全文获取类型
收费全文 | 1421篇 |
免费 | 124篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 40篇 |
2020年 | 21篇 |
2019年 | 30篇 |
2018年 | 37篇 |
2017年 | 28篇 |
2016年 | 54篇 |
2015年 | 86篇 |
2014年 | 83篇 |
2013年 | 97篇 |
2012年 | 114篇 |
2011年 | 114篇 |
2010年 | 61篇 |
2009年 | 55篇 |
2008年 | 71篇 |
2007年 | 74篇 |
2006年 | 77篇 |
2005年 | 70篇 |
2004年 | 54篇 |
2003年 | 45篇 |
2002年 | 51篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 12篇 |
1998年 | 14篇 |
1997年 | 10篇 |
1995年 | 8篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 9篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1980年 | 6篇 |
1978年 | 4篇 |
1976年 | 5篇 |
1974年 | 5篇 |
1970年 | 3篇 |
1967年 | 4篇 |
1966年 | 5篇 |
1965年 | 4篇 |
1963年 | 7篇 |
排序方式: 共有1545条查询结果,搜索用时 187 毫秒
1.
ThuyTien Nguyen I. Ricardo Argueta-Morales Stephen Guimond William Clark Andres Ceballos Ruben Osorio 《Computer methods in biomechanics and biomedical engineering》2016,19(7):789-799
Stroke is the most devastating complication after ventricular assist device (VAD) implantation with a 19% incidence and 65% mortality in the pediatric population. Current pediatric VAD technology and anticoagulation strategies alone are suboptimal. VAD implantation assisted by computational methods (CFD) may contribute reducing the risk of cerebral embolization. Representative three-dimensional aortic arch models of an infant and a child were generated. An 8 mm VAD outflow-graft (VAD-OG) anastomosed to the aorta was rendered and CFD was applied to study blood flow patterns. Particle tracks, originating in the VAD, were computed with a Lagrangian phase model and the percentage of particles entering the cerebral vessels was calculated. Eight implantation configurations (infant = 5 and child = 3) and 5 particle sizes (0.5, 1, 2, 3, and 4 mm) were considered. For the infant model, percentage of particles entering the cerebral vessels ranged from 15% for a VAD-OG anastomosed at 90° to the aorta, to 31% for 30° VAD-OG anastomosis (overall percentages: X2 = 10,852, p < 0.0001). For the child model, cerebral embolization ranged from 9% for the 30° VAD-OG anastomosis to 15% for the 60° anastomosis (overall percentages: χ2 = 10,323, p < 0.0001). Using detailed CFD calculations, we demonstrate that the risk of stroke depends significantly on the VAD implantation geometry. In turn, the risk probably depends on patient-specific anatomy. CFD can be used to optimize VAD implantation geometry to minimize stroke risk. 相似文献
2.
Amaria Darmellah Amel Rayah Rodolphe Auger Marie-Hélène Cuif Magali Prigent Monique Arpin Andres Alcover Cécile Delarasse Jean M. Kanellopoulos 《The Journal of biological chemistry》2012,287(41):34583-34595
The amyloid precursor protein (APP) can be cleaved by α-secretases in neural cells to produce the soluble APP ectodomain (sAPPα), which is neuroprotective. We have shown previously that activation of the purinergic P2X7 receptor (P2X7R) triggers sAPPα shedding from neural cells. Here, we demonstrate that the activation of ezrin, radixin, and moesin (ERM) proteins is required for the P2X7R-dependent proteolytic processing of APP leading to sAPPα release. Indeed, the down-regulation of ERM by siRNA blocked the P2X7R-dependent shedding of sAPPα. We also show that P2X7R stimulation triggered the phosphorylation of ERM. Thus, ezrin translocates to the plasma membrane to interact with P2X7R. Using specific pharmacological inhibitors, we established the order in which several enzymes trigger the P2X7R-dependent release of sAPPα. Thus, a Rho kinase and the MAPK modules ERK1/2 and JNK act upstream of ERM, whereas a PI3K activity is triggered downstream. For the first time, this work identifies ERM as major partners in the regulated non-amyloidogenic processing of APP. 相似文献
3.
4.
