全文获取类型
收费全文 | 357260篇 |
免费 | 2079篇 |
国内免费 | 646篇 |
专业分类
化学 | 170916篇 |
晶体学 | 5414篇 |
力学 | 18524篇 |
综合类 | 9篇 |
数学 | 52699篇 |
物理学 | 112423篇 |
出版年
2019年 | 2298篇 |
2018年 | 11094篇 |
2017年 | 11878篇 |
2016年 | 8235篇 |
2015年 | 3428篇 |
2014年 | 4420篇 |
2013年 | 10828篇 |
2012年 | 12080篇 |
2011年 | 21214篇 |
2010年 | 13594篇 |
2009年 | 13485篇 |
2008年 | 18900篇 |
2007年 | 22257篇 |
2006年 | 9097篇 |
2005年 | 13967篇 |
2004年 | 10480篇 |
2003年 | 9906篇 |
2002年 | 7970篇 |
2001年 | 7486篇 |
2000年 | 5982篇 |
1999年 | 4405篇 |
1998年 | 3909篇 |
1997年 | 3864篇 |
1996年 | 3762篇 |
1995年 | 3442篇 |
1994年 | 3592篇 |
1993年 | 3273篇 |
1992年 | 3745篇 |
1991年 | 3751篇 |
1990年 | 3684篇 |
1989年 | 3548篇 |
1988年 | 3661篇 |
1987年 | 3553篇 |
1986年 | 3366篇 |
1985年 | 4455篇 |
1984年 | 4742篇 |
1983年 | 3966篇 |
1982年 | 4102篇 |
1981年 | 4025篇 |
1980年 | 4001篇 |
1979年 | 3982篇 |
1978年 | 4302篇 |
1977年 | 4146篇 |
1976年 | 4233篇 |
1975年 | 3901篇 |
1974年 | 3943篇 |
1973年 | 4130篇 |
1972年 | 2886篇 |
1971年 | 2400篇 |
1970年 | 2209篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
A. Lashgari S. Ghammamy R. Ramirez-Tagle G. Salgado-Moran 《Journal of Structural Chemistry》2015,56(8):1505-1513
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data. 相似文献
13.
14.
15.
Physics of Atomic Nuclei - We have studied the mechanisms influencing production of cumulative pions and protons in the fragmentation of the incident deuterons into cumulative pions and protons... 相似文献
16.
17.
In this work, the effect of various properties of materials on vacuum breakdown initiated by laser radiation is considered. Estimating calculations are performed which show that the material of the target electrode distinctly affects the minimum energy of laser radiation needed for igniting a vacuum spark. The experimental studies carried out confirm the estimating calculations, and a number of materials are revealed which can be arranged in order of increase in the energy needed for the formation of breakdown in vacuum by the impact of a laser pulse. 相似文献
18.
Robert G. W. Anderson 《Ambix》2015,62(4):333-344
Following colonisation of South America by the Spanish, many new naturally occurring substances were sent to Europe. One of these was the silvery, unreactive metal, platinum, discovered in New Grenada in the mid-eighteenth century. It was often found in granular form, associated with gold, and the challenge to chemists was to refine it, produce it as wire or sheet, and determine its chemical properties. This interested the professor of chemistry at the University of Edinburgh, Joseph Black, who was able to obtain samples from London-based Spanish contacts, particularly Ignacio Luzuriaga. This paper examines how Black transmitted his knowledge of the metal to large numbers of students attending his annual course. 相似文献
19.
20.