全文获取类型
收费全文 | 31079篇 |
免费 | 4953篇 |
国内免费 | 3288篇 |
专业分类
化学 | 21096篇 |
晶体学 | 337篇 |
力学 | 2030篇 |
综合类 | 247篇 |
数学 | 3719篇 |
物理学 | 11891篇 |
出版年
2024年 | 111篇 |
2023年 | 648篇 |
2022年 | 1231篇 |
2021年 | 1259篇 |
2020年 | 1239篇 |
2019年 | 1201篇 |
2018年 | 1108篇 |
2017年 | 1050篇 |
2016年 | 1537篇 |
2015年 | 1488篇 |
2014年 | 1763篇 |
2013年 | 2344篇 |
2012年 | 2748篇 |
2011年 | 2788篇 |
2010年 | 1872篇 |
2009年 | 1842篇 |
2008年 | 1984篇 |
2007年 | 1705篇 |
2006年 | 1505篇 |
2005年 | 1292篇 |
2004年 | 969篇 |
2003年 | 762篇 |
2002年 | 674篇 |
2001年 | 543篇 |
2000年 | 547篇 |
1999年 | 652篇 |
1998年 | 546篇 |
1997年 | 531篇 |
1996年 | 504篇 |
1995年 | 470篇 |
1994年 | 390篇 |
1993年 | 349篇 |
1992年 | 290篇 |
1991年 | 253篇 |
1990年 | 243篇 |
1989年 | 187篇 |
1988年 | 146篇 |
1987年 | 128篇 |
1986年 | 94篇 |
1985年 | 95篇 |
1984年 | 65篇 |
1983年 | 52篇 |
1982年 | 54篇 |
1981年 | 25篇 |
1980年 | 14篇 |
1979年 | 8篇 |
1973年 | 2篇 |
1957年 | 7篇 |
1936年 | 1篇 |
1935年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
941.
We study thermal entanglement of XXZ Heisenberg chain under rectangle magnetic field. Under this magnetic field B, the region of thermal entanglement in terms of B and temperature T can be extended. Moreover, one can improve threshold temperature, where entanglement vanish, just by increasing the strength
of magnetic field. This effect is similar to that of the anisotropic coupling of spin in XY plane but provide us a realizable method to improve threshold temperature. 相似文献
942.
943.
Precise measurement of magnetic moment of short-lived β-emitting nuclei12B ( I π=1+, T 1/2=20.18 ms)
Zhou Dongmei Zheng Yongnan Du Enpeng Xu Yongjun Zhu Jiazheng Yuan Daqing Wang Zhiqiang Luo Hailong Zuo Yi Ma Ruigang Duan Xiao M. Mihara M. Fukuda K. Matsuta T. Minamisono Zhu Shengyun 《中国科学G辑(英文版)》2004,47(5):531-539
The spin polarized β-emitting nuclei12B (I
π=1+,T
1/2=20.18 ms) were produced by the nuclear reaction11B(d, p)12B and by the selection technique of the incident deuteron energy and the12B recoil angle following the nuclear reaction. The nuclear magnetic moment of the short-lived nuclei12B was measured by β-NMR with the β-NMR and β-NQR setup established for the first time in China. The nuclear magnetic moment
of12B was determined to be μ=0.99993±0.00048 nm org=0.99993±0.00048 after the precise correction of the Knight shift. 相似文献
944.
The sound field both in the loudspeaker box and in the room is calculated by an analytical solution of three-dimensional wave equation. It is shown in theory that the amplitude response in small rooms is affected by the following positions: driver position on the front panel of the box, box position in the room, absorption material position in the box and absorption material position on the interior walls of the room. Both our computer prediction and experiments prove that the optimum positions are beneficial to the amplitude response. 相似文献
945.
Shu Fen Wang Wen Guo Zou Su Wen Liu Dong Xu Duo Rong Yuan Guang Jun Zhou 《Journal of Physics and Chemistry of Solids》2004,65(7):1243-1245
The photoluminescence properties of the Bi3+ in sol-gel derived ZnTiO3 nanocrystals have been investigated. An ultra-violet emission at 360 nm and a visible emission band at 506 nm have been observed, originating from two kinds of emission centers. The former is ascribed to the 3P1-1S0 transition of Bi3+ and the latter to the recombination of the electrons with the photo-generated holes trapped in the zinc vacancies. In all cases the latter contribution is predominant. 相似文献
946.
采用溶胶-凝胶法在聚乙烯吡咯烷酮(PVP)修饰的碳纳米管表面均匀沉积纳米级二氧化钛粒子制得复合光催化剂。采用透射电子显微镜(TEM)、X射线衍射仪(XRD)、紫外-可见吸收光谱仪(UV-Vis)和X射线光电子能谱仪(XPS)等手段对复合光催化剂进行表征。结果表明,二氧化钛粒子是呈球形、团聚,随机沉积在未修饰碳纳米管任意表面,甚至部分碳纳米管表面是完全裸露的。经PVP修饰后的碳纳米管,二氧化钛纳米粒子均匀沉积在碳纳米管表面,二氧化钛为纯锐钛矿晶体结构,没有金红石和板钛矿相。表面修饰碳纳米管/二氧化钛复合光催化剂在紫外光照射下降解亚甲基蓝,相比纯的二氧化钛和碳纳米管/二氧化钛复合光催化剂,具有非常高的催化活性。 相似文献
947.
A metal bellows-based fiber Bragg grating(FBG) accelerometer is proposed and experimentally demonstrated. The optical fiber(containing the FBG) is pre-tensioned,and the two ends of the optical fiber are fixed directly from the shell to the inertial mass. In this design,the FBG is uniformly tensioned to obtain a constant strain distribution over it. By employing this configuration,the FBG always has a sharp reflection characteristic with no broadening in its reflection spectrum during wavelength shifting. Dy... 相似文献
948.
We investigate the diffusion interaction and quantitative analysis of zinc dialkyldithiophosphate (ZDDP) mixed with lube base oil (LBO) at different concentrations using terahertz time-domain spectroscopy (THzTDS).When the concentration exceeds 6.78%,the characteristic absorption peaks exhibit significantly shift,and the absorption coefficient peak value is nonlinear against concentration.Moreover,the absorption coefficients of mixed samples follow the Beer’s law at a concentration below 6.78%.The quantitative analysis enables a strategy for monitoring the formulation of lubricating oil in real time. 相似文献
949.
基于自再现原理,利用菲涅耳-基尔霍夫衍射积分方程,引入腔镜失调、激光介质上的增益分布以及光阑口径,采用本征矢量法分析了大口径平凹腔薄片激光器的本征模式,并计算了相应的光束质量因子M2.建立了千瓦级薄片激光系统和光纤扫描光斑诊断装置,开展了高功率激光输出特性研究.结果表明,在大口径高功率平凹腔中多个本征模式可同时起振,获... 相似文献
950.