全文获取类型
收费全文 | 269篇 |
免费 | 2篇 |
国内免费 | 4篇 |
专业分类
化学 | 143篇 |
晶体学 | 1篇 |
力学 | 14篇 |
数学 | 57篇 |
物理学 | 60篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2020年 | 6篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2014年 | 6篇 |
2013年 | 15篇 |
2012年 | 15篇 |
2011年 | 12篇 |
2010年 | 4篇 |
2009年 | 5篇 |
2008年 | 12篇 |
2007年 | 4篇 |
2006年 | 13篇 |
2005年 | 5篇 |
2004年 | 7篇 |
2003年 | 12篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1975年 | 3篇 |
1969年 | 2篇 |
1936年 | 2篇 |
1928年 | 2篇 |
1893年 | 2篇 |
排序方式: 共有275条查询结果,搜索用时 15 毫秒
1.
2.
3.
J. D. Lamb F. R. Nordmeyer R. G. Smith A. Van Orden R. Allison R. P. Lash 《Journal of Radioanalytical and Nuclear Chemistry》1992,159(2):285-292
Ion chromatography (IC) can be used to separate radioiodine from fission products and other ionic species in complex reprocessing solution matrices. A preliminary concentration and separation of the radioiodine is performed using a column filled with a platinum-coated copper bed which converts all forms of iodine to iodide and selectively adsorbs the iodide. The separation is completed by employing an anion chromatographic system. The iodide peak aliquot is collected for subsequent radioanalysis by low energy photon spectroscopy. Results indicate quantitative separation and recovery of iodine. The entire system is automated under computer control and is able to handle small (l) and large (500 ml) sample sizes. 相似文献
4.
5.
N-Heterocyclic carbenes (NHCs) are an important class of reactive organic molecules used as ligands, organocatalysts, and σ-donors in a variety of electroneutral ylide or betaine adducts with main-group compounds. An emerging class of betaine adducts made from the reaction of NHCs with carbodiimides (CDIs) form zwitterionic amidinate-like structures with tunable properties based on the highly modular NHC and CDI scaffolds. The adduct stability is controlled by the substituents on the CDI nitrogens, while the NHC substituents greatly affect the configuration of the adduct in the solid state. This Perspective is intended as a primer to these adducts, touching on their history, synthesis, characterization, and general properties. Despite the infancy of the field, NHC–CDI adducts have been applied as amidinate-type ligands for transition metals and nanoparticles, as junctions in zwitterionic polymers, and to stabilize distonic radical cations. These applications and potential future directions are discussed. N-heterocyclic carbene-carbodiimide betaine adducts are zwitterionic amidinate-like structures with tunable properties that have applications as ligands, junctions in supramolecular polymers, and stabilizers for radical cations. 相似文献
6.
7.
Sanford TW Allshouse GO Marder BM Nash TJ Mock RC Spielman RB Seamen JF McGurn JS Jobe D Gilliland TL Vargas M Struve KW Stygar WA Douglas MR Matzen MK Hammer JH De Groot JS Eddleman JL Peterson DL Mosher D Whitney KG Thornhill JW Pulsifer PE Apruzese JP Maron Y 《Physical review letters》1996,77(25):5063-5066
8.
Jerald S. Bradshaw Ralph B. Nielsen Pui-Kwan Tse Giuseppi Arena Bruce E. Wilson N. Kent Dalley John D. Lamb James J. Christensen Reed M. Izatt 《Journal of heterocyclic chemistry》1986,23(2):361-368
A series of macrocyclic polyether (crown) ligands containing the proton-ionizable s-triazole subcyclic unit were prepared by reacting the 1-THP blocked 3,5-bis(chloromethyl)-1H-1,2,4-triazole with various oligoethylene glycols. The starting bis(chloromethyl)triazole is a vessicant and must be used with caution. Triazolo-18-crown-6 ( 5 ) formed stable complexes with barium, strontium, copper and benzylammonium cations but not with potassium or lithium. The crystal structure of 5 showed the triazole proton to be on nitrogen 3 which is outside the macroring cavity. 相似文献
9.
Jan F. Biernat Maria Bochenska Jerald S. Bradshaw Hiroyuki Koyama Gypzy Lindh John D. Lamb James J. Christensen Reed M. Izatt 《Journal of inclusion phenomena and macrocyclic chemistry》1987,5(6):729-738
Five new macrocyclic ligands each containing two sulfonamide groups have been prepared. Three of these compounds contain one or two chloro substituents and the other two have one or two pyridine subcyclic units. A seventeen-membered ring ligand (4) was found to be an excellent transport agent for all alkali metal cations in a water-methylene chloride-water bulk liquid membrane system when the pH of the source phase was 13 or higher. The chlorine-substituted analog (5) was a poor transport agent for the alkali metal cations possibly because the chlorine atom blocked entry to the macrocycle cavity. An open-chain analog containing two sulfonamide groups was particularly effective in transporting cesium ions. 相似文献
10.
The first isolation of a phosphonium amide, (Ph3PEt)+(NPh2)−, obtained via the deprotonation of a secondary amine (diphenylamine) with a phosphorus ylide (triphenylphosphonium ethylide), is described. An X-ray crystal structure provides the first observation of an essentially ion-separated Ph2N− anion in the solid state, though weak association with Ph3PEt+ cations take plac through C---H…N hydrogen bonding. Cryoscopic and NMR spectroscopic data suggest that this association is not maintained in benzene solution. 相似文献