全文获取类型
收费全文 | 652篇 |
免费 | 28篇 |
专业分类
680篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 24篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 13篇 |
2017年 | 13篇 |
2016年 | 15篇 |
2015年 | 26篇 |
2014年 | 37篇 |
2013年 | 39篇 |
2012年 | 50篇 |
2011年 | 50篇 |
2010年 | 33篇 |
2009年 | 30篇 |
2008年 | 38篇 |
2007年 | 41篇 |
2006年 | 27篇 |
2005年 | 28篇 |
2004年 | 34篇 |
2003年 | 27篇 |
2002年 | 20篇 |
2001年 | 8篇 |
2000年 | 13篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 4篇 |
1972年 | 1篇 |
1969年 | 1篇 |
1957年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有680条查询结果,搜索用时 0 毫秒
91.
Yadlapalli RK Chourasia OP Vemuri K Sritharan M Perali RS 《Bioorganic & medicinal chemistry letters》2012,22(8):2708-2711
A series of dihydropyrimidine derivatives were synthesized by utilizing Biginelli reaction and evaluated for their in vitro anticancer activity against MCF-7 human breast cancer (HBC) cell line using sulforhodamine B (SRB) assay and antitubercular activity against Mycobacterium tuberculosis (MTB) H(37)Rv using Microplate Alamar Blue Assay (MABA). Compounds 13p, 13t were exhibited 70.6% and 63.7% of HBC cell growth inhibition at 10 μM concentration. Interestingly compound 13p was also found to be the most potent in the series against MTB H(37)Rv with MIC value of 0.125 μg/mL. 相似文献
92.
Dinesh Addla Balasubramanian Sridhar Anjana Devi Srinivas Kantevari 《Bioorganic & medicinal chemistry letters》2012,22(24):7475-7480
A series of novel 1-benzyl-2-butyl-4-chloroimidazole embodied 4-azafluorenone hybrids, designed via molecular hybridization approach, were synthesized in very good yields using one pot condensation of 1-benzyl-2-butyl-4-chloroimidazole-5-carboxaldehyde, 1,3-indanedione, aryl/heteroaryl methyl ketones and ammonium acetate. All the synthetic derivatives were fully characterized by spectral data and evaluated for antimicrobial activity by disc diffusion method against selected bacteria and fungal strains. Among the 15 new compounds screened, 4-(1-benzyl-2-butyl-4-chloro-1H-imidazol-5-yl)-2-(furan-2-yl)-5H-indeno[1,2-b]pyridin-5-one(10k) has pronounced activity with higher zone of inhibition (ZoI) against Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Aspergillus flavus and Candida albicans. Also 4-(1-benzyl-2-butyl-4-chloro-1H-imidazol-5-yl)-2-(dibenzo[b,d]thiophen-2-yl)-5H-indeno [1,2-b]pyridin-5-one (10n) and 4-(1-benzyl-2-butyl-4-chloro-1H-imidazol-5-yl)-2-(3-tosyl-3H-inden-1-yl)-5H-indeno[1,2-b]pyridin-5-one (10o) showed selective higher inhibitory activity against Aspergillus flavus and Candida albicans. The results demonstrated potential importance of molecular hybridization in the development of 10k as potential antimicrobial agent. 相似文献
93.
W Dou S Mukherjee H Li M Venkatesh H Wang S Kortagere A Peleg SS Chilimuri ZT Wang Y Feng ER Fearon S Mani 《PloS one》2012,7(7):e36075
Pregnane X Receptor (PXR), a master regulator of drug metabolism and inflammation, is abundantly expressed in the gastrointestinal tract. Baicalein and its O-glucuronide baicalin are potent anti-inflammatory and anti-cancer herbal flavonoids that undergo a complex cycle of interconversion in the liver and gut. We sought to investigate the role these flavonoids play in inhibiting gut inflammation by an axis involving PXR and other potential factors. The consequences of PXR regulation and activation by the herbal flavonoids, baicalein and baicalin were evaluated in vitro in human colon carcinoma cells and in vivo using wild-type, Pxr-null, and humanized (hPXR) PXR mice. Baicalein, but not its glucuronidated metabolite baicalin, activates PXR in a Cdx2-dependent manner in vitro, in human colon carcinoma LS174T cells, and in the murine colon in vivo. While both flavonoids abrogate dextran sodium sulfate (DSS)-mediated colon inflammation in vivo, oral delivery of a potent bacterial β-glucuronidase inhibitor eliminates baicalin's effect on gastrointestinal inflammation by preventing the microbial conversion of baicalin to baicalien. Finally, reduction of gastrointestinal inflammation requires the binding of Cdx2 to a specific proximal site on the PXR promoter. Pharmacological targeting of intestinal PXR using natural metabolically labile ligands could serve as effective and potent therapeutics for gut inflammation that avert systemic drug interactions. 相似文献
94.
