全文获取类型
收费全文 | 418篇 |
免费 | 11篇 |
国内免费 | 67篇 |
专业分类
化学 | 483篇 |
晶体学 | 2篇 |
综合类 | 2篇 |
物理学 | 9篇 |
出版年
2023年 | 2篇 |
2021年 | 18篇 |
2020年 | 16篇 |
2019年 | 19篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 33篇 |
2015年 | 21篇 |
2014年 | 16篇 |
2013年 | 29篇 |
2012年 | 14篇 |
2011年 | 14篇 |
2010年 | 13篇 |
2009年 | 27篇 |
2008年 | 30篇 |
2007年 | 30篇 |
2006年 | 25篇 |
2005年 | 20篇 |
2004年 | 21篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 2篇 |
排序方式: 共有496条查询结果,搜索用时 15 毫秒
91.
YU Shanshan ;YIN Hongbing ;WANG Xinying ;FENG Li ;XU Chunchun ;LI Jing ;HAN Hongxiang ;LIU Shuying 《高等学校化学研究》2014,30(5):778-784
A novel thermostable β-galactosidase gene, designated as GkGallA, from the thermophilic bacterium Geobacillus kaustophilus HTA426 was cloned and heterologously overexpressed in Escherichia coli(E, coli). Based on the sequence analysis, GkGallA belongs to the glycosyl hydrolase family 1 that was the first β-galactosidase of bacterial origins expressed by us in this family. The apparent molecular weight of GkGallA determined by sodium deodecyl sulfate-polyacrylamide gel electrophoresis is 52000. It exhibited the highest activity toward p-nitrophenyl-β-D-galactopyranoside at pH 7.8 and 70℃ and displayed high thermal stability, Divalent cations are prerequisite for the activity of GKGallA, with the highest activity in the presence of Mn2+. Moreover, the three-dimensional structure of GkGaI1A was modeled to speculate the structure of the catalytic residues and the reac- tion mechanism. The catalytic residues consisting of Glu166 and Glu355 were verified by site-directed mutagenesis. 相似文献
92.
93.
含有二糖结构的核苷类似物的合成 总被引:2,自引:0,他引:2
利用Ferrier重排反应合成了两个系列的连有核音的2,3-不饱和糖苷(其中核耷包括尿苷、腺苷、肌苷等).这些新化合物的结构通过NMR和MS(HRFAB)得到证实. 相似文献
94.
The enzyme soluble epoxide hydrolase (sEH) plays a central role in metabolism of bioactive lipid signaling molecules. The substrate-specific hydrolase activity of sEH converts epoxyeicosatrienoic acids (EETs) to less bioactive dihydroxyeicosatrienoic acids. EETs exhibit anti-inflammatory, analgesic, antihypertensive, cardio-protective and organ-protective properties. Accordingly, sEH inhibition is a promising therapeutic strategy for addressing a variety of diseases. In this review, we describe small molecule architectures that have been commonly deployed as sEH inhibitors with respect to angiogenesis, inflammation and cancer. We juxtapose commonly used synthetic scaffolds and natural products within the paradigm of a multitarget approach for addressing inflammation and inflammation induced carcinogenesis. Structural insights from the inhibitor complexes and novel strategies for development of sEH-based multitarget inhibitors are also presented. While sEH inhibition is likely to suppress inflammation-induced carcinogenesis, it can also lead to enhanced angiogenesis via increased EET concentrations. In this regard, sEH inhibitors in combination chemotherapy are described. Urea and amide-based architectures feature prominently across multitarget inhibition and combination chemotherapy applications of sEH inhibitors. 相似文献
95.
AbstractSaussurea involucrata, known for the abundant bioactive components, is a precious traditional Chinese medicine. In this study, a novel guaiane sesquiterpenoid glycoside named (1R, 5R, 6R, 7R, 8S, 11S)-11, 13-dihydrodehydrocostuslactone-8-O-6'-2''(E)-butenoyl-β-D-glucopyranoside (1), together with seven known compounds (2–8) were isolated from the dried aerial part of S. involucrata. Their structures were elucidated by spectroscopic and physico-chemical analyses. The antioxidant and anti-inflammatory activities of compound 1 were investigated. And compound 1 showed weak radical scavenging activity and low inhibitory activity on nitric oxide (NO) production. 相似文献
96.
Shulan Cai Jianzhang Li Bin Xie Leijin He Xiaolan Zhang 《Journal of Dispersion Science and Technology》2014,35(1):93-97
A macrocyclic ligand was synthesized and characterized. The kinetics of hydrolysis of bis(p-nitrophenyl)phosphate (BNPP) in the catalytic system containing macrocyclic ligand and praseodymium(III) was investigated. The analysis of specific absorption spectrums of the hydrolytic reaction systems indicated that key intermediates made up of BNPP and praseodymium(III) complexes are formed in the reaction process of BNPP catalytic hydrolysis. In this, the mechanism of BNPP catalytic hydrolysis proposed is based on the analytic result of specific absorption spectrum, and the corresponding kinetic constants are calculated. The results showed that the praseodymium(III) complexes as hydrolase mimics exhibit good catalytic activity and similar catalytic character to natural enzyme. 相似文献
97.
By using Y(OTf)3 as the catalyst, a series of 2,3-unsaturated-glucosides have been synthesized from 3,4,6-tri-O-acetyl-d-glucal, 3,4-di-O-acetyl-l-rhamnal, and 3,4,6-tri-O-benzyl-d-glucal under mild reaction conditions in good yields with high anomeric selectivities. It was found that, in this reaction, 3,4,6-tri-O-benzyl-d-glucal behaved differently from the other two glucals when it was reacted with phenol, O-benzyl glucoside instead of O-phenyl glucoside formed as the sole product. An explanation is given for this phenomenon. 相似文献
98.
《Mendeleev Communications》2023,33(1):109-111
Antimycobacterial activity of certain ureas as well as spirocyclic piperidines described in the literature prompted us to synthesize and test a series of hybrids of spirocyclic piperidine with ureas. Surprisingly, no activity was detected against Mycobacterium tuberculosis. However, significant antibacterial activity was identified and confirmed against common gram-positive as well as gram-negative bacteria. 相似文献
99.
Pham Thi Nhat Trinh Nguyen Huu An Pham Ngoc An Mai Dinh Tri Cao Van Du Phan Nhat Minh 《Natural product research》2018,32(14):1648-1652
A new benzofuran derivative, pumiloside (1), together with seven known flavonoid glycosides, afzelin (2), astragalin (3), quercitrin (4), isoquercitrin (5), kaempferol 3-O-rutinoside (6), rutin (7) and kaempferol 3-O-sophoroside (8) were isolated from the leaves of Ficus pumila. Their structures were established by spectroscopic data and comparison with the literature values. 相似文献
100.