全文获取类型
收费全文 | 32625篇 |
免费 | 5216篇 |
国内免费 | 3944篇 |
专业分类
化学 | 23140篇 |
晶体学 | 460篇 |
力学 | 1995篇 |
综合类 | 335篇 |
数学 | 3738篇 |
物理学 | 12117篇 |
出版年
2024年 | 54篇 |
2023年 | 588篇 |
2022年 | 732篇 |
2021年 | 1037篇 |
2020年 | 1282篇 |
2019年 | 1223篇 |
2018年 | 1069篇 |
2017年 | 1074篇 |
2016年 | 1483篇 |
2015年 | 1603篇 |
2014年 | 1765篇 |
2013年 | 2423篇 |
2012年 | 2875篇 |
2011年 | 3016篇 |
2010年 | 2100篇 |
2009年 | 2034篇 |
2008年 | 2301篇 |
2007年 | 2075篇 |
2006年 | 1841篇 |
2005年 | 1524篇 |
2004年 | 1175篇 |
2003年 | 978篇 |
2002年 | 940篇 |
2001年 | 677篇 |
2000年 | 667篇 |
1999年 | 631篇 |
1998年 | 503篇 |
1997年 | 506篇 |
1996年 | 531篇 |
1995年 | 440篇 |
1994年 | 435篇 |
1993年 | 328篇 |
1992年 | 291篇 |
1991年 | 266篇 |
1990年 | 196篇 |
1989年 | 154篇 |
1988年 | 155篇 |
1987年 | 107篇 |
1986年 | 116篇 |
1985年 | 98篇 |
1984年 | 69篇 |
1983年 | 63篇 |
1982年 | 52篇 |
1981年 | 36篇 |
1980年 | 46篇 |
1979年 | 33篇 |
1978年 | 30篇 |
1977年 | 16篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
FTIR光谱遥测红外药剂的燃烧温度 总被引:2,自引:0,他引:2
本文利用遥感FTIR光谱,对红外药剂的燃烧特性进行了研究。在分辨率为4cm^-1时,收集4700-740cm^-1波段的光谱。从HF等燃烧产物发射的分子振转基带精细结构的谱线强度分布,可以对燃烧温度进行遥感测定,并给出了燃烧温度随时间的变化关系,实验结果表明燃烧表面附近温度梯度很大,存在着急剧的变化温度场,同时也说明,在不干扰火焰温度场的情况下,利用遥感FTIR光谱对剧烈的、非稳态快速燃烧的火焰温度进行连续实时的遥感测量,是一种快速、准确、灵敏度高的测温方法,显示了它在燃烧温度测量、产物浓度测试以及燃烧机理研究等方面的应用前景。 相似文献
62.
本文以一道题为例对研究性教学中的习题环节进行了实例研究.大致按照事件发生的顺序叙述以再现现场情景. 相似文献
63.
采用基于第一原理的全势能线性缀加平面波加局域轨道((L)APW lo)方法对Nd(Fe,Si)11Cx化合物(x=0,2)的电子结构进行了计算,得到了化合物态密度和磁矩等信息.计算结果表明NdFe9Si2化合物中Si原子主要与4b和32i位Fe原子产生杂化,导致Fe原子磁矩减小.NdFe9Si2C2化合物C原子使32i位Fe原子磁矩进一步降低,同时减弱了Si原子的影响,使得4b位Fe原子磁矩增大. 相似文献
64.
65.
Bo Jin Xi Wang Jing Chen Feng Zhang Xinli Cheng Zhijun Chen 《Applied Surface Science》2006,252(16):5627-5631
The oxidation of SiGe film epitaxial grown on top of SOI wafers has been studied. These SiGe/SOI samples were oxidized at 700, 900, 1100 °C. Germanium atoms were rejected from SiGe film to SOI layer. A new Si1−xGex (x is minimal) layer formed at SiGe/Si interface. As the germanium atoms diffused, the new Si1−xGex (x is minimal) layer moved to Si/SiO2 interface. Propagation of threading dislocation in SiGe film to SOI substrate was hindered by the new SiGe/Si interface. Strain in SOI substrate transferred from SiGe film was released through dislocation nucleation and propagation inner. The relaxation of SiGe film could be described as: strain relaxed through strain equalization and transfer process between SiGe film and SOI substrates. Raman spectroscopy was used to characterize the strain of SiGe film. Microstructure of SiGe/SOI was observed by transmission electron microscope (TEM). 相似文献
66.
A novel technique to overcome the long-term drift and hysteresis of a scanning Fabry–Perot filter was developed and applied to wavelength and power monitoring of DWDM system. By using the comb peaks generated by a temperature-stabilized, near threshold-biased Fabry–Perot diode laser as wavelength reference for the scanning Fabry–Perot filter, wavelength and power measurement accuracy of better than ±10 pm and 0.2 dB, respectively, were achieved. 相似文献
67.
68.
Newton-Leibniz integration rule only applies to commuting functions of continuum variables, while operators made of Dirac’s symbols (ket versus bra, e.g., |q〉〈q| of continuous parameter q) in quantum mechanics are usually not commutative. Therefore, integrations over the operators of type |〉〈| cannot be directly performed by Newton-Leibniz rule. We invented an innovative technique of integration within an ordered product (IWOP) of operators that made the integration of non-commutative operators possible. The IWOP technique thus bridges this mathematical gap between classical mechanics and quantum mechanics, and further reveals the beauty and elegance of Dirac’s symbolic method and transformation theory. Various applications of the IWOP technique, including constructing the entangled state representations and their applications, are presented. 相似文献
69.
70.
Soliton interaction under the influence of higher-order effects 总被引:6,自引:0,他引:6
In this paper, we present exact N-soliton solution by employing simple, straightforward Darboux transformation based on the Lax pair for Hirota equation, a higher-order nonlinear Schrödinger (HNLS) equation. As examples, one- and two-soliton solutions in explicit forms are given and their properties are also analyzed. A bound solution without interaction will be theoretically predicted if one can adjust frequency shift for each soliton appropriately. Further, we obtain the approximate eigenvalues by employing two-soliton solution and discuss analytically the interaction between neighboring solitons under the influence of the higher-order effects. It is shown that the combined effects of the higher-order effects can restrain the interaction between neighboring solitons to some extent. The results are proved by directly solving HNLS equation numerically. 相似文献