全文获取类型
收费全文 | 3995篇 |
免费 | 71篇 |
国内免费 | 9篇 |
专业分类
化学 | 2749篇 |
晶体学 | 16篇 |
力学 | 68篇 |
数学 | 925篇 |
物理学 | 317篇 |
出版年
2019年 | 34篇 |
2016年 | 71篇 |
2015年 | 51篇 |
2014年 | 34篇 |
2013年 | 113篇 |
2012年 | 89篇 |
2011年 | 140篇 |
2010年 | 102篇 |
2009年 | 114篇 |
2008年 | 136篇 |
2007年 | 125篇 |
2006年 | 136篇 |
2005年 | 119篇 |
2004年 | 94篇 |
2003年 | 91篇 |
2002年 | 66篇 |
1999年 | 28篇 |
1998年 | 31篇 |
1997年 | 42篇 |
1996年 | 58篇 |
1995年 | 71篇 |
1994年 | 50篇 |
1993年 | 59篇 |
1992年 | 89篇 |
1991年 | 83篇 |
1990年 | 74篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 61篇 |
1986年 | 59篇 |
1985年 | 76篇 |
1984年 | 87篇 |
1983年 | 79篇 |
1982年 | 74篇 |
1981年 | 101篇 |
1980年 | 58篇 |
1979年 | 77篇 |
1978年 | 69篇 |
1977年 | 92篇 |
1976年 | 63篇 |
1975年 | 79篇 |
1974年 | 84篇 |
1973年 | 64篇 |
1972年 | 52篇 |
1971年 | 47篇 |
1970年 | 37篇 |
1967年 | 29篇 |
1966年 | 29篇 |
1962年 | 29篇 |
1958年 | 28篇 |
排序方式: 共有4075条查询结果,搜索用时 62 毫秒
1.
2.
3.
4.
Dr. Xiaoyan Sun Prof. Dr. Shaodong Zhou Dr. Lei Yue Dr. Maria Schlangen Prof. Dr. Helmut Schwarz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(14):3550-3559
Thermal gas-phase reactions of the ruthenium-oxide clusters [RuOx]+ (x=1–3) with methane and dihydrogen have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. For methane activation, as compared to the previously studied [RuO]+/CH4 couple, the higher oxidized Ru systems give rise to completely different product distributions. [RuO2]+ brings about the generations of [Ru,O,C,H2]+/H2O, [Ru,O,C]+/H2/H2O, and [Ru,O,H2]+/CH2O, whereas [RuO3]+ exhibits a higher selectivity and efficiency in producing formaldehyde and syngas (CO+H2). Regarding the reactions with H2, as compared to CH4, both [RuO]+ and [RuO2]+ react similarly inefficiently with oxygen-atom transfer being the main reaction channel; in contrast, [RuO3]+ is inert toward dihydrogen. Theoretical analysis reveals that the reduction of the metal center drives the overall oxidation of methane, whereas the back-bonding orbital interactions between the cluster ions and dihydrogen control the H−H bond activation. Furthermore, the reactivity patterns of [RuOx]+ (x=1–3) with CH4 and H2 have been compared with the previously reported results of Group 8 analogues [OsOx]+/CH4/H2 (x=1–3) and the [FeO]+/H2 system. The electronic origins for their distinctly different reaction behaviors have been addressed. 相似文献
5.
6.
Dr. Shaodong Zhou Dr. Jilai Li Dr. Maria Schlangen Prof. Dr. Helmut Schwarz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):3073-3076
Carbon‐atom extrusion from the ipso‐position of a halobenzene ring (C6H5X; X=F, Cl, Br, I) and its coupling with a methylene ligand to produce acetylene is not confined to [LaCH2]+; also, the third‐row transition‐metal complexes [MCH2]+, M=Hf, Ta, W, Re, and Os, bring about this unusual transformation. However, substrates with substituents X=CN, NO2, OCH3, and CF3 are either not reactive at all or give rise to different products when reacted with [LaCH2]+. In the thermal gas‐phase processes of atomic Ln+ with C7H7Cl substrates, only those lanthanides with a promotion energy small enough to attain a 4fn5d16s1 configuration are reactive and form both [LnCl]+ and [LnC5H5Cl]+. Branching ratios and the reaction efficiencies of the various processes seem to correlate with molecular properties, like the bond‐dissociation energies of the C?X or M+?X bonds or the promotion energies of lanthanides. 相似文献
7.
8.
9.
10.