全文获取类型
收费全文 | 1106篇 |
免费 | 95篇 |
专业分类
1201篇 |
出版年
2022年 | 10篇 |
2021年 | 12篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 8篇 |
2017年 | 10篇 |
2016年 | 23篇 |
2015年 | 48篇 |
2014年 | 53篇 |
2013年 | 61篇 |
2012年 | 66篇 |
2011年 | 69篇 |
2010年 | 36篇 |
2009年 | 55篇 |
2008年 | 79篇 |
2007年 | 52篇 |
2006年 | 61篇 |
2005年 | 66篇 |
2004年 | 70篇 |
2003年 | 70篇 |
2002年 | 66篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 14篇 |
1996年 | 11篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 8篇 |
1970年 | 3篇 |
排序方式: 共有1201条查询结果,搜索用时 15 毫秒
61.
62.
63.
64.
65.
Hai-Sheng?Li Kuntala?Shome Raúl?Rojas Mark?A?Rizzo Chandrasekaran?Vasudevan Eric?Fluharty Lorraine?C?Santy James?E?Casanova Guillermo?RomeroEmail author 《BMC cell biology》2003,4(1):13
Background
Phospholipase D (PLD) is involved in many signaling pathways. In most systems, the activity of PLD is primarily regulated by the members of the ADP-Ribosylation Factor (ARF) family of GTPases, but the mechanism of activation of PLD and ARF by extracellular signals has not been fully established. Here we tested the hypothesis that ARF-guanine nucleotide exchange factors (ARF-GEFs) of the cytohesin/ARNO family mediate the activation of ARF and PLD by insulin. 相似文献66.
Van Sickle MD Oland LD Mackie K Davison JS Sharkey KA 《American journal of physiology. Gastrointestinal and liver physiology》2003,285(3):G566-G576
The aim of this study was to investigate the efficacy, receptor specificity, and site of action of Delta9-tetrahydrocannabinol (THC) as an antiemetic in the ferret. THC (0.05-1 mg/kg ip) dose-dependently inhibited the emetic actions of cisplatin. The ED50 for retching was approximately 0.1 mg/kg and for vomiting was 0.05 mg/kg. A specific cannabinoid (CB)1 receptor antagonist SR-141716A (5 mg/kg ip) reversed the effect of THC, whereas the CB2 receptor antagonist SR-144528 (5 mg/kg ip) was ineffective. THC applied to the surface of the brain stem was sufficient to inhibit emesis induced by intragastric hypertonic saline. The site of action of THC in the brain stem was further assessed using Fos immunohistochemistry. Fos expression induced by cisplatin in the dorsal motor nucleus of the vagus (DMNX) and the medial subnucleus of the nucleus of the solitary tract (NTS), but not other subnuclei of the NTS, was significantly reduced by THC rostral to obex. At the level of the obex, THC reduced Fos expression in the area postrema and the dorsal subnucleus of the NTS. The highest density of CB1 receptor immunoreactivity was found in the DMNX and the medial subnucleus of the NTS. Lower densities were observed in the area postrema and dorsal subnucleus of the NTS. Caudal to obex, there was moderate density of staining in the commissural subnucleus of the NTS. These results show that THC selectively acts at CB1 receptors to reduce neuronal activation in response to emetic stimuli in specific regions of the dorsal vagal complex. 相似文献
67.
