全文获取类型
收费全文 | 9452篇 |
免费 | 748篇 |
国内免费 | 763篇 |
出版年
2024年 | 3篇 |
2023年 | 119篇 |
2022年 | 186篇 |
2021年 | 567篇 |
2020年 | 355篇 |
2019年 | 469篇 |
2018年 | 462篇 |
2017年 | 316篇 |
2016年 | 447篇 |
2015年 | 683篇 |
2014年 | 792篇 |
2013年 | 781篇 |
2012年 | 923篇 |
2011年 | 850篇 |
2010年 | 496篇 |
2009年 | 448篇 |
2008年 | 498篇 |
2007年 | 415篇 |
2006年 | 326篇 |
2005年 | 265篇 |
2004年 | 233篇 |
2003年 | 241篇 |
2002年 | 197篇 |
2001年 | 147篇 |
2000年 | 113篇 |
1999年 | 126篇 |
1998年 | 71篇 |
1997年 | 67篇 |
1996年 | 62篇 |
1995年 | 50篇 |
1994年 | 36篇 |
1993年 | 25篇 |
1992年 | 41篇 |
1991年 | 22篇 |
1990年 | 21篇 |
1989年 | 38篇 |
1988年 | 14篇 |
1987年 | 9篇 |
1986年 | 9篇 |
1985年 | 22篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1975年 | 1篇 |
1945年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
51.
Liu Xianchen Yang Yanyun Liu Zhen-Zhen Luo Yachen Fan Fang Jia Cun-Xian 《Sleep and biological rhythms》2019,17(3):339-348
Sleep and Biological Rhythms - Insomnia is prevalent in adolescents. Although several insomnia scales/questionnaires are available to assess insomnia symptoms and severity for adults, no insomnia... 相似文献
52.
53.
54.
The spectra of k-mer frequencies can reveal the structures and evolution of genome sequences. We confirmed that the trimodal spectrum of 8-mers in human genome sequences is distinguished only by CG2, CG1 and CG0 8-mer sets, containing 2,1 or 0 CpG, respectively. This phenomenon is called independent selection law. The three types of CG 8-mers were considered as different functional elements. We conjectured that (1) nucleosome binding motifs are mainly characterized by CG1 8-mers and (2) the core structural units of CpG island sequences are predominantly characterized by CG2 8-mers. To validate our conjectures, nucleosome occupied sequences and CGI sequences were extracted, then the sequence parameters were constructed through the information of the three CG 8-mer sets respectively. ROC analysis showed that CG1 8-mers are more preference in nucleosome occupied segments (AUC > 0.7) and CG2 8-mers are more preference in CGI sequences (AUC > 0.99). This validates our conjecture in principle. 相似文献
55.
Jingting Zhang Wei Ren Pingli An Zhihua Pan Liwei Wang Zhiqiang Dong Di He Jia Yang Shufen Pan Hanqin Tian 《PloS one》2015,10(9)
It has long been concerned how crop water use efficiency (WUE) responds to climate change. Most of existing researches have emphasized the impact of single climate factor but have paid less attention to the effect of developed agronomic measures on crop WUE. Based on the long-term field observations/experiments data, we investigated the changing responses of crop WUE to climate variables (temperature and precipitation) and agronomic practices (fertilization and cropping patterns) in the semi-arid area of northern China (SAC) during two periods, 1983–1999 and 2000–2010 (drier and warmer). Our results suggest that crop WUE was an intrinsical system sensitive to climate change and agronomic measures. Crops tend to reach the maximum WUE (WUEmax) in warm-dry environment while reach the stable minimum WUE (WUEmin) in warm-wet environment, with a difference between WUEmax and WUEmin ranging from 29.0%-55.5%. Changes in temperature and precipitation in the past three decades jointly enhanced crop WUE by 8.1%-30.6%. Elevated fertilizer and rotation cropping would increase crop WUE by 5.6–11.0% and 19.5–92.9%, respectively. These results indicate crop has the resilience by adjusting WUE, which is not only able to respond to subsequent periods of favorable water balance but also to tolerate the drought stress, and reasonable agronomic practices could enhance this resilience. However, this capacity would break down under impact of climate changes and unconscionable agronomic practices (e.g. excessive N/P/K fertilizer or traditional continuous cropping). Based on the findings in this study, a conceptual crop WUE model is constructed to indicate the threshold of crop resilience, which could help the farmer develop appropriate strategies in adapting the adverse impacts of climate warming. 相似文献
56.
57.
