全文获取类型
收费全文 | 4212篇 |
免费 | 716篇 |
国内免费 | 405篇 |
专业分类
化学 | 2858篇 |
晶体学 | 59篇 |
力学 | 303篇 |
综合类 | 19篇 |
数学 | 440篇 |
物理学 | 1654篇 |
出版年
2024年 | 7篇 |
2023年 | 116篇 |
2022年 | 102篇 |
2021年 | 167篇 |
2020年 | 195篇 |
2019年 | 181篇 |
2018年 | 167篇 |
2017年 | 141篇 |
2016年 | 237篇 |
2015年 | 201篇 |
2014年 | 236篇 |
2013年 | 327篇 |
2012年 | 407篇 |
2011年 | 411篇 |
2010年 | 272篇 |
2009年 | 234篇 |
2008年 | 250篇 |
2007年 | 236篇 |
2006年 | 226篇 |
2005年 | 191篇 |
2004年 | 133篇 |
2003年 | 105篇 |
2002年 | 86篇 |
2001年 | 75篇 |
2000年 | 87篇 |
1999年 | 74篇 |
1998年 | 68篇 |
1997年 | 62篇 |
1996年 | 62篇 |
1995年 | 54篇 |
1994年 | 30篇 |
1993年 | 40篇 |
1992年 | 41篇 |
1991年 | 23篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 1篇 |
1983年 | 7篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1971年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有5333条查询结果,搜索用时 593 毫秒
11.
A simple model has been developed to describe the Zeeman patterns of far-infrared laser magnetic resonance spectra of the monobromomethyl radical CH2Br observed at 447.3 and 671.1μm. A satisfactory agreement between the experimental spectra of the radical and their simulation with this simple model has been achieved. This approach can be used to gain further information about the structure and the spectrum of this interesting radical. 相似文献
12.
13.
14.
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
15.
Discrete global descent method for discrete global optimization and nonlinear integer programming 总被引:2,自引:0,他引:2
A novel method, entitled the discrete global descent method, is developed in this paper to solve discrete global optimization
problems and nonlinear integer programming problems. This method moves from one discrete minimizer of the objective function
f to another better one at each iteration with the help of an auxiliary function, entitled the discrete global descent function.
The discrete global descent function guarantees that its discrete minimizers coincide with the better discrete minimizers
of f under some standard assumptions. This property also ensures that a better discrete minimizer of f can be found by some classical local search methods. Numerical experiments on several test problems with up to 100 integer
variables and up to 1.38 × 10104 feasible points have demonstrated the applicability and efficiency of the proposed method. 相似文献
16.
1689-nm diode lasers used in medical apparatus have been fabricated and characterized. The lasers had pnpn InP current confinement structure, and the active region consisted of 5 pairs of InGaAs quantum wells and InGaAsP barriers. 相似文献
17.
18.
19.
20.
Novel oxyfluoride glasses are developed with the composition of 30SiO2-15Al2O3-28PbF2-22CdF2-0.1TmF3 - xYbF3 - (4.9 - x) AlF3(x=0, 0.5, 1.0, 1.5, 2.0) in tool fraction, Furthermore, the upconversion luminescence characteristics under a 970nm excitation are investigated. Intense blue, red and near infrared luminescences peaked at 453nm, 476nm, 647nm and 789nm, which correspond to the transitions of Tm^3+: ^1D2 →^3F4, ^1G4 →^3H6, ^1G4 →^3F4, and ^3H4 →^3H6, respectively, are observed. Due to the sensitization of Yb^3+ ions, all the upconversion luminescence intensities are enhanced considerably with Yb^3+ concentration increasing. The upconversion mechanisms are discussed based on the energy matching rule and quadratic dependence on excitation power. The results indicate that the dominant mechanism is the excited state absorption for those upconversion emissions. 相似文献