全文获取类型
收费全文 | 162篇 |
免费 | 12篇 |
国内免费 | 43篇 |
专业分类
217篇 |
出版年
2024年 | 3篇 |
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 14篇 |
2013年 | 9篇 |
2012年 | 14篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 11篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有217条查询结果,搜索用时 7 毫秒
91.
紫毛香茶菜中的黄酮类化合物 总被引:2,自引:0,他引:2
从紫毛香茶菜(Isodon enanderianus)的茎叶提取物中分离到7个黄酮类化合物,经波谱分析鉴定,其中一个为新的黄酮甙,即5-羟基-6,7,4-三甲氧基黄酮-8-O-β-D-葡萄糖甙(1);其它6个已知的黄酮类化合物分别为芫花素(genkwanin,2)、滨蓟素(cirsimar-tin,3)、胡麻素(pedalitin,4)、鼬瓣花亭(ladanetin,5)、isothymusin-8-O-β-D-glucoside(6)和槲皮甙(quercitrin,7)。 相似文献
92.
苜蓿银纹夜蛾核多角体病毒(Autographa californica nucleopolyhedrovirus,AcMNPV)基因组含有3个细胞凋亡抑制基因,即p35,iap1和iap2.其中,p35作为一个有效的依赖于天冬氨酸的半胱氨酸蛋白酶(caspase)抑制因子,能够抑制多种因素诱发细胞凋亡,而iap1和iap2的功能仍未完全明晰,本研究对IAP1和IAP2的功能进行了详细分析.缺失了p35的AcMNPV仍可抑制棉铃虫核多角体病毒(Helicoverpa armigera single nucleocapsid NPV,HearNPV)诱导的BTI-Tn-5B1-4(Tn-Hi5)细胞凋亡并挽救HearNPV在Tn-Hi5细胞中复制及HearNPV出芽型病毒粒子的产生.进一步构建了瞬时表达质粒以及分别表达AcMNPV的p35,iap1和iap2基因的重组HearNPV,转染瞬时表达的IAP1和IAP2对HearNPV感染诱导的Tn-Hi5细胞凋亡有抑制效果,而重组病毒感染Tn-Hi5细胞也可抑制其凋亡并在其中复制,然而重组HearNPV表达的p35,iap1和iap2并未能挽救出芽型病毒粒子的产生.结果表明,AcMNPV的iap1和iap2基因表达产物作为细胞凋亡抑制因子是有功能的。 相似文献
93.
DORIS GOMEZ CHRISTINA RICHARDSON MARC THÉRY THIERRY LENGAGNE JEAN‐PAUL LÉNA SANDRINE PLÉNET PIERRE JOLY 《Biological journal of the Linnean Society. Linnean Society of London》2011,103(3):633-647
In nocturnal treefrogs, mate choice implies the use of acoustic and visual signals. Multimodality is suspected to have evolved for either information redundancy or information complementariness. It is essential to explore multimodality in a natural context to understand the selection pressures operating on the signals. In the present study, we investigated calling and coloration in relation to male biometry and condition in four populations of European treefrog (Hyla arborea) varying in size and genetic isolation. We compared the signal intensity between core and satellite populations to estimate the impact of genetic diversity on male secondary sexual traits. The results obtained show important regional variations in both traits, likely as a result of local adaptations. Call and coloration are weakly correlated within an individual, implying that these traits likely convey different information about the signaller's identity or quality, thus supporting the hypothesis of complementariness of multiple messages. By contrast to the experimental evidence, we find that call and coloration are not related to male condition (as estimated by the residual of mass over size), suggesting that the condition‐dependence of these traits may be mediated by complex mechanisms not accurately reflected by the chosen estimator. Finally, male call and colour phenotypes present no robust pattern of variation with isolation status, probably because of variation in local selective pressures and in history of population dynamics. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 633–647. 相似文献
94.
95.
96.
Alex?SF?Doney Bettina?Fischer Joanne?E?Cecil Patricia?TW?Cohen Douglas?I?Boyle Graham?Leese Andrew?D?Morris Colin?NA?PalmerEmail author 《BMC genetics》2003,4(1):11
Background
The ARE insertion/deletion polymorphism of PPP1R3A has been associated with variation in glycaemic parameters and prevalence of diabetes. We have investigated its role in age of diagnosis, body weight and glycaemic control in 1,950 individuals with type 2 diabetes in Tayside, Scotland, and compared the ARE2 allele frequencies with 1,014 local schoolchildren. 相似文献97.
98.
SUNG JIN CHO PYO YUN CHO MYUNG SIK LEE YOUNGEUN NA JOO HUN LEE KI SEOK KOH 《Invertebrate reproduction & development.》2013,57(2-3):103-108
Summary Previous studies have shown that spatiotemporal regulation of extracellular matrix (ECM) by proteinases is implicated in the initial step of regeneration. In amphibian regeneration, the up-regulation of proteinases such as metalloproteinases (MMPs) and cathepsin D, and proteinase-related proteins such as proteinase tissue inhibitors and activators has been demonstrated. Since the earthworm could provide a unique and valuable model to investigate the mechanism of regeneration, we studied the developmental change in proteinase expression during earthworm tail regeneration. Zymographic analysis revealed that proteinase activities began to increase within 1 h after amputation and reached a maximum at 7 days post-amputation. This peak in activity was approximately 22-fold greater than the unamputated controls. Thereafter, the proteinase activities tended to decrease followed by another peak at 30 days before returning to control levels. At least four types of proteinase were distinguishable at 7 and 30 days post-amputation, with molecular weights of 25, 28, 38, and 44 kDa, respectively. All proteinase activities were strongly inhibited by addition of phenylmethylsulfonyl fluoride (PMSF) and aprotinin, specific inhibitors for serine proteinase. Pepstatin A, E-64, iodoacetamide and a metal ion-free medium were not effective inhibitors, indicating that proteinases expressed during earthworm tail regeneration would be serine proteinases. In addition, we were able to detect two types of plasminogen activator (PA) with molecular weights of 40 and 47 kDa, respectively. PA activities were predominantly expressed at 1, 5, and 25 days post-amputation, which preceded two peaks of serine proteinase activities appearing at approximately 7 and 30 days after amputation, respectively. This fact supports the view that serine proteinases expressed in respond to tail amputation may be plasmin-like proteinases activated by PA. 相似文献
99.
100.
目的:通过检测SD大鼠脑缺血再灌注模型血清中血管内皮生长因子(VEGF)与神经元凋亡动态表迭变化的关系,以探讨两者之间的相关性。方法:将40只大鼠随机分为8组:对照组、假手术组和脑缺血30min再灌注12h组、1d组、3d组、5d组、7d组、及14d组,每组5只。采用ELISA双抗夹心法检测大鼠血清中血管内皮生长因子、原位细胞凋亡TUNEL法检测脑组织中的凋亡神经细胞数。结果:再灌注12h、1d、3d、5d、7d及14d大鼠血清VEGF表达和凋亡神经元百分比的变化均为负相关性(均为P〈0.05)。结论:在脑缺血再灌注大鼠模型中,缺血诱导使VEGF的表达发生变化,VEGF通过直接或间接的途径抑制神经元凋亡。 相似文献