全文获取类型
收费全文 | 656篇 |
免费 | 9篇 |
国内免费 | 5篇 |
专业分类
化学 | 456篇 |
晶体学 | 14篇 |
力学 | 15篇 |
数学 | 86篇 |
物理学 | 99篇 |
出版年
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2016年 | 13篇 |
2015年 | 6篇 |
2014年 | 11篇 |
2013年 | 34篇 |
2012年 | 32篇 |
2011年 | 43篇 |
2010年 | 17篇 |
2009年 | 24篇 |
2008年 | 33篇 |
2007年 | 39篇 |
2006年 | 38篇 |
2005年 | 24篇 |
2004年 | 20篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 12篇 |
1996年 | 7篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 12篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 6篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 5篇 |
排序方式: 共有670条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
Bond IA Budding E Conway MJ Fenton KB Fujii H Fujii Z Fujimoto M Hasegawa H Hayashida N Honda M Hotta N Humble JE Kabe S Kasahara K Kifune T Masaike A Matsubara Y Mitsui K Miura Y Mori M Murakami K Muraki Y Nagano M Nakamura K Nakamura T Norris PM Ohashi Y Okada A Saito T Sakata M Sato H Shibata S Shima M Storey JR Tanimori T Teshima M Torii S Uchino K Watase Y Woodhams MD Yamamoto Y Yock PC Yuda T 《Physical review letters》1988,61(20):2292-2295
6.
Stulz E Scott SM Ng YF Bond AD Teat SJ Darling SL Feeder N Sanders JK 《Inorganic chemistry》2003,42(20):6564-6574
The synthesis of linear multiporphyrin arrays with mono- and bisphosphine-substituted porphyrins as ligand donors and ruthenium(II) or rhodium(III) porphyrins as ligand acceptors is described. With appropriate amounts of the building blocks mixed, linear dimeric and trimeric arrays have been synthesized and analyzed by (1)H NMR and (31)P NMR spectroscopy. The Ru/Rh acceptor porphyrins can be located either at the periphery or in the center of the array. Likewise, the monophosphine porphyrins can be positioned at the periphery, thus allowing a high degree of freedom in the overall composition of the arrays. This way, both donor and acceptor porphyrins can act as chain extenders or terminators. One of the trimeric complexes with two nickel and one ruthenium porphyrin has also been analyzed by X-ray crystallography. Attempts have also been made to synthesize higher order arrays by mixing appropriate amounts of the porphyrins; however, from the NMR data it cannot be concluded if monodisperse five, seven, or nine porphyrin arrays are present or if the solutions are composed of a statistical mixture of smaller and larger arrays. 相似文献
7.
Investigations of the “classical” cadmium(II) bromide and iodide complex ion systems show conclusively that in the presence of moderately strong anion-induced adsorption, apparent polarographic stability constants are larger than those determined by other methods such as potentiometry. Such systems can exhibit seemingly normal d.c. polarographic behaviour, but adsorption is readily detected by a.c. methods. The authors therefore strongly recommend that in systems in which adsorption is detected, polarography should not be used to determine stability constants. Theoretical approaches to explain the observed phenomena are discussed and it is concluded that apparently differing approaches that have appeared in the literature are in fact equivalent. 相似文献
8.
S. A. Rod’kina 《Chemistry of Natural Compounds》2007,43(5):515-518
The fatty-acid (FA) composition of total lipids from the Okhotsk sea marine sponge Forcepia uschakowi was studied. A total of 56 acids were identified by GC and GC—MS. The principal saturated acids were 16∶0 and 18∶0. The main
monoene acid was 15-Me-24∶1(14), which was observed for the first time in sponge lipids. Polyunsaturated acids represented
of 64.1% of the total FA of F. uschakowi. Of these, the principal ones were non-methylene-separated acids 26∶2(5,9) and 26∶3(5,9,19), which are typical of sponges,
and bromo-acid 6-Br-26∶2(5,9).
__________
Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 422–424, September–October, 2007. 相似文献
9.
Bond AD García F Jantos K Lawson GT McPartlin M Wright DS 《Chemical communications (Cambridge, England)》2002,(12):1276-1277
The novel, deca-lithium cage [(mtaNHLi)(As2(Nmta)5)-Li(4).2thf]2 (1) (mtaN = 5-methylthiazolyl, C4H4N2S) contains an imido-bridged tetraanion [(mtaN)2As(mu-Nmta)-As(Nmta)2]4-, which represents a new type of multi-functional imido group 15 ligand framework (homologous with group 15 anions of the type [As(NR)3]3-). 相似文献
10.
Bashall A Bond AD Doyle EL García F Kidd S Lawson GT Parry MC McPartlin M Woods AD Wright DS 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(15):3377-3385
Amination of [ClP(micro-NtBu)](2) (1) using NH(3) in THF gives the cyclophospha(III)zane dimer [H(2)NP(micro-NtBu)](2) (2), in good yield. (31)P NMR spectroscopic studies of the reaction of 1 with 2 in THF/Et(3)N show that almost quantitative formation of the cyclic tetramer [[P(micro-NtBu)](2)(micro-NH)](4) (3) occurs. The remarkable selectivity of this reaction can (in part) be attributed to pre-organisation of 1 and 2, which prefer cis arrangements in the solid state and solution. The macrocycle 3 can be isolated in yields of 58-67 % using various reaction scales. The isolation of the major by-product of the reaction (ca. 0.5-1 % of samples of 3), the pentameric, host-guest complex [[P(micro-NtBu)(2)](2)(micro-NH)](5)(HCl).2 THF] (4.2 THF), gives a strong indication of the mechanism involved. In situ (31)P NMR spectroscopic studies support a stepwise condensation mechanism in which Cl(-) ions play an important role in templating and selection of 3 and 4. Amplification of the pentameric arrangement occurs in the presence of excess LiX (X=Cl, Br, I). In addition, the cyclisation reaction is solvent- and anion-dependent. The X-ray structures of 2 and 4.2 THF are reported. 相似文献