全文获取类型
收费全文 | 3947篇 |
免费 | 136篇 |
国内免费 | 16篇 |
专业分类
化学 | 2351篇 |
晶体学 | 14篇 |
力学 | 189篇 |
数学 | 816篇 |
物理学 | 729篇 |
出版年
2023年 | 30篇 |
2022年 | 36篇 |
2021年 | 52篇 |
2020年 | 57篇 |
2019年 | 53篇 |
2018年 | 63篇 |
2017年 | 29篇 |
2016年 | 99篇 |
2015年 | 113篇 |
2014年 | 110篇 |
2013年 | 261篇 |
2012年 | 243篇 |
2011年 | 252篇 |
2010年 | 152篇 |
2009年 | 159篇 |
2008年 | 173篇 |
2007年 | 198篇 |
2006年 | 190篇 |
2005年 | 153篇 |
2004年 | 132篇 |
2003年 | 99篇 |
2002年 | 121篇 |
2001年 | 52篇 |
2000年 | 42篇 |
1999年 | 34篇 |
1998年 | 42篇 |
1997年 | 40篇 |
1996年 | 44篇 |
1995年 | 32篇 |
1994年 | 38篇 |
1992年 | 27篇 |
1991年 | 34篇 |
1990年 | 28篇 |
1989年 | 29篇 |
1988年 | 37篇 |
1987年 | 26篇 |
1985年 | 28篇 |
1984年 | 31篇 |
1983年 | 31篇 |
1982年 | 31篇 |
1979年 | 32篇 |
1978年 | 31篇 |
1977年 | 34篇 |
1976年 | 48篇 |
1975年 | 42篇 |
1974年 | 50篇 |
1973年 | 60篇 |
1972年 | 38篇 |
1971年 | 39篇 |
1970年 | 29篇 |
排序方式: 共有4099条查询结果,搜索用时 15 毫秒
31.
32.
Frédéric Cadoret 《Tetrahedron letters》2007,48(31):5491-5495
Competition experiments were performed by adding pre-formed solutions of diisopropyloxy(η2-cyclopentene)titanium in diethyl ether to various mixtures of unsaturated compounds at low temperature, establishing the following reactivity scale: aldehyde > nitrile > ketone > terminal alkyne > internal alkyne > terminal alkene > ester, carbonate. 相似文献
33.
Monot Frédéric Benoit Yves Ballerini Daniel Vandecasteele Jean-Paul 《Applied biochemistry and biotechnology》1990,(1):375-386
Utilization of lipases for synthesis of esters of hydrophilic polyols has been investigated. The choice of a suitable solvent
is crucial in this type of reaction. An interesting case is fatty acid esters from neopentylpolyols, such as trimethylolpropane,
which are of great interest as high temperature lubricants. Enzymatic synthesis of trimethylolpropane tricaprylate was studied
as an alternative to chemical manufacturing. Triester production occurred only if the water produced by esterification was
continuously removed from the medium. In these condition, kinetics of appearance and transformation of mono-, di- and triesters
were determined in order to define optimal conditions. 相似文献
34.
35.
36.
37.
M. B. Ordyan V. S. Grigoryan R. V. Avetisyan Ya. T. Éidus 《Russian Chemical Bulletin》1971,20(5):1034-1036
Conclusions When the hydrocarbomethoxylation of 1-hexene with formic acid is run at atmospheric pressure and temperatures close to room temperature, in the presence of conc. H3PO4, an increase in the relative amount of the latter, as well as an increase in the reaction temperature in the investigated range, both favor an increase in the yields of the methyl esters of the C7 acids, in particular, those containing two methyl groups on the quaternary carbon atom in the -position. An increase in the relative amount of formic acid also favors an increase in the amounts of these esters in the obtained mixtures of esters.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1116–1118, May, 1971. 相似文献
38.
39.
Martinho M Banse F Bartoli JF Mattioli TA Battioni P Horner O Bourcier S Girerd JJ 《Inorganic chemistry》2005,44(25):9592-9596
The green complex S=1 [(TPEN)FeO]2+ [TPEN=N,N,N',N'-tetrakis(2-pyridylmethyl)ethane-1,2-diamine] has been obtained by treating the [(TPEN)Fe]2+ precursor with meta-chloroperoxybenzoic acid (m-CPBA). This high-valent complex belongs to the emerging family of synthetic models of Fe(IV)=O intermediates invoked during the catalytic cycle of biological systems. This complex exhibits spectroscopic characteristics that are similar to those of other models reported recently with a similar amine/pyridine environment. Thanks to its relative stability, vibrational data in solution have been obtained by Fourier transform infrared. A comparison of the Fe=O and Fe=(18)O wavenumbers reveals that the Fe-oxo vibration is not a pure one. The ability of the green complex to oxidize small organic molecules has been studied. Mixtures of oxygenated products derived from two- or four-electron oxidations are obtained. The reactivity of this [FeO]2+ complex is then not straightforward, and different mechanisms may be involved. 相似文献
40.
Russian Chemical Bulletin - 相似文献