全文获取类型
收费全文 | 575篇 |
免费 | 29篇 |
国内免费 | 7篇 |
专业分类
化学 | 438篇 |
力学 | 5篇 |
数学 | 89篇 |
物理学 | 79篇 |
出版年
2023年 | 6篇 |
2022年 | 8篇 |
2021年 | 17篇 |
2020年 | 8篇 |
2019年 | 19篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 25篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 25篇 |
2012年 | 27篇 |
2011年 | 39篇 |
2010年 | 20篇 |
2009年 | 20篇 |
2008年 | 39篇 |
2007年 | 37篇 |
2006年 | 43篇 |
2005年 | 27篇 |
2004年 | 33篇 |
2003年 | 19篇 |
2002年 | 28篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 1篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 1篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 2篇 |
排序方式: 共有611条查询结果,搜索用时 15 毫秒
61.
Castro-Perez J Roddy TP Nibbering NM Shah V McLaren DG Previs S Attygalle AB Herath K Chen Z Wang SP Mitnaul L Hubbard BK Vreeken RJ Johns DG Hankemeier T 《Journal of the American Society for Mass Spectrometry》2011,22(9):1552-1567
A high content molecular fragmentation for the analysis of phosphatidylcholines (PC) was achieved utilizing a two-stage [trap (first generation fragmentation) and transfer (second generation fragmentation)] collision-induced dissociation (CID) in combination with travelling-wave ion mobility spectrometry (TWIMS). The novel aspects of this work reside in the fact that a TWIMS arrangement was used to obtain a high level structural information including location of fatty acyl substituents and double bonds for PCs in plasma, and the presence of alkali metal adduct ions such as [M?+?Li]+ was not required to obtain double bond positions. Elemental compositions for fragment ions were confirmed by accurate mass measurements. A very specific first generation fragment ion m/z 577 (M-phosphoryl choline) from the PC [16:0/18:1 (9Z)] was produced, which by further CID generated acylium ions containing either the fatty acyl 16:0 (C15H31CO+, m/z 239) or 18:1 (9Z) (C17H33CO+, m/z 265) substituent. Subsequent water loss from these acylium ions was key in producing hydrocarbon fragment ions mainly from the α-proximal position of the carbonyl group such as the hydrocarbon ion m/z 67 (+H2C-HC?=?CH-CH?=?CH2). Formation of these ions was of important significance for determining double bonds in the fatty acyl chains. In addition to this, and with the aid of 13C labeled lyso-phosphatidylcholine (LPC) 18:1 (9Z) in the ω-position (methyl) TAP fragmentation produced the ion at m/z 57. And was proven to be derived from the α-proximal (carboxylate) or distant ω-position (methyl) in the LPC. 相似文献
62.
63.
64.
Increasing the Chemical‐Shift Dispersion of Unstructured Proteins with a Covalent Lanthanide Shift Reagent 下载免费PDF全文
Dr. Christoph Göbl Moritz Resch Dr. Madeleine Strickland Christoph Hartlmüller Martin Viertler Dr. Nico Tjandra Prof. Dr. Tobias Madl 《Angewandte Chemie (International ed. in English)》2016,55(47):14847-14851
The study of intrinsically disordered proteins (IDPs) by NMR often suffers from highly overlapped resonances that prevent unambiguous chemical‐shift assignments, and data analysis that relies on well‐separated resonances. We present a covalent paramagnetic lanthanide‐binding tag (LBT) for increasing the chemical‐shift dispersion and facilitating the chemical‐shift assignment of challenging, repeat‐containing IDPs. Linkage of the DOTA‐based LBT to a cysteine residue induces pseudo‐contact shifts (PCS) for resonances more than 20 residues from the spin‐labeling site. This leads to increased chemical‐shift dispersion and decreased signal overlap, thereby greatly facilitating chemical‐shift assignment. This approach is applicable to IDPs of varying sizes and complexity, and is particularly helpful for repeat‐containing IDPs and low‐complexity regions. This results in improved efficiency for IDP analysis and binding studies. 相似文献
65.
66.
General,Highly Selective Synthesis of 1,3‐ and 1,4‐Difunctionalized Building Blocks by Regiodivergent Epoxide Opening 下载免费PDF全文
Nico Funken Felix Mühlhaus Prof. Dr. Andreas Gansäuer 《Angewandte Chemie (International ed. in English)》2016,55(39):12030-12034
We describe a regiodivergent epoxide opening (REO) featuring a catalyst‐controlled synthesis of enantiomerically and diastereomerically highly enriched or pure syn‐ and anti‐ 1,3‐ and 1,4‐difunctionalized building blocks from a common epoxide precursor. The REO is attractive for natural product synthesis and as a branching reaction for diversity‐oriented synthesis with epoxides. 相似文献
67.
Reactions of propargyl trimethyl silane with ω-ethoxy lactams 1a-c under the influence of boron trifluoride etherate afford ω-allenyl lactams 3a-c; 5-allenyl-2-pyrrolidinone is hydrolysed to γ-allenyl-GABA. 相似文献
68.
69.