -doped GdVO4 crystal and the values of α and β parameters were estimated from the experimentally measured data points. 相似文献
8.
Pierluigi Contucci Sandro Graffi Stefano Isola 《Journal of statistical physics》2002,106(5-6):895-914
For the long-range deterministic spin models with glassy behaviour of Marinari, Parisi and Ritort we prove weighted factorization properties of the correlation functions which represent the natural generalization of the factorization rules valid for the Curie–Weiss case. 相似文献
9.
10.
V. I. Dashkevich 《Journal of Applied Spectroscopy》2002,69(6):862-870
Based on a semiclassical theory, investigations were made of the dynamics and spectral composition of pulsed generation with self-injection of priming radiation from the active part of a three-mirror linear resonator, the passive part of which contains an active loss modulator and serves as the output reflector of the laser. It is shown that there exists a range of resonator parameters at which pulsed lasing has virtually a single frequency irrespective of the detuning of the frequencies of the priming radiation and of the nearest eigenmode of the composite resonator. Considering graphically the phase conditions of generation, it is established that among pulsed lasers with self-injection of priming radiation which are constructed on the basis of three-mirror linear and branched resonators, the most efficient for creating single-frequency generation are those in which the length of the main resonator, where generation of the pulse occurs, is larger than the length of the additional one intended for forming the priming radiation. With an inverse ratio of the lengths of the resonators, the conditions of single-frequency pulsed generation becomes dependent on the priming radiation frequency. 相似文献