全文获取类型
收费全文 | 1097篇 |
免费 | 102篇 |
国内免费 | 139篇 |
出版年
2024年 | 1篇 |
2023年 | 46篇 |
2022年 | 46篇 |
2021年 | 111篇 |
2020年 | 69篇 |
2019年 | 86篇 |
2018年 | 62篇 |
2017年 | 46篇 |
2016年 | 51篇 |
2015年 | 70篇 |
2014年 | 93篇 |
2013年 | 67篇 |
2012年 | 100篇 |
2011年 | 75篇 |
2010年 | 48篇 |
2009年 | 39篇 |
2008年 | 48篇 |
2007年 | 52篇 |
2006年 | 37篇 |
2005年 | 36篇 |
2004年 | 18篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1960年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有1338条查询结果,搜索用时 431 毫秒
31.
Ma Xuan Liu Chunyan Kong Xiaocong Liu Jing Zhang Siju Liang Shanshan Luan Weijiang Cao Xiaofeng 《中国科学:生命科学英文版》2021,64(4):495-511
Evidence is emerging that t RNA-derived fragments(t RFs) are regulatory molecules. Studies of t RFs in plants have been based on conventional small RNA sequencing, and focused on profiling of t RF-5 and t RF-3 species. A more comprehensive and quantitative analysis of the entire t RF population is highly necessary. Here, we employ t RNA-seq and YAMAT-seq, and develop a bioinformatics tool to comprehensively profile the expressions of t RNAs and t RFs in plants. We show that in Arabidopsis,approximately half of t RNA genes are extremely weakly expressed, accounting for only 1% of total t RNA abundance, while~12% of t RNA genes contribute to ~80% of t RNA abundance. Our t RNA sequencings in various plants reveal that t RNA expression profiles exhibit a cross-species conserved pattern. By characterizing the composition of a highly heterogeneous t RF population, we show that t RNA halves and previously unnoticed 10–16-nt tiny t RFs represent substantial portions. The highly accumulated 13-nt and 16-nt tiny t RFs in Arabidopsis indicate that tiny t RFs are not random t RNA degradation products. Finally,we provide a user-friendly database for displaying the dynamic spatiotemporal expressions of t RNAs and t RFs in the model plants Arabidopsis and rice. 相似文献
32.
Cluster Computing - Cloud platforms usually offer several types of Virtual Machines (VMs) with different guarantees in terms of availability and volatility, provisioning the same resource through... 相似文献
33.
34.
Yichi Zhang Yan Luo Kaijing Li Min Zhang Bing Huang Yuting Peng Wenchong Wang Weihua Li Yizhi Liu 《Cytotherapy》2013,15(11):1416-1425
Background aimsRecent advances in stem cell research have raised the possibility of stem cells repairing or replacing retinal photoreceptor cells that are either dysfunctional or lost in many retinal diseases. Various types of stem cells have been used to replace retinal photoreceptor cells. Recently, peripheral blood stem cells, a small proportion of pluripotent stem cells, have been reported to mainly exist in the peripheral blood mononuclear cells (PBMCs).MethodsIn this study, the effects of pre-induced adult human PBMCs (hPBMCs) on the degenerative retinas of rd1 mice were investigated. Freshly isolated adult hPBMCs were pre-induced with the use of the conditioned medium of rat retinas for 4 days and were then labeled with chloromethyl-benzamidodialkylcarbocyanine (CM-DiI) and then transplanted into the subretinal space of the right eye of rd1 mice through a trans-scleral approach. The right eyes were collected 30 days after transplantation. The survival and migration of the transplanted cells in host retinas were investigated by whole-mount retinas, retinal frozen sections and immunofluorescent staining.ResultsAfter subretinal transplantation, pre-induced hPBMCs were able to survive and widely migrate into the retinas of rd1 mice. A few CM-DiI–labeled cells migrated into the inner nuclear layer and the retinal ganglion cell layer. Some transplanted cells in the subretinal space of rd1 host mice expressed the human photoreceptor–specific marker rhodopsin.ConclusionsThis study suggests that pre-induced hPBMCs may be a potential cell source of cell replacement therapy for retinal degenerative diseases. 相似文献
35.
Chuanyin Li Qing Wu Bo Liu Yuting Yao Ying Chen Huili Zhang Changqiang Wang Jiumei Cao Shengfang Ge 《PloS one》2013,8(3)
Background
Circulating endothelial cells (CECs) are markers of vascular damage that have clinical relevance in many diseases, including acute myocardial infarction (AMI), and may be predictors of treatment responses. Herein, we investigated the diagnostic and prognostic value of CEC monitoring in AMI patients and a murine model.Methodology/Principal Findings
CECs were defined as Hoechst 33342+/CD45−/CD31+/CD146+/CD133− in human blood samples and Hoechst 33342+/CD45−/CD31+/KDR+/CD117− in murine samples. To evaluate the validity and variability of our CEC detection system, peripheral blood samples of vascular endothelial growth factor-treated athymic nude mice and AMI patients were collected and subjected to intra-assay analysis. CEC detection by flow cytometry and real-time PCR were compared. Blood samples were obtained from 61 AMI patients, 45 healthy volunteers and 19 samples of the original AMI patients accepted one month treatment, via flow cytometry and expressed as a percentage of peripheral blood mononuclear cells.Results
Our CEC detection method was validated and had limited variability. CEC concentrations were higher in AMI patients compared to healthy controls. One month post-treatment, CECs levels decreased significantly.Conclusions/Significance
CEC levels may be useful as a diagnostic and prognostic biomarker in AMI patients. 相似文献36.
