全文获取类型
收费全文 | 455篇 |
免费 | 24篇 |
国内免费 | 1篇 |
专业分类
化学 | 343篇 |
晶体学 | 1篇 |
力学 | 10篇 |
数学 | 17篇 |
物理学 | 102篇 |
无线电 | 7篇 |
出版年
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 11篇 |
2020年 | 6篇 |
2019年 | 12篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 30篇 |
2015年 | 10篇 |
2014年 | 8篇 |
2013年 | 24篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 26篇 |
2009年 | 23篇 |
2008年 | 33篇 |
2007年 | 30篇 |
2006年 | 20篇 |
2005年 | 28篇 |
2004年 | 18篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 7篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 5篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1957年 | 1篇 |
1898年 | 1篇 |
排序方式: 共有480条查询结果,搜索用时 62 毫秒
51.
Lin G Chen CH Pink M Pu J Li L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(35):9658-9668
Spore photoproduct (SP) is the exclusive DNA photodamage product found in bacterial endospores. Its photoformation and repair by a metalloenzyme spore photoproduct lyase (SPL) composes the unique SP biochemistry. Despite the fact that the SP was discovered almost 50 years ago, its crystal structure is still unknown and the lack of structural information greatly hinders the study of SP biochemistry. Employing a formacetal linker and organic synthesis, we successfully prepared a dinucleotide SP isostere 5R-CH(2) SP, which contains a neutral CH(2) moiety between the two thymine residues instead of a phosphate. The neutral linker dramatically facilitates the crystallization process, allowing us to obtain the crystal structure for this intriguing thymine dimer half a century after its discovery. Further ROESY spectroscopic, DFT computational, and enzymatic studies of this 5R-CH(2) SP compound prove that it possesses similar properties with the 5R-SP species, suggesting that the revealed structure truly reflects that of SP generated in Nature. 相似文献
52.
53.
Albrecht C Bode M Pérez JM Daniels J Schnakenburg G Streubel R 《Dalton transactions (Cambridge, England : 2003)》2011,40(11):2654-2665
Synthesis of the first oxaphosphirane chromium(0) and molybdenum(0) complexes of the type [{(R(1)PCH(R(2))-O}M(CO)(5)] (R(1) = C(5)Me(5)) (8a-e, 15a-e) and (R(1) = CH(SiMe(3))(2)) (9a-e, 16a-e) via reaction of dichloro(organo)- (1, 2, 10, 11) and chloro(organo)phosphane complexes (3,4,12) with lithium bases and aldehydes 7a-e is reported. Furthermore, bicyclic 1,3-oxaphospholane complexes 17 and 18 have been obtained via O-protonation of oxaphosphirane complexes 8a and 15a with HCl. All complexes were characterized by NMR, IR spectroscopic, mass spectrometric investigations and, in addition, single-crystal X-ray structures of complexes 8a-e, 9a,c, 15a,b,e, 16a-c, 17, 18 are presented and discussed. 相似文献
54.
Flores JA Andino JG Tsvetkov NP Pink M Wolfe RJ Head AR Lichtenberger DL Massa J Caulton KG 《Inorganic chemistry》2011,50(17):8121-8131
The ligand class 2,2'-pyridylpyrrolide is surveyed, both for its structural features and its electronic structure, when attached to monovalent K, Cu, Ag, Au, and Rh. The influence of pyrrolide ring substituents is studied, as well as the question of push/pull interaction between the pyridyl and pyrrolide halves. The π donor ability of the pyrrolide is found to be less than that of an analogous phenyl. However, in contrast to the phenyl analog, the HOMO is pyrrolide π in character for pyridylpyrrolide complexes of copper and rhodium, while it is conventionally metal localized for planar, d(8) rhodium pyridylphenyl. Monovalent three-coordinate copper complexes show great deviations from Y-shaped toward T-shaped structures, including cases where the pyridyl ligand bonds only weakly. 相似文献
55.
Rajca A Shiraishi K Boratyński PJ Pink M Miyasaka M Rajca S 《The Journal of organic chemistry》2011,76(20):8447-8457
Oxidation of diaryldiamine 2, a tetrahydrodiazapentacene derivative, provides diarylnitroxide diradical 1 accompanied by an intermediate nitroxide monoradical and a multitude of isolable diamagnetic products. DFT-computed tensors for EPR spectra and paramagnetic (1)H NMR isotropic shifts for nitroxide diradical 1 show good agreement with the experimental EPR spectra in rigid matrices and paramagnetic (1)H NMR spectra in solution, respectively. Examination of the diamagnetic products elucidates their formation via distinct pathways involving C-O bond-forming reactions, including Baeyer-Villiger-type oxidations. An unusual diiminoketone structure and two spirocyclic structures of the predominant diamagnetic products are confirmed by either X-ray crystallography or correlations between DFT-computed and experimental spectroscopic data such as (1)H, (13)C, and (15)N NMR chemical shifts and electronic absorption spectra. 相似文献
56.
An intimate interplay of O-H···O/C-H···F hydrogen bonds and π-π stacking interactions allows a phenyleneethynylene-based dendritic molecule to fold and self-assemble into two distinctively different molecular crystals as pseudopolymorphs. 相似文献
57.
Ts. Venkova T. Morek G. V. Martí H. Schnare A. Krämer-Flecken W. Gast A. Georgiev G. Hebbinghaus R. M. Lieder G. Sletten K. M. Spohr K. H. Maier W. Urban 《Zeitschrift für Physik A Hadrons and Nuclei》1993,344(4):417-423
Two new isomers have been observed in180Os. A high-K isomer withI, K ≧20 and a half-life ofT 1/2=12+4 ns have been established. It deexcites via two transitions into the 18+ level of the yrare band indicating an unusually smallK-hindrance factor. Evidence for an isomer withI, K>16 and a half-life ofT 1/2=41±10 ns was found. A half-life of 17±3 ns was measured for the previously known 7? state at 1862 keV. The decay scheme of the previously known 7? isomer at 1928 keV has been extended and a revised version is presented. 相似文献
58.
59.
J. Hernández F. Canal F. Dios L. Gastón 《International Journal of Infrared and Millimeter Waves》1988,9(3):295-301
Multilayer structures are of great interest in the fabrication of single mode devices for Integrated Optics. this work it is shown that a multilayer structure allows not only single-mode behaviour but it enhaces the non-reci procity of the quide. 相似文献
60.
A method is presented of measuring the force acting on a sample in the inhomogeneous part of the electronic field of a condensor. This paper describes a new method which is based upon the widely diverging values of the dielectric constants of most substances. 相似文献