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   3751篇
  免费   453篇
  国内免费   1344篇
  2024年   40篇
  2023年   73篇
  2022年   163篇
  2021年   173篇
  2020年   174篇
  2019年   183篇
  2018年   155篇
  2017年   131篇
  2016年   175篇
  2015年   235篇
  2014年   276篇
  2013年   282篇
  2012年   351篇
  2011年   318篇
  2010年   245篇
  2009年   256篇
  2008年   286篇
  2007年   266篇
  2006年   267篇
  2005年   227篇
  2004年   239篇
  2003年   194篇
  2002年   160篇
  2001年   162篇
  2000年   138篇
  1999年   78篇
  1998年   43篇
  1997年   34篇
  1996年   36篇
  1995年   26篇
  1994年   26篇
  1993年   11篇
  1992年   13篇
  1991年   21篇
  1990年   8篇
  1989年   10篇
  1988年   7篇
  1987年   7篇
  1986年   5篇
  1985年   9篇
  1984年   4篇
  1983年   5篇
  1982年   9篇
  1981年   3篇
  1976年   2篇
  1965年   2篇
  1963年   2篇
  1958年   2篇
  1957年   4篇
  1953年   3篇
排序方式: 共有5548条查询结果,搜索用时 15 毫秒
131.
人类基因组中,用于蛋白质编码的核酸序列约占1.5%,另外98.5%的非蛋白编码基因被视为"噪音"序列,并未引起人们的注意。随着测序技术的发展,人们发现大部分的基因被转录成RNA,其中多数为长度大于200nt且不编码蛋白质的长链非编码RNA(Long non-coding RNA, lncRNA),其作用机制包括支架分子、引导分子等,广泛参与细胞发育、增殖及迁移过程,且其水平的改变又与肿瘤、代谢性疾病等相关。本文主要对lncRNA的分类、作用机制及涉及的疾病等进行综述,为进一步研究lncRNA的功能机制奠定基础。  相似文献   
132.
Yun  Jianmin  Zhao  Fengqin  Zhang  Wenwei  Yan  Haijiao  Zhao  Fengyun  Ai  Duiyuan 《Annals of microbiology》2019,69(3):279-289

This study reveals the microbial community succession and diversity during the whole solid-fermentation processes of naturally fermented Liangzhou fumigated vinegar (LZFV). Dynamics and diversity of microbial community succession in “Daqu” starter and other fermentation stages (starch saccharification, alcoholic fermentation, and acetic acid fermentation) were monitored using a metagenomic approach involving high-throughput sequencing. Meanwhile, dynamic changes of characteristic flavor compounds of vinegar were determined by gas chromatograph (GC) analysis. The result showed that the microbiota composition exhibited rich diversity. Twenty-five bacterial and 18 fungal genera were found in the whole fermentation process where Lactobacillus, Acetobacter, Aspergillus, Saccharomyces, and Alternaria were the predominant microorganisms. Alpha diversity metrics showed that bacterial diversity in Daqu was greater than that in AF and AAF. By contrast, fungal diversity increased from Daqu to AF and decreased in the initial stage (5–8 days) of AAF then remained relatively steady. Hence, these results could help understand dynamics of microbial community succession in continuous fermentation of traditional Chinese vinegars. The LZFV fermentation is a continuous process with spontaneous growth that affects the dynamics of microbial communities. Continuous changes of micro-environment conditions in substrate affect the diversity and structure of microbiota. Microbial growth and metabolism were closely related to the changes in the physicochemical characteristics of the cultures. The microbial flora composition showed rich diversity, and with the increase in brewing time and the change in micro-ecological environmental conditions; the microbial community showed a complex dynamic changes.

  相似文献   
133.
目的:探讨持续性血液滤过联合高流量吸氧治疗重症急性呼吸综合征的疗效及对血清炎症因子水平的影响。方法:选择2013年2月至2016年2月我院接诊的60例重症急性呼吸综合征患者,通过随机数表法将其分为观察组(n=30)和对照组(n=30)。观察组采用持续性血液滤过联合高流量吸氧进行治疗,对照组采用持续性血液滤过进行治疗。比较两组临床疗效、治疗前后动脉血氧分压(PaO_2)、动脉血二氧化碳分压(PaCO_2)、氧合指数、氢离子浓度指数(pH)值、呼吸频率(RR)、心率(HR)、血清C反应蛋白(CRP)、白介素6(IL-6)、白介素8(IL-8)、肿瘤坏死因子α(TNF-α)水平的变化及不良反应的发生情况。结果:治疗后,观察组有效率为76.67%,显著高于对照组(50.00%,P0.05)。两组治疗后PaO_2、PaCO_2、氧合指数、pH值、RR、HR均较治疗前明显改善,观察组患者PaO_2、氧合指数明显高于对照组,PaCO_2、pH值、RR、HR、血清CRP、IL-6、IL-8及TNF-α水平均显著低于对照组(P0.05)。治疗期间,观察组患者不良反应总发生率(10.00%)显著低于对照组(36.67%,P0.05);观察组死亡1例(3.33%),对照组死亡6例(20.00%),观察组病死率显著低于对照组(P0.05)。结论:持续性血液滤过联合高流量吸氧治疗重症急性呼吸综合征患者的临床疗效及安全性明显优于单用持续性血液滤过治疗,可能与其更有效减轻炎症反应有关。  相似文献   
134.
