全文获取类型
收费全文 | 1482篇 |
免费 | 62篇 |
国内免费 | 7篇 |
专业分类
化学 | 1059篇 |
晶体学 | 4篇 |
力学 | 32篇 |
数学 | 159篇 |
物理学 | 297篇 |
出版年
2022年 | 15篇 |
2021年 | 11篇 |
2020年 | 36篇 |
2019年 | 28篇 |
2018年 | 19篇 |
2017年 | 12篇 |
2016年 | 46篇 |
2015年 | 50篇 |
2014年 | 46篇 |
2013年 | 54篇 |
2012年 | 74篇 |
2011年 | 71篇 |
2010年 | 40篇 |
2009年 | 47篇 |
2008年 | 69篇 |
2007年 | 61篇 |
2006年 | 62篇 |
2005年 | 60篇 |
2004年 | 57篇 |
2003年 | 58篇 |
2002年 | 56篇 |
2001年 | 41篇 |
2000年 | 20篇 |
1999年 | 16篇 |
1998年 | 14篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 23篇 |
1994年 | 31篇 |
1993年 | 27篇 |
1992年 | 30篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1979年 | 8篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1974年 | 16篇 |
1972年 | 12篇 |
1967年 | 7篇 |
1966年 | 14篇 |
1943年 | 8篇 |
1927年 | 7篇 |
排序方式: 共有1551条查询结果,搜索用时 0 毫秒
1.
2.
3.
4.
5.
Ammar R Ball RC Banerjee S Bhat PC Bosetti P Bromberg C Canough GE Coffin T Dershem TO Dixon RL Fenker HC Ganguli SN Gensch U Girtler P Goshaw AT Grard F Gurtu A Hamilton C Henri VP Hernandez JJ Hrubec J Iori M Jones LW Kuhn D Knauss D Leedom ID Legros P Lemonne J Leutz H Liu X Malhotra PK Marraffino JM Mendez GE Miller R Naumann T Nguyen A Nowak H Pilette P Poirier J Poppleton A Raghavan R Rasner K Reucroft S Robertson WJ Roe BP Roth A Senko M Struczinski W Subramanian A Touboul MC Vonck B 《Physical review letters》1988,61(19):2185-2188
6.
Chiral separations by host-guest complexation with cyclodextrin and crown ether in capillary zone electrophoresis 总被引:2,自引:0,他引:2
Summary Capillary zone electrophoresis using cyclodextrins and a chiral crown ether as buffer constituents was studied for the enantiomeric separation of drugs and amino acids. Based on results obtained from separation of racemic -amino acids both chiral selectors are compared with respect to resolution, efficiency and retention time. For (±)-Quinagolide effects of buffer composition and temperature are examined using -cyclodextrin as chiral agent. Optimum conditions were pH 2.5 at 30 mmol L–1 -cyclodextrin. A linear dependence of retention on -cyclodextrin concentration allowed calculation of formation constants of the host-guest complexes. Buffer concentration and temperature also influence resolution. The application of a chiral crown ether to the separation of optical isomers in capillary zone electrophoresis is described for the first time. Chiral recognition of solutes depends on the formation of protonated alkyl amines and separation is attributed to the formation of diastereomeric host-guest complexes with different interactions for each enantiomer. The effects of crown ether concentration on resolution are presented. 相似文献
7.
S. Banerjee S. N. Ganguli A. Gurtu R. Raghavan A. Subramanian Y. Goldschmidt-Clermont R. T. Ross S. Squarcia K. Dziunikowska T. Haupt P. Girtler D. Kuhn K. W. J. Barnham J. Wells P. R. S. Wright J. Macnaughton F. Mandl F. Shabaan M. Bardadin-Otwinowska M. Szczekowski 《Zeitschrift fur Physik C Particles and Fields》1986,31(3):401-408
Results on inclusive ? production inK ? p interactions at 110 GeV/c are presented. The production cross section is found to be larger than in πp andpp interactions at similar energies, suggesting OZI allowed \(s\bar s\) fusion to be the dominant mechanism in ? production. Thex distributions of ? and \(\bar K^{*0} \) are found to be similar to each other over the entirex range suggesting an overall strangeness suppression factor of 0.20±0.04 in the sea to be the dominant source of the difference in the cross section for ? and \(\bar K^{*0} \) . There is no evidence of a narrowφπ ? state around 2.1 GeV/c2 as suggested byK + experiments, but there is some excess of events in the region 1.94?1.98 GeV/c2 consistent with theF-meson mass as observed ine + e ? experiments. 相似文献
8.
Transition metal heteropolyanions have been used to catalyze a variety of organic oxidations but have not previously been used for O2 generation, despite sharing some structural similarities with dioxoruthenium water-oxidation catalysts. In this study, we report that the di-Ru-substituted polyoxometalate (POM) [Ru2Zn2(H2O)2(ZnW9O34)2]14- can be used to catalyze the electrochemical generation of O2. By comparing the behavior of this compound to that observed using a mono-Ru-substituted POM catalyst, we show that adjacent Ru sites are necessary to observe O2 generation. These observations suggest a reaction pathway involving two Ru-bound oxygen species combining to form O2 and are consistent with the accepted mechanism of electrochemical oxygen evolution. Finally, analysis of the observed electrode kinetics yields a Tafel slope of roughly 120 mV, which is similar to values reported previously for perovskite anodes. 相似文献
9.
10.
Paul H. Chen William F. Kuhn Fritz Will Robert M. Ikeda 《Journal of mass spectrometry : JMS》1970,3(2):199-209
The mass spectra of three bicyclic γ-lactones have been studied, and the fragmentation pathways have been proposed with the aid of accurate mass measurements and metastable transitions. An unusually low [M ? CH3] ion and the presence of an abundant [M ? C5H9] ion in the mass spectrum of dihydroactinidiolide were interpreted as a possible rearrangement involving a methyl migration. The eliminations of methyl radical, carbon monoxide and ketene are important processes in many cases. 相似文献