全文获取类型
收费全文 | 1129篇 |
免费 | 32篇 |
国内免费 | 67篇 |
专业分类
化学 | 207篇 |
晶体学 | 4篇 |
力学 | 140篇 |
综合类 | 1篇 |
数学 | 103篇 |
物理学 | 579篇 |
综合类 | 194篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 19篇 |
2021年 | 11篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 21篇 |
2017年 | 24篇 |
2016年 | 35篇 |
2015年 | 34篇 |
2014年 | 71篇 |
2013年 | 89篇 |
2012年 | 59篇 |
2011年 | 91篇 |
2010年 | 47篇 |
2009年 | 96篇 |
2008年 | 79篇 |
2007年 | 57篇 |
2006年 | 35篇 |
2005年 | 43篇 |
2004年 | 37篇 |
2003年 | 30篇 |
2002年 | 30篇 |
2001年 | 34篇 |
2000年 | 27篇 |
1999年 | 21篇 |
1998年 | 19篇 |
1997年 | 26篇 |
1996年 | 22篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 24篇 |
1992年 | 10篇 |
1991年 | 4篇 |
1990年 | 15篇 |
1989年 | 4篇 |
1988年 | 10篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有1228条查询结果,搜索用时 0 毫秒
51.
52.
《Physics letters. A》2020,384(31):126794
An analytical approach for the electronic stopping force for non-relativistic energies that has no adjustable parameters has been developed. The approach combines the Bohr model for the close collisions and the Firsov model for the distant collisions. In order to combine the two models, a probabilistic model was introduced. We have applied our model to 16O in 12C, 16O in 27Al, 84 Kr in 27Al, 5Li in 12C, 12C in 12C, and 132Xe in 12C systems and compared with SRIM/MSTAR software, the original Bohr model, the Firsov model and available experimental data. We have found that the calculated electronic stopping force values are in agreement with the general qualitative behaviour of the electronic stopping force as a function of particle velocity reported in the literature. The proposed analytical formula is expected to be valid for other projectile-target combinations but more experimental data are needed to verify this assumption. 相似文献
53.
《Wave Motion》2017
Two methods for computing the complex-valued effective wavenumber of a rough beam in the context of linear time-harmonic theory are presented. The roughness of the beam is modelled as a continuous random process of known characteristic length and root-mean-square amplitude for either the beam mass or the beam rigidity. The first method is based on a random sampling method, with the effective wave field calculated as the mean of a large ensemble of wave fields for individual realisations of the roughness. The individual wave fields are calculated using a step approximation, which is validated for a deterministic problem via comparison to results produced by an integral equation approach. The second method assumes a splitting of the length scale of the fluctuations and an observation scale, employing a multiple-scale approximation to derive analytical expressions for the effective attenuation rate and phase change. Numerical comparisons show agreement of the results of the random sampling method and the multiple-scale approximation for a wide range of parameters. It is shown that the effective wavenumbers only differ by a real constant between the cases of varying beam mass and rigidity. 相似文献
54.
Vijay S. Raykar 《Physics letters. A》2010,374(45):4618-4621
A differential effective medium theory together with Brownian motion is used to predict Effective Thermal Conductivity (ETC) of CNT nanofluids. ETC was influenced significantly by Brownian motion and enhancement was higher in dilute nanofluids. A theoretical model employing an effective volume fraction with dispersibility factor agrees well with experimental data. 相似文献
55.
There are over two million modern English words, thus English becomes a language with the largest vocabulary in the world. Moreover, English vocabulary is constantly being renewed and enlarged with the development of the society and advancement of science and technology. So vocabulary development becomes language learners’ top priority. Unfortunately, learning English words by rote can’t guarantee that students will have a large vocabulary, let alone enable students to make practical use of the words they h... 相似文献
56.
The binding energy of an off-center hydrogenic donor impurity in weakly oblate Ellipsoidal Quantum Dot (EQD), using the expansion method within the framework of effective mass approximation in strong confinement, is investigated. In this regard, the binding energies of different states of GaAs structures, as functions of the donor position and ellipticity parameter, are calculated. The results show that variations of binding energies are proportional to the ellipticity constant, the dot dimension and the location of impurity. 相似文献
57.
本文根据[1]提出的基本原理,在[2]的基础上,通过矫正自然灾害和耕地面积的影响,并在考虑农业基建投资动态折旧的前提下,给出了农业技术进步的计量经济模型。最后通过实例分析加以说明。 相似文献
58.
本文提出了SAP80结构分析程序的特殊结点识别与处理方法,对特殊结点自动识别处理,减少了用户工作量,增大了解题规模,减少了方程阶数,增加了解题速度。 相似文献
59.
本文计及晶格的原子结构讨论了二维Frenkel激子的性质。用二次量子化方法处理晶格振动及其与激子的相互作用,导出了二维Frenkel激子的自陷能以及它的有效质量与温度的关系。 相似文献
60.
锥拟凹与锥伪凹概念及其应用 总被引:1,自引:0,他引:1
张宇明 《华中科技大学学报(自然科学版)》1988,(5)
本文在锥序意义下将最小点的概念推广,并利用它将通常的拟凹与伪凹函数概念推广。文中用这些概念给出了多目标规划有效解的一个充分条件。 相似文献