全文获取类型
收费全文 | 459099篇 |
免费 | 4010篇 |
国内免费 | 1064篇 |
专业分类
化学 | 225914篇 |
晶体学 | 7513篇 |
力学 | 22353篇 |
综合类 | 15篇 |
数学 | 62010篇 |
物理学 | 146368篇 |
出版年
2021年 | 2844篇 |
2020年 | 3262篇 |
2019年 | 3636篇 |
2018年 | 11832篇 |
2017年 | 12546篇 |
2016年 | 10107篇 |
2015年 | 4901篇 |
2014年 | 6762篇 |
2013年 | 17044篇 |
2012年 | 16375篇 |
2011年 | 25932篇 |
2010年 | 16944篇 |
2009年 | 16904篇 |
2008年 | 22852篇 |
2007年 | 25909篇 |
2006年 | 13331篇 |
2005年 | 17727篇 |
2004年 | 13863篇 |
2003年 | 12781篇 |
2002年 | 10793篇 |
2001年 | 11505篇 |
2000年 | 8986篇 |
1999年 | 6780篇 |
1998年 | 5362篇 |
1997年 | 5352篇 |
1996年 | 5146篇 |
1995年 | 4736篇 |
1994年 | 4531篇 |
1993年 | 4253篇 |
1992年 | 5171篇 |
1991年 | 5030篇 |
1990年 | 4957篇 |
1989年 | 4793篇 |
1988年 | 4860篇 |
1987年 | 4883篇 |
1986年 | 4571篇 |
1985年 | 5959篇 |
1984年 | 6191篇 |
1983年 | 4981篇 |
1982年 | 5182篇 |
1981年 | 5247篇 |
1980年 | 4920篇 |
1979年 | 5280篇 |
1978年 | 5421篇 |
1977年 | 5454篇 |
1976年 | 5352篇 |
1975年 | 4929篇 |
1974年 | 4863篇 |
1973年 | 4997篇 |
1972年 | 3289篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
931.
932.
P. González D. Fernández J. Pou E. García J. Serra B. León M. Pérez-Amor T. Szörényi 《Applied Physics A: Materials Science & Processing》1993,57(2):181-185
A study of the gas-phase parameters involved in ArF laser induced chemical vapour deposition of silicon-oxide thin films is presented. A complete set of experiments has been performed showing the influence of the concentration of the precursor gases, N2O and SiH4, and their influence on total and partial pressures on film growth and properties. In this paper we demonstrate the ability of this LCVD method to deposit silicon oxide films of different compositions and densities by appropriate control of gas composition and total pressure. Moreover, a material specific calibration plot comprising data obtained using different preparation techniques is presented, allowing determination of the stoichiometry of SiO
x
films by using FTIR spectroscopy independently of the deposition method. For the range of processing conditions examined, the experimental results suggest that chemical processes governing deposition take place mainly in the gas phase. 相似文献
933.
We review data on methods for synthesis, chemical and pharmacological properties of pyrido[1,2-a)pyrimidines.Scientific-Research Institute of Pharmacology of the Russian Academy of Medical Sciences, All-Union Science Center for Biologically Active Substances, Staraya Kupavna, 124432. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 579–596, May, 1994. Original article submitted March 3, 1994. 相似文献
934.
Flowing and static gas-phase samples of HNO3 in O2 and N2 were analyzed by long-path ultraviolet/visible (UV/VIS) spectroscopy to reveal the presence of both NO2 and NO3, the concentrations of which were calculated using differential absorption cross sections. NO2 is produced predominantly by the heterogeneous decomposition of HNO3, whereas NO3 is generated in the gas phase by the thermal decomposition of N2O5, a product of the self-disproportionation of liquid HNO3. © 1993 John Wiley & Sons, Inc. 相似文献
935.
936.
It is found that, in the spherical coordinate system, the fundamental solution of the Helmholtz equation in a wedge satisfies the Sommerfeld radiation conditions at infinity uniformly in angle coordinates.Deceased.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 45, No. 9, pp. 1312–1314, September, 1993. 相似文献
937.
The effect of 57Fe hyperfine interaction radiofrequency (rf) modulation by external rotating magnetic field was studied in thin Permalloy foil by means of Mössbauer spectroscopy. The rf effect was investigated as a function of intensity for several rf field frequencies. The experiments show that the external rotating rf field causes considerable changes in the hyperfine pattern. The obtained spectra are in disagreement with those obtained by Perlow [Phys. Rev. 172 (1968) 319]. They also are inconsistent with magnetostriction hypothesis. Proceeding from the Mössbauer spectrum analysis one may conclude that the magnetization of investigated foil changes its direction in a complex manner. However, the undertaken experiments show that the essential number of Mössbauer nuclei experience the rotating magnetic field influence. 相似文献
938.
939.
940.
Mössbauer spectroscopy was used to investigate the reactions of microbes with iron minerals in aqueous solutions and as components of rocks in banded iron formations and granite. A microbial biofilm that formed on a wall of an excavated granite vault in a deep underground laboratory initiated this research. At the aerobic face of the biofilm, iron was found in a form of ferrihydrite; in the anaerobic face against the rock, iron was found as very small siderite particles. Laboratory incubations of the biofilm microbial consortium showed different mineral species could be formed. When the microbial consortium from the biofilm was incubated with magnetite grains, up to about 10% of the iron was altered in three weeks to hematite. The ability of the consortium to precipitate iron both as Fe2+ and Fe3+ in close proximity may have a bearing on the deposition of banded iron formations. These reactions could also be important in microbially induced corrosion. 相似文献