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   27411篇
  免费   2497篇
  国内免费   3128篇
  2024年   27篇
  2023年   267篇
  2022年   432篇
  2021年   1170篇
  2020年   972篇
  2019年   1156篇
  2018年   1119篇
  2017年   909篇
  2016年   1090篇
  2015年   1675篇
  2014年   2058篇
  2013年   2190篇
  2012年   2676篇
  2011年   2445篇
  2010年   1600篇
  2009年   1458篇
  2008年   1822篇
  2007年   1556篇
  2006年   1391篇
  2005年   1197篇
  2004年   1175篇
  2003年   1063篇
  2002年   956篇
  2001年   475篇
  2000年   358篇
  1999年   288篇
  1998年   270篇
  1997年   173篇
  1996年   162篇
  1995年   158篇
  1994年   128篇
  1993年   97篇
  1992年   93篇
  1991年   75篇
  1990年   42篇
  1989年   56篇
  1988年   34篇
  1987年   35篇
  1986年   38篇
  1985年   31篇
  1984年   9篇
  1983年   13篇
  1982年   23篇
  1981年   6篇
  1977年   5篇
  1969年   3篇
  1967年   4篇
  1965年   4篇
  1963年   3篇
  1962年   4篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
992.

Objective

To examine the effect of PCI-24781 (abexinostat) on the blastocyst formation rate in pig somatic cell nuclear transferred (SCNT) embryos and acetylation levels of the histone H3 lysine 9 and histone H4 lysine 12.

Results

Treatment with 0.5 nM PCI-24781 for 6 h significantly improved the development of cloned embryos, in comparison to the control group (25.3 vs. 10.5 %, P < 0.05). Furthermore, PCI-24781 treatment led to elevated acetylation of H3K9 and H4K12. TUNEL assay and Hoechst 33342 staining revealed that the percentage of apoptotic cells in blastocysts was significantly lower in PCI-24781-treated SCNT embryos than in untreated embryos. Also, PCI-24781-treated embryos were transferred into three surrogate sows, one of whom became pregnant and two fetuses developed.

Conclusion

PCI-24781 improves nuclear reprogramming and the developmental potential of pig SCNT embryos.
  相似文献   
993.
A novel bacterium, strain SZ28, identified as Acinetobacter sp., showed anaerobic denitrification ability using Mn(II) as the electron donor. Nitrate-nitrogen concentration decreased from nearly 16.52–mg L?1 to 4.4–mg L?1, without accumulation of nitrite as an intermediate, with a maximum of 0.063–mg NO3?-N L?1 h?1, reaching a peak of 0.085–mg NO3?-N L?1 h?1 in sodium acetate. The nitrate removal rate reached 0.067–mg NO3?-N L?1 h?1, 0.059–mg NO3?-N L?1 h?1, and 0.078 mg NO3?-N L?1 h?1 using Mn(II), S(II), and Fe(II) as electron donors, respectively. The optimum pH was 6.0, with a removal rate of 0.063–mg NO3?-N L?1 h?1  相似文献   
994.
995.
996.
997.
998.
Applied Microbiology and Biotechnology - A novel heterotrophic nitrification-aerobic denitrification bacterium, Alcaligenes sp. TB (GenBank accession no. JQ044686), was isolated from a rotating...  相似文献   
999.
In methane-rich environments, methane-oxidizing bacteria usually occur predominantly among consortia including other types of microorganisms. In this study, artificial coal bed gas and methane gas were used to enrich mixed methanotrophic cultures from the soil of a coal mine in China, respectively. The changes in microbial community structure and function during the enrichment were examined. The microbial diversity was reduced as the enrichment proceeded, while the capacity for methane oxidation was significantly enhanced by the increased abundance of methanotrophs. The proportion of type II methanotrophs increased greatly from 7.84 % in the sampled soil to about 50 % in the enrichment cultures, due to the increase of methane concentration. After the microbial community of the cultures got stable, Methylomonas and Methylocystis became the dominant type I and type II methanotrophs, while Methylophilus was the prevailing methylotroph. The sequences affiliated with pigment-producing strains, Methylomonas rubra, Hydrogenophaga sp. AH-24, and Flavobacterium cucumis, could explain the orange appearance of the cultures. Comparing the two cultures, the multi-carbon sources in the artificial coal bed gas caused more variety of non-methanotrophic bacteria, but did not help to maintain the diversity or to increase the quantity and activity of methanotrophs. The results could help to understand the succession and interaction of microbial community in a methane-driven ecosystem.  相似文献   
1000.
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