全文获取类型
收费全文 | 13131篇 |
免费 | 392篇 |
国内免费 | 40篇 |
专业分类
化学 | 8691篇 |
晶体学 | 44篇 |
力学 | 222篇 |
综合类 | 1篇 |
数学 | 2360篇 |
物理学 | 2245篇 |
出版年
2019年 | 105篇 |
2016年 | 219篇 |
2015年 | 210篇 |
2014年 | 282篇 |
2013年 | 468篇 |
2012年 | 357篇 |
2011年 | 374篇 |
2010年 | 276篇 |
2009年 | 260篇 |
2008年 | 410篇 |
2007年 | 372篇 |
2006年 | 414篇 |
2005年 | 403篇 |
2004年 | 337篇 |
2003年 | 326篇 |
2002年 | 330篇 |
2001年 | 252篇 |
2000年 | 217篇 |
1999年 | 147篇 |
1998年 | 139篇 |
1997年 | 176篇 |
1996年 | 202篇 |
1995年 | 181篇 |
1994年 | 183篇 |
1993年 | 218篇 |
1992年 | 186篇 |
1991年 | 144篇 |
1990年 | 162篇 |
1989年 | 173篇 |
1988年 | 170篇 |
1987年 | 169篇 |
1986年 | 156篇 |
1985年 | 253篇 |
1984年 | 229篇 |
1983年 | 149篇 |
1982年 | 197篇 |
1981年 | 179篇 |
1980年 | 229篇 |
1979年 | 215篇 |
1978年 | 223篇 |
1977年 | 246篇 |
1976年 | 205篇 |
1975年 | 200篇 |
1974年 | 155篇 |
1973年 | 207篇 |
1972年 | 108篇 |
1971年 | 109篇 |
1967年 | 175篇 |
1966年 | 166篇 |
1965年 | 109篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Robin F. Weitkamp Beate Neumann Hans‐Georg Stammler Berthold Hoge 《Angewandte Chemie (International ed. in English)》2020,59(14):5494-5499
We report on the first examples of isolated silanol–silanolate anions, obtained by utilizing weakly coordinating phosphazenium counterions. The silanolate anions were synthesized from the recently published phosphazenium hydroxide hydrate salt with siloxanes. The silanol–silanolate anions are postulated intermediates in the hydroxide‐mediated polymerization of aryl and alkyl siloxanes. The silanolate anions are strong nucleophiles because of the weakly coordinating character of the phosphazenium cation, which is perceptible in their activity in polysiloxane depolymerization. 相似文献
2.
We report on the first observation and studies of a weak delocalizing logarithmic temperature dependence of the conductivity,
which causes the conductivity of the 2D metal to increase as T decreases down to 16 mK. The prefactor of the logarithmic dependence is found to decrease gradually with density, to vanish
at a critical density n
c
, 2∼2×1012 cm−2, and then to have the opposite sign at n>n
c
,2. The second critical density sets the upper limit on the existence region of the 2D metal, whereas the conductivity at the
critical point, G
c
,2∼120e
2/h, sets an upper (low-temperature) limit on its conductivity.
Pis’ma Zh. éksp. Teor. Fiz. 68, No. 6, 497–501 (25 September 1998)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
3.
Let A be a symmetric matrix of size n×n with entries in some (commutative) field K. We study the possibility of decomposing A into two blocks by conjugation by an orthogonal matrix T∈Matn(K). We say that A is absolutely indecomposable if it is indecomposable over every extension of the base field. If K is formally real then every symmetric matrix A diagonalizes orthogonally over the real closure of K. Assume that K is a not formally real and of level s. We prove that in Matn(K) there exist symmetric, absolutely indecomposable matrices iff n is congruent to 0, 1 or −1 modulo 2s. 相似文献
4.
D. De Salvador A. Coati E. Napolitani M. Berti A.V. Drigo M.S. Carroll J.C. Sturm J. Stangl G. Bauer L. Lazzarini 《Applied Physics A: Materials Science & Processing》2002,75(6):667-672
In this work we investigate the diffusion and precipitation of supersaturated substitutional carbon in 200-nm-thick SiGeC
layers buried under a silicon cap layer of 40 nm. The samples were annealed in either inert (N2) or oxidizing (O2) ambient at 850 °C for times ranging from 2 to 10 h. The silicon self-interstitial (I) flux coming from the surface under
oxidation enhances the C diffusion with respect to the N2-annealed samples. In the early stages of the oxidation process, the loss of C from the SiGeC layer by diffusion across the
layer/cap interface dominates. This phenomenon saturates after an initial period (2–4 h), which depends on the C concentration.
This saturation is due to the formation and growth of C-containing precipitates that are promoted by the I injection and act
as a sink for mobile C atoms. The influence of carbon concentration on the competition between precipitation and diffusion
is discussed.
Received: 19 October 2001 / Accepted: 19 December 2001 / Published online: 20 March 2002 / Published online: 20 March 2002 相似文献
5.
6.
7.
8.
9.
10.
Hans Maaß 《Mathematische Annalen》1941,118(1):312-318
Ohne Zusammenfassung 相似文献