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   4355篇
  免费   356篇
  国内免费   534篇
  2024年   10篇
  2023年   34篇
  2022年   71篇
  2021年   141篇
  2020年   139篇
  2019年   170篇
  2018年   209篇
  2017年   205篇
  2016年   235篇
  2015年   196篇
  2014年   256篇
  2013年   286篇
  2012年   286篇
  2011年   280篇
  2010年   274篇
  2009年   224篇
  2008年   237篇
  2007年   217篇
  2006年   186篇
  2005年   184篇
  2004年   187篇
  2003年   195篇
  2002年   186篇
  2001年   169篇
  2000年   111篇
  1999年   66篇
  1998年   37篇
  1997年   59篇
  1996年   22篇
  1995年   34篇
  1994年   24篇
  1993年   20篇
  1992年   21篇
  1991年   18篇
  1990年   24篇
  1989年   26篇
  1988年   15篇
  1985年   14篇
  1984年   17篇
  1983年   14篇
  1982年   15篇
  1981年   8篇
  1980年   11篇
  1979年   11篇
  1978年   16篇
  1977年   10篇
  1976年   10篇
  1974年   8篇
  1973年   10篇
  1970年   9篇
排序方式: 共有5245条查询结果,搜索用时 15 毫秒
81.
The interfacial instability between a thiophosphate solid electrolyte and oxide cathodes results in rapid capacity fade and has driven the need for cathode coatings. In this work, the stability, evolution, and performance of uncoated, Li2ZrO3‐coated, and Li3B11O18‐coated LiNi0.5Co0.2Mn0.3O2 cathodes are compared using first‐principles computations and electron microscopy characterization. Li3B11O18 is identified as a superior coating that exhibits excellent oxidation/chemical stability, leading to substantially improved performance over cells with Li2ZrO3‐coated or uncoated cathodes. The chemical and structural origin of the different performance is interpreted using different microscopy techniques which enable the direct observation of the phase decomposition of the Li2ZrO3 coating. It is observed that Li is already extracted from the Li2ZrO3 in the first charge, leading to the formation of ZrO2 nanocrystallites with loss of protection of the cathode. After 50 cycles separated (Co, Ni)‐sulfides and Mn‐sulfides can be observed within the Li2ZrO3‐coated material. This work illustrates the severity of the interfacial reactions between a thiophosphate electrolyte and oxide cathode and shows the importance of using coating materials that are absolutely stable at high voltage.  相似文献   
82.
83.
Shen  He  Wu  Shuyu  Chen  Xi  Xu  Bai  Ma  Dezun  Zhao  Yannan  Zhuang  Yan  Chen  Bing  Hou  Xianglin  Li  Jiayin  Cao  Yudong  Fu  Xianyong  Tan  Jun  Yin  Wen  Li  Juan  Meng  Li  Shi  Ya  Xiao  Zhifeng  Jiang  Xingjun  Dai  Jianwu 《中国科学:生命科学英文版》2020,63(12):1879-1886
Science China Life Sciences - Spinal cord injury (SCI), especially complete transected SCI, leads to loss of cells and extracellular matrix and functional impairments. In a previous study, we...  相似文献   
84.
FK506‐sensitive proline rotamases (FPRs), also known as FK506‐binding proteins (FKBPs), can mediate immunosuppressive drug resistance in budding yeast but their physiological roles in filamentous fungi remain opaque. Here, we report that three FPRs (cytosolic/nuclear 12.15‐kD Fpr1, membrane‐associated 14.78‐kD Fpr2 and nuclear 50.43‐kD Fpr3) are all equally essential for cellular Ca2+ homeostasis and contribute significantly to calcineurin activity at different levels in the insect‐pathogenic fungus Beauveria bassiana although the deletion of fpr1 alone conferred resistance to FK506. Radial growth, conidiation, conidial viability and virulence were less compromised in the absence of fpr1 or fpr2 than in the absence of fpr3, which abolished almost all growth on scant media and reduced growth moderately on rich media. The Δfpr3 mutant was more sensitive to Na+, K+, Mn2+, Ca2+, Cu2+, metal chelate, heat shock and UVB irradiation than was Δfpr2 while both mutants were equally sensitive to Zn2+, Mg2+, Fe2+, H2O2 and cell wall‐perturbing agents. In contrast, the Δfpr1 mutant was less sensitive to fewer stress cues. Most of 32 examined genes involved in DNA damage repair, Na+/K+ detoxification or osmotolerance and Ca2+ homeostasis were downregulated sharply in Δfpr2 and Δfpr3 but rarely so affected in Δfpr1, coinciding well with their phenotypic changes. These findings uncover important, but differential, roles of three FPRs in the fungal adaptation to insect host and environment and provide novel insight into their essential roles in calcium signalling pathway.  相似文献   
85.