Yuxin Yang Shuting Song Qiuyu Meng Liyan Wang Xiaonan Li Sijie Xie Yingjie Chen Xiaoxue Jiang Chen Wang Yanan Lu Xiaoru Xin Hu Pu Xin Gui Tianming Li Jie Xu Jiao Li Song Jia Dongdong Lu 《Journal of cellular and molecular medicine》2020,24(5):2772-2790
Several microRNAs are associated with carcinogenesis and tumour progression. Herein, our observations suggest both miR24-2 and Pim1 are up-regulated in human liver cancers, and miR24-2 accelerates growth of liver cancer cells in vitro and in vivo. Mechanistically, miR24-2 increases the expression of N6-adenosine-methyltransferase METTL3 and thereafter promotes the expression of miR6079 via RNA methylation modification. Furthermore, miR6079 targets JMJD2A and then increased the tri-methylation of histone H3 on the ninth lysine (H3K9me3). Therefore, miR24-2 inhibits JMJD2A by increasing miR6079 and then increases H3K9me3. Strikingly, miR24-2 increases the expression of Pim1 dependent on H3K9me3 and METTL3. Notably, our findings suggest that miR24-2 alters several related genes (pHistone H3, SUZ12, SUV39H1, Nanog, MEKK4, pTyr) and accelerates progression of liver cancer cells through Pim1 activation. In particular, Pim1 is required for the oncogenic action of miR24-2 in liver cancer. This study elucidates a novel mechanism for miR24-2 in liver cancer and suggests that miR24-2 may be used as novel therapeutic targets of liver cancer. 相似文献
58.
Xue Gao Qian Zhang Yu-Qian Zhao Jie Yang Heng-Bin He Gui-Xia Jia 《Molecular Plant Pathology》2020,21(6):749-760
Grey mould is one of the most determinative factors of lily growth and plays a major role in limiting lily productivity. MicroRNA159 (miR159) is a highly conserved microRNA in plants, and participates in the regulation of plant development and stress responses. Our previous studies revealed that lre-miR159a participates in the response of Lilium regale to Botrytis elliptica according to deep sequencing analyses; however, the response mechanism remains unknown. Here, lre-miR159a and its target LrGAMYB gene were isolated from L. regale. Transgenic Arabidopsis overexpressing lre-MIR159a exhibited larger leaves and smaller necrotic spots on inoculation with Botrytis than those of wild-type and overexpressing LrGAMYB plants. The lre-MIR159a overexpression also led to repressed expression of two targets of miR159, AtMYB33 and AtMYB65, and enhanced accumulation of hormone-related genes, including AtPR1, AtPR2, AtNPR1, AtPDF1.2, and AtLOX for both the jasmonic acid and salicylic acid pathways. Moreover, lower levels of H2O2 and were observed in lre-MIR159a transgenic Arabidopsis, which reduced the damage from reactive oxygen species accumulation. Taken together, these results indicate that lre-miR159a positively regulates resistance to grey mould by repressing the expression of its target LrGAMYB gene and activating a defence response. 相似文献
59.
Ye Yuan Jing‐Yi Jiang Jia‐Mei Wang Jia Sun Chao Li Bao‐Qin Liu Jing Yan Xiao‐Na Meng Hua‐Qin Wang 《Journal of cellular and molecular medicine》2019,23(8):5006-5016
BAG3 is constitutively expressed in multiple types of cancer cells and its high expression is associated with tumour progression and poor prognosis of PDAC . However, little is known about the role of BAG3 in the regulation of stromal microenvironment of PDAC. The current study demonstrated that beside PDAC tumour cells, BAG3 was also expressed in some activated stroma cells in PDAC tissue, as well as in activated PSCs. In addition, the current study demonstrated that BAG3 expression in PSCs was involved in maintenance of PSCs activation and promotion of PDACs invasion via releasing multiple cytokines. The current study demonstrated that BAG3‐positive PSCs promoted invasion of PDACs via IL‐8, MCP1, TGF‐β2 and IGFBP2 in a paracrine manner. Furthermore, BAG3 sustained PSCs activation through IL‐6, TGF‐β2 and IGFBP2 in an autocrine manner. Thereby, the current study provides a new insight into the involvement of BAG3 in remodelling of stromal microenvironment favourable for malignant progression of PDAC, indicating that BAG3 might serve as a potential target for anti‐fibrosis of PDAC. 相似文献
60.
Xingjie Gao Jing Wang Meiqi Li Jia Wang Jian Lv Lu Zhang Caifeng Sun Jiamei Ji Wenbo Yang Zinan Zhao Weifeng Mao 《Journal of cellular and molecular medicine》2019,23(10):6797-6804
Berberine (BBR) is a natural isoquinoline alkaloid, which is used in traditional medicine for its anti‐microbial, anti‐protozoal, anti‐diarrhoeal activities. Berberine interacts with DNA and displays anti‐cancer activities, yet its effects on cellular DNA repair and on synthetic treatments with chemotherapeutic drugs remain unclear. In this study, we investigated the effects of BBR on DNA repair and on sensitization of breast cancer cells to different types of DNA damage anti‐tumoural drugs. We found BBR arrested cells in the cell cycle S phase and induced DNA breaks. Cell growth analysis showed BBR sensitized MDA‐MB‐231 cells to cisplatin, camptothecin and methyl methanesulfonate; however, BBR had no synergistic effects with hydroxurea and olaparib. These results suggest BBR only affects specific DNA repair pathways. Western blot showed BBR down‐regulated XRCC1 expressions, and the rescued XRCC1 recovered the resistance of cancer cells to BBR. Therefore, we conclude that BBR interferes with XRCC1‐mediated base excision repair to sensitize cancer cells to chemotherapeutic drugs. These finding can contribute to understanding the effects of BBR on cellular DNA repair and the clinical employment of BBR in treatment of breast cancer. 相似文献