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   5498篇
  免费   458篇
  国内免费   254篇
  2023年   39篇
  2022年   115篇
  2021年   220篇
  2020年   151篇
  2019年   199篇
  2018年   202篇
  2017年   154篇
  2016年   189篇
  2015年   274篇
  2014年   346篇
  2013年   378篇
  2012年   443篇
  2011年   416篇
  2010年   258篇
  2009年   223篇
  2008年   271篇
  2007年   233篇
  2006年   226篇
  2005年   194篇
  2004年   164篇
  2003年   156篇
  2002年   151篇
  2001年   102篇
  2000年   120篇
  1999年   109篇
  1998年   57篇
  1997年   47篇
  1996年   36篇
  1995年   49篇
  1994年   37篇
  1993年   32篇
  1992年   78篇
  1991年   54篇
  1990年   50篇
  1989年   53篇
  1988年   40篇
  1987年   33篇
  1986年   26篇
  1985年   35篇
  1984年   23篇
  1983年   20篇
  1982年   11篇
  1981年   12篇
  1980年   18篇
  1979年   11篇
  1978年   16篇
  1975年   12篇
  1974年   12篇
  1973年   19篇
  1972年   11篇
排序方式: 共有6210条查询结果,搜索用时 15 毫秒
1.
2.
Hepatitis E virus (HEV) is a single-strand positive-sense RNA virus in the family Hepeviridae. The disease caused by HEV, hepatitis E, is an important public health problem in developing countries of Asia and Africa and is also endemic in many industrialized countries, including the United States. HEV has been identified from several other animal species in addition to humans, including the pig, chicken, mongoose, deer, rabbit, ferret, bat, and fish. Here we report the complete genome sequence of the first strain of HEV from rabbits in the United States. Sequence and phylogenetic analyses revealed that the U.S. rabbit HEV is a distant member of the zoonotic genotype 3 HEV, thus raising a concern for potential zoonotic human infection. A unique 90-nucleotide insertion within the X domain of the ORF1 was identified in the rabbit HEV, and this insertion may play a role in the species tropism of HEV.  相似文献   
3.
4.
We investigated the correlation between the beneficial effect of Lactobacillus acidophilus on gut microbiota composition, metabolic activities, and reducing cow's milk protein allergy. Mice sensitized with β‐lactoglobulin (β‐Lg) were treated with different doses of L. acidophilus KLDS 1.0738 for 4 weeks, starting 1 week before allergen induction. The results showed that intake of L. acidophilus significantly suppressed the hypersensitivity responses, together with increased fecal microbiota diversity and short‐chain fatty acids (SCFAs) concentration (including propionate, butyrate, isobutyrate, and isovalerate) when compared with the allergic group. Moreover, treatment with L. acidophilus induced the expression of SCFAs receptors, G‐protein–coupled receptors 41 (GPR41) and 43 (GPR43), in the spleen and colon of the allergic mice. Further analysis revealed that the GPR41 and GPR43 messenger RNA expression both positively correlated with the serum concentrations of transforming growth factor‐β and IFN‐γ (p < .05), but negatively with the serum concentrations of IL‐17, IL‐4, and IL‐6 in the L. acidophilus–treated group compared with the allergic group (p < .05). These results suggested that L. acidophilus protected against the development of allergic inflammation by improving the intestinal flora, as well as upregulating SCFAs and their receptors GPR41/43.  相似文献   
5.
Somatic embryogenesis and plantlet formation were obtained from 60–75 day old cell cultures of carnation. Callus was generated on MS basal medium supplemented with 2,4-dichchlorophenoxy acetic acid (2,4-D). Removal of 2,4-D during subsequent subculturing of cell suspensions resulted in formation of embroids. These somatic embryos originated from single cells and their early development proceeded normally with clearly defined apical and root meristems. Some embryos developed into plants and were acclimatized to ex vitro conditions.  相似文献   
6.
7.
8.
9.
New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3al) were evaluated against Mycobacterium tuberculosis H37Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis.  相似文献   
10.
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