全文获取类型
收费全文 | 1044篇 |
免费 | 142篇 |
出版年
2022年 | 14篇 |
2021年 | 18篇 |
2020年 | 17篇 |
2019年 | 29篇 |
2018年 | 33篇 |
2017年 | 29篇 |
2016年 | 43篇 |
2015年 | 56篇 |
2014年 | 37篇 |
2013年 | 51篇 |
2012年 | 60篇 |
2011年 | 57篇 |
2010年 | 44篇 |
2009年 | 30篇 |
2008年 | 48篇 |
2007年 | 41篇 |
2006年 | 48篇 |
2005年 | 45篇 |
2004年 | 37篇 |
2003年 | 40篇 |
2002年 | 29篇 |
2001年 | 29篇 |
2000年 | 25篇 |
1999年 | 29篇 |
1998年 | 18篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 10篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 11篇 |
1987年 | 18篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1972年 | 9篇 |
1970年 | 6篇 |
1969年 | 4篇 |
排序方式: 共有1186条查询结果,搜索用时 15 毫秒
91.
Medina-Leendertz S Valero N Chacín-Bonilla L Añez F Giraldoth D Arias J Espina G Díaz S Bonilla E 《Neurochemical research》2001,26(3):231-234
In mice infected with the Venezuelan equine encephalomyelitis (VEE) virus and exposed to high intensity light (2500 lux) with a 12 h light: 12 h dark photoperiod, a significant increase in the levels of melatonin in the olfactory bulb was observed. The significance of these findings deserves further studies to understand the mechanisms involved in this effect since the olfactory bulbs have been proposed as first portal for VEE virus entry into the CNS. The increase in melatonin content could represent one of the mechanisms of defense against the viral attack. 相似文献
92.
Begega A Cienfuegos S Rubio S Santín JL Miranda R Arias JL 《Behavioural processes》2001,53(1-2):75-85
This study was designed to assess the effect of ageing on spatial (allocentric and egocentric) strategies in rats. Two different tasks were designed for this purpose: one involving Morris' circular pool (distal extramaze cues) and another using the T water maze (egocentric cues). In the first task, the aged rats showed some difficulty in acquiring allocentric spatial learning skills. After increasing the number of trials in this task, there was no significant improvement in the performance of the aged group of rats compared to the adult group. However, in the second spatial task (using egocentric cues), both age groups gave a similar performance. Therefore, the effect of ageing on spatial learning depends on the strategy required to acquire this learning. 相似文献
93.
Solid cultures of the producing strain grown on Bennett medium develop abundant mycelium and intense sporulation. Under these
conditions biosynthesis of APHE antibiotics (APHE-1 to -3) is accomplished. Further studies show that APHE-3 is basically
produced during spore formation and mostly present in spores, while APHE-1 and APHE-2 are the predominant antibiotics in the
mycelium. APHE compounds are present in almost all streptomycetes tested, indicating a possible role in the life cycle of
these microorganisms.
Received: 19 July 1999 / Received revision: 22 October 1999 / Accepted: 22 October 1999 相似文献
94.
Lawrence N Klein T Brennan K Martinez Arias A 《Development (Cambridge, England)》2000,127(14):3185-3195
The delta and Serrate proteins interact with the extracellular domain of the Notch receptor and initiate signalling through the receptor. The two ligands are very similar in structure and have been shown to be interchangeable experimentally; however, loss of function analysis indicates that they have different functions during development and analysis of their signalling during wing development indicates that the Fringe protein can discriminate between the two ligands. This raises the possibility that the signalling of delta and Serrate through Notch requires different domains of the Notch protein. Here we have tested this possibility by examining the ability of delta and Serrate to interact and signal with Notch molecules in which different domains had been deleted. This analysis has shown that EGF-like repeats 11 and 12, the RAM-23 and cdc10/ankyrin repeats and the region C-terminal to the cdc10/ankyrin repeats of Notch are necessary for both delta and Serrate to signal via Notch. They also indicate, however, that delta and Serrate utilise EGF-like repeats 24-26 of Notch for signalling, but there are significant differences in the way they utilise these repeats. 相似文献
95.