Guojing Liu Feng Chen Yu Cai Zhibin Chen Qingxian Luan Xiaoqian Yu 《Microbiology and immunology》2020,64(2):99-112
Periodontitis is a major cause of tooth loss in adults that initially results from dental plaque. Subgingival plaque pathogenesis is affected by both community composition and plaque structures, although limited data are available concerning the latter. To bridge this knowledge gap, subgingival plaques were obtained using filter paper (the fourth layer) and curette (the first-third layers) sequentially and the phylogenetic differences between the first–third layers and the fourth layer were characterized by sequencing the V3–V4 regions of 16S rRNA. A total of 11 phyla, 148 genera, and 308 species were obtained by bioinformatic analysis, and no significant differences between the operational taxonomic unit numbers were observed for these groups. In both groups, the most abundant species were Porphyromonas gingivalis and Fusobacterium nucleatum. Actinomyces naeslundii, Streptococcus intermedius, and Prevotella intermedia possessed relatively high proportions in the first–third layers; while in the fourth layer, both traditional pathogens (Treponema denticola and Campylobacter rectus) and novel pathobionts (Eubacterium saphenum, Filifactor alocis, Treponema sp. HOT238) were prominent. Network analysis showed that either of them exhibited a scale-free property and was constructed by two negatively correlated components (the pathogen component and the nonpathogen component), while the synergy in the nonpathogen component was lower in the first–third layers than that in the fourth layer. After merging these two parts into a whole plaque group, the negative/positive correlation ratio increased. With potential connections, the first–third layers and the fourth layer showed characteristic key nodes in bacterial networks. 相似文献
37.
Chengdi Wang Wenliang Qiao Yuting Jiang Min Zhu Jun Shao Tao Wang Dan Liu Weimin Li 《Journal of cellular physiology》2020,235(5):4913-4927
38.
MFN2 silencing promotes neural differentiation of embryonic stem cells via the Akt signaling pathway
Siqi Yi Chenghao Cui Xiaotian Huang Xiaohui Yin Yang Li Jinhua Wen Qingxian Luan 《Journal of cellular physiology》2020,235(2):1051-1064
Mitofusin 2 (MFN2) is a regulatory protein participating in mitochondria dynamics, cell proliferation, death, differentiation, and so on. This study aims at revealing the functional role of MFN2 in the pluripotency maintenance and primitive differetiation of embryonic stem cell (ESCs). A dox inducible silencing and routine overexpressing approach was used to downregulate and upregulate MFN2 expression, respectively. We have compared the morphology, cell proliferation, and expression level of pluripotent genes in various groups. We also used directed differentiation methods to test the differentiation capacity of various groups. The Akt signaling pathway was explored by the western blot assay. MFN2 upregulation in ESCs exhibited a typical cell morphology and similar cell proliferation, but decreased pluripotent gene markers. In addition, MFN2 overexpression inhibited ESCs differentiation into the mesendoderm, while MFN2 silencing ESCs exhibited a normal cell morphology, slower cell proliferation and elevated pluripotency markers. For differentiation, MFN2 silencing ESCs exhibited enhanced three germs' differentiation ability. Moreover, the protein levels of phosphorylated Akt308 and Akt473 decreased in MFN2 silenced ESCs, and recovered in the neural differentiation process. When treated with the Akt inhibitor, the neural differentiation capacity of the MFN2 silenced ESCs can reverse to a normal level. Taken together, the data indicated that the appropriate level of MFN2 expression is essential for pluripotency and differentiation capacity in ESCs. The increased neural differentiation ability by MFN2 silencing is strongly related to the Akt signaling pathway. 相似文献
39.
40.
水热增加下黑土细菌群落共生网络特征 总被引:2,自引:0,他引:2
黑土是有机质含量高且肥沃的土壤类型之一,气候变化会显著改变黑土中微生物群落的结构,同时影响群落间的潜在相互作用关系。[目的] 揭示水热增加对黑土中的细菌群落结构及潜在互作关系的影响。[方法] 基于土壤移置试验,采用16S rRNA高通量测序解析农田黑土(原位黑土、水热增加1和水热增加2)中的细菌群落结构对水热增加的响应;使用CoNet构建微生物群落共生网络,识别共生网络中的枢纽微生物;利用结构方程模型、相关性分析探究水热条件变化下土壤性质、微生物交互作用、多样性之间的直接、间接关系。[结果] 黑土中的微生物以疣微菌、变形杆菌、酸性杆菌和放线菌为主。水热增加下土壤微生物共生网络的拓扑性质发生显著变化,网络中表征微生物潜在竞争关系的负连线随着水热增加而显著增加。气候因素通过改变微生物潜在相互作用影响了群落水平分类多样性。物种竞争增强可能直接导致了土壤有机碳含量的降低。[结论] 水热增加会显著改变黑土中微生物之间的潜在交互作用,枢纽微生物的响应更加敏感。 相似文献