全文获取类型
收费全文 | 3770篇 |
免费 | 194篇 |
国内免费 | 200篇 |
出版年
2024年 | 6篇 |
2023年 | 39篇 |
2022年 | 40篇 |
2021年 | 66篇 |
2020年 | 84篇 |
2019年 | 92篇 |
2018年 | 95篇 |
2017年 | 68篇 |
2016年 | 77篇 |
2015年 | 109篇 |
2014年 | 155篇 |
2013年 | 206篇 |
2012年 | 99篇 |
2011年 | 146篇 |
2010年 | 112篇 |
2009年 | 158篇 |
2008年 | 207篇 |
2007年 | 192篇 |
2006年 | 157篇 |
2005年 | 140篇 |
2004年 | 126篇 |
2003年 | 101篇 |
2002年 | 108篇 |
2001年 | 90篇 |
2000年 | 89篇 |
1999年 | 82篇 |
1998年 | 82篇 |
1997年 | 83篇 |
1996年 | 73篇 |
1995年 | 96篇 |
1994年 | 77篇 |
1993年 | 91篇 |
1992年 | 79篇 |
1991年 | 82篇 |
1990年 | 72篇 |
1989年 | 87篇 |
1988年 | 64篇 |
1987年 | 63篇 |
1986年 | 49篇 |
1985年 | 53篇 |
1984年 | 51篇 |
1983年 | 55篇 |
1982年 | 63篇 |
1981年 | 29篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1974年 | 2篇 |
1971年 | 2篇 |
排序方式: 共有4164条查询结果,搜索用时 15 毫秒
1.
W.J. Malaisse F. Malaisse-Lagae A. Sener 《Biochimica et Biophysica Acta (BBA)/General Subjects》1984,797(2):194-202
1. Because L-asparagine augments insulin release evoked by L-leucine, the metabolism of these two amino acids was investigated in rat pancreatic islets. 2. L-Leucine inhibited the uptake and deamidation of L-asparagine, but failed to exert any obvious primary effect upon the further catabolism of aspartate derived from exogenous asparagine. 3. L-Asparagine augmented the oxidation of L-leucine, and effect possibly attributable to activaion of 2-ketoisocaproate dehydrogenase. 4. The association of L-asparagine and L-leucine exerted a sparing action on the utilization of endogenous amino acids, so that the integrated rate of nutrients oxidation was virtually identical in the sole presence of L-leucine and simultaneous presence of L-asparagine and L-leucine, respectively. 5. It is proposed that the enhancing action of L-asparagine upon insulin release evoked by L-leucine is attributable to an increased generation rate of cytosolic NADPH rather than any increase in nutrients oxidation. 相似文献
2.
Serotonin Inhibits Acetylcholine Release from Rat Striatum Slices: Evidence for a Presynaptic Receptor-Mediated Effect 总被引:4,自引:2,他引:2
Rat brain striatum slices were incubated with [3H]choline, perfused with a physiological buffer, and stimulated by perfusion with a K+-enriched buffer for 2 min. The tritium overflow evoked by K+ was decreased by 5-hydroxytryptamine (serotonin, 5-HT) (maximal inhibition 10(-6) M). This effect of 5-HT was mimicked by several agonists (5-methoxytryptamine, N,N-dimethyl-tryptamine, bufotenin) and blocked by serotonergic antagonists (methiothepin, methysergide, cinanserin) but not by haloperidol; methiothepin and methysergide alone slightly increased the K+-evoked overflow of tritium (3H). Inhibition of the tritium release by 5-HT was not suppressed in the presence of tetrodotoxin (TTX) (10(-6) M). These results suggest that 5-HT tonically inhibits acetylcholine (ACh) release from striatal cholinergic neurons by acting on a presynaptic receptor localized on cholinergic terminals. 相似文献
3.
Recovery time after experience of a given minimum temperature below torpor threshold is related to the value of that minimum, the length of time spent at that minimum, and the temperature prevailing during the recovery period above torpor threshold. A model can predict recovery time for flies experiencing a given temperature fluctuation if the length of time spent at the minimum is expressed as a proportion of LE50 at that minimum.The model has applications in defining the optimal protocol for chilling insects for use in the Sterile Insect Release Method. The model was confirmed by experiments showing that it is likely that flies will recover from non-lethal frosts before ant predators become active.
Résumé Le temps de récupération après avoir subi une température minimal située au-dessous du seuil d'engourdissement dépend de la valeur de ce minimum, du temps passé à ce minimum, et de la température au-dessus du seuil d'engourdissement pendant la période de récupération. Un modèle mathématique permet d'estimer le temps de récupération après avoir subi une chute de température déterminée, en fonction du temps passé au minimum thermique exprimé comme une fraction du LE50 (temps nécessaire pour tuer 50% des mouches) à ce minimum.Ce modèle s'est trouvé étayé par des observations montrant qu'il est probable que les mouches se remettent des gelées sublétales avant la reprise d'activité des fourmis prédatrices. Ce modèle peut être utilisé pour définir les conditions optimales de refroidissement des insectes utilisés lors de la libération d'individus stériles.相似文献
4.
5.
6.
7.
《FEBS letters》1988,240(1-2):88-94
Four subtypes of muscarinic acetylcholine receptor (mAChR) were stably expressed in neuroblastoma-glioma hybrid cells (NG108-15). By combining fluorescent indicator dye (fura-2) studies with electrophysiological measurements it is shown that stimulation of mAChR I and mAChR III readily leads to release of calcium from intracellular stores and to associated conductance changes, whereas stimulation of mAChR II and mAChR IV exerts no such effect. Dose-response curves describing the amplitude or the delay of the calcium rise induced by acetylcholine suggest that the apparent affinity of mAChR III for its agonist is higher by about one order of magnitude than that of mAChR I. Ionic substitution experiments and current fluctuation analysis indicate that calcium activates a K+-specific conductance of ‘small’ single-channel amplitude similar to the SK type [1]. Furthermore, an outward current (M current) suppressed by activation of mAChR I and mAChR III has a single-channel amplitude corresponding to a conductance of approximately 3 pS. 相似文献
8.
9.
Xiuling Li Songbai Yang Zhonglin Tang Kui Li Max F. Rothschild Bang Liu Bin Fan 《Animal genetics》2014,45(3):329-339
Due to the direction, intensity, duration and consistency of genetic selection, especially recent artificial selection, the production performance of domestic pigs has been greatly changed. Therefore, we reasoned that there must be footprints or selection signatures that had been left during domestication. In this study, with porcine 60K BeadChip genotyping data from both commercial Large White and local Chinese Tongcheng pigs, we calculated the extended haplotype homozygosity values of the two breeds using the long‐range haplotype method to detect selection signatures. We found 34 candidate regions, including 61 known genes, from Large White pigs and 25 regions comprising 57 known genes from Tongcheng pigs. Many selection signatures were found on SSC1, SSC4, SSC7 and SSC14 regions in both populations. According to quantitative trait loci and network pathway analyses, most of the regions and genes were linked to growth, reproduction and immune responses. In addition, the average genetic differentiation coefficient FST was 0.254, which means that there had already been a significant differentiation between the breeds. The findings from this study can contribute to further research on molecular mechanisms of pig evolution and domestication and also provide valuable references for improvement of their breeding and cultivation. 相似文献
10.