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   5150篇
  免费   472篇
  国内免费   393篇
  2024年   15篇
  2023年   84篇
  2022年   151篇
  2021年   281篇
  2020年   187篇
  2019年   267篇
  2018年   238篇
  2017年   152篇
  2016年   252篇
  2015年   370篇
  2014年   363篇
  2013年   389篇
  2012年   460篇
  2011年   384篇
  2010年   288篇
  2009年   249篇
  2008年   279篇
  2007年   250篇
  2006年   209篇
  2005年   158篇
  2004年   148篇
  2003年   140篇
  2002年   102篇
  2001年   90篇
  2000年   60篇
  1999年   75篇
  1998年   50篇
  1997年   40篇
  1996年   40篇
  1995年   31篇
  1994年   30篇
  1993年   34篇
  1992年   32篇
  1991年   28篇
  1990年   24篇
  1989年   12篇
  1988年   17篇
  1987年   7篇
  1986年   8篇
  1985年   11篇
  1984年   4篇
  1983年   2篇
  1982年   2篇
  1981年   1篇
  1976年   1篇
排序方式: 共有6015条查询结果,搜索用时 296 毫秒
231.
Liu  Lei  Zeng  Dong  Yang  Mingyue  Wen  Bin  Lai  Jing  Zhou  Yi  Sun  Hao  Xiong  Lvcheng  Wang  Jie  Lin  Yicen  Pan  Kangcheng  Jing  Bo  Wang  Ping  Ni  Xueqin 《Probiotics and antimicrobial proteins》2019,11(4):1278-1292

Probiotics could promote animal growth and enhance immune function. This study investigated the effects of Clostridium butyricum (CB) on the growth performance, intestinal immune, and gut microbiota of weaning rex rabbits. A total of 60 healthy female rabbits (5-month-old) were divided equally into four groups and mated on the same day: control group (CTRL, fed with basal feed), low-dose group (LDG, fed with basal feed + 1.0 × 103 CFU/g CB), middle-dose group (MDG, fed with basal feed + 1.0 × 104 CFU/g CB), and high-dose group (HDG, fed with basal feed + 1.0 × 105 CFU/g CB). Then, 30 weaning rex rabbits (35-day-old) were collected from each group for this experiment, and they were offered the same feeds as their mother. The results demonstrated that high-dose CB treatment significantly increased average daily weight gain of weaning rex rabbits. Further studies suggested that CB enhanced small intestinal digestive enzyme activity and improved mucosal morphology and antioxidant status. Supplemented with CB, small intestinal barrier function was maintained with the upregulation of mRNA levels of ZO-1, claudin, and occludin as well as the increase of sIgA production. Moreover, the relative expressions of MyD88, TLR2, and TLR4 were elevated in HDG; simultaneously, pro-inflammatory cytokines including IL-6, INF-γ, and TNF-α were decreased after CB administration. In addition, CB showed beneficial effects in improving weaning rex rabbit intestinal microflora via increasing the abundance of beneficial bacteria. Therefore, our results indicated CB can promote rex rabbit growth, which is likely to the enhancement of immune function and the improvement of intestinal microbiota.

  相似文献   
232.
Fluorescence imaging, as a commonly used scientific tool, is widely applied in various biomedical and material structures through visualization technology. Highly selective and sensitive luminescent biological probes, as well as those with good water solubility, are urgently needed for biomedical research. In contrast to the traditional aggregation‐caused quenching of fluorescence, in the unique phenomenon of aggregation‐induced emission (AIE), the individual luminogens have extremely weak or no emissivity because they each have free intramolecular motion; however, when they form aggregates, these components immediately “light up”. Since the discovery of “turn‐on” mechanism, researchers have been studying and applying AIE in a variety of fields to develop more sensitive, selective, and efficient strategies for the AIE dyes. There are numerous advantages to the use of AIE‐based methods, including low background interference, strong contrast, high performance in intracellular imaging, and the ability for long‐term monitoring in vivo. In this review, two typical examples of AIEgens, TPE‐Cy and TPE‐Ph‐In, are described, including their structure properties and applications. Recent progress in the biological applications is mainly focused on. Undoubtedly, in the near future, an increasing number of encouraging and practical ideas will promote the development of more AIEgens for broad use in biomedical applications.  相似文献   
233.
