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   18865篇
  免费   1557篇
  国内免费   1018篇
  2023年   204篇
  2022年   251篇
  2021年   807篇
  2020年   601篇
  2019年   736篇
  2018年   828篇
  2017年   548篇
  2016年   845篇
  2015年   1153篇
  2014年   1309篇
  2013年   1466篇
  2012年   1766篇
  2011年   1555篇
  2010年   964篇
  2009年   848篇
  2008年   1069篇
  2007年   934篇
  2006年   822篇
  2005年   731篇
  2004年   585篇
  2003年   547篇
  2002年   473篇
  2001年   357篇
  2000年   294篇
  1999年   285篇
  1998年   171篇
  1997年   134篇
  1996年   99篇
  1995年   111篇
  1994年   78篇
  1993年   70篇
  1992年   96篇
  1991年   96篇
  1990年   87篇
  1989年   68篇
  1988年   56篇
  1987年   53篇
  1986年   39篇
  1985年   44篇
  1984年   23篇
  1983年   23篇
  1982年   21篇
  1981年   13篇
  1979年   20篇
  1978年   16篇
  1977年   19篇
  1976年   15篇
  1975年   14篇
  1972年   15篇
  1969年   10篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
52.
Intestinal mucosal injuries are directly or indirectly related to many common acute and chronic diseases. Long non-coding RNAs (lncRNAs) are expressed in many diseases, including intestinal mucosal injury. However, the relationship between lncRNAs and intestinal mucosal injury has not been determined. Here, we investigated the functions and mechanisms of action of lncRNA Bmp1 on damaged intestinal mucosa. We found that Bmp1 was increased in damaged intestinal mucosal tissue and Bmp1 overexpression was able to alleviate intestinal mucosal injury. Bmp1 overexpression was found to influence cell proliferation, colony formation, and migration in IEC-6 or HIEC-6 cells. Moreover, miR-128-3p was downregulated after Bmp1 overexpression, and upregulation of miR-128-3p reversed the effects of Bmp1 overexpression in IEC-6 cells. Phf6 was observed to be a target of miR-128-3p. Furthermore, PHF6 overexpression affected IEC-6 cells by activating PI3K/AKT signaling which was mediated by the miR-128-3p/PHF6 axis. In conclusion, Bmp1 was found to promote the expression of PHF6 through the sponge miR-128-3p, activating the PI3K/AKT signaling pathway to promote cell migration and proliferation.Subject terms: Cell growth, Cell migration  相似文献   
53.
RIG-1 signalling is responsible for the detection of cytoplasmic viral RNA molecules. DEXH (Asp-Glu-X-His) box polypeptide 58 (encoded by DHX58) is a negative regulator of the RIG-1 signalling pathway. In human, the DHX58 gene can be upregulated and can inhibit the RIG-1 signalling pathway during viral infection. In this study, porcine DHX58 gene expression patterns were studied. According to our results, the porcine DHX58 gene was upregulated not only by the stimulation of Poly I:C but also by the stimulation of 1ipopolysaccharides (LPS). One polymorphism (g.4919G>C), detected in the ninth intron, was significantly associated with some blood parameters including the red cell distribution width of 1-day-old pigs and white blood cell counts, lymphocyte absolute counts, and platelet distribution width of 17-day-old pigs (P < 0.05). Moreover, the individuals with the genotype GG have a significantly higher mean white blood cell count than individuals with genotype CC or GC (P < 0.05). Our study indicates that DHX58 is an important gene that is associated with the immune response in swine.  相似文献   
54.
55.
