全文获取类型
收费全文 | 22432篇 |
免费 | 4189篇 |
国内免费 | 6488篇 |
专业分类
化学 | 16698篇 |
晶体学 | 786篇 |
力学 | 1527篇 |
综合类 | 536篇 |
数学 | 3282篇 |
物理学 | 10280篇 |
出版年
2024年 | 32篇 |
2023年 | 302篇 |
2022年 | 674篇 |
2021年 | 723篇 |
2020年 | 856篇 |
2019年 | 847篇 |
2018年 | 746篇 |
2017年 | 950篇 |
2016年 | 883篇 |
2015年 | 1180篇 |
2014年 | 1364篇 |
2013年 | 1902篇 |
2012年 | 1982篇 |
2011年 | 2143篇 |
2010年 | 1944篇 |
2009年 | 1950篇 |
2008年 | 2130篇 |
2007年 | 1901篇 |
2006年 | 1786篇 |
2005年 | 1501篇 |
2004年 | 1162篇 |
2003年 | 863篇 |
2002年 | 848篇 |
2001年 | 750篇 |
2000年 | 875篇 |
1999年 | 481篇 |
1998年 | 267篇 |
1997年 | 229篇 |
1996年 | 219篇 |
1995年 | 182篇 |
1994年 | 178篇 |
1993年 | 186篇 |
1992年 | 137篇 |
1991年 | 101篇 |
1990年 | 114篇 |
1989年 | 105篇 |
1988年 | 105篇 |
1987年 | 65篇 |
1986年 | 59篇 |
1985年 | 35篇 |
1984年 | 33篇 |
1983年 | 34篇 |
1982年 | 33篇 |
1981年 | 27篇 |
1980年 | 26篇 |
1979年 | 22篇 |
1978年 | 26篇 |
1973年 | 11篇 |
1971年 | 13篇 |
1965年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
基于一个描述夸克胶子火柱演化的相对论流体力学模型,研究了夸克相、强子相互作用以及非热过程(DrellYan对、粲强子衰变)的中等质量双轻子的产生.发现由于相边对夸克胶子物质演化的影响和RHIC能量核碰撞产生的夸克胶子物质具有高的初始温度,夸克相对双轻子的贡献显著增强,比那些来自强子相互作用的贡献重要,甚至能与来自非热的贡献比较.表明中等质量双轻子的增强是一个在核碰撞中产生了夸克胶子物质的可能信号.
关键词:
夸克-胶子物质
双轻子增强
相对论流体力学模型 相似文献
105.
Y. Qu J.X. Zhang A. Uddin C.Y. Liu S. Yuan M.C.Y. Chan B. Bo G. Liu H. Jiang 《Applied Physics A: Materials Science & Processing》2006,82(2):305-308
Ridge-waveguide InGaAsN triple-quantum-well strain-compensated lasers grown by metal organic chemical vapor deposition were fabricated with pulsed anodic oxidation. The laser’s output power reached 145 mW in continuous-wave mode at room temperature for a 4-?m -stripe-width laser. Continuous-wave single longitudinal mode operation was maintained at a high injection current level with a wavelength of 1287.3 nm at room temperature. Single longitudinal mode operation at 1317.2 nm was achieved at twice the threshold current at 100 °C. The band gap of InGaAsN in the quantum wells at different temperatures was calculated and compared to the measured temperature-dependent laser wavelength. 相似文献
106.
用三个关系式与Mathematica软件求第二类自然数幂和公式 总被引:1,自引:1,他引:0
首先介绍三个第二类自然数幂和关系式并对其中的两式给出证明,接着利用这些关系式与数学软件M athem atica4.0,给出求解第二类自然数幂和公式的若干机械计算方法. 相似文献
107.
In situ flying height testing technology is becoming more and more important in slider–disk interaction analysis and manufacturing quality control of disk drives and head-related components. Triple harmonic method is a quite promising choice for in situ flying height analysis, compared with other in situ methods reported up to now. This paper reports results of investigations on engineering issues of applying triple harmonic method for in situ flying height analysis. The paper reports results of analysis on the effects of various testing conditions on flying height testing repeatability and accuracy. Results suggest that working at reasonable high channel density and working on the ratio between third and first harmonics will be an advantage in terms of both flying height testing sensitivity and testing repeatability. Comparing with media thickness effect, the gap-length variation among different heads will be important if it is to study flying height difference among different heads and the testing is at high channel density. Also, it is suggested to work at AC erased track, in order to reduce the non-linearity caused by hard transition. 相似文献
108.
合成了一种新型金属杂冠醚配合物[Mn6(4-amashz)6(DMF)6]·12DMF,并用X射线衍射法对其结构进行了表征.研究了该化合物修饰金电极催化氧还原的性质,结果表明,该化合物具有平面碟状结构,对在碱性溶液中的氧有显著的催化还原作用. 相似文献
109.
In the presence of an applied static and uniform magnetic field, a cylindrical Kadomtsev-Petviashivili equation is derived for a relativistic electromagnetic solitary wave propagating in collisionless plasma consisting electrons, positrons, and ions in the case of weak relativistic limit. This equation is solved in a stationary frame to obtain explicit expression for the velocity, amplitude and width of solitons. The amplitude of the solitary wave has a maximum value at a critical αc of the ratio of the ion equilibrium density to the electron one, and it increases as the applied magnetic field becomes larger. 相似文献
110.
The nonradiative recombination effect on carrier dynamics in GalnNAs/GaAs quantum wells is studied by timeresolved photoluminescence (TRPL) and polarization-dependent TRPL at various excitation intensities. It is found that both recombination dynamics and spin relaxation dynamics strongly depend on the excitation intensity. Under moderate excitation intensities the PL decay curves exhibit unusual non-exponential behaviour. This result is well simulated by a rate equation involving both the radiative and non-radiative recombinations via the introduction of a new parameter of the effective concentration of nonradiative recombination centres in the rate equation. In the spin dynamics study, the spin relaxation also shows strong excitation power dependence. Under the high excitation power an increase of spin polarization degree with time is observed. This new finding provides a useful hint that the spin process can be controlled by excitation power in GaInNAs systems. 相似文献