全文获取类型
收费全文 | 460篇 |
免费 | 42篇 |
出版年
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 20篇 |
2014年 | 23篇 |
2013年 | 39篇 |
2012年 | 45篇 |
2011年 | 29篇 |
2010年 | 28篇 |
2009年 | 17篇 |
2008年 | 20篇 |
2007年 | 25篇 |
2006年 | 15篇 |
2005年 | 21篇 |
2004年 | 19篇 |
2003年 | 11篇 |
2002年 | 17篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 4篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1974年 | 3篇 |
1971年 | 6篇 |
1969年 | 1篇 |
1966年 | 1篇 |
1964年 | 1篇 |
1962年 | 2篇 |
排序方式: 共有502条查询结果,搜索用时 984 毫秒
491.
492.
493.
Nathalie Neveu Liliane Krespi Nabila Kacem Jean-Pierre Nénon 《Entomologia Experimentalis et Applicata》2000,96(3):231-237
Host-stage selection by Trybliographa rapae Westwood (Hymenoptera: Figitidae) was studied in choice and no-choice experiments in the laboratory. The parasitoid was able to reproduce in first, second, and third instars of the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae), but oviposition occurred more frequently in third instars when all three developmental stages were offered simultaneously. Oviposition in third instars increased the rate of development of offspring and their body size, but did not alter sex ratio. Results are discussed in the light of predictions made by the theory of optimal host acceptance. 相似文献
494.
Nabila E. Abdelmeguid Mahmoud I. Khalil Nada S. Badr Afrah F. Alkhuriji Mohamed S.A. El-Gerbed Ahmed S. Sultan 《Saudi Journal of Biological Sciences》2021,28(4):2254-2266
Colostrum, the sole diet for newborns, is an emerging nutraceutical. To date, the chemopreventive effect of Bovine Colostrum against liver injury induced by the potent carcinogen, 7,12-dimethyl-Benz[a]anthracene (DMBA) is unexplored. Humans are daily exposed to DMBA which is a highly lipophilic environmental organic pollutant. The study aimed to investigate the hepatoprotective role of Bovine Colostrum against DMBA-induced hepatotoxicity using a rat model. Fifty male rats were divided into five groups; GI (control), GII (olive oil, vehicle for DMBA), GIII (DMBA), GIV (DMBA + Bovine Colostrum), GV (Bovine Colostrum). After 12 weeks, body weight changes and mortality were calculated. Histological and ultrastructural examinations of liver tissue were performed. Expressions of p53, TGFβ2, TNF-α, S6K2, and c20orf20 were assessed by RT-PCR. Post-treatment with Bovine Colostrum increased both the body weight and the survival rate of rats treated with DMBA. In addition, remarkable protection against the pathological effect of DMBA was noted. Ultrastructurally, Bovine Colostrum ameliorated/prevented most of the toxic effects of DMBA on hepatocytes, including irregularities of nuclear envelope, clumping, and margination of heterochromatin aggregates, segregated nucleoli, and mitochondrial pleomorphism. Bovine Colostrum administration down-regulated p53, C20orf20, and S6K2 mRNA levels, and up-regulated TNF-α and TGFβ2. In conclusion, Bovine Colostrum have a protective effect against DMBA-induced toxicity on the liver of albino rats. Consequently, Bovine Colostrum may prevent polycyclic aromatic hydrocarbons-induced hepatotoxicity and may be useful in promoting human health if supplemented in the diet. 相似文献
495.
496.
OH radical-induced products of tyrosine peptides 总被引:1,自引:0,他引:1
L R Karam M Dizdaroglu M G Simic 《International journal of radiation biology and related studies in physics, chemistry, and medicine》1984,46(6):715-724
Reactions of radiation-generated OH radicals with tyrosine and its homopeptides, i.e. L-Tyr-L-Tyr and L-Tyr-L-Tyr-L-Tyr, in N2O saturated solutions were shown to give crosslinks between the peptide chains with high yields. High-performance liquid chromatography, capillary gas chromatography and mass spectrometry were used for isolation and identification of the monomeric and dimeric products. Evidence is presented for the crosslinking to occur through C-C and C-O-C bonds. To the best of our knowledge, the formation of the ether type of crosslink is demonstrated for the first time. Mechanisms of product formation are also discussed, which involve radicals that were described in previous pulse radiolysis studies. 相似文献
497.
498.
The pyruvate dehydrogenase complex has been demonstrated in high speed pellet preparations from sonicated ribbed mussel gill mitochondria. The activity of the complex is inhibited by low chloride (less than 100 mM) concentrations, EDTA (1 mM), succinate, ATP, and NAD/NADH ratios below 4. Inhibition by EDTA is relieved by addition of 10 mM MgCl2-1 mM CaCl2. ATP inhibition was enhanced by NaF and reversed by high Mg++ concentrations in the absence of NaF. Pyruvate and thiamine pyrophosphate inhibited the inactivation by ATP. The nonhydrolyzable ATP analog AMP-PNP caused inhibition of the overall catalytic activity that was identical to ATP. Factors involved in the ATP inhibition and Mg++ reversal are lost with freezing or cold storage. Preliminary results using gamma-32P-ATP indicate that a protein kinase that phosphorylates the alpha subunit of E1 (pyruvate dehydrogenase) from the mammalian PDC is associated with the gill PDC. The activity of the complex may be regulated by a phosphorylation/dephosphorylation mechanism and by the relative levels of substrates, products, and other metabolites in the mitochondria. 相似文献
499.
500.