首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   127篇
  免费   19篇
  146篇
  2022年   1篇
  2021年   2篇
  2018年   2篇
  2017年   2篇
  2016年   4篇
  2015年   9篇
  2014年   11篇
  2013年   6篇
  2012年   11篇
  2011年   5篇
  2010年   10篇
  2009年   4篇
  2008年   5篇
  2007年   1篇
  2006年   6篇
  2005年   5篇
  2004年   4篇
  2003年   4篇
  2002年   1篇
  2001年   3篇
  2000年   7篇
  1999年   9篇
  1998年   5篇
  1997年   6篇
  1996年   3篇
  1993年   3篇
  1992年   5篇
  1991年   2篇
  1990年   1篇
  1988年   2篇
  1986年   1篇
  1984年   2篇
  1983年   1篇
  1980年   2篇
  1978年   1篇
排序方式: 共有146条查询结果,搜索用时 0 毫秒
1.
Interferons are known to potentiate various biological effects of tumor necrosis factor (TNF). Recently, two different types of TNF receptors with molecular masses of 60 kDa (p60) and 80 kDa (p80), primarily expressed by epithelial cells and myeloid cells, respectively, have been identified. In the present report, we examined the effect of interferon-gamma (IFN-gamma) on each type of TNF receptor. Our results indicate that IFN-gamma induces TNF receptors on both myeloid (e.g. HL-60) and epithelial cells (e.g. HeLa). Furthermore, by using antibodies specific to each type of receptor, we demonstrate that both TNF receptors are equally inducible by IFN-alpha, IFN-beta and IFN-gamma. Thus, the increase in TNF receptors by interferons may play a role in their synergistic cellular response.  相似文献   
2.
Feeding of aflatoxin B1 at the rate of 0.5 ppm to young Japanese quail resulted in significant (p<0.01) decrease in body weight gain that became apparent on the third week. There was no significant difference in the mean values of haemoglobin, packed cell volume and total erythrocyte counts of quail chicks given aflatoxin B1 in feed in comparison to those fed on a similar diet without aflatoxin. However, the total leucocyte count revealed an increase on the third week which was due to an increase in the percentage of heterophils and decrease in lymphocytes.  相似文献   
3.
T K Pandita 《Mutation research》1986,171(2-3):131-138
The insecticide Thimet 10-G was tested for mutagenic activity by 4 different genetic systems. It was unable to induce gene mutation in Salmonella, transfection inhibition in Mycobacterium, micronuclei formation in mice, and sister-chromatid exchange (SCE) in human lymphocytes were evaluated. It caused in mice an increase in the ratio of normochromatic to polychromatic erythrocytes and in human lymphocytes a decrease in mitotic index and delay in cell cycle. The results indicate that the insecticide is not mutagenic in the 4 test systems used at present.  相似文献   
4.
5.
6.

Background  

There have been many algorithms and software programs implemented for the inference of multiple sequence alignments of protein and DNA sequences. The "true" alignment is usually unknown due to the incomplete knowledge of the evolutionary history of the sequences, making it difficult to gauge the relative accuracy of the programs.  相似文献   
7.

Background

A new subgroup of HIV-1, designated Group P, was recently detected in two unrelated patients of Cameroonian origin. HIV-1 Group P phylogenetically clusters with SIVgor suggesting that it is the result of a cross-species transmission from gorillas. Until today, HIV-1 Group P has only been detected in two patients, and its degree of adaptation to the human host is largely unknown. Previous data have shown that pandemic HIV-1 Group M, but not non-pandemic Group O or rare Group N viruses, efficiently antagonize the human orthologue of the restriction factor tetherin (BST-2, HM1.24, CD317) suggesting that primate lentiviruses may have to gain anti-tetherin activity for efficient spread in the human population. Thus far, three SIV/HIV gene products (vpu, nef and env) are known to have the potential to counteract primate tetherin proteins, often in a species-specific manner. Here, we examined how long Group P may have been circulating in humans and determined its capability to antagonize human tetherin as an indicator of adaptation to humans.

Results

Our data suggest that HIV-1 Group P entered the human population between 1845 and 1989. Vpu, Env and Nef proteins from both Group P viruses failed to counteract human or gorilla tetherin to promote efficient release of HIV-1 virions, although both Group P Nef proteins moderately downmodulated gorilla tetherin from the cell surface. Notably, Vpu, Env and Nef alleles from the two HIV-1 P strains were all able to reduce CD4 cell surface expression.

Conclusions

Our analyses of the two reported HIV-1 Group P viruses suggest that zoonosis occurred in the last 170 years and further support that pandemic HIV-1 Group M strains are better adapted to humans than non-pandemic or rare Group O, N and P viruses. The inability to antagonize human tetherin may potentially explain the limited spread of HIV-1 Group P in the human population.  相似文献   
8.
9.
New pyrrolobenzodiazepine-anthraquinone hybrids have been designed and synthesized, found to effectively bind to DNA and also exhibit cytotoxicity against many cancer cell lines  相似文献   
10.
Nitric oxide (NO)-mediated smooth muscle relaxation is mediated by cGMP through activation of cGMP-dependent protein kinase I (cGKI). We studied the importance of cGKI for lower urinary tract function in mice lacking the gene for cGKI (cGKI-/-) and in litter-matched wild-type mice (cGKI+/+) in vitro and in vivo. cGKI deficiency did not result in any changes in bladder gross morphology or weight. Urethral strips from cGKI-/- mice showed an impaired relaxant response to nerve-derived NO. The cGMP analog 8-bromo-cGMP (8-BrcGMP) and the NO-donor SIN-1 relaxed the wild-type urethra (50-60%) but had only marginal effects in the cGKI-deficient urethra. Bladder strips from cGKI-/- mice responded normally to electrical field stimulation and to carbachol but not to 8-BrcGMP. In vivo, the cGKI-deficient mice showed bladder hyperactivity characterized by decreased intercontraction intervals and nonvoiding bladder contractions. Loss of cGKI abolishes NO-cGMP-dependent relaxations of urethral smooth muscle and results in hyperactive voiding. These data suggest that certain voiding disturbances may be associated with impaired NO-cGKI signaling.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号