全文获取类型
收费全文 | 3925篇 |
免费 | 152篇 |
国内免费 | 16篇 |
专业分类
化学 | 2347篇 |
晶体学 | 14篇 |
力学 | 189篇 |
数学 | 816篇 |
物理学 | 727篇 |
出版年
2023年 | 29篇 |
2022年 | 31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4093条查询结果,搜索用时 18 毫秒
921.
Fabrice Moggia Frédéric Fages Bernard Mandrand Eric Levillain 《Tetrahedron letters》2006,47(20):3371-3374
Two ferrocene-containing iron(III) chelators were synthesized from desferrioxamine B and kojic acid and their electronic absorption and electrochemical properties were studied in acetonitrile in the absence and presence of ferric ions. The results show a complex behavior arising from the occurrence of competing redox and complexation processes. Such systems are a first step toward the generation of chemosensors for the electrochemical detection of iron(III) in a solution. 相似文献
922.
A model previously developed in the -electron approximation to describe the effects of substituents on molecular properties has been generalized, to take into account all valence electrons (the MINDO/3 method), and used in the enthalpy-offormation calculations. The model has been tested on four classes of hydrocarbons.Makeyevskii Institute of Civil Engineering. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 5, pp. 633–637, September–October, 1991. Original article submitted October 12, 1990. 相似文献
923.
Sylvie le Stang Frédéric Paul Claude Lapinte 《Chemistry of Heterocyclic Compounds》1999,35(9):1063-1074
The functionalized complexes [(dppe)Cp*Fe(CC)]2-(Py) (Py=2,6-C5H3N and 3,5-C5H3N (dppe=1,2-bis(diphenylphosphino)ethane) were isolated in good yields from reaction of the chloro complex (dppe)Cp*FeCl with the protected bis-acetylenic heterocyclic precursor. These electron-rich pyridyl ligands constitute interesting examples of organometallic heterocycles bearing redox-active substituents. Attempts to find an alternative route starting from the alkynyl complex [(dppe)Cp*Fe(CCH)] and the corresponding dibromopyridines using a Sonogashira cross-coupling reaction are also described. By this route, the monofunctionalized products [(dppe)Cp*Fe(CC)]-2,6-Py-Br and [(dppe)Cp*Fe(CC)]-3,5-Py-Br could be cleanly isolated. These compounds open the way to the generation of heteroaromatics featuring nonequivalent alkyne substituents such as [(dppe)Cp*Fe(CC)]-2,6-Py-[(CC)SiMe3] or [(dppe)Cp*Fe(CC)]-3,5-Py-[(CC)SiMe3] by further coupling.In commemoriation of the centenary of Academician A. N. Nesmeyanov.UMR CNRS 6509 Organométalliques et catalyse: Chimie et Electrochimie Moléculaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1207–1218, September, 1999. 相似文献
924.
Jacopin C Sawicki M Plancque G Doizi D Taran F Ansoborlo E Amekraz B Moulin C 《Inorganic chemistry》2003,42(16):5015-5022
A detailed study, using a panel of spectroscopic analytical methods, of the complexation between 1-hydroxyethane-1,1'-diphosphonic acid (HEDP) and uranyl ion (UO(2)(2+)) is reported. Results suggest that the metal complex is present as only 1:1 (metal/ligand) species at low concentration (<10(-)(4) M). The conditional constants of this complex were determined at various pH using time-resolved laser-induced fluorescence (TRLIF) and electrospray ionization mass spectrometry (ESI-MS). Further investigations indicate the presence of a 1:2 (metal/ligand) complex at higher concentrations ( approximately 10(-)(2) M). Selectivity studies as well as structural aspects are presented. 相似文献
925.
Roberta Collino Joël Therasse Frédéric Chaput Jean-Pierre Boilot Yves Levy 《Journal of Sol-Gel Science and Technology》1996,7(1-2):81-85
In this work we investigated the biological properties of sol-gel films in aqueous medium. Functionalized silica films were prepared by the sol-gel process, from organically modified silicon alkoxides with amino or thiol groups. Covalent binding of proteins with different orientations according to the hydrophilic or hydrophobic character of the surface was studied. This binding occurred via a covalent coupling agent providing a very stable linkage. No denaturation was detected and a good detection of the antigen was observed. Immunoassays have demonstrated the biological activity of grafted antibodies. 相似文献
926.
Bureau B Boussard-Plédel C LeFloch M Troles J Smektala F Lucas J 《The journal of physical chemistry. B》2005,109(13):6130-6135
Some resolved solid state (77)Se NMR spectra are presented in the Te(x)Se(1-x) vitreous system at ambient temperature. They exhibit three different kinds of Se lines assigned to the following Se atom neighborhoods: Se-Se-Se, Se-Se-Te, and Te-Se-Te. Different models were considered to describe the way the Se and Te atoms are linked into the chains: clustering process, homogeneous distribution, random distribution. Finally, thanks to the measurements of the relative intensities of the lines, it appears that Se and Te atoms are mainly randomly distributed with a small preference for heteropolar bonds. The (125)Te spectra are also shown but their resolution is too weak to be informative concerning the vitreous network. 相似文献
927.
928.
929.
930.
Ching Hsueh Frédéric Doumenc Béatrice Guerrier 《The European physical journal. Special topics》2013,219(1):51-57
A 2D model is currently under development to describe the flow and concentration fields inside a Hele-Shaw cell with evaporation for a receding meniscus (dip-coating-like configuration). An original approach is proposed to address the difficult problem of the boundary conditions close to the contact line. The model is used to study the deposit thickness as a function of some process parameters. 相似文献