全文获取类型
收费全文 | 4671篇 |
免费 | 1746篇 |
国内免费 | 1992篇 |
专业分类
化学 | 2460篇 |
晶体学 | 95篇 |
力学 | 467篇 |
综合类 | 187篇 |
数学 | 997篇 |
物理学 | 4203篇 |
出版年
2024年 | 54篇 |
2023年 | 159篇 |
2022年 | 238篇 |
2021年 | 185篇 |
2020年 | 118篇 |
2019年 | 156篇 |
2018年 | 114篇 |
2017年 | 176篇 |
2016年 | 158篇 |
2015年 | 188篇 |
2014年 | 383篇 |
2013年 | 304篇 |
2012年 | 289篇 |
2011年 | 335篇 |
2010年 | 320篇 |
2009年 | 326篇 |
2008年 | 342篇 |
2007年 | 324篇 |
2006年 | 373篇 |
2005年 | 361篇 |
2004年 | 341篇 |
2003年 | 315篇 |
2002年 | 301篇 |
2001年 | 284篇 |
2000年 | 213篇 |
1999年 | 214篇 |
1998年 | 195篇 |
1997年 | 209篇 |
1996年 | 185篇 |
1995年 | 192篇 |
1994年 | 187篇 |
1993年 | 156篇 |
1992年 | 167篇 |
1991年 | 167篇 |
1990年 | 160篇 |
1989年 | 143篇 |
1988年 | 24篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1980年 | 3篇 |
1975年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有8409条查询结果,搜索用时 562 毫秒
11.
Xuechu Shen 《量子光学学报》2006,12(B08):55-56
The single and a few coupled quantum dots are important for future quantum information sciences and their investigation is also a big challenge in physics. We investigate here the electronic and exciton states and their interaction with each other via micro photoluminescence. The luminescence for single and a few dots as well as a dot molecule of CdSe/ZnSe are measured with very high resolution, under liquid He temperature and magnetic fields and with different polarization of excitation laser. The observed sharp spectral lines are attributed to the atomlike transitions of exciton, trion, biexciton… in the investigated single QD or QD molecule. Band filling, Zeeman splitting, spin transition and their relaxation are observed and investigated'from the spectra and compared with those of same material in different dimensions, and compared with the primary calculation as well. In addition, quite a few new phenomena, which can not be understood based on our present model and knowledge, are also observed; and some very interesting problems are left for further investigation. 相似文献
12.
13.
14.
一根导热棒 ,如果在它的两端存在温差 ,便会有热量从高温端流向低温端 .这种能量在固体中的传输 ,不是沿着棒按照直线路径完成的 ;其间 ,导热声子将遭遇到频繁的碰撞 ,从而产生热阻 .表征材料导热性能的物理量是热导率κ[单位是W /(m·K) ],而传输的热流密度 jQ(W /m2 )与温度梯度成正比 ,即 jQ=-κdT/dX .如果声子在传输过程中不经历散射 ,则不论导热棒多长 ,jQ 将不依赖于温度梯度 ,而仅仅取决于两端的温差 .引入声子平均自由程l ,经典理论给出 ,κ =(1/3)Cvl,其中C是单位体积材料的热容 ,v是声子的平均速度 .在低温下 ,对于无杂质缺… 相似文献
15.
Quantum Inequality for Negative Energy Density States of Massive Dirac Field in Four-Dimensional Spacetime 下载免费PDF全文
Negative energy density and the quantum inequality are examined for the Dirac field. A proof is given of the quantum inequality for negative energy densities in the massive Dirac field produced by the superposition of two single particle electron states. 相似文献
16.
李治明 《新疆大学学报(理工版)》2004,21(2):135-141,146
研究了具有开发的单种群非自治周期系统.利用非自治微分方程理论.以及变分法理论和泛函极值的Euler方程方法,得到了该开发系统的持续生存性.周期解存在性,全局渐近稳定性.研究了在开发情况下的最大收获量问题,以及取得最大经济效益下的收获问题等. 相似文献
17.
The authors study the singular integrals under the Hormander condition and the measure not satisfying the doubling condition. At first, if the corresponding singular integral is bounded from L2 to itself, it is proved that the maximal singular integral is bounded from L∞to RBMO except that it is infinite μ-a.e. on Rd. A sufficient condition and a necessary condition such that the maximal singular integral is bounded from L2 to itself are also obtained. There is a small gap between the two conditions. 相似文献
18.
本文讨论了每个元都有幂等元作为右单位元的左消半群与幂单半群N的Schuzenberger积M◇N的ρ类,证明了这种半群M与N的Schuzenberger积M◇N的ρ类是右E一半适合半群和弱E-headged半群. 相似文献
19.
20.
Spectral property and its shape transition on ^72-84Kr isotopes in microscopic core plus two-quasiparticle approach 总被引:1,自引:0,他引:1 下载免费PDF全文
By using a microscopic sdIBM-2 2q.p, approach, the levels of the ground-band, 7-band and partial two-quasi-particle bands for ^72-84Kr isotopes are calculated. The data obtained are in good agreement with the recent experimental results, and successfully reproduce the nuclear shape phase transition of ^72-S4Kr isotopes at zero temperature.The ground-state band is described successfully up to J^π=18^ and Ex=10.0MeV. Based on this model, the aligned requisite minimum energy has been deduced. The theoretical calculations indicate that no distinct change of nuclear states is caused by the abruptly broken pair of a boson, and predict that the first backbending of Kr isotopes may be the result of aligning of two quasi-neutrons in orbit g9/2, which galus the new experimental support of the measurements of g factors in the ^78-86Kr isotopes. 相似文献