In this study, we developed a novel simple fluorescence resonance‐energy transfer (FRET) system between two‐color CdTe quantum dots (QDs) assisted by cetyltrimethylammonium bromide (CTAB). Mercaptopropionic (MPA)‐capped CdTe QDs serving as both donors and acceptors were successfully synthesized by changing the refluxing time in aqueous solution. CTAB micelles formed in water and minimized the distance between the donors and acceptors significantly by electrostatic interactions, improving FRET efficiency. Several factors that affected the fluorescence spectra of the FRET system were investigated. The prepared FRET system was feasible as an effective fluorescent probe to detect Hg(II) in aqueous solution. At pH 7.0, a linear relationship between the quenched fluorescence intensity of orange‐emitting acceptors (QDs(A)) and Hg(II) concentration was acquired in the range 5–250 nmol/L with a detection limit of 1.95 nmol/L. The developed method showed excellent analytical performance for Hg(II) with high sensitivity and acceptable selectivity, reproducibility and stability. This finding indicated that the method has a promising potential application for environmental monitoring. This study demonstrated the great promise of QDs for expedient, low‐cost and high‐sensitivity detection of Hg(II).  相似文献   
135.
136.
Ring1 and YY1 binding protein (RYBP), a new member of the polycomb group protein family, has been reported to play an important role in various biological processes. Recently, more and more studies have demonstrated an implication of RYBP in cancer development. However, the specific role of RYBP in anaplastic thyroid cancer (ATC) remains unknown. In this study, we investigated for the first time the expression pattern and biological functions of RYBP in ATC. We showed that RYBP was lowly expressed in ATC tissues and cell lines. We also found that overexpression of RYBP inhibited ATC cell proliferation, invasion, and cisplatin resistance. Furthermore, we observed that upregulation of RYBP decreased the phosphorylation of EGFR and ERK1/2 in ATC cells. Taken together, our data indicated that RYBP might be considered as a promising therapeutic target for the treatment of ATC.  相似文献   
137.
Journal of Industrial Microbiology & Biotechnology - Extremely thermoacidophilic Crenarchaeota belonging to the order Sulfolobales, such as Metallosphaera sedula, are metabolically versatile...  相似文献   
138.
为了筛选适宜南京地区的优良城市绿化树种,在野外调查和问卷调查的基础上,利用层次分析法(AHP)建立江苏宁镇山脉乡土树种评价体系,对该区域的乡土树种进行客观的定量分析。结果表明:(1)乡土树种作为城市绿化树种应首先考虑抗逆性,其次是生态价值、美学价值和生物学特性;(2)参与评价的41种宁镇山脉乡土树种可分为4类,其中I类乡土树种应大力推广应用,Ⅱ类乡土树种可作为森林城市树种多样性的有益补充,Ⅲ类和Ⅳ类乡土树种作为城市绿化树种仍有一定的差距。13种Ⅰ类乡土树种作为城市绿化树种具有良好的应用前景。  相似文献   
139.
Li  Z. G.  Shi  Y. H.  Ai  L. 《Russian Journal of Plant Physiology》2019,66(4):564-571
Russian Journal of Plant Physiology - Methylglyoxal (MG) has traditionally been known as a toxic byproduct of cellular metabolism in plants, which now has been found to function as a novel...  相似文献   
140.
再论可持续性科学: 新形势与新机遇   总被引:3,自引:0,他引:3  
近10年来,可持续性科学蓬勃发展,已成为21世纪全球普遍关注的一个重要的新科学领域.然而,在大力提倡可持续发展和生态文明建设的中国,可持续性科学尚未引起科学家和实践者的足够重视.为促进可持续性科学在中国的发展,2014年邬建国等曾撰文介绍什么是可持续性科学.本文进一步探讨了这一问题,并补充阐述了可持续性科学与可持续发展研究的关系、可持续性科学的科学范式及其8个基本论题.基于对可持续性科学发展动态的分析,作者认为,一方面,可持续性科学已进入系统推进的成熟发展期;另一方面,虽然我国可持续发展研究、实践与教育的热情高涨,但在可持续性科学领域起步较晚,落后于主要发达国家和南非.为此,本文在文献综述的基础上,提出促进中国发展可持续性科学的“三位一体”策略:一是“请进来”以服务中国实践;二是“走出去”以贡献中国智慧;三是“中西医结合”以引领学科发展.  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