全文获取类型
收费全文 | 608篇 |
免费 | 16篇 |
国内免费 | 3篇 |
专业分类
化学 | 403篇 |
晶体学 | 19篇 |
力学 | 30篇 |
数学 | 45篇 |
物理学 | 130篇 |
出版年
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 12篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 21篇 |
2012年 | 25篇 |
2011年 | 47篇 |
2010年 | 8篇 |
2009年 | 9篇 |
2008年 | 34篇 |
2007年 | 32篇 |
2006年 | 25篇 |
2005年 | 24篇 |
2004年 | 24篇 |
2003年 | 19篇 |
2002年 | 14篇 |
2001年 | 19篇 |
2000年 | 18篇 |
1999年 | 16篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 10篇 |
1994年 | 20篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 7篇 |
1990年 | 13篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 13篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 10篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1940年 | 2篇 |
排序方式: 共有627条查询结果,搜索用时 31 毫秒
31.
32.
Gerald Doyle 《Journal of organometallic chemistry》1975,101(1):85-91
Anionic complexes of the type [M(CO)4(dpet)]? (where M is Cr, Mo or W and dpet is the anion of 2-(diphenylphosphino)ethanthiol) are readily prepared by the reaction of the Tl(dpet) and [M(CO)5X]? anions (X = halogen). These complex anions appear to have the normal octahedral geometry with the dpet ligand coordinated through both the P and S atoms. When treated with methyl or allyl halides, neutral complexes of the type M(CO)4(dpet—R) are formed (where R is an allyl or methyl group now bound to the sulfur atom). By treating TlI salts of o-aminothiophenol (atp), o-methylmercaptophenol (nmp) and methylxanthic acid (mxt), with [M(CO)5]? anions, the respective complexes [M(CO)4(atp)]?, [M(CO)4(mmp)]? and [M(CO)5(mxt)]? are formed. 相似文献
33.
Bond AD Doyle EL García F Kowenicki RA McPartlin M Riera L Wright DS 《Chemical communications (Cambridge, England)》2003,(24):2990-2991
The in situ reaction of the phosphazane dimer [CIP(mu-N-2-NC5H4)]2 (2) with CuCl in the presence of CsH5N/H2O gives the title complex [(P(mu-N-2-NC5H4))2(mu-O)]2(CuCl x (C5H5N)2)4 (1), containing a tricyclic [(P(mu-N-2-NC5H4))2(mu-O)]2 ligand which is isoelectronic with species of the type [(P(mu-NR))2NR]2. 相似文献
34.
Doyle EL García F Humphrey SM Kowenicki RA Riera L Woods AD Wright DS 《Dalton transactions (Cambridge, England : 2003)》2004,(5):807-812
The reaction of [ClP(mu-NtBu)]2 (1) with H2O (1 : 2 equivalents) in the presence of excess Et3N gives the new chain compound [(mu-O)[P(mu-NtBu)2P(H)=O]2] (3), consisting of two P2N2 rings linked by a mu-O atom and terminating in P(V)(H)=O groups. A similar chain species is obtained from the reaction of the lithiate of [(tBuNH)P(mu-NtBu)2P(H)=O] (5) with [ClP(mu-NtBu)2P(NHtBu)] (2), the product being [(mu-O)[P(mu-NtBu)2P(NHtBu)]2] (6). Compounds 3 and 6 are the first examples of O-bridged chain phosphazanes and potential precursors to new phosphorus-nitrogen macrocycles. The syntheses and X-ray structures of 3, 5 and 6 are reported. 相似文献
35.
Ion flotation is a separation process involving the adsorption of a surfactant and counterions at an air/aqueous solution interface. It shows promise for removing toxic heavy metal ions from dilute aqueous solutions. Here we report the effect of a neutral chelating ligand, triethylenetetraamine (Trien), on the ion flotation of cations with dodecylsulfate, DS(-), introduced as sodium dodecylsulfate, SDS. Ion flotation in the aqueous SD-Cu(II)-Ca(II)-Trien system gave strongly preferential removal of Cu(II) over Ca(II), which is a reversal of the order of selectivity seen in the SDS-Cu(II)-Ca(II) system containing no Trien. The removal rates of Cu(2+) and Ni(2+) with DS(-) were much faster in the presence of Trien than for simple aquo ions, and the final metal concentration was significantly lower. Surface tension measurements showed that Trien enhanced the surface activity and adsorption density for SDS-Cu(II) and SDS-Ni(II) solutions. The overall change in the Gibbs free energy for adsorption resulting from complexation was -3.60 kJ/mol for Cu(II) and -3.50 kJ/mol for Ni(II). This included the effects of hydrophobic interactions between the metal-Trien complexes at the air/solution interface, along with changes in the amount of dehydration associated with cosorption of the metal-Trien complex with DS(-) at the air/solution interface. 相似文献
36.
The factors affecting the reflectance of an absorbing substance mixed with material not absorbing at the wavelength of measurement were investigated and it was found that the effect of particle size could be eliminated by prolonged grinding. It is shown that the percentage by weight of the absorbing substance is directly proportional to the quantity (A/R)1.383 (R = percentage reflectance ; A = 100 — R) and that this quantity is additive for 2 absorbing substances. A method is developed for the accurate determination of low concentrations of one and two absorbing substances mixed with non-absorbing material. The method is applicable to poorly crystallized substances which give no characteristic X-ray powder diffraction patterns as well as to crystalline solids. The reflectance of some substances is shown to be dependent on the previous history of the particular sample. The method is not applicable if there is physical interaction between the components of the mixture. 相似文献
37.
David Alker Kevin J. Doyle Laurence M. Harwood Andrew McGregor 《Tetrahedron: Asymmetry》1990,1(12):873-876
The preparation of the cyclic sulphamidate of (S)-prolinol has been achieved by reaction with sulphuryl chloride at low temperature. This material has been shown to be susceptible to acid catalysed nucleophilic attack to furnish 2-(NN-dialkylamino)methyl- and 2-(methoxymethy]pyrrolidines after hydrolysis of the intermediate sulphamic acid derivatives. 相似文献
38.
The development of a stereospecific synthesis of a key intermediate in the synthesis of (±)-zoapatanol from the Weiland-Miescher ketone is described. 相似文献
39.
40.