全文获取类型
收费全文 | 345篇 |
免费 | 1篇 |
专业分类
化学 | 186篇 |
晶体学 | 3篇 |
力学 | 7篇 |
数学 | 42篇 |
物理学 | 108篇 |
出版年
2021年 | 2篇 |
2019年 | 3篇 |
2017年 | 3篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 3篇 |
2011年 | 19篇 |
2010年 | 2篇 |
2009年 | 4篇 |
2008年 | 9篇 |
2007年 | 18篇 |
2006年 | 8篇 |
2005年 | 13篇 |
2004年 | 5篇 |
2003年 | 12篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 11篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 15篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1966年 | 3篇 |
1965年 | 2篇 |
1938年 | 2篇 |
1933年 | 2篇 |
1932年 | 2篇 |
1925年 | 2篇 |
排序方式: 共有346条查询结果,搜索用时 15 毫秒
121.
S. R. Trotman J. M. Kolthoff G. S. Buchanan S. B. Schryver A. Schotte F. Kirchhof P. Krais G. Neumann und E. C. Hendrickson 《Fresenius' Journal of Analytical Chemistry》1933,94(1-2):72-77
Ohne Zusammenfassung 相似文献
122.
123.
Sodium dodecyl sulphate-polyacrylamide gel electrophoresis of human parotid salivary proteins. 总被引:4,自引:0,他引:4
J A Beeley D Sweeney J C Lindsay M L Buchanan L Sarna K S Khoo 《Electrophoresis》1991,12(12):1032-1041
The proteins in human parotid saliva have been separated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis into 20 or more well resolved species. The Coomassie Brilliant Blue (CBB) R-250 and silver staining procedures have been modified to overcome the problems encountered with staining of proline-rich proteins. By means of the CBB R-250 procedure which stains proline-rich proteins pink-violet, immunoblotting, concanavalin A binding, periodate-Schiff staining and zinc binding, all of the major proteins have been characterised. Substantial individual-to-individual differences were observed in the protein patterns formed. Comparison of parotid, submandibular, and whole saliva from a single individual indicated that fewer proline-rich proteins are expressed in submandibular saliva than in parotid, but whole saliva contains much lower levels than either duct secretion. The results will form a useful base for future research into the functions of salivary proteins. 相似文献
124.
Overlayer experiments show that the 3.8 eV satellite in X-ray photoemission from silver is due almost entirely to the excitation of extrinsic surface plasmons. 相似文献
125.
Acid, aldehyde and carbon dioxide were the major products of the vacuum photodegradations of poly(vinyl acetate) (PVAC), poly(vinyl propanoate) (PVPR) and poly(ethylene-co-vinyl acetate) (PEVAC). Aldehydes have not previously been reported as formed from the acid portions of esters undergoing photolysis. The generality of aldehyde formation has been demonstrated by the detection of the respective aldehydes in the liquid-phase photolysis of butane-1,3-diol diacetate (BDAC) and butane-1,3-diol dipropanoate (BDPR) in this study, which is the first to report the quantum yields for acid and aldehyde formation in low molecular mass esters. Two mechanisms, one involving hydrogen abstraction by the acyl radical formed in a Norrish Type I cleavage process and the other involving an intramolecular hydrogen abstraction by an excited carbonyl group followed by fragmentation, have been proposed to account for aldehyde formation. The absence of propanal from the product distribution in the photo-oxidation of PVPR could be explained by both mechanisms. 相似文献
126.
E and Z 2-phenylcyclopropyl bromides react with the title reagents to yield E and Z cinnamyl acetates respectively. No reaction is observed when halide nucleophiles or other aprotic solvents are used suggesting a novel mechanistic role for the acetate ion. 相似文献
127.
128.
Transition structures have been optimised using the B3LYP/6-31+G* density functional level method, in vacuum and in implicit (PCM) and explicit (DFT/MM) aqueous solvation, for the degenerate rearrangement of the alpha-lactone derived by the formal addition of Cl(+) to acrylate anion and for the dyotropic rearrangement of this to the beta-lactone. Despite being lower in energy than the alpha-lactone, there is no direct pathway to the beta-lactone from the acrylate chloronium zwitterion, which is the transition structure for the degenerate rearrangement. This may be rationalised by consideration of the unfavorable angle of attack by the carboxylate nucleophile on the beta-position; attack on the alpha-position involves a less unfavorable angle. Formation of the beta-lactone may occur by means of a dyotropic rearrangement of the alpha-lactone. This involves a high energy barrier for the acrylate derived alpha-lactone, but dyotropic rearrangement of the beta,beta-dimethyl substituted alpha-lactone to the corresponding beta-lactone involves a much lower barrier, estimated at about 46 kJ mol(-1) in water, and is predicted to be a facile process. 相似文献
129.
Dr. Kritika Bajaj Dr. Sarah A. Andres Dr. Dillon T. Hofsommer Okolocha Chekwube Michael Dr. Mark S. Mashuta Prof. Paula J. Bates Prof. Robert M. Buchanan Prof. Craig A. Grapperhaus 《欧洲无机化学杂志》2023,26(34):e202300447
A series of isomeric bis(alkylthiocarbamate) copper complexes have been synthesized, characterized, and evaluated for antiproliferation activity. The complexes were derived from ligand isomers with 3-methylpentyl (H2L2) and cyclohexyl (H2L3) backbone substituents, which each yield a pair of linkage isomers. The thermodynamic products CuL2a/3a have two imino N and two S donors resulting in three five-member chelate rings (555 isomers). The kinetic isomers CuL2b/3b have one imino and one hydrazino N donor and two S donors resulting in four-, six-, and five-member rings (465 isomers). The 555 isomers have more accessible CuII/I potentials (E1/2=−811/−768 mV vs. ferrocenium/ferrocene) and lower energy charge transfer bands than their 465 counterparts (E1/2=−923/-854 mV). Antiproliferation activities were evaluated against the lung adenocarcinoma cell line (A549) and nonmalignant lung fibroblast cell line (IMR-90) using the MTT assay. CuL2a was potent (A549EC50=0.080 μM) and selective (IMR-90EC50/A549EC50=25) for A549. Its linkage isomer CuL2b had equivalent A549 activity, but lower selectivity (IMR-90EC50/A549EC50=12.5). The isomers CuL3a and CuL3b were less potent with A549EC50 values of 1.9 and 0.19 M and less selective with IMR-90EC50/A549EC50 ratios of 2.3 and 2.65, respectively. There was no correlation between reduction potential and A549 antiproliferation activity/selectivity. 相似文献
130.
An enantioselective and diastereoselective aza-[3+3] annulation of pyrrolidine-based exo-cyclic vinylogous amides and urethanes with chiral vinyl iminium salts is described. This asymmetric annulation manifold is possible because of an unexpected regiochemical reversal whereby head-to-tail annulations dominated over the predicted head-to-head. It should find prevalent synthetic applications in the enantioselective synthesis of indolizidines. 相似文献