96.
Newly synthesized canalicular ectoenzymes and a cell adhesion molecule (cCAM105) have been shown to traffic from the Golgi to the basolateral plasma membrane, from where they transcytose to the apical bile canalicular domain. It has been proposed that all canalicular proteins are targeted via this indirect route in hepatocytes. We studied the membrane targeting of rat canalicular proteins by in vivo [(35)S]methionine metabolic labeling followed by preparation of highly purified Golgi membranes and canalicular (CMVs) and sinusoidal/basolateral (SMVs) membrane vesicles and subsequent immunoprecipitation. In particular, we compared membrane targeting of newly synthesized canalicular ABC (ATP-binding cassette) transporters MDR1, MDR2, and SPGP (sister of P-glycoprotein) with that of cCAM105. Significant differences were observed in metabolic pulse-chase labeling experiments with regard to membrane targeting of these apical proteins. After a chase time of 15 min, cCAM105 appeared exclusively in SMVs, peaked at 1 h, and progressively declined thereafter. In CMVs, cCAM105 was first detected after 1 h and subsequently increased for 3 h. This findings confirm the transcytotic targeting of cCAM105 reported in earlier studies. In contrast, at no time point investigated were MDR1, MDR2, and SPGP detected in SMVs. In CMVs, MDR1 and MDR2 appeared after 30 min, whereas SPGP appeared after 2 h of labeling. In Golgi membranes, each of the ABC transporters peaked at 30 min and was virtually absent thereafter. These data suggest rapid, direct targeting of newly synthesized MDR1 and MDR2 from the Golgi to the bile canaliculus and transient sequestering of SPGP in an intracellular pool en route from the Golgi to the apical plasma membrane. This study provides biochemical evidence for direct targeting of newly synthesized apical ABC transporters from the Golgi to the bile canaliculus in vivo. 相似文献
97.
98.
Biological adaptive systems share some common features: variation among their constituent elements and continuity of core information. Some of them, such as the immune system, are endowed with memory of past events. In this study we provide direct evidence that evolving viral quasispecies possess a molecular memory in the form of minority components that populate their mutant spectra. The experiments have involved foot-and-mouth disease virus populations with known evolutionary histories. The composition and behavior of the viral population in response to a selective constraint were influenced by past evolutionary history in a way that could not be predicted from examination of consensus nucleotide sequences of the viral populations. The molecular memory of the viral quasispecies influenced both the nature and the intensity of the response of the virus to a selective constraint. 相似文献
99.
Rodolfo FaríasRodríguez Robert B. Mellor Carlos Arias Juan José PeñaCabriales 《Physiologia plantarum》1998,102(3):353-359
Nine cultivars of common bean were grown in the presence of a natural microflora without exogenous rhizobial inoculation. Nodules were harvested 30 days post planting (early flowering stage) and the presence of trehalose determined. Amounts present varied according to cultivar and were between 0.20 and 1.63 mg g−1 nodule dry weight. Rhizobial strains were isolated from the nodules of three selected cultivars (Canario 101, Flor de Mayo Bajio and Flor de Mayo 38). Trehalose levels in nodules produced after either mixed strain reinfection, or after axenic homologous reinfection or after axenic cross‐reinfection could be manipulated by applying drought stress. Mixed reinfection nodules from stressed plants accumulated between two and six times the trehalose concentration found in non‐stressed control plants. After axenic cross‐reinfection up to 48‐fold increases in nodule trehalose content were recorded during drought stress. Those cultivars exhibiting high nodule trehalose levels and/or a high degree of trehalose stimulation in response to drought stress also exhibited a high leaf relative water content and were also the most drought resistant. During drought stress nodule trehalase levels rose only slightly. 相似文献
100.