全文获取类型
收费全文 | 1036篇 |
免费 | 44篇 |
国内免费 | 1篇 |
专业分类
化学 | 768篇 |
晶体学 | 10篇 |
力学 | 31篇 |
数学 | 143篇 |
物理学 | 129篇 |
出版年
2023年 | 9篇 |
2022年 | 14篇 |
2021年 | 13篇 |
2020年 | 38篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 29篇 |
2014年 | 17篇 |
2013年 | 50篇 |
2012年 | 55篇 |
2011年 | 71篇 |
2010年 | 27篇 |
2009年 | 36篇 |
2008年 | 56篇 |
2007年 | 55篇 |
2006年 | 42篇 |
2005年 | 57篇 |
2004年 | 41篇 |
2003年 | 38篇 |
2002年 | 42篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 7篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 23篇 |
1995年 | 10篇 |
1994年 | 10篇 |
1993年 | 11篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 15篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1977年 | 11篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 11篇 |
1972年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有1081条查询结果,搜索用时 31 毫秒
81.
A. Cameron Church James H. Pawlow Kenneth B. Wagener 《Journal of organometallic chemistry》2001,620(1-2)
Various nucleophiles were reacted with the substrate di-n-hexyldichlorosilane as model reactions for the substitution of two geminal Si---Cl bonds on polymer backbone repeat units. The reactants examined were chosen on the basis of steric bulk, electronic factors, and resulting stability of the product. Linear and branched alcohol nucleophiles used in conjunction with an amine proton acceptor produced disubstituted products in moderate yields, whereas bulkier reagents substituted only one silicon---chlorine bond. Due to their vastly increased nucleophilicity, alkyllithium reagents were found to have increased activity and were found to produce very high yields. 相似文献
82.
Boyer Steven; Gordon Cameron McA.; Zhang Xingru 《Journal London Mathematical Society》2009,79(1):72-84
We show that the distance between a finite filling slope anda reducible filling slope on the boundary of a hyperbolic knotmanifold is one. 相似文献
83.
D. Mohan Ganga Radhakrishnan S. Rajadurai K. Venkata Rao Gordon G. Cameron 《Journal of polymer science. Part A, Polymer chemistry》1989,27(6):2123-2133
Polyacrylamide has been grafted onto casein in phosphate buffer medium using potassium peroxodisulfate as initiator. The influence of synthetic variables on percent grafting, grafting efficiency, rates of conversion of monomer, and the rates of graft copolymerization have been discussed. A possible kinetic scheme based on experimental results has been derived. 相似文献
84.
Alexander Thomas Cameron und Basil Charles McEwan 《Fresenius' Journal of Analytical Chemistry》1912,51(6):391
Ohne Zusammenfassung 相似文献
85.
A. Saifer M. Kornblum S. P. Worden I. B. Rushing I. P. Barnes A. P. Surer M. Farren Greta Hammarsten B. Melichar L. Vsetecka S. A. Poworinskaja Raimonde Duval J. M. Le Goff E. Justin-Mueller G. Haslewood E. King A. T. Cameron J. S. Guthrie F. D. White Th. Findley Regine Kapeller-Adler N. P. Meschkowa Rangier Lafrançaise P. A. Clifford H. J. Wichmann F. Timm E. Komm F. Kiermeier und A. Douglas-Sauermann 《Fresenius' Journal of Analytical Chemistry》1938,115(7-8):296-300
Ohne Zusammenfassung 相似文献
86.
Recursive formulas are presented that give the number of order conditions for single-step Runge–Kutta methods for index 2 DAEs. 相似文献
87.
88.
89.
