全文获取类型
收费全文 | 354篇 |
免费 | 33篇 |
国内免费 | 1篇 |
专业分类
388篇 |
出版年
2023年 | 2篇 |
2021年 | 4篇 |
2020年 | 17篇 |
2019年 | 40篇 |
2018年 | 29篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 22篇 |
2012年 | 5篇 |
2011年 | 1篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 12篇 |
2007年 | 15篇 |
2006年 | 17篇 |
2005年 | 10篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 14篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 19篇 |
1995年 | 15篇 |
1994年 | 4篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 12篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有388条查询结果,搜索用时 15 毫秒
91.
Myocardial ischemia-reperfusion (I/R) is associated with the activation of matrix metalloproteinases (MMPs) and serine proteases. We hypothesized that activation of MMPs and the serine protease plasmin contribute to early cardiac myocyte death following I/R and that broad-spectrum protease inhibition with doxycycline (DOX) preserves myocyte viability. Rats treated daily with or without DOX beginning 48 h prior to experimentation were subjected to 30 min of coronary occlusion and 2 days of reperfusion. DOX pre-treatment reduced infarct size by 37%. DOX attenuated increases in MMP-9 and plasmin levels as determined by gelatin zymography and immunoblot, respectively. Neutrophil extravasation was unaltered by DOX as assessed by myeloperoxidase (MPO) activity. To examine the contribution of MMP-9 and plasmin to myocyte injury, cultures of neonatal rat ventricular myocytes (NRVMs) were treated for 48 h with 83 kDa MMP-9 or plasminogen in the presence or absence of DOX. MMP-9 treatment did not affect myocyte viability. Plasminogen treatment led to increased plasmin activity, resulting in loss of 1-integrin, NRVM detachment and apoptosis. DOX co-treatment inhibited plasmin activity and preserved NRVM attachment, whereas co-treatment with the broad-spectrum MMP inhibitor GM6001 had no effect. These results indicate that plasmin causes disruption of myocyte attachment and viability independently of MMP activation in vitro and that inhibition of plasmin by DOX may reduce I/R-induced myocyte death in vivo through the inhibition of plasmin. (Mol Cell Biochem 270: 1–11, 2005) 相似文献
92.
Spheroids from adipose‐derived stem cells exhibit an miRNA profile of highly undifferentiated cells 下载免费PDF全文
A. Barbara Di Stefano PhD Federica Grisafi MSc Marta Castiglia PhD Alessandro Perez PhD Luigi Montesano MD Alessandro Gulino PhD Francesca Toia MD Daniele Fanale PhD Antonio Russo MD Francesco Moschella MD Angelo A. Leto Barone MD Adriana Cordova MD 《Journal of cellular physiology》2018,233(11):8778-8789
Two‐dimensional (2D) cell cultures have been extensively used to investigate stem cell biology, but new insights show that the 2D model may not properly represent the potential of the tissue of origin. Conversely, three‐dimensional cultures exhibit protein expression patterns and intercellular junctions that are more representative of their in vivo condition. Multiclonal cells that grow in suspension are defined as “spheroids,” and we have previously demonstrated that spheroids from adipose‐derived stem cells (S‐ASCs) displayed enhanced regenerative capability. With the current study, we further characterized S‐ASCs to further understand the molecular mechanisms underlying their stemness properties. Recent studies have shown that microRNAs (miRNAs) are involved in many cellular mechanisms, including stemness maintenance and proliferation, and adipose stem cell differentiation. Most studies have been conducted to identify a specific miRNA profile on adherent adipose stem cells, although little is still known about S‐ASCs. In this study, we investigate for the first time the miRNA expression pattern in S‐ASCs compared to that of ASCs, demonstrating that cell lines cultured in suspension show a typical miRNA expression profile that is closer to the one reported in induced pluripotent stem cells. Moreover, we have analyzed miRNAs that are specifically involved in two distinct moments of each differentiation, namely early and late stages of osteogenic, adipogenic, and chondrogenic lineages during long‐term in vitro culture. The data reported in the current study suggest that S‐ASCs have superior stemness features than the ASCs and they represent the true upstream stem cell fraction present in adipose tissue, relegating their adherent counterparts. 相似文献
93.
