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   13893篇
  免费   1249篇
  国内免费   1223篇
  16365篇
  2024年   34篇
  2023年   158篇
  2022年   369篇
  2021年   601篇
  2020年   456篇
  2019年   521篇
  2018年   537篇
  2017年   401篇
  2016年   604篇
  2015年   887篇
  2014年   1022篇
  2013年   1045篇
  2012年   1267篇
  2011年   1248篇
  2010年   742篇
  2009年   668篇
  2008年   857篇
  2007年   763篇
  2006年   655篇
  2005年   573篇
  2004年   543篇
  2003年   451篇
  2002年   407篇
  2001年   266篇
  2000年   214篇
  1999年   175篇
  1998年   111篇
  1997年   103篇
  1996年   96篇
  1995年   65篇
  1994年   59篇
  1993年   41篇
  1992年   69篇
  1991年   51篇
  1990年   38篇
  1989年   35篇
  1988年   40篇
  1987年   28篇
  1986年   20篇
  1985年   19篇
  1984年   13篇
  1983年   25篇
  1982年   13篇
  1981年   13篇
  1980年   7篇
  1979年   8篇
  1978年   8篇
  1977年   5篇
  1974年   4篇
  1965年   7篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
CsPbI2Br is emerging as a promising all‐inorganic material for perovskite solar cells (PSCs) due to its more stable lattice structure and moisture resistance compared to CsPbI3, although its device performance is still much behind this counterpart. Herein, a preannealing process is developed and systematically investigated to achieve high‐quality CsPbI2Br films by regulating the nucleation and crystallization of perovskite. The preannealing temperature and time are specifically optimized for a dopant‐free poly(3‐hexylthiophene) (P3HT)‐based device to target dopant‐induced drastic performance degradation for spiro‐OMeTAD‐based devices. The resulting P3HT‐based device exhibits comparable power conversion efficiency (PCE) to spiro‐OMeTAD‐based devices but much enhanced ambient stability with over 95% PCE after 1300 h. A diphenylamine derivative is introduced as a buffer layer to improve the energy‐level mismatch between CsPbI2Br and P3HT. A record‐high PCE of 15.50% for dopant‐free P3HT‐based CsPbI2Br PSCs is achieved by alleviating the open‐circuit voltage loss with the buffer layer. These results demonstrate that the preannealing processing together with a suitable buffer layer are applicable strategies for developing dopant‐free P3HT PSCs with high efficiency and stability.  相似文献   
92.
Kong  Wen-Hua  Zhao  Rong  Zhou  Jun-Bo  Wang  Fang  Kong  De-Guang  Sun  Jian-Bin  Ruan  Qiong-Fang  Liu  Man-Qing 《中国病毒学》2020,35(6):752-757
Virologica Sinica - The immense patient number caused by coronavirus disease 2019 (COVID-19) global pandemic brings the urge for more knowledge about its immunological features, including the...  相似文献   
93.
Human intestinal microbiota is important to host health and is associated with various diseases. It is a challenge to identify the functions and metabolic activity of microorganisms at the single-cell level in gut microbial community. In this study, we applied Raman microspectroscopy and deuterium isotope probing (Raman–DIP) to quantitatively measure the metabolic activities of intestinal bacteria from two individuals and analysed lipids and phenylalanine metabolic pathways of functional microorganisms in situ. After anaerobically incubating the human faeces with heavy water (D2O), D2O with specific substrates (glucose, tyrosine, tryptophan and oleic acid) and deuterated glucose, the C–D band in single-cell Raman spectra appeared in some bacteria in faeces, due to the Raman shift from the C–H band. Such Raman shift was used to indicate the general metabolic activity and the activities in response to the specific substrates. In the two individuals' intestinal microbiota, the structures of the microbial communities were different and the general metabolic activities were 76 ± 1.0% and 30 ± 2.0%. We found that glucose, but not tyrosine, tryptophan and oleic acid, significantly stimulated metabolic activity of the intestinal bacteria. We also demonstrated that the bacteria within microbiota preferably used glucose to synthesize fatty acids in faeces environment, whilst they used glucose to synthesize phenylalanine in laboratory growth environment (e.g. LB medium). Our work provides a useful approach for investigating the metabolic activity in situ and revealing different pathways of human intestinal microbiota at the single-cell level.  相似文献   
94.
95.
96.
Nisar  M.  Ali  Z.  Ali  A.  Aman  R.  Park  H. J.  Ullah  I.  Ullah  A.  Yun  D. J. 《Russian Journal of Plant Physiology》2020,67(3):515-520
Russian Journal of Plant Physiology - Plant root architecture modulates during developmental stages and adjusts with the environmental condition. The cytosolic calcium which is a ubiquitous...  相似文献   
97.
Non‐small‐cell lung carcinoma (NSCLC) continues to top the list of cancer mortalities worldwide. The role of circular RNAs (circRNAs) in tumorigenesis has been increasingly appreciated, although it is relatively unexplored in NSCLC. Herein, we reported the role of hsa_circ_0085131 in NSCLC. In the present study, NSCLC tumor specimens exhibited a higher hsa_circ_0085131 level in comparison to para‐tumor samples. And the higher level of hsa_circ_0085131 was associated with recurrence and poorer survival of NSCLC. Moreover, hsa_circ_0085131 promoted cell proliferation and cisplatin (DDP)‐resistance. Furthermore, hsa_circ_0085131 regulated cell DDP‐resistance by modulating autophagy. Hsa_circ_0085131 acted as a competing endogenous RNA of miR‐654‐5p to release autophagy‐associated factor ATG7 expression, thereby promoting cell chemoresistance. In conclusion, hsa_circ_0085131 enhances DDP‐resistance of NSCLC cells through sequestering miR‐654‐5p to upregulate ATG7, leading to cell autophagy. Therefore, these findings advocate targeting the hsa_circ_0085131/miR‐654‐5p/ATG7 axis as a potential therapeutic option for patients with NSCLC who are resistant to DDP.  相似文献   
98.
99.
Dendrolimus spp. are important destructive pests of conifer forests, and Dendrolimus punctatus Walker (Lepidoptera; Lasiocampidae) is the most widely distributed Dendrolimus species. During periodic outbreaks, this species is said to make “fire without smoke” because large areas of pine forest can be quickly and heavily damaged. Yet, little is known about the molecular mechanisms that underlie the unique ecological characteristics of this forest insect. Here, we combined Pacific Biosciences (PacBio) RSII single‐molecule long reads and high‐throughput chromosome conformation capture (Hi‐C) genomics‐linked reads to produce a high‐quality, chromosome‐level reference genome for D. punctatus. The final assembly was 614 Mb with contig and scaffold N50 values of 1.39 and 22.15 Mb, respectively, and 96.96% of the contigs anchored onto 30 chromosomes. Based on the prediction, this genome contained 17,593 protein‐coding genes and 56.16% repetitive sequences. Phylogenetic analyses indicated that D. punctatus diverged from the common ancestor of Hyphantria cunea, Spodoptera litura and Thaumetopoea pityocampa ~ 108.91 million years ago. Many gene families that were expanded in the D. punctatus genome were significantly enriched for the xenobiotic biodegradation system, especially the cytochrome P450 gene family. This high‐quality, chromosome‐level reference genome will be a valuable resource for understanding mechanisms of D. punctatus outbreak and host resistance adaption. Because this is the first Lasiocampidae insect genome to be sequenced, it also will serve as a reference for further comparative genomics.  相似文献   
100.
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