全文获取类型
收费全文 | 27050篇 |
免费 | 988篇 |
国内免费 | 157篇 |
专业分类
化学 | 18208篇 |
晶体学 | 255篇 |
力学 | 926篇 |
综合类 | 1篇 |
数学 | 2346篇 |
物理学 | 6459篇 |
出版年
2023年 | 154篇 |
2022年 | 410篇 |
2021年 | 487篇 |
2020年 | 432篇 |
2019年 | 448篇 |
2018年 | 333篇 |
2017年 | 317篇 |
2016年 | 727篇 |
2015年 | 631篇 |
2014年 | 793篇 |
2013年 | 1489篇 |
2012年 | 1947篇 |
2011年 | 2135篇 |
2010年 | 1295篇 |
2009年 | 1143篇 |
2008年 | 1741篇 |
2007年 | 1641篇 |
2006年 | 1532篇 |
2005年 | 1428篇 |
2004年 | 1262篇 |
2003年 | 982篇 |
2002年 | 967篇 |
2001年 | 672篇 |
2000年 | 575篇 |
1999年 | 338篇 |
1998年 | 252篇 |
1997年 | 293篇 |
1996年 | 334篇 |
1995年 | 257篇 |
1994年 | 274篇 |
1993年 | 276篇 |
1992年 | 264篇 |
1991年 | 204篇 |
1990年 | 154篇 |
1989年 | 139篇 |
1988年 | 140篇 |
1987年 | 118篇 |
1986年 | 95篇 |
1985年 | 168篇 |
1984年 | 112篇 |
1983年 | 97篇 |
1982年 | 122篇 |
1981年 | 88篇 |
1980年 | 79篇 |
1978年 | 80篇 |
1977年 | 85篇 |
1976年 | 94篇 |
1975年 | 101篇 |
1974年 | 79篇 |
1973年 | 102篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
983.
H.-S. Kim C. Lee M. Takai S. Namba S.-K. Min 《Applied Physics A: Materials Science & Processing》1991,52(3):188-191
Microprobe photoluminescence (PL) measurements at 77 K were used to study the effect of the GaAs layer thickness on optical quality and variations in strain in GaAs/Si containing microcracks. PL peak intensities increase with the increase in thickness of GaAs layers and the peak intensity for the 5.5 m GaAs layer was a factor of 20 higher than those for the 1–2 m GaAs layers. Spatial nonuniformities in strain in the vicinity of two microcracks reveal that stress was almost released at the intersection of two microcracks and is maximum half way between two microcracks.On leave from Semiconductor Materials Lab., Korea Institute of Science and Technology (KIST) 相似文献
984.
985.
986.
987.
988.
989.
Chu-In Charles Lee 《Annals of the Institute of Statistical Mathematics》1992,44(1):107-120
The Laplace continued fraction is derived through a power series. It provides both upper bounds and lower bounds of the normal tail probability % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% qaaiqbfA6agzaaraaaaa!3DC0!\[\bar \Phi\](x), it is simple, it converges for x>0, and it is by far the best approximation for x3. The Laplace continued fraction is rederived as an extreme case of admissible bounds of the Mills' ratio, % MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiGc9yrFr0xXdbba91rFfpec8Eeeu0x% Xdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs% 0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaacaqabeaadaqaaqGaaO% qaaiqbfA6agzaaraaaaa!3DC0!\[\bar \Phi\](x)/(x), in the family of ratios of two polynomials subject to a monotone decreasing absolute error. However, it is not optimal at any finite x. Convergence at the origin and local optimality of a subclass of admissible bounds are investigated. A modified continued fraction is proposed. It is the sharpest tail bound of the Mills' ratio, it has a satisfactory convergence rate for x1 and it is recommended for the entire range of x if a maximum absolute error of 10-4 is required.The efforts of the author were supported by the NSERC of Canada. 相似文献
990.
Summary We prove here:
Theorem. LetT be a countable complete superstable non -stable theory with fewer than continuum many countable models. Then there is a definable groupG with locally modular regular generics, such thatG is not connected-by-finite and any type inG
eq orthogonal to the generics has Morley rank.
Corollary. LetT be a countable complete superstable theory in which no infinite group is definable. ThenT has either at most countably many, or exactly continuum many countable models, up to isomorphism.Supported by NSF grant DMS 90-06628 相似文献