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   202篇
  免费   13篇
  国内免费   29篇
  2024年   2篇
  2023年   8篇
  2022年   11篇
  2021年   31篇
  2020年   7篇
  2019年   13篇
  2018年   7篇
  2017年   7篇
  2016年   4篇
  2015年   17篇
  2014年   16篇
  2013年   12篇
  2012年   19篇
  2011年   17篇
  2010年   5篇
  2009年   12篇
  2008年   7篇
  2007年   5篇
  2006年   9篇
  2005年   4篇
  2004年   3篇
  2003年   7篇
  2002年   2篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1998年   2篇
  1996年   4篇
  1995年   1篇
  1994年   3篇
  1993年   1篇
  1990年   1篇
  1988年   1篇
  1986年   1篇
  1984年   1篇
排序方式: 共有244条查询结果,搜索用时 930 毫秒
111.

Background  

Histone methylation can dramatically affect chromatin structure and gene expression and was considered irreversible until recent discoveries of two families of histone demethylases, the KDM1 (previously LSD1) and JmjC domain-containing proteins. These two types of proteins have different functional domains and distinct substrate specificities. Although more and more KDM1 and JmjC proteins have been shown to have histone demethylase activity, our knowledge about their evolution history is limited.  相似文献   
112.
Chen SA  Wang X  Zhao B  Yuan X  Wang Y 《Biotechnology letters》2003,25(15):1235-1238
Saffron callus was grown in a two-stage culture on B5 medium supplemented with casein hydrolysate (300 mg l–1) at 22 °C in dark with naphthalene acetic acid (2 mg l–1) and 6-benzyladenine (1 mg l–1) to give maximum biomass (16 g dry wt l–1), and with indole 3-acetic acid (2 mg l–1) and 6-benzyladenine (0.5 mg l–1) for crocin formation. The maximum crocin production (0.43 g l–1) was achieved by this two-stage culture method, which was three times that by a one-stage method.  相似文献   
113.
114.
The oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), is a major pest of fruit trees worldwide. Females oviposit on the young leaves of peach [Prunus persica (L.) Batsch (Rosaceae)] shoots at twilight, when light intensity changes markedly. Previous researches have shown that the oviposition response of this moth is guided particularly by visual and olfactory cues from host plants. However, the relative importance of visual and olfactory cues in their oviposition preference is largely unknown. As a crepuscular moth, how do choices change as light intensity drops rapidly from day to night? In the present study, through two‐choice behavioural experiments, the oviposition responses of G. molesta to visual and olfactory cues (alone or in combination) from peach shoots were tested at four light intensities ranging from daylight to starlight. Grapholita molesta showed similar oviposition responses to plant cues under 1 000, 100, 1 and 0.01 mW m?2 illumination. Olfactory cues from peach shoots attracted significantly more oviposition than the negative control, whereas visual cues alone did not. Furthermore, olfactory cues were more attractive than visual cues, and no significant interaction was observed between the responses to the two cues. Our findings indicate that G. molesta females mainly rely on olfactory cues to recognize oviposition sites, regardless of differences in light intensity. These results do not provide evidence for attraction to visual cues, but the possibility that the brightness of leaves might be used to guide oviposition is discussed.  相似文献   
115.
116.
Guo  Qingdong  Guo  Jun  Liu  Wei  Hu  Shijie  Hu  Xuean  Wang  Qianliang  Jiang  Xiaofan 《Cellular and molecular neurobiology》2022,42(7):2245-2256
Cellular and Molecular Neurobiology - Circular RNAs (circRNAs) have pivotal functions in regulating diverse biological processes of human tumors, including glioma. Herein, a novel circRNA epidermal...  相似文献   
117.

Aim

To test the fitness-gain curve model proposes that cosexual plants adjust their sex ratios and resource allocation depending on their size. In this study, the monoecious species Sagittaria potamogetifolia was used as a model to determine the effects of plant size and density on gender modification and reproductive allocation.

Methods and materials

Various traits, including flower number and plant biomass, were measured under four different artificially constructed population density treatments. More male flowers were produced than female flowers per individual at high densities, while the opposite trend was observed at low densities. This trend was particularly evident in the highest density treatment.

Results

A trade-off was discovered between male–female sex allocations in the highest density treatment (40 individuals m?2). The allometric growth of reproductive organs compared with plant size was detected, as evidenced by the reproductive structures’ biomass and flower numbers. However, in the highest density treatment, size was weakly negatively correlated with femaleness.