The immunosuppressive drug cyclosporin A (CsA) binds to its receptor protein cyclophilin 18 (Cyp18) in two distinct kinetic phases, while the mechanism remains elusive. Stopped-flow measurements coupled with titration and competition experiments were used to investigate the puzzling two-phase process of CsA and Cyp18 interaction. This study leads to the dissection of different conformational fractions of either direct fast binding or slow binding with rate-limiting conformational inter-conversion and the real-time measurement of kon value (8.34 ± 0.22 x106 M-1s-1) in solution. Furthermore, our study indicates that the structure of CsA during dissociation from the protein possesses a distribution of conformations different from those in solution under equilibrium condition. 相似文献
5.
6.
Although UT-2 cells, a mutant clone of Chinese hamster ovary cells, have been shown to require mevalonate for growth due to a deficiency in 3-hydroxy-3-methylglutaryl-CoA reductase, the precise mevalonate-derived product(s) essential for proliferation has not been identified. These studies show that UT-2 cells proliferate in the presence of free geranylgeraniol (GG-OH), as well as mevalonate. Cell growth was optimal when the culture medium was supplemented with 5–10 μMGG-OH. Under these growth conditions [3H]GG-OH is actively incorporated into UT-2 proteins. Prominent [3H]geranylgeranylated polypeptides in the size range (19–27 kDa) of the small GTP-binding proteins are observed by SDS–PAGE. Analysis of the butanol-soluble products released from the metabolically labeled proteins by digestion with Pronase E reveals that the proteins contain [3H]geranylgeranylated cysteine residues. Even though [3H]farnesol is also incorporated into cysteinyl residues of a different set of UT-2 proteins, farnesol added at 10 μMdid not satisfy the mevalonate requirement for cell growth. These results show that UT-2 cells divide in the presence of exogenously supplied GG-OH, providing evidence that one or more geranylgeranylated proteins are essential for entry of UT-2 cells, and probably other mammalian cells, into the cell cycle. 相似文献
7.
A Xenogeneic-Free Protocol for Isolation and Expansion of Human Adipose Stem Cells for Clinical Uses
8.
Dopamine-β-hydroxylase is stable in serum frozen for several years and in the same normotensive white males studied over 3–7 years, levels of this enzyme in serum usually remained relatively constant. In four of nine patients in whom there was an increase in blood pressure, serum DBH levels decreased to a greater extent than in any of the 13 subjects in whom there was no significant change in blood pressure. Normal blood donors with systolic blood pressures less than 110 had higher levels of serum DBH than did donors with blood pressures over 130. The relationship of serum DBH changes to sympathetic neuronal function in patients with elevated blood pressure is discussed. 相似文献
9.
10.
Andres Jaanus Susanna Hajdu Seppo Kaitala Agneta Andersson Kaire Kaljurand Iveta Ledaine Inga Lips Irina Olenina 《Hydrobiologia》2006,554(1):137-146
During the latest years medium-sized (15–30 μm), single-celled dinoflagellates have been reported to form blooms in the northern
Baltic Proper and the Gulf of Finland in winter and spring. Recent studies (Kremp et al., 2003. Proceedings of the 7th International conference of Modern and Fossil Dinoflagellates, September 21–25, Nagasaki, Japan,
66 pp.) indicate that those blooms are caused by two isomorphic species – Scrippsiella hangoei (Schiller) Larsen, and a new species, tentatively belonging to the genus Woloszynskia. Until now there has been no report on how widely distributed these phytoplankton species are in the Baltic Sea. In this
study, the occurrence of Scrippsiella/Woloszynskia complex in the entire Baltic Sea was investigated, by using monitoring data from 1997 to 2003. The species occurred in a
salinity range from 2 to 8 PSU. Highest concentrations were observed at salinity 4.5–6.5 PSU. Maximum cell densities of Scrippsiella/Woloszynskia complex in the water column were mainly obtained in April or in the beginning of May by the water temperature <3 °C prior
to stratification was formed. In the central Gulf of Finland, the second maximum was found in 1999 and 2002 by the temperature
>6 °C. Bloom formations in the Baltic Proper and in the Gulf of Finland may not only be explained by optimum temperature and
salinity, but also with other factors e.g. high nutrient concentrations and good seeding conditions from the sediments. 相似文献