95.
Pregnane glycosides from Caralluma adscendens var. fimbriata 总被引:1,自引:0,他引:1
Kunert O Rao VG Babu GS Sujatha P Sivagamy M Anuradha S Rao BV Kumar BR Alex RM Schühly W Kühnelt D Rao GV Rao AV 《化学与生物多样性》2008,5(2):239-250
Eleven novel pregnane glycosides, 2-7 and 9-13, of which four, i.e., 10-13, comprised a new pregnane-type genin exhibiting a hydroxymethylene instead of a Me group at C(19), and the known pregnane glycoside stalagmoside V (8) were isolated from whole plants of Caralluma adscendens var. fimbriata, a native Indian succulent plant. Their structures were elucidated by extensive 2D-NMR spectroscopic studies. 相似文献
96.
97.
98.
We have carried out a systematic analysis in order to evaluate whether Intra-Chain Disulfide Bridged Peptides (ICDBPs) observed in proteins of known three-dimensional structure adopt structurally similar conformations as they may correspond to structural/functional motifs. 406 representative ICDBPs comprising between 3 to 17 amino acid residues could be classified according to peptide sequence length and main-chain secondary structure conformation into 146 classes. ICDBPs comprising 6 amino acid residues are maximally represented in the Protein Data Bank. They also represent the maximum number of main-chain secondary structure conformational classes. Individual ICDBPs in each class represent different protein superfamilies and correspond to different amino acid sequences. We identified 145 ICDBP pairs that had not less-than 0.5 A root mean square deviation value corresponding to their equivalent peptide backbone atoms. We believe these ICDBPs represent structural motifs and possible candidates in order to further explore their structure/function role in the corresponding proteins. The common conformational classes observed for ICDBPs defined according to the main-chain secondary structure conformations; H (helix), B (residue in a isolated beta bridge), C (coil), E (extended beta strand), G (3(10) helix), I (pi helix), S (bend), T (hydrogen-bonded turn) were; "CHHH", "CTTC", "CSSS" and "CSSC" (for ICDBP length 4), "CSSCC" (length 5), "EETTEE", "CCSSCC", "CCSSSC" (length 6), "EETTTEE" (length 7), "EETTTTEE" (length 8), "EEEETTEEEE" (length 10), "EEEETTTEEEE" (length 11) and "EEEETTTTEEEE" (length 12). 相似文献
99.
Albrecht M. Koppenhöfer Cesar R. Rodriguez-Saona Sridhar Polavarapu Robert J. Holdcraft 《Biocontrol Science and Technology》2008,18(1):21-31
A series of laboratory and greenhouse experiments evaluated the entomopathogenic nematodes Steinernema scarabaei Stock & Koppenhöfer, Heterorhabditis bacteriophora Poinar, and H. zealandica Poinar for control of second- and third-instar cranberry white grub, Phyllophaga georgiana Horn (Coleoptera: Scarabaeidae), in cranberries. Steinernema scarabaei was the most effective species with 76–100% control at a rate of 2.5×109 IJ/ha in the greenhouse experiments. H. zealandica and especially H. bacteriophora were generally less effective and required rates of 5×109 IJ/ha for acceptable control. Larval stage had no effect on H. zealandica and H. bacteriophora performance, whereas S. scarabaei was more effective against third instars than second instars in the laboratory but not in the greenhouse experiments. Steinernema scarabaei, should it become commercially available, could be an effective alternative to chemical insecticides for P. georgiana management. 相似文献
100.