全文获取类型
收费全文 | 781篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
化学 | 530篇 |
晶体学 | 3篇 |
力学 | 13篇 |
数学 | 80篇 |
物理学 | 170篇 |
出版年
2021年 | 8篇 |
2020年 | 16篇 |
2019年 | 4篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 18篇 |
2013年 | 28篇 |
2012年 | 36篇 |
2011年 | 37篇 |
2010年 | 18篇 |
2009年 | 28篇 |
2008年 | 33篇 |
2007年 | 35篇 |
2006年 | 45篇 |
2005年 | 49篇 |
2004年 | 30篇 |
2003年 | 26篇 |
2002年 | 27篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 14篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 14篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 8篇 |
1990年 | 13篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 12篇 |
1973年 | 12篇 |
1972年 | 6篇 |
1962年 | 3篇 |
1942年 | 3篇 |
1933年 | 3篇 |
1924年 | 3篇 |
1881年 | 3篇 |
排序方式: 共有796条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
6.
James J. Li R. Alan Chrusciel Monica B. Norton David B. Reitz Timothy J. Hagen Sofya Tsymbalov E. Ann Hallinan 《Journal of heterocyclic chemistry》1994,31(6):1689-1696
Lithiation of 8-chlorodibenz[b,f][1,4]oxazepine-10-tert-butylcarbamate ( 1 ) is described. Electrophilic substitution of the resulting N-Boc dibenzoxazepine α- lithioamine 2 with ketones, aldehydes, nitriles, iso-cyanates and imines, followed by an in-situ cyclization, gave fused carbamates 5–26 , fused 2H-imidazol-2-ones 27–29 , fused hydantoins 30–32 , and fused ureas 33–35 , respectively, in 11–66% yield. 相似文献
7.
8.
Jörn Müller Helmuth Menig Gottfried Huttner Albin Frank 《Journal of organometallic chemistry》1980,185(2):251-263
The complexes [Ir(COD)(η5-C7H9)] and [Ir(COD)(η5-C8H11)] are obtained by the isoprophyl Grignard synthesis of [Ir(COD)Cl]2 (COD = η4-1,5-cyclooctadiene) in the presence of cycloheptatriene, and cyclooctatriene, respectively. The later reaction yields [IrH(COD)(δ4-1,3,6-C8H10)] as a by-product which, in contrast to other [IrH(η4-cyclodiene)2] complexes, does not show H-addition-elimination equilibria. Reduction of [Ir(1,3-C7H10)2Cl] with C2H5OH/Na2CO3 yields [Ir(η4-1,3-C7H10)](η5-C7H9)] which was characterized by X-ray analysis. [Ir(COD)Cl]2 reacts with Na2C8H8, and after hydrolysis unstable [Ir(COD)(η5-C8H9)] is formed which by protonation with HPF6 is converted into the [Ir(COD)(η6-1,3,5-C8H10)]+ cation. All these compounds are fluxional in solution. 相似文献
9.
Herwig G. Winkler Hagen T. Spath Prof. Dr. Karl Torkar 《Monatshefte für Chemie / Chemical Monthly》1975,106(2):535-545
The phase diagrams of the systems CsN3/Zn(N3)2 and KN3/Zn(N3)2 have been obtained employing the microscopic technique ofL. Kofler andA. Kofler. Within the system CsN3/Zn(N3)2 three eutectics at 148°C, 142°C, and 210°C were found. Besides Cs2Zn(N3)4, melting incongruently in the interval 153°C to 170°C, there exist two further compounds of the most probable composition Cs3Zn2(N3)7 and CsZn2(N3)5, melting congruently at 170°C and 210°C, resp. In the system KN3/Zn(N3)2 there exist two eutectics at 203°C and 172°C and two compounds, one of them, i.e. K2Zn(N3)4, melting congruently at 206°C, the other one, with composition KZn3(N3)7 or KZn4(N3)9, melting incongruently at 210°C.
Mit 8 Abbildungen
Herrn Professor Dr.Heribert Grubitsch zum 70. Geburtstag gewidmet. 相似文献
Mit 8 Abbildungen
Herrn Professor Dr.Heribert Grubitsch zum 70. Geburtstag gewidmet. 相似文献
10.
A novel capsule composed of an azo dye, Congo red (CR), and different polymers, including poly(styrenesulfonate, sodium salt) (PSS), poly(allylamine hydrochloride) (PAH), and poly(diallyldimethylammonium chloride) (PDDA), have been successfully fabricated by the layer-by-layer self-assembly technique. The stepwise linear deposition process was monitored by means of UV-visible absorption measurements. The formation of hollow capsules was verified by confocal laser scanning microscopy (CLSM) and scanning force microscopy (SFM). The resulting hollow PSS/PAH/CR/PDDA capsules displayed a sensitive response to visible light. Optical changes of the hollow capsules prior to and after the photoreaction were investigated in detail by means of UV-visible spectroscopy, CLSM, and SFM. It was found that the photochemical reaction of the assembled hollow capsules depends strongly on the matrix. Qualitative results on the permeability of the hollow capsule walls with CR as one component indicate that the permeability of the walls can be easily photo-controlled at varying irradiation time intervals without addition of external chemicals. 相似文献