全文获取类型
收费全文 | 153篇 |
免费 | 1篇 |
国内免费 | 4篇 |
专业分类
系统科学 | 4篇 |
理论与方法论 | 12篇 |
现状及发展 | 40篇 |
研究方法 | 24篇 |
综合类 | 70篇 |
自然研究 | 8篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 6篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 7篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 15篇 |
2011年 | 11篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 14篇 |
2007年 | 10篇 |
2006年 | 9篇 |
2005年 | 7篇 |
2004年 | 13篇 |
2003年 | 5篇 |
2002年 | 11篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1977年 | 1篇 |
1969年 | 2篇 |
1946年 | 1篇 |
排序方式: 共有158条查询结果,搜索用时 359 毫秒
61.
62.
63.
Tammela T Zarkada G Wallgard E Murtomäki A Suchting S Wirzenius M Waltari M Hellström M Schomber T Peltonen R Freitas C Duarte A Isoniemi H Laakkonen P Christofori G Ylä-Herttuala S Shibuya M Pytowski B Eichmann A Betsholtz C Alitalo K 《Nature》2008,454(7204):656-660
Angiogenesis, the growth of new blood vessels from pre-existing vasculature, is a key process in several pathological conditions, including tumour growth and age-related macular degeneration. Vascular endothelial growth factors (VEGFs) stimulate angiogenesis and lymphangiogenesis by activating VEGF receptor (VEGFR) tyrosine kinases in endothelial cells. VEGFR-3 (also known as FLT-4) is present in all endothelia during development, and in the adult it becomes restricted to the lymphatic endothelium. However, VEGFR-3 is upregulated in the microvasculature of tumours and wounds. Here we demonstrate that VEGFR-3 is highly expressed in angiogenic sprouts, and genetic targeting of VEGFR-3 or blocking of VEGFR-3 signalling with monoclonal antibodies results in decreased sprouting, vascular density, vessel branching and endothelial cell proliferation in mouse angiogenesis models. Stimulation of VEGFR-3 augmented VEGF-induced angiogenesis and sustained angiogenesis even in the presence of VEGFR-2 (also known as KDR or FLK-1) inhibitors, whereas antibodies against VEGFR-3 and VEGFR-2 in combination resulted in additive inhibition of angiogenesis and tumour growth. Furthermore, genetic or pharmacological disruption of the Notch signalling pathway led to widespread endothelial VEGFR-3 expression and excessive sprouting, which was inhibited by blocking VEGFR-3 signals. Our results implicate VEGFR-3 as a regulator of vascular network formation. Targeting VEGFR-3 may provide additional efficacy for anti-angiogenic therapies, especially towards vessels that are resistant to VEGF or VEGFR-2 inhibitors. 相似文献
64.
Roberto da Silva Camargo Luiz Carlos Forti Carlos Alberto Oliveira de Matos Antonio D. Brescovit 《Journal of Natural History》2015,49(27-28):1653-1658
Attacobius attarum spiders exhibit a phoretic behaviour on the winged sexual of Atta leaf-cutting ants during their mating flight. However, it is unclear if this behaviour is for dispersion or to facilitate the predation of ants in the new colonies. A nest of Atta sexdens was monitored on the day of the mating flight, and the winged ants, as well as the spiders, were collected. The results obtained corroborate the hypothesis that phoretic behaviour is commonly used for dispersion of the spider A. attarum, predominantly females. Of these spiders, 64 individuals of A. attarium were collected, of which 62 were females (96.9%) and two were males (3.1%). Regarding the winged leaf-cutting ants sampled, 378 females and 361 males were collected, totaling 739 individuals. Of these, 64 individuals (8.7%) had a spider attached to its back for phoretic dispersal and none was observed on the queens after the nuptial flight. In our study, A. attarum females perform phoretic dispersal into the environment on winged leaf-cutting ants but do not settle in the new nests. 相似文献
65.
A novel AMPK-dependent FoxO3A-SIRT3 intramitochondrial complex sensing glucose levels 总被引:1,自引:1,他引:0
Alessia Peserico Fulvio Chiacchiera Valentina Grossi Antonio Matrone Dominga Latorre Marta Simonatto Aurora Fusella James G. Ryall Lydia W. S. Finley Marcia C. Haigis Gaetano Villani Pier Lorenzo Puri Vittorio Sartorelli Cristiano Simone 《Cellular and molecular life sciences : CMLS》2013,70(11):2015-2029
66.
Patricia J. Lardone Amalia Rubio Isabel Cerrillo Araceli G��mez-Corvera Antonio Carrillo-Vico Marina Sanchez-Hidalgo Juan M. Guerrero Patricia Fernandez-Riejos Victor Sanchez-Margalet Patrocinio Molinero 《Cellular and molecular life sciences : CMLS》2010,67(18):3163-3172
Melatonin has been proposed as regulating the immune system by affecting cytokine production in immunocompetent cells, enhancing
the production of several T helper (Th)1 cytokines. To further investigate the melatonin’s role in IL-2/IL-2R system, we established
an inducible T-REx expression system in Jurkat cells in which the protein levels of HIOMT enzyme or MT1 receptor were significantly down-regulated upon tetracycline incubation. We found that T-REx Jurkat cells with lower levels
of HIOMT activity, and consequently lower content of endogenous melatonin, showed IL-2 production decrease after activation
with lectin. Likewise, tetracycline-inducible stable cell line expressing MT1 antisense produced decreased amounts of IL-2 (mRNA and protein levels) after stimulation. Moreover, in T-Rex-MT1 cells incubated with tetracycline, a sub-optimal PHA dose failed to induce the early activation marker CD25 on the cell surface.
