全文获取类型
收费全文 | 5610篇 |
免费 | 429篇 |
国内免费 | 360篇 |
出版年
2024年 | 8篇 |
2023年 | 61篇 |
2022年 | 137篇 |
2021年 | 284篇 |
2020年 | 203篇 |
2019年 | 229篇 |
2018年 | 218篇 |
2017年 | 186篇 |
2016年 | 276篇 |
2015年 | 354篇 |
2014年 | 442篇 |
2013年 | 452篇 |
2012年 | 478篇 |
2011年 | 427篇 |
2010年 | 259篇 |
2009年 | 225篇 |
2008年 | 274篇 |
2007年 | 231篇 |
2006年 | 172篇 |
2005年 | 129篇 |
2004年 | 137篇 |
2003年 | 124篇 |
2002年 | 112篇 |
2001年 | 98篇 |
2000年 | 89篇 |
1999年 | 92篇 |
1998年 | 63篇 |
1997年 | 61篇 |
1996年 | 39篇 |
1995年 | 51篇 |
1994年 | 55篇 |
1993年 | 53篇 |
1992年 | 70篇 |
1991年 | 48篇 |
1990年 | 34篇 |
1989年 | 29篇 |
1988年 | 28篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 18篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1972年 | 5篇 |
排序方式: 共有6399条查询结果,搜索用时 15 毫秒
171.
Xin Li Tian-Tian Li Xiao-Hui Zhang Li-Fei Hou Xiao-Qian Yang Feng-Hua Zhu Wei Tang Jian-Ping Zuo 《PloS one》2013,8(8)
Background
Artemisinin analogue SM934 was previously reported to possess immunosuppressive properties. The aim of this study was to determine the effects and the underlying mechanisms of SM934 in murine experimental autoimmune encephalomyelitis (EAE).Methods
Female C57BL/6 mice immunized with MOG35–55 were treated with or without SM934, then the clinical scores and other relevant parameters were assessed. Th1, Th17 and regulatory T (Treg) cell profiles were determined through ELISA, qRT-PCR, flow cytometry and BrdU incorporation assay. The effects of SM934 on Th1, Th17 and Treg cells differentiation were explored through intracellular staining and flow cytometry examination.Results
In vivo, administration of SM934 significantly inhibited the development of EAE and suppressed the elevation of serum IL-17. Ex vivo, upon antigen-recall stimulation, IL-2, IFN-γ, IL-17 and IL-6 production were decreased, whereas IL-10 and TGF-β production were increased from the splenocytes isolated from SM934-treated mice. Consistently, both flow cytometry and qRT-PCR results showed that SM934 treatment significantly increased the Treg, while strongly suppressed the Th17 and Th1, responses in the peripheral. Furthermore, in the spinal lesion, SM934 treatment dramatically decreased the infiltration of CD4+ T cells, within which the Treg cells percentage was enlarged, whereas the Th17, but not Th1 percentage, was significantly decreased comparing with the vehicle-treated groups. Finally, both BrdU incorporation and in vitro Treg differentiation assays revealed that SM934 treatment could directly promote the expansion of Treg cells in vivo and in vitro.Conclusion
Taken together, this study demonstrated that SM934 treatment could ameliorate the murine EAE disease, which might be mediated by inducing Treg differentiation and expansion. 相似文献172.
173.
Rui Wei Jin Yang Wenfang Hou Guoqiang Liu Meijuan Gao Lin Zhang Haining Wang Genhong Mao Hongwei Gao Guian Chen Tianpei Hong 《PloS one》2013,8(8)
Human embryonic stem cells (hESCs) are pluripotent and capable of undergoing multilineage differentiation into highly specialized cells including pancreatic islet cells. Thus, they represent a novel alternative source for targeted therapies and regenerative medicine for diabetes. Significant progress has been made in differentiating hESCs toward pancreatic lineages. One approach is based on the similarities of pancreatic β cell and neuroepithelial development. Nestin-positive cells are selected as pancreatic β cell precursors and further differentiated to secrete insulin. The other approach is based on our knowledge of developmental biology in which the differentiation protocol sequentially reproduces the individual steps that are known in normal β cell ontogenesis during fetal pancreatic development. In the present study, the hESC cell line PKU1.1 was induced to differentiate into insulin-producing cells (IPCs) using both protocols. The differentiation process was dynamically investigated and the similarities and differences between both strategies were explored. Our results show that IPCs can be successfully induced with both differentiation strategies. The resulting IPCs from both protocols shared many similar features with pancreatic islet cells, but not mature, functional β cells. However, these differently-derived IPC cell types displayed specific morphologies and different expression levels of pancreatic islet development-related markers. These data not only broaden our outlook on hESC differentiation into IPCs, but also extend the full potential of these processes for regenerative medicine in diabetes. 相似文献
174.
