全文获取类型
收费全文 | 8963篇 |
免费 | 243篇 |
国内免费 | 19篇 |
专业分类
化学 | 6074篇 |
晶体学 | 71篇 |
力学 | 201篇 |
综合类 | 5篇 |
数学 | 1041篇 |
物理学 | 1833篇 |
出版年
2023年 | 65篇 |
2022年 | 248篇 |
2021年 | 252篇 |
2020年 | 209篇 |
2019年 | 229篇 |
2018年 | 225篇 |
2017年 | 156篇 |
2016年 | 338篇 |
2015年 | 274篇 |
2014年 | 339篇 |
2013年 | 560篇 |
2012年 | 607篇 |
2011年 | 683篇 |
2010年 | 463篇 |
2009年 | 471篇 |
2008年 | 591篇 |
2007年 | 514篇 |
2006年 | 444篇 |
2005年 | 369篇 |
2004年 | 330篇 |
2003年 | 250篇 |
2002年 | 227篇 |
2001年 | 149篇 |
2000年 | 135篇 |
1999年 | 88篇 |
1998年 | 78篇 |
1997年 | 76篇 |
1996年 | 68篇 |
1995年 | 57篇 |
1994年 | 66篇 |
1993年 | 71篇 |
1992年 | 73篇 |
1991年 | 39篇 |
1990年 | 35篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 30篇 |
1983年 | 28篇 |
1982年 | 23篇 |
1981年 | 27篇 |
1980年 | 26篇 |
1979年 | 24篇 |
1978年 | 26篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 13篇 |
1973年 | 11篇 |
排序方式: 共有9225条查询结果,搜索用时 0 毫秒
41.
42.
43.
44.
J. C. Moreno J. Nilsen J. A. Koch B. J. MacGowan J. H. Scofield L. B. Da Silva 《Applied physics. B, Lasers and optics》1994,58(1):3-5
Neon-like niobium X-ray lasers have been studied using both slab and thin-foil target geometries. Niobium foils of various lengths were irradiated from both sides with two beams of the frequency-doubled Nova laser system using a line focus. We looked for gain by measuring spectrally integrated line intensities at different plasma lengths. Gain was observed in four neon-like niobium lines corresponding to 3s–3p transitions. The line profile of theJ = 0–1 line ( = 145.9 ) shows splitting due to the hyperfine effect. Improved contrast in the hyperfine structure is observed as the plasma length is increased. Hyperfine splitting may be relevant to other 3s–3p transitions in neon-like niobium as well as other neon-like X-ray laser systems. 相似文献
45.
T. Missana C. N. Afonso M. F. da Silva 《Applied Physics A: Materials Science & Processing》1994,59(6):653-658
Interdiffusion processes are induced by nanosecond laser pulses from an excimer laser. The Bi-based systems studied are formed by a Bi layer and a Sb or Ge layer. Configurations with Bi at the surface layer or at the innermost layer are both studied. Real-time reflectivity measurements are performed during the irradiation to determine the process kinetics and times and Rutherford backscattering spectrometry is used to obtain the concentration depth profiles. It will be shown that there is an interfacially initiated diffusion process in the Bi-Sb system and that the diffusion coefficients of this system within the liquid phase are in the 10–5–10–6 cm2/s range. The Bi-Ge system shows instead little mixing, the diffusion coefficients of the system within the liquid phase being at least two orders of magnitude lower. The differences observed when Bi is the surface layer or the innermost one are related to the different thermal responses of the system. 相似文献
46.
47.
48.
49.
50.
Silva Silvio S. Ribeiro JoÃo D. Felipe Maria G. A. Vitolo Michelle 《Applied biochemistry and biotechnology》1997,(1):557-564
Batch fermentations of sugar cane bagasse hemicellulosic hydrolysate treated for removing the inhibitors of the fermentation
were performed byCandida guilliermondii FTI20037 for xylitol production. The fermentative parameters agitation and aeration rate were studied aiming the maximization
of xylitol production from this agroindustrial residue. The maximal xylitol volumetric productivity (0.87 g/L h) and yield
(0.67 g/g) were attained at 400/min and 0.45 v.v.m. (KLa 27/h). According to the results, a suitable control of the oxygen input permitting the xylitol formation from sugar cane
bagasse hydrolysate is required for the development of an efficient fermentation process for large-scale applications. 相似文献