全文获取类型
收费全文 | 623篇 |
免费 | 21篇 |
国内免费 | 3篇 |
专业分类
化学 | 500篇 |
晶体学 | 3篇 |
力学 | 23篇 |
数学 | 26篇 |
物理学 | 95篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 21篇 |
2021年 | 19篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 16篇 |
2017年 | 18篇 |
2016年 | 24篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 56篇 |
2012年 | 50篇 |
2011年 | 57篇 |
2010年 | 31篇 |
2009年 | 16篇 |
2008年 | 41篇 |
2007年 | 42篇 |
2006年 | 38篇 |
2005年 | 26篇 |
2004年 | 16篇 |
2003年 | 18篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1990年 | 1篇 |
1989年 | 7篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1958年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有647条查询结果,搜索用时 15 毫秒
41.
Lima Rodrigues Mahesh S. Majik Santosh G. Tilve Solimabi Wahidulla 《Tetrahedron letters》2018,59(37):3413-3415
(?)-Elemoxide, a fragrant compound was synthesised using commercially available elemol in four steps with overall yield of 32%. The cyclic ether skeleton was constructed via intramolecular hydroalkoxylation using I2 and PhSiH3 catalytic system. Also, intramolecular oxymercuration-demercuration was employed as an alternate approach for cyclization. The various regioselective strategies involving epoxidation of alkene, reduction of epoxide and intramolecular cyclization were the highlights of the work. The key intermediate diol serves as a versatile intermediate for the synthesis of elemoxide and elemene. 相似文献
42.
Damodar Koirala Sabyasachy Mistry Paul G. Wenthold 《Journal of the American Society for Mass Spectrometry》2017,28(7):1313-1323
The dissociation of anionic dipeptides Phe*Gly and GlyPhe*, where Phe* refers to sulfonated phenyl alanine, has been investigated by using ion trap mass spectrometry. The dipeptides undergo collision-induced dissociation (CID) to give the same products, indicating that they rearrange to a common structure before dissociation. The rearrangement does not occur with the dipeptide methyl esters. The structures of the b2 ions were investigated to determine the effect that having a remote, anionic site has on product formation. Comparison with the CID spectra for authentic structures shows that the b2 ion obtained from GlyPhe* has predominantly a diketopiperazine structure. The CID spectra for the Phe*Gly b2 ion and the authentic oxazolone are similar, but differences in intensity suggest a two-component mixture. Isotopic labeling studies are consistent with the formation of two products, with one resulting from loss of a non-mobile proton on the Gly α-carbon. The results are attributed to the formation of an oxazole and oxazolone enol product. Electronic structure calculations predict that the enol structure of the Phe*Gly b2 ion is lower in energy than the keto version due to intramolecular hydrogen bonding with the sulfonate group. 相似文献
43.
Mandipogula Mahesh Veladi Panduranga Girish Prabhu Roopesh Kumar L P. Venkata Ramana 《合成通讯》2017,47(7):716-721
A simple protocol involving metal-free oxidative amidation of benzyl alcohols with amino acid esters has been presented. The amidation proceeds in a radical pathway unlike in conventional metal-mediated extrusion of dihydrogen. The method is advantageous in terms of metal-free conditions, nonexpensive commercial starting substrates. Also various substituents in the starting materials are tolerated and sterically hindered amino acid side chains could provide good yields of amide products. 相似文献
44.
45.
46.
47.
V. K. Mahesh M. Maheshwari V. Kumar 《Fresenius' Journal of Analytical Chemistry》1982,310(3-4):253-254
48.
Jayapal P Robinson D Sundararajan M Hillier IH McDouall JJ 《Physical chemistry chemical physics : PCCP》2008,10(13):1734-1738
Multi-reference M?ller-Plesset calculations of a model of the Ni-SI state of nickel-iron hydrogenase predict a singlet rather than a triplet state for this species, and show that it is better described with a BP86 rather than a B3LYP functional. 相似文献
49.
Na Z Li L Uttamchandani M Yao SQ 《Chemical communications (Cambridge, England)》2012,48(58):7304-7306
A microarray immobilized with 105 aldehyde-containing small molecules was screened against mammalian cell lysates over-expressing cathepsin L to identify two potent inhibitors, which were subsequently converted into cell-permeable probes capable of live-cell imaging of endogenous cysteinyl cathepsin activities by two-photon fluorescence microscopy. 相似文献
50.
[reaction: see text] Novel chiral imidazolium salts have been synthesized as examples of chiral ionic liquids with a spiro skeleton. Effects of N-substituents and counteranions on the melting point of spiro imidazolium salts and their chiral discrimination abilities are described. 相似文献