Subject
Chronic obstructive pulmonary disease (COPD) is a common disease worldwide. This study aimed to investigate the health status of patients with newly diagnosed COPD.Methods
A total of 45 healthy controls and 218 patients with newly diagnosed COPD were recruited. Pulmonary function test (PFT) values, COPD assessment test (CAT) scores, exacerbation history, and demographics were recorded.Results
Forced expiratory volume in 1 s percent (FEV1%) predicted was significantly decreased and the CAT score was significantly increased in patients with COPD compared with healthy controls (P <0.001). Among the COPD patients, the most commonly reported respiratory symptoms were cough (86.7%), sputum (80.3%), and dyspnea (45%). A total of 86.2% patients were in the moderate or severe stage (spirometric classification) of COPD, and 71.5% were in Group C or Group D (combined assessment). A total of 33.9% of the patients had 2 or more exacerbations in the previous year. Nearly half of the patients (45.4%) had a high CAT score of ≥10. Patients with a history of more exacerbations had a higher CAT score.Conclusions
Most COPD patients were symptomatic and appeared to have moderate to severe airflow limitation or a high risk of exacerbation before definitely being diagnosed with COPD using the PFT. 相似文献175.
Due to its accuracy, sensitivity and high throughput, real time quantitative PCR (RT-qPCR) has been widely used in analysing gene expression. The quality of data from such analyses is affected by the quality of reference genes used. Expression stabilities for nine candidate reference genes widely used in soybean were evaluated under different stresses in this study. Our results showed that EF1A and ACT11 were the best under salinity stress, TUB4, TUA5 and EF1A were the best under drought stress, ACT11 and UKN2 were the best under dark treatment, and EF1B and UKN2 were the best under virus infection. EF1B and UKN2 were the top two genes which can be reliably used in all of the stress conditions assessed. 相似文献
176.
177.
178.
Paula da Fonseca-Pereira Paulo V.L. Souza Liang-Yu Hou Saskia Schwab Peter Geigenberger Adriano Nunes-Nesi Stefan Timm Alisdair R. Fernie Ina Thormählen Wagner L. Araújo Danilo M. Daloso 《Plant, cell & environment》2020,43(1):188-208
Thioredoxins (TRXs) are important proteins involved in redox regulation of metabolism. In plants, it has been shown that the mitochondrial metabolism is regulated by the mitochondrial TRX system. However, the functional significance of TRX h2, which is found at both cytosol and mitochondria, remains unclear. Arabidopsis plants lacking TRX h2 showed delayed seed germination and reduced respiration alongside impaired stomatal and mesophyll conductance, without impacting photosynthesis under ambient O2 conditions. However, an increase in the stoichiometry of photorespiratory CO2 release was found during O2-dependent gas exchange measurements in trxh2 mutants. Metabolite profiling of trxh2 leaves revealed alterations in key metabolites of photorespiration and in several metabolites involved in respiration and amino acid metabolism. Decreased abundance of serine hydroxymethyltransferase and glycine decarboxylase (GDC) H and L subunits as well as reduced NADH/NAD+ ratios were also observed in trxh2 mutants. We further demonstrated that the redox status of GDC-L is altered in trxh2 mutants in vivo and that recombinant TRX h2 can deactivate GDC-L in vitro, indicating that this protein is redox regulated by the TRX system. Collectively, our results demonstrate that TRX h2 plays an important role in the redox regulation of mitochondrial photorespiratory metabolism. 相似文献
179.
Chen Ting-Ting Liu Fang-Fei Xiao Dong-Wang Jiang Xiao-Yi Li Pan Zhao Shu-Man Hou Bing-kai Li Yan-jie 《Plant molecular biology》2020,102(4-5):389-401
Plant Molecular Biology - This study revealed that the Arabidopsis UGT75B1 plays an important role in modulating ABA activity by glycosylation when confronting stress environments. The cellular ABA... 相似文献
180.
Jiqiang Zhang Ziru Niu Tianhua Li Yanqiang Wu Rui Xi Yuhua Li Guanghua Li Jialin Hou 《Phyton》2020,89(1):147-166
Considering the current low level of mechanization for domestic green
onion planting and the high labor intensity of artificial planting, a 2ZYX-2 green
onion ditching and transplanting machine, which can complete ditching, ridging,
transplanting, repression, soil covering and other operations, is designed in this
study. The Central Composite test design method was carried out with the speed
of the transplanting machine, the depth of the opener and the horizontal position
of the opener as the experimental factors and with the qualification ratio of
perpendicularity, the variation coefficient of the plant spacing and the
qualification ratio of the planting depth as the test index. Through the analysis of
the model interaction and response surface, the change laws that the influence
the machine’s forward speed, the depth of the opener and the horizontal position
of the opener were studied. The regression model was optimized by
Design-Expert 8.0.6 software, and the accuracy of the predicted results was
verified by experiments. The optimal working parameters showed that the
forward speed of the machine was 0.06 m/s, the depth of the opener was 102 mm,
and the horizontal position of the opener was 29 mm. Under conditions of
optimal working parameters, the qualification rate of the verticality was 86.83%,
the coefficient of variation for the plant spacing was 2.77, and the pass rate of
planting depth was 88.26%. The research related to the thesis can provide a
reference for the mechanized planting of green onion, which is of great
significance to the cost-effectiveness of the green onion industry. 相似文献