全文获取类型
收费全文 | 361篇 |
免费 | 14篇 |
专业分类
化学 | 328篇 |
晶体学 | 3篇 |
力学 | 3篇 |
数学 | 5篇 |
物理学 | 36篇 |
出版年
2022年 | 4篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2016年 | 7篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 21篇 |
2011年 | 12篇 |
2010年 | 17篇 |
2009年 | 11篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 8篇 |
2002年 | 6篇 |
2000年 | 5篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 12篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 9篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 10篇 |
1968年 | 5篇 |
1967年 | 3篇 |
1966年 | 7篇 |
1930年 | 3篇 |
排序方式: 共有375条查询结果,搜索用时 15 毫秒
51.
Martin Tamm 《Acta Mathematica》1981,146(1):167-199
52.
Tibur Schmidlin Remo Gamboni Peter Strazewski Christoph Tamm 《Helvetica chimica acta》1983,66(6):1796-1805
The stereo- and regiochemical course in the [2+4]cycloaddition of the chiral alkylidene malonic ester 1 to selected derivatives of (2E, 4E)-4-methyl-2, 4-hexadien-l-ol ( 2 ) and (2E, 4E)-4-methyl-2, 4-hexadien-l-al ( 12 ) has been investigated. The results are discussed on the basis of semiquantitative PMO theory. 相似文献
53.
From cultures of Myrothecium roridum TODE ex FRIES 2′-dehydroverrucarin ( 1 ) was isolated. 1 is a genuin metabolite of the micro-organism. 相似文献
54.
55.
Ignat'eva DV Goryunkov AA Tamm NB Ioffe IN Avdoshenko SM Sidorov LN Dimitrov A Kemnitz E Troyanov SI 《Chemical communications (Cambridge, England)》2006,(16):1778-1780
Two isomers of C70(CF3)12 have been isolated from a mixture obtained by trifluoromethylation of C70 with CF3I; their molecular structures determined by X-ray crystallography are in good agreement with the results of theoretical DFT calculations for the most stable C70(CF3)12 isomers. 相似文献
56.
Ludwig Hackl Dr. Alex R. Petrov Dr. Thomas Bannenberg Dr. Matthias Freytag Prof. Dr. Peter G. Jones Prof. Dr. Matthias Tamm 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16148-16155
The reaction of 1,2-dipiperidinoacetylene ( 1 ) with 0.5 equivalents of SnCl2 or GeCl2⋅dioxane afforded the 1,2,3,4-tetrapiperidino-1,3-cyclobutadiene tin and germanium dichloride complexes 2 a and 2 b , respectively. A competing redox reaction was observed with excess amounts of SnCl2, which produced a tetrapiperidinocyclobutadiene dication with two trichlorostannate(II) counterions. Heating neat 1 to 110 °C for 16 h cleanly produced the dimer 1,3,4,4-tetrapiperidino-3-buten-1-yne ( 3 ); its reaction with stoichiometric amounts of SnCl2 or GeCl2⋅dioxane furnished the 1,3,4,4-tetrapiperidino-1,2-cyclobutadiene tin and germanium dichloride complexes 4 a and 4 b , respectively. Transition-metal complexes containing this novel four-membered cyclic bent allene (CBA) ligand were prepared by reaction of 3 with [(tht)AuCl], [RhCl(CO)2]2, and [(Me3N)W(CO)5] to form [(CBA)AuCl] ( 5 ), [(CBA)RhCl(CO)2] ( 6 ), and [(CBA)W(CO)5] ( 7 ). The molecular structures of all compounds 2 – 7 were determined by X-ray diffraction analyses, and density functional theory (DFT) calculations were carried out to rationalise the formation of 3 and 4 a . 相似文献
57.
Facile Separation,Spectroscopic Identification,and Electrochemical Properties of Higher Trifluoromethylated Derivatives of [70]Fullerene 下载免费PDF全文
Maria P. Kosaya Alexey V. Rybalchenko Dr. Natalia S. Lukonina Olga N. Mazaleva Dr. Ilya N. Ioffe Dr. Vitaliy Yu. Markov Prof. Dr. Sergey I. Troyanov Prof. Dr. Lev N. Sidorov Dr. Nadezhda B. Tamm Dr. Alexey A. Goryunkov 《化学:亚洲杂志》2018,13(15):1920-1931
We survey the structure and electronic properties of the family of higher trifluoromethylated C70(CF3)n molecules with n=14, 16, 18, and 20. Twenty‐two available compounds, of which thirteen are newly obtained and characterized, demonstrate the broad diversity of π‐system topologies, which enabled us to study the interplay between the CF3 addition pattern and the electronic properties. UV/Vis spectroscopic and cyclic voltammetric studies demonstrate the importance of the exact addition pattern rather than the plain number of addends. Of particular interest is the skew pentagonal pyramid (SPP) addition pattern, which enables formation of closed‐shell cyclopentadienyl anions C70(CF3)n? 1 ? through CF3 detachment upon electron transfer. A detailed study of the process is presented for a SPP‐C70(CF3)16 where potentiostatic electrolysis at the second reduction potential gives C70(CF3)15? oxidizable to a persistent C70(CF3)15· radical. Together with the literature data for the lower C70(CF3)n compounds with n=2–12, the present results show good correlation between the experimental boundary level positions and the DFT predictions. The compounds turn out to be electron acceptor molecular semiconductors with experimental LUMO energies and HOMO–LUMO gaps within the ranges of ?4.3 to ?3.7 eV and 1.6 to 3.3 eV, respectively, depending on the shape of the conjugated fragments. The HOMO levels fall within the range of ?5.6 to ?6.9 eV and show linear correlation with the number of addends. 相似文献
58.
W Graf J L Robert J C Vederas C Tamm P H Solomon I Miura N Nakanishi 《Helvetica chimica acta》1974,57(6):1801-1815
Sequential single frequency decoupling and partially relaxed Fourier transform (PRFT) are used to assign the natural abundance 13C-NMR. spectra of cytochalasin B (phomin) ( 1 ) and cytochalasin D ( 2 ). Cultures of Phoma spec. S 298 were fed [2-13C]-sodium acetate, and the distribution of this precursor in cytochalasin B (phomin) ( 1 ) was determined by 13C-NMR. spectroscopy. Likewise, the labelling patterns in cytochalasin D (zygosporin A) ( 2 ) from Zygos-posium masonii could be identified after incorporation of [2-13C]-sodium acetate and [l-13C]-sodium acetate. The results confirm previous proposals for the biogenesis of the cytochalasans from phenylalanine, methionine, and a C18, or C16, polyketide part. 相似文献
59.
Room-temperature ring-closing alkyne metathesis of 1,2-, 1,3-, and 1,4-bis(3-pentynyloxymethyl)benzenes has been investigated in the presence of catalytic amounts of an imidazolin-2-iminato tungsten alkylidyne complex. The m- and p-diynes selectively form the respective [10]metacyclophane or [10.10]paracyclophane, respectively, whereas a mixture of monomeric and dimeric cycloalkynes is obtained in the case of the o-diyne. DFT calculations reveal that the different selectivities can be attributed to the relative thermodynamic stability of the emerging cyclophanes. 相似文献