The results shown here support the relevance of endogenous melatonin and its signaling in T cell activation. 相似文献
67.
Hatlestad GJ Sunnadeniya RM Akhavan NA Gonzalez A Goldman IL McGrath JM Lloyd AM 《Nature genetics》2012,44(7):816-820
Anthocyanins are red and violet pigments that color flowers, fruits and epidermal tissues in virtually all flowering plants. A single order, Caryophyllales, contains families in which an unrelated family of pigments, the betalains, color tissues normally pigmented by anthocyanins. Here we show that CYP76AD1 encoding a novel cytochrome P450 is required to produce the red betacyanin pigments in beets. Gene silencing of CYP76AD1 results in loss of red pigment and production of only yellow betaxanthin pigment. Yellow betalain mutants are complemented by transgenic expression of CYP76AD1, and an insertion in CYP76AD1 maps to the R locus that is responsible for yellow versus red pigmentation. Finally, expression of CYP76AD1 in yeast verifies its position in the betalain biosynthetic pathway. Thus, this cytochrome P450 performs the biosynthetic step that provides the cyclo-DOPA moiety of all red betacyanins. This discovery will contribute to our ability to engineer this simple, nutritionally valuable pathway into heterologous species. 相似文献
68.
Renna MD Oyadeyi AS Bossi E Kottra G Peres A 《Cellular and molecular life sciences : CMLS》2011,68(17):2961-2975
The functional and structural basis of reverse operation of PepT1 has been studied in Xenopus oocytes expressing the wild-type
and mutated forms of this protein. Using brief pulses from a negative holding potential, wild-type and Arg282 mutants exhibit
outward currents in the presence of Gly-Gln. The reversal potential of these currents is affected by both pH and substrate
concentration, confirming coupled transport in the wild type and in the mutants as well. Long-lasting voltage and current-clamp
experiments show that the outward currents are only temporary, and reflect accumulation and/or depletion effects near the
membrane. The ability to operate in reverse mode was confirmed in all isoforms by intracellular injection of substrate. The
role of Arg282 and Asp341 in the reverse transport was also investigated using charged substrates. Positive Lys-Gly (but not
Gly-Lys) showed enhanced transport currents in the Arg282 mutants. In contrast, negative Gly-Asp and Asp-Gly elicited modest
currents in all isoforms. 相似文献
69.
Antonio Di Tizzano 《Cellular and molecular life sciences : CMLS》1946,2(3):86-99
Summary After a short reference to the fundamental principles of the oxidation-reduction potential and the meaning of the symbolr
H introduced byClark, the author proceeds to set out, among the numerous applications which this important notion has found in various scientific fields, those found in Bacteriology and Hygiene.As regards Bacteriology, the oxidation-reduction potential of the sterile culture media and of various aerobic and anaerobic micro-organisms has been investigated in connection with their growth. The oxidation-reduction potential has proved to be a very good means of classification and identification of the various bacterial strains.Moreover, although the studies performed are not numerous the said oxidation-reduction potential has also been shown to have a great importance in the determination of the immunisation processes of the organism and in its serological behaviour.The oxidation-reduction potential, furthermore, has found very large applications in the field of alimentation, from the problem of fermentations, such as the alcoholic fermentation and the bread fermentation, to the distinction between raw and boiled milk by means ofSchardinger's reaction.In the future, the possibilities for application and development of the oxidation-reduction potential appear to be even more considerable. 相似文献
70.
Shenglian Yao Xi Liu Xiumei Wang Antonio Merolli Xiongbiao Chen Fuzhai Cui 《自然科学进展(英文版)》2013,23(2):103-112
The discovery of neural stem cells (NSCs), which have the ability to self-renew and differentiate into all types of neural lineages, offers promising prospect for the treatment of brain neurological disorders such as stroke/cerebral ischemia, traumatic brain injury and neurodegenerative disorders. However, only limited number of NSCs could survive or propagate due to tissue inflammation or blood-brain barrier. Therefore, it is necessary to develop an appropriate culture system that highly mimics the natural NSCs niche to direct stem cell fate and behavior for nerve regeneration. Both biophysical and biochemical properties of the NSC niche, including topology, mechanical properties, bioactive molecules, and their spatial and temporal presentations should be considered for the design of functionalized scaffolds, which could not only serve as the delivery vehicles of NSCs but also stimulate specific cellular responses at the molecular level, such as support endogenous or exogenous cells proliferation, migration and homing, even promote the growth of axon at the injured brain site. This review attempts to outline the varieties of biomaterial 相似文献