1. Our previous studies demonstrated that when neural stem cells (NSCs) of the C17.2 clonal line are transplanted into the intact or 6-hydroxydopamine (6-OHDA) lesioned rat striatum, in most, but not all grafts, cells spontaneously express the dopamine (DA) biosynthetic enzymes, tyrosine hydroxylase (TH), and aromatic L-amino acid decarboxylase (Yang, M., Stull, N. D., Snyder, E. Y., Berk, M. A., and Iacovitti, L. (2002). Exp. Neurol.).2. These results suggested that there were certain conditions which were more conducive to the development of DA traits in NSCs and possibly other neurotransmitter phenotypes.3. In the present study, we modified a number of variables in vitro (i.e. passage number, confluence) and/or in vivo (degree, type, and site of injury) before assessing the survival, migration, and differentiation of engrafted NSCs.4. We found that low confluence cultures were comprised exclusively of flattened polygonal cells, which when transplanted, migrated widely in the brain but did not express TH.5. In contrast, high confluence cultures contained both polygonal cells and an overlying bed of fusiform cells.6. When these NSCs were maintained for 12–20 passages and then transplanted, virtually all engrafted cells in 65% of the grafts expressed TH but not markers of other neurotransmitter systems.7. Importantly, all TH+ grafts were accompanied by significant physical damage to the brain while TH– grafts were not, suggesting that local injury-related factors were also important.8. Of no apparent influence on TH expression, regardless of how cells were grown prior to implantation, was the site of transplantation (cortex or striatum) or the degree of chemical lesion (intact, partial or full).9. We conclude that transplanted NSCs can express traits specifically associated with DA neurons but only when cells are grown under certain conditions in vitro and then transplanted in proximity to injury-induced factors present in vivo. 相似文献
68.
A novel hierarchical clustering algorithm was applied to the distribution of Meissner corpuscles in the skin of mammals. This method, called end-to-end linkage (EEL), is useful for grouping data that consists of chain-like contingencies in the multivariable space. Unlike the traditional techniques which uncover hyperspherical clusters (e.g. single linkage), EEL considers the shortest distance between the predefined end pairs of the two clusters as an inter-group distance. This scheme allows characterizing the internal structure of data better than other hierarchical techniques. The anatomical data used in the case study is important for studying the sense of touch. The results show a substantial improvement over the traditional single-linkage method. On average, the number of correctly classified corpuscles is increased to twice the number identified by the single-linkage method. EEL can also be used for analyzing other sensory modalities where geometric relationships need to be explored. In addition, the report contains corpuscle density and epidermal-ridge width data obtained from several species. 相似文献
69.
Transcriptome analysis of root transporters reveals participation of multiple gene families in the response to cation stress 总被引:31,自引:4,他引:27
70.
Abbott MJ Bogachus LD Turcotte LP 《Journal of applied physiology (Bethesda, Md. : 1985)》2011,111(1):125-134
AMP-activated protein kinase (AMPK) is a fuel sensor in skeletal muscle with multiple downstream signaling targets that may be triggered by increases in intracellular Ca(2+) concentration ([Ca(2+)]). The purpose of this study was to determine whether increases in intracellular [Ca(2+)] induced by caffeine act solely via AMPKα(2) and whether AMPKα(2) is essential to increase glucose uptake, fatty acid (FA) uptake, and FA oxidation in contracting skeletal muscle. Hindlimbs from wild-type (WT) or AMPKα(2) dominant-negative (DN) transgene mice were perfused during rest (n = 11), treatment with 3 mM caffeine (n = 10), or muscle contraction (n = 11). Time-dependent effects on glucose and FA uptake were uncovered throughout the 20-min muscle contraction perfusion period (P < 0.05). Glucose uptake rates did not increase in DN mice during muscle contraction until the last 5 min of the protocol (P < 0.05). FA uptake rates were elevated at the onset of muscle contraction and diminished by the end of the protocol in DN mice (P < 0.05). FA oxidation rates were abolished in the DN mice during muscle contraction (P < 0.05). The DN transgene had no effect on caffeine-induced FA uptake and oxidation (P > 0.05). Glucose uptake rates were blunted in caffeine-treated DN mice (P < 0.05). The DN transgene resulted in a greater use of intramuscular triglycerides as a fuel source during muscle contraction. The DN transgene did not alter caffeine- or contraction-mediated changes in the phosphorylation of Ca(2+)/calmodulin-dependent protein kinase I or ERK1/2 (P > 0.05). These data suggest that AMPKα(2) is involved in the regulation of substrate uptake in a time-dependent manner in contracting muscle but is not necessary for regulation of FA uptake and oxidation during caffeine treatment. 相似文献