A large‐depth‐of‐field full‐field optical angiography (LD‐FFOA) method is developed to expand the depth‐of‐field (DOF) using a contrast pyramid fusion algorithm (CPFA). The absorption intensity fluctuation modulation effect is utilized to obtain full‐field optical angiography (FFOA) images at different focus positions. The CPFA is used to process these FFOA images with different focuses. By selecting high‐contrast areas, the CPFA can highlight the characteristics and details of blood vessels to obtain LD‐FFOA images. In the optimal case of the proposed method, the DOF for FFOA is more than tripled using 10 differently focused FFOA images. Both the phantom and animal experimental results show that the LD‐FFOA resolves FFOA defocusing issues induced by surface and thickness inhomogeneities in biological samples. The proposed method can be potentially applied to practical biological experiments.   相似文献   
234.
The oriental armyworm, Mythimna separata, is a serious agricultural pest in China. Seasonal and roundtrip migration has recently led to sudden, localized outbreaks and crop losses. To evaluate genetic differentiation between populations in eastern and western China and elucidate gene flow, the genetic structure of 20 natural populations from nine provinces was examined using seven microsatellite markers. The results indicated high genetic diversity. However, little to moderate (0 < FST < 0.15) genetic differentiation was detected, and there was no correlation between genetic distance and geographical distance. Bayesian clustering analysis identified three groups whereas discriminant analysis of principal components identified ten clusters that were considered as two clear‐cut clusters and one admixed group. Gene flow occurred frequently in most population pairs, and an asymmetrical migration rate was detected in several pairwise population comparisons. The bottleneck test showed that few populations had experienced recent bottlenecks. Correspondingly, large‐scale and long‐distance migration of M. separata has caused low genetic differentiation and frequent gene exchange. Our findings are important for studying genetic evolution and help to improve predictions of M. separata outbreaks in China.  相似文献   
235.
236.
237.
238.
The heavy metal ATPase(HMA)subfamily is mainly involved in heavy metal(HM)tolerance and transport in plants,but an understanding of the definite roles and mechanisms of most HMA members are still limited.In the present study,we identified 14 candidate HMA genes named BrrHMAl—BrrHMA8 from the turnip genome and analyzed the phylogeny,gene structure,chromosome distribution,and conserved domains and motifs of HMAs in turnip(Brassica rapa var.rapa).According to our phylogenetic tree,the BrrHMAs are divided into a Zn/Cd/Co/Pb subclass and Cu/Ag subclass.The BrrHMA members show similar structural characteristics within subclasses.To explore the roles of BrrHMAs in turnip,we compared the gene sequences and expression patterns of the BrrHMA genes between a Cd-tolerant landrace and a Cd-sensitive landrace.Most BrrHMA genes showed similar spatial expression patterns in both Cd-tolerant and Cd-sensitive turnip landraces;some BrrHMA genes,however,were differentially expressed in specific tissue in Cd-tolerant and Cd-sensitive turnip.Specifically,BrrHMA genes in the Zn/Cd/Co/Pb subclass shared the same coding sequence but were differentially expressed in Cd-tolerant and Cd-sensitive turnip landraces under Cd stress.Our findings suggest that the stable expression and up-regulated expression of BrrHMA Zn/Cd/Co/Pb subclass genes under Cd stress may contribute to the higher Cd tolerance of turnip landraces.  相似文献   
239.
植物TOR激酶响应上游信号的研究进展   总被引:1,自引:0,他引:1  
孟彦彦  张楠  熊延 《植物学报》2022,57(1):1-11
雷帕霉素靶蛋白(TOR)是真核生物中高度保守的丝氨酸/苏氨酸蛋白激酶, 能整合营养、能量、生长因子及环境信号, 协调细胞增殖、生长和代谢等过程, 是真核生物生长发育的核心调控因子。近年来, 随着相关研究系统的建立, 植物TOR的功能和机制研究取得了众多突破, 发现其进化上保守的生物学功能及植物中特有的信号通路。该文概述了TOR蛋白复合体的构成, 以及植物TOR响应糖、营养元素(氮、磷和硫)、激素及逆境胁迫信号来调控下游基因转录、蛋白翻译、代谢、细胞自噬和胁迫应答等生物学过程的分子机制, 并提出了植物TOR领域一些亟待解决的科学问题, 以期为全面揭示植物TOR的生物学功能提供参考。  相似文献   
240.
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