全文获取类型
收费全文 | 9834篇 |
免费 | 2273篇 |
国内免费 | 1243篇 |
专业分类
化学 | 6145篇 |
晶体学 | 225篇 |
力学 | 312篇 |
综合类 | 77篇 |
数学 | 198篇 |
物理学 | 6393篇 |
出版年
2024年 | 24篇 |
2023年 | 106篇 |
2022年 | 283篇 |
2021年 | 332篇 |
2020年 | 392篇 |
2019年 | 330篇 |
2018年 | 351篇 |
2017年 | 461篇 |
2016年 | 534篇 |
2015年 | 475篇 |
2014年 | 636篇 |
2013年 | 1339篇 |
2012年 | 727篇 |
2011年 | 783篇 |
2010年 | 564篇 |
2009年 | 616篇 |
2008年 | 585篇 |
2007年 | 614篇 |
2006年 | 543篇 |
2005年 | 509篇 |
2004年 | 401篇 |
2003年 | 366篇 |
2002年 | 366篇 |
2001年 | 251篇 |
2000年 | 252篇 |
1999年 | 201篇 |
1998年 | 207篇 |
1997年 | 153篇 |
1996年 | 119篇 |
1995年 | 104篇 |
1994年 | 97篇 |
1993年 | 113篇 |
1992年 | 102篇 |
1991年 | 69篇 |
1990年 | 54篇 |
1989年 | 45篇 |
1988年 | 34篇 |
1987年 | 31篇 |
1986年 | 28篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 12篇 |
1982年 | 28篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1974年 | 5篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2– was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2]
n
·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993. 相似文献
12.
Bruno Lengeler 《Mikrochimica acta》1987,91(1-6):455-475
The synchrotron radiation (SR) emitted by circulating high-energy electrons has extraordinary properties: The light is intensive and bright, it is tunable and highly collimated, and finally, it is linearly polarized. These exceptional properties have initiated a unique revival of many spectroscopies using electromagnetic radiation. The techniques of special concern for materials analysis which are treated in this article are: X-ray absorption, reflection, fluorescence, diffraction and topography. A number of examples will be given in order to illustrate the possibilities of these techniques when SR is used.On leave of absence from Institut für Festkörperforschung, KFA Jülich, D-5170 Jülich, Federal Republic of Germany 相似文献
13.
V. I. Dashkevich 《Journal of Applied Spectroscopy》2002,69(6):862-870
Based on a semiclassical theory, investigations were made of the dynamics and spectral composition of pulsed generation with self-injection of priming radiation from the active part of a three-mirror linear resonator, the passive part of which contains an active loss modulator and serves as the output reflector of the laser. It is shown that there exists a range of resonator parameters at which pulsed lasing has virtually a single frequency irrespective of the detuning of the frequencies of the priming radiation and of the nearest eigenmode of the composite resonator. Considering graphically the phase conditions of generation, it is established that among pulsed lasers with self-injection of priming radiation which are constructed on the basis of three-mirror linear and branched resonators, the most efficient for creating single-frequency generation are those in which the length of the main resonator, where generation of the pulse occurs, is larger than the length of the additional one intended for forming the priming radiation. With an inverse ratio of the lengths of the resonators, the conditions of single-frequency pulsed generation becomes dependent on the priming radiation frequency. 相似文献
14.
15.
Structural surface velocity distribution is often used to predict structural borne sound radiation. However the sampling interval of velocity should be chosen carefully to increase the prediction accuracy and to reduce the system cost. In this paper, several factors affecting the sampling interval are theoretically analyzed and discussed for a vibrating baffled rectangular plate. A new rule for the determination of the sampling interval is formulated. Using this rule, the results from both numerical simulations and experiments may be explained well. 相似文献
16.
17.
By use of the 2-m Mcmath-Pierce telescope at Kitt Peak, the high-quality spectra of a plage with moderate brightness near the center of solar disk were obtained. The data include seven spectral lines, which are Hα, Hβ, CaII H and K lines and the infrared triplet. With the consideration of fine structures of solar plages, a two-component atmospheric model is constructed by keeping the cool component to be the quiet atmosphere. Three cases of the hot component are given for different filling factors where the temperature and density distribution are adjusted in order to reproduce the seven observed spectral profiles. We also briefly discuss the influence of the column density at the base of the corona, m0, and the macro-turbulent velocity on the required filling factor and computed profiles. The two-component model is compared with precious one-component semi-empirical models. The limitation of the model is pointed out and further improvement is indicated. 相似文献
18.
19.
利用国家同步辐射实验室合肥光源的真空紫外同步辐射,使NO分子和Ar原子混合物的超声分子束发生光电离,测量了Ar,NO和异类团簇Ar·NO的光电离效率谱. 在谱中,在与Ar原子的共振线对应的能量区域(11.5—12.0 eV)观察到一个强的类共振结构. 这个结果表明,在异类团簇Ar·NO的内部,稀有气体Ar原子的激发能转移到与它接触的分子NO上,使分子NO发生电离.
关键词:
Ar·NO团簇
同步辐射
光电离
能量转移 相似文献
20.
在北京同步辐射装置(BSRF)1W1B光束线和XAFS实验站上国内首次建立了硬X射线波段的磁圆二色实验(XMCD)方法. 以单晶金刚石作为相位延迟片, 在透射劳埃(Laue)模式下, 利用衍射双折射效应, 将入射的单色线偏振光转变为相应的左旋和右旋圆偏振光, 测量磁化样品对左旋和右旋圆偏振光吸收的差异, 获得了XMCD信号. 本实验使用透射方法测量了Pt-Fe合金Pt L2,3边的XMCD, 获得了XMCD信号. XMCD实验方法的建立, 为研究磁性材料尤其是磁性薄膜材料的电子结构和磁结构提供了实验基础. 相似文献