Simon J. Bonyhady Cameron Jones Prof. Sharanappa Nembenna Dr. Andreas Stasch Dr. Alison J. Edwards Dr. Garry J. McIntyre Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(3):938-955
The preparation and characterization of a series of magnesium(II) iodide complexes incorporating β‐diketiminate ligands of varying steric bulk and denticity, namely, [(ArNCMe)2CH]? (Ar=phenyl, (PhNacnac), mesityl (MesNacnac), or 2,6‐diisopropylphenyl (Dipp, DippNacnac)), [(DippNCtBu)2CH]? (tBuNacnac), and [(DippNCMe)(Me2NCH2CH2NCMe)CH]? (DmedaNacnac) are reported. The complexes [(PhNacnac)MgI(OEt2)], [(MesNacnac)MgI(OEt2)], [(DmedaNacnac)MgI(OEt2)], [(MesNacnac)MgI(thf)], [(DippNacnac)MgI(thf)], [(tBuNacnac)MgI], and [(tBuNacnac)MgI(DMAP)] (DMAP=4‐dimethylaminopyridine) were shown to be monomeric by X‐ray crystallography. In addition, the related β‐diketiminato beryllium and calcium iodide complexes, [(MesNacnac)BeI] and [{(DippNacnac)CaI(OEt2)}2] were prepared and crystallographically characterized. The reductions of all metal(II) iodide complexes by using various reagents were attempted. In two cases these reactions led to the magnesium(I) dimers, [(MesNacnac)MgMg(MesNacnac)] and [(tBuNacnac)MgMg(tBuNacnac)]. The reduction of a 1:1 mixture of [(DippNacnac)MgI(OEt2)] and [(MesNacnac)MgI(OEt2)] with potassium gave a low yield of the crystallographically characterized complex [(DippNacnac)Mg(μ‐H)(μ‐I)Mg(MesNacnac)]. All attempts to form beryllium(I) or calcium(I) dimers by reductions of [(MesNacnac)BeI], [{(DippNacnac)CaI(OEt2)}2], or [{(tBuNacnac)CaI(thf)}2] have so far been unsuccessful. The further reactivity of the magnesium(I) complexes [(MesNacnac)MgMg(MesNacnac)] and [(tBuNacnac)MgMg(tBuNacnac)] towards a variety of Lewis bases and unsaturated organic substrates was explored. These studies led to the complexes [(MesNacnac)Mg(L)Mg(L)(MesNacnac)] (L=THF or DMAP), [(MesNacnac)Mg(μ‐AdN6Ad)Mg(MesNacnac)] (Ad=1‐adamantyl), [(tBuNacnac)Mg(μ‐AdN6Ad)Mg(tBuNacnac)], and [(MesNacnac)Mg(μ‐tBu2N2C2O2)Mg(MesNacnac)] and revealed that, in general, the reactivity of the magnesium(I) dimers is inversely proportional to their steric bulk. The preparation and characterization of [(tBuNacnac)Mg(μ‐H)2Mg(tBuNacnac)] has shown the compound to have different structural and physical properties to [(tBuNacnac)MgMg(tBuNacnac)]. Treatment of the former with DMAP has given [(tBuNacnac)Mg(H)(DMAP)], the X‐ray crystal structure of which disclosed it to be the first structurally authenticated terminal magnesium hydride complex. Although attempts to prepare [(MesNacnac)Mg(μ‐H)2Mg(MesNacnac)] were not successful, a neutron diffraction study of the corresponding magnesium(I) complex, [(MesNacnac)MgMg(MesNacnac)] confirmed that the compound is devoid of hydride ligands. 相似文献
90.
Helmich F Lee CC Schenning AP Meijer EW 《Journal of the American Chemical Society》2010,132(47):16753-16755
Chiral memory at the supramolecular level is obtained via a new approach using chiral Zn porphrins and achiral Cu porphyrins. In a "sergeant-and-soldiers" experiment, the Zn "sergeant" transfers its own chirality to Cu "soldiers" and, after chiral amplification, the "sergeant" is removed from the coaggregates by axial ligation with a Lewis base. After this extraction, the preferred helicity observed for the aggregates containing achiral Cu porphyrins reveals a chiral memory effect that is stable and can be erased and partially restored upon subsequent heating and cooling. 相似文献