Hydrodistillation of the dried leaves of eleven species of the genus Eucalyptus L 'Hér ., i.e., E. astringens Maiden , E. camaldulensis Dehnh ., E. diversifolia Bonpl ., E. falcata Turcz ., E. ficifolia F. Muell ., E. gomphocephala DC., E. lehmannii (Schauer ) Benth ., E. maculata Hook ., E. platypus Hook ., E. polyanthemos Schauer, and E. rudis Endl ., harvested from Korbous arboreta (region of Nabeul, northeast of Tunisia) in April 2006, afforded essential oils in yields varying from 0.1±0.1 to 3.8±0.1%, dependent on the species. E. astringens and E. ficifolia showed the highest and the lowest mean percentage of essential oil amongst all the species examined, respectively. Analysis by GC (RI) and GC/MS allowed the identification of 138 components, representing 74.0 to 99.1% of the total oil. The contents of the different samples varied according to the species. The main components were 1,8‐cineole, followed by trans‐pinocarveol ( 1 ), spathulenol ( 2 ), α‐pinene, p‐cymene, (E,E)‐farnesol, cryptone, globulol ( 3 ), β‐phellandrene, α‐terpineol, viridiflorol, and α‐eudesmol. The principal‐component and the hierarchical‐cluster analyses separated the eleven Eucalyptus leaf essential oils into seven groups, each constituting a chemotype.  相似文献   
56.
Abstract Field trials by sex pheromone of aphid to trap peach aphids Myzus persicae have been carried out in 1995 and in 1996. Suitable time and the effect of ratio of two components nepetalactone and nepetalactol to apply the lure have been observed.  相似文献   
57.
X Han  D A Steinhauer  S A Wharton  L K Tamm 《Biochemistry》1999,38(45):15052-15059
The amino-terminal region of the membrane-anchored subunit of influenza virus hemagglutinin, the fusion peptide, is crucial for membrane fusion of this virus. The peptide is extruded from the interior of the protein and inserted into the lipid bilayer of the target membrane upon induction of a conformational change in the protein by low pH. Although the effects of several mutations in this region on the fusion behavior and the biophysical properties of the corresponding peptides have been studied, the structural requirements for an active fusion peptide have still not been defined. To probe the sensitivity of the fusion peptide structure and function to small hydrophobic perturbations in the middle of the hydrophobic region, we have individually replaced the alanine residues in positions 5 and 7 with smaller (glycine) or bulkier (valine) hydrophobic residues and measured the extent of fusion mediated by these hemagglutinin constructs as well as some biophysical properties of the corresponding synthetic peptides in lipid bilayers. We find that position 5 tolerates a smaller and position 7 a larger hydrophobic side chain. All peptides contained segments of alpha-helical (33-45%) and beta-strand (13-16%) conformation as determined by CD and ATR-FTIR spectroscopy. The order parameters of the peptide helices and the lipid hydrocarbon chains were determined from measurements of the dichroism of the respective infrared absorption bands. Order parameters in the range of 0.0-0.6 were found for the helices of these peptides, which indicate that these peptides are most likely aligned with their alpha-helices at oblique angles to the membrane normal. Some (mostly fusogenic) peptides induced significant increases of the order parameter of the lipid hydrocarbon chains, suggesting that the lipid bilayer becomes more ordered in the presence of these peptides, possibly as a result of dehydration at the membrane surface.  相似文献   
58.
Weng  Shaoting  Zhao  Yitian  Yu  Changhong  Wang  Xiaofan  Xiao  Xuehan  Han  Liqiang  Zhang  Kunpeng  Wang  Jiang  Yang  Guoyu 《Biotechnology letters》2021,43(11):2111-2129
Biotechnology Letters - An ideal rAAV gene editing system not only effectively edits genes at specific site, but also prevents the spread of the virus from occurring off-target or carcinogenic...  相似文献   
59.
Endogenous retroviruses provide important insights into the deep history of this viral lineage. Endogenous foamy viruses are thought to be very rare and only a few cases have been identified to date. Here we report a novel endogenous foamy virus (CaEFV) within the genome of the Cape golden mole (Chrysochloris asiatica). The identification of CaEFV reveals the presence of foamy virus in the placental mammal superorder Afrotheria. Phylogenetic analyses place CaEFV basal to other foamy viruses of Eutherian origin, suggesting an ancient codivergence between foamy virus and placental mammals. These findings have implications for understanding the long-term evolution, diversity, and biology of retroviruses.  相似文献   
60.
We designed and synthesized a series of haptens to elicit catalytic antibodies with phosphatase activity against nerve agents. The design is based on the novel concept of multiple reactive immunization which aims to afford two or more catalytic residues within the antibody's binding cleft. The haptens showed the desired reactivity in vitro and were submitted for immunization.  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