全文获取类型
收费全文 | 3758篇 |
免费 | 101篇 |
国内免费 | 12篇 |
专业分类
化学 | 2657篇 |
晶体学 | 44篇 |
力学 | 65篇 |
数学 | 175篇 |
物理学 | 930篇 |
出版年
2023年 | 17篇 |
2022年 | 26篇 |
2021年 | 31篇 |
2020年 | 66篇 |
2019年 | 68篇 |
2018年 | 46篇 |
2017年 | 30篇 |
2016年 | 64篇 |
2015年 | 61篇 |
2014年 | 79篇 |
2013年 | 170篇 |
2012年 | 167篇 |
2011年 | 199篇 |
2010年 | 127篇 |
2009年 | 122篇 |
2008年 | 190篇 |
2007年 | 211篇 |
2006年 | 191篇 |
2005年 | 144篇 |
2004年 | 123篇 |
2003年 | 134篇 |
2002年 | 133篇 |
2001年 | 110篇 |
2000年 | 126篇 |
1999年 | 78篇 |
1998年 | 50篇 |
1997年 | 49篇 |
1996年 | 41篇 |
1995年 | 41篇 |
1994年 | 42篇 |
1993年 | 55篇 |
1992年 | 47篇 |
1991年 | 47篇 |
1990年 | 36篇 |
1989年 | 49篇 |
1988年 | 49篇 |
1987年 | 42篇 |
1986年 | 35篇 |
1985年 | 49篇 |
1984年 | 51篇 |
1983年 | 48篇 |
1982年 | 45篇 |
1981年 | 30篇 |
1980年 | 32篇 |
1979年 | 48篇 |
1978年 | 43篇 |
1977年 | 47篇 |
1975年 | 26篇 |
1974年 | 30篇 |
1967年 | 16篇 |
排序方式: 共有3871条查询结果,搜索用时 15 毫秒
81.
82.
83.
A familyF of subsets is calledk-dense if there exists ak-element setA such that all 2
k
of its subsets can be obtained in the formAF for someFF. Best possible bounds are obtained for the maximum number of sets in notk-densek-partite families. This is a consequence of a new rank formula for inclusion matrices. 相似文献
84.
85.
Isao Watanabe Kusuo Nishiyama Kanetada Nagamine Kenji Kawano Ken-ichi Kumagai 《Hyperfine Interactions》1994,86(1):603-608
Zero field positive muon spin rotation method (
+SR) is applied on La2–x
Sr
x
CuO4 around forx=0.12 at which the high-T
c
superconductivity (SC) is suppressed. The magnetically ordered state of Cu-moments, which is not a spin glass state but an antiferromagnetic like state, appears below 15 K for 0.105x0.120. The magnetic phase boundary is very similar to the one of the La2–x
Ba
x
CuO4 in which the structural transition from the low temperature orthorhombic (LTO) phase to the low temperature tetragonal (LTT) phase is observed aroundx=0.12. The present study suggests that there is no big difference of the electronic state of the CuO2 plane between the La-Ba system and the La-Sr system and that the magnetic ordering of Cu-moments plays an important role for the suppression of the high-T
c
SC aroundx=0.12 in both of the systems, although the LTO-LTT structural transition has not been observed yet in the La-Sr system. 相似文献
86.
87.
Ishikawa T Watanabe T Tanigawa H Saito T Kotake KI Ohashi Y Ishii H 《The Journal of organic chemistry》1996,61(8):2774-2779
Nitrosation of 3-methoxyphenol and 1-naphthol were examined under both acidic (NaNO(2)-EtCO(2)H-H(2)O) and basic (i-AmNO(2)-K(2)CO(3)-DMF) conditions. Acidic nitrosations afforded ortho-directed products, whereas para-directed nitrosations were observed under basic conditions to yield p-quinone monooximes. The basic para-directed nitrosation was further examined using 15 phenols, two naphthols, and four phenolic heterocyclics. A one-pot operation of the basic nitrosation followed by methylation with dimethyl sulfate gave the corresponding methyl ethers in high yield. Two p-quinone monooximes derived from 3-methoxyphenol and 8-hydroxyquinoline showed a moderate activity against HSV-1, and the latter oxime was also effective against HSV-2. On the other hand, p-quinone monooximes derived from methyl salicylate, 1-naphthol, 7-hydroxy-2-methylbenzo[b]furan, and 8-hydroxycoumarin showed the comparable activity to that of DDI against HIV-1. 相似文献
88.
89.
90.
Inoue IH Watanabe M Kinoshita T Kakizaki A Kato R Kobayashi A Kobayashi H Fujimori A 《Physical review. B, Condensed matter》1993,47(19):12917-12920