Red‐spotted grouper nervous necrosis virus (RGNNV), the causative agent of viral nervous necrosis disease, has caused high mortality and heavy economic losses in marine aquaculture worldwide. However, changes in host cell metabolism during RGNNV infection remain largely unknown. Here, the global metabolic profiling during RGNNV infection and the roles of cellular fatty acid synthesis in RGNNV infection were investigated. As the infection progressed, 71 intracellular metabolites were significantly altered in RGNNV‐infected cells compared with mock‐infected cells. The levels of metabolites involved in amino acid biosynthesis and metabolism were significantly decreased, whereas those that correlated with fatty acid synthesis were significantly up‐regulated during RGNNV infection. Among them, tryptophan and oleic acid were assessed as the most crucial biomarkers for RGNNV infection. In addition, RGNNV infection induced the formation of lipid droplets and re‐localization of fatty acid synthase (FASN), indicating that RGNNV induced and required lipogenesis for viral infection. The exogenous addition of palmitic acid (PA) enhanced RGNNV infection, and the inhibition of FASN and acetyl‐CoA carboxylase (ACC) significantly decreased RGNNV replication. Additionally, not only inhibition of palmitoylation and phospholipid synthesis, but also destruction of fatty acid β‐oxidation significantly decreased viral replication. These data suggest that cellular fatty acid synthesis and mitochondrial β‐oxidation are essential for RGNNV to complete the viral life cycle. Thus, it has been demonstrated for the first time that RGNNV infection in vitro overtook host cell metabolism and, in that process, cellular fatty acid synthesis was an essential component for RGNNV replication.  相似文献   
86.
Plasma Physics Reports - Compression of a fiber array with a deuterated target mounted on its axis is studied at the Angara-5-1 facility (3.5 MA, 100 ns). Cylindrical arrays with an initial...  相似文献   
87.
为探索越南粉苞茉莉(Jasminum dichotomum)扦插生根的影响因素,建立扦插繁育技术体系,以1年生越南粉苞茉莉枝条为插穗,采用L16(44)正交试验,探讨生长调节剂种类及其浓度、处理时间、基质种类对越南粉苞茉莉茎段扦插生根的影响,利用排队评分法和公式评分法对正交试验进行分析。结果表明,A2B3C3D2为试验的最优处理组合,即将插穗在250 mg·L-1 IBA和500 mg·L-1 NAA混合药剂中浸泡20 min后扦插于沙子上。  相似文献   
88.
89.
90.
为了明确TaCO9-1A基因在小麦生长发育中的具体调控机理,该研究以同源克隆的方法成功获得了大麦(Hordeum vulgare)光周期基因HvCO9在小麦(Triticum aestivum)中的直系同源基因TaCO9,并对其进行生物信息学分析、亚细胞定位、转录激活以及表达模式分析;利用农杆菌侵染法转化拟南芥,并对过表达株系进行表型分析。结果表明:(1)TaCO9包含2个外显子和1个内含子,CDS区全长876 bp,编码291个氨基酸,蛋白序列含有特有的CCT结构域,且在不同物种间高度保守。(2)生物信息学分析表明,TaCO9基因编码的蛋白质分子量约为30.7 kD,等电点为6.24;TaCO9的启动子区含有光响应、激素应答和胁迫应答等多种顺式作用元件。(3)亚细胞定位和转录活性分析表明,TaCO9主要定位于细胞核中,且具有转录激活活性。(4)qRT-PCR结果表明,TaCO9基因在各个组织中均有表达,叶片中的表达量最高;在光照14 h条件下TaCO9的表达量显著高于光照10 h和12 h条件下的表达量,且TaCO9在大粒小麦‘西农817’子房与籽粒中的表达量显著高于‘中国春’。(5)经潮霉素筛选成功获得3个转基因拟南芥株系;进一步功能鉴定结果表明,过表达转TaCO9基因拟南芥植株的开花期迟于野生型(对照)3~4 d,但角果和籽粒较野生型大。  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