【背景】随着CO_2排放增加,全球变暖愈发严峻,嗜热蓝细菌作为能够在45°C及以上环境中生长并实现生物固碳的微生物,具有重要的研究意义。【目的】对从广东惠州地区采集的藻种进行分离鉴定,并筛选出2株嗜热蓝细菌,研究其生长特性,为嗜热蓝细菌的后续应用提供依据。【方法】通过16SrRNA基因、藻蓝蛋白链A基因(PhycoA)序列分析确定从惠州地区采集到的菌株的分类学位置。对PKUAC-GDTS1-24和PKUAC-GDTS1-29两株嗜热蓝细菌进行形态观察和主要细胞成分(灰分、糖类、脂质、蛋白质和色素)分析。【结果】共分离出12株嗜热蓝细菌,其中PKUAC-GDTS1-24和PKUAC-GDTS1-29菌株,形态上呈蓝绿色球形毛状体,是由细胞形成密集的簇,彼此附着形成的。两株嗜热蓝细菌的主要细胞成分是糖类,分别占细胞干重的36.42%和28.46%。PKUAC-GDTS1-24的灰分、脂质和蛋白质含量分别为24.41%、21.40%和26.64%。PKUAC-GDTS1-29的细胞中,灰分、脂质和蛋白质含量分别为24.72%、23.92%和12.93%。藻蓝蛋白(Phycocyanin,PC)在PKUAC-GDTS1-24和PKUAC-GDTS1-29中的含量分别为157.29 mg/g DW和374.86 mg/g DW,类胡萝卜素分别为65.13 mg/g DW和18.87 mg/g DW。【结论】基于系统发育树研究,本实验的2个分离株属于细鞘丝藻亚科(Leptolyngbyaceae),与研究较少的纤发鞘丝蓝细菌属(Leptolyngbya)菌株相近,可能是广东和四川温泉中存在的一种新型丝状轻度嗜热蓝细菌属或Leptolyngbya新种。嗜热菌株PKUAC-GDTS1-24和PKUAC-GDTS1-29的形态和细胞组成相似,通过比较,2个菌株的藻胆蛋白含量远远高于其他研究报道的Leptolyngbya蓝细菌,尤其是PKUAC-GDTS1-29可以作为藻蓝蛋白生产的潜在菌株。 相似文献
94.
Hari C. Sharma Abdul Rashid War Mandeep Pathania Suraj P Sharma S. MD. Akbar Rajendra S Munghate 《Arthropod-Plant Interactions》2016,10(2):171-181
Global atmospheric concentration of CO2 is likely to increase from 350 to 750 ppm over the next 100 years. The present studies were undertaken to understand the effects of elevated CO2 on enzymatic activity and secondary metabolites in chickpea in relation to expression of resistance to pod borer, Helicoverpa armigera. Fifteen-day-old chickpea plants [ICCL 86111—resistant and JG 11—commercial cultivar] grown in the greenhouse were transferred to open-top chambers (OTC) and kept under 350, 550 and 750 ppm of CO2. Twenty neonates of H. armigera were released on each plant at 7 days after shifting the pots to the OTCs. Un-infested plants were maintained as controls. After 7 days of infestation, the activities of defensive enzymes [peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and tyrosine ammonia lyase (TAL)] and amounts of total phenols and condensed tannins increased with an increase in CO2 concentration in chickpea. The nitrogen balance index was greater in plants kept at 350 ppm CO2 than in plants kept under ambient conditions. The H. armigera-infested plants had higher H2O2 content; amounts of oxalic and malic acids were greater at 750 ppm CO2 than at 350 ppm CO2. Plant damage was greater at 350 ppm than at 550 and 750 ppm CO2. This information will be useful for understanding effects of increased levels of CO2 on expression of resistance to insect pests to develop strategies to mitigate the effects of climate change. 相似文献
95.
96.
97.
98.
99.
100.
Moayad M Aljarabah Neil R Borley James MD Wheeler 《International Seminars in Surgical Oncology : ISSO》2007,4(1):20