Conclusion

Thus, S. potamogetifolia has a reproductive strategy that easily adjusts to different reproductive environmental densities.  相似文献   
118.
Ji  Ru  Hua  Yanan  Chen  Kejian  Long  Kaiwen  Fu  Yanjun  Zhang  Xiaofan  Zhuang  Songlin 《Plasmonics (Norwell, Mass.)》2019,14(1):165-171
Plasmonics - Metasurfaces, which are composed of two-dimensional arrays of subwavelength structures, can reshape the wavefront arbitrarily by introducing phase discontinuities with the entire...  相似文献   
119.

Objective

Monocytes and macrophages can infiltrate into tumor microenvironment and regulate the progression of tumors. This study aimed at determining the frequency of different subsets of circulating monocytes and tumor infiltrating macrophages (TIMs) in patients with colorectal cancer (CRC).

Methods

The frequency of different subsets of circulating monocytes was characterized in 46 CRC patients and 22 healthy controls (HC) by flow cytometry. The frequency of different subsets of macrophages was analyzed in TIMs from 30 tumor tissues and in lamina propria mononuclear cells (LPMCs) from 12 non-tumor tissues. The concentrations of plasma cytokines and carcinoembryonic antigen (CEA) were determined. The potential association of these measures with the values of clinical parameters was analyzed.

Results

In comparison with that in the HC, the percentages of circulating CD14+CD169+, CD14+CD169+CD163+ and CD14+CD169+CD206+ monocytes and TIMs CD14+CD169+ as well as IL-10+CD14+CD169+, but not IL-12+ CD14+CD169+ macrophages were significantly increased, accompanied by higher levels of plasma IL-10 in the CRC patients. The percentages of CD14+CD169+ circulating monocytes and TIM macrophages were associated with the stage of disease and correlated positively with the levels of plasma IL-10 and CEA in CRC patients.

Conclusion

Our data suggest that an increase in the frequency of CD14+CD169+ cells may be associated with the development and progression of CRC and is concomitant rise of both, pro-tumor (M2-like, IL-10 producing) and anti-tumor (M1-like, IL-12 producing) monocytes and infiltrating macrophages. The frequency of CD14+CD169+ circulating monocytes and infiltrating macrophages may serve as a biomarker for evaluating the pathogenic degrees of CRC.  相似文献   
120.
microRNA (miRNA) plays a role in the pathogenesis of ischemic stroke, and single nucleotide polymorphisms in miRNA genes may contribute to disease susceptibility. However, the effect of miR-146a, miR-196a2, and miR-499 polymorphisms on ischemic stroke susceptibility has been rarely reported. Using the TaqMan assay, we evaluated the association of hsa-miR-146a/rs2910164, hsa-miR-196a2/rs11614913, and hsa-miR-499/rs3746444 polymorphisms with the risk of ischemic stroke in a Chinese population with 531 ischemic stroke patients and 531 control subjects. Rs2910164 C/G genotypes were significantly associated with increased risk of ischemic stroke in different genetic model (homozygote comparison: OR = 2.00, 95% CI, 1.29–3.12, P = 0.002; additive model: OR = 1.35, 95% CI, 1.10–1.65, P = 0.004;dominant model: OR = 1.33, 95% CI, 1.00–1.75, P = 0.049; recessive model: OR = 1.82, 95% CI, 1.20–2.74, P = 0.004). Subjects with allele G of hsa-miR-146a/ rs2910164 also showed increased risk of ischemic stroke (OR = 1.33, 95% CI, 1.09–1.62, P = 0.005). Stratification analysis showed that the association between rs2910164 and the risk of ischemic stroke was more pronounced in subjects over 60 years old, females, non-drinkers, subjects without hypertension or diabetes mellitus. There were significant combined effects between miR-146a/rs2910164 and fasting glucose/low-density lipoprotein cholesterol levels on ischemic stroke susceptibility. However, we failed to find any association between the alleles/genotypes of rs11614913 T/C and ischemic stroke, respectively (P> 0.05). In summary, this study provides evidence that miR-146a/rs2910164 might be associated with a significantly increased risk of ischemic stroke in a Chinese population, and the combined effects between miRNA polymorphism and fasting glucose /blood lipid levels may contribute to stroke pathogenesis.  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