全文获取类型
收费全文 | 530篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
系统科学 | 9篇 |
理论与方法论 | 1篇 |
现状及发展 | 75篇 |
研究方法 | 92篇 |
综合类 | 332篇 |
自然研究 | 22篇 |
出版年
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 2篇 |
2013年 | 5篇 |
2012年 | 35篇 |
2011年 | 67篇 |
2010年 | 9篇 |
2008年 | 35篇 |
2007年 | 31篇 |
2006年 | 45篇 |
2005年 | 42篇 |
2004年 | 27篇 |
2003年 | 36篇 |
2002年 | 33篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1973年 | 1篇 |
1972年 | 7篇 |
1971年 | 5篇 |
1970年 | 8篇 |
1969年 | 4篇 |
1968年 | 5篇 |
1967年 | 6篇 |
1966年 | 6篇 |
1965年 | 3篇 |
1964年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有531条查询结果,搜索用时 328 毫秒
221.
Bond J Roberts E Springell K Lizarraga SB Lizarraga S Scott S Higgins J Hampshire DJ Morrison EE Leal GF Silva EO Costa SM Baralle D Raponi M Karbani G Rashid Y Jafri H Bennett C Corry P Walsh CA Woods CG 《Nature genetics》2005,37(4):353-355
Autosomal recessive primary microcephaly is a potential model in which to research genes involved in human brain growth. We show that two forms of the disorder result from homozygous mutations in the genes CDK5RAP2 and CENPJ. We found neuroepithelial expression of the genes during prenatal neurogenesis and protein localization to the spindle poles of mitotic cells, suggesting that a centrosomal mechanism controls neuron number in the developing mammalian brain. 相似文献
222.
223.
Summary The inhibition of cyclic nucleotide phosphodiesterase from the nerve cord ofManduca sexta was studied using theophylline as a model compound. 11 putative neurotransmitters had no effect on enzyme activity.Supported in part by NIH grant NS-09161-20 to R. W. Newburgh 相似文献
224.
225.
226.
227.
Many representations of sensory stimuli in the neocortex are arranged as topographic maps. These cortical maps are not fixed, but show experience-dependent plasticity. For instance, sensory deprivation causes the cortical area representing the deprived sensory input to shrink, and neighbouring spared representations to enlarge, in somatosensory, auditory or visual cortex. In adolescent and adult animals, changes in cortical maps are most noticeable in the supragranular layers at the junction of deprived and spared cortex. However, the cellular mechanisms of this experience-dependent plasticity are unclear. Long-term potentiation and depression have been implicated, but have not been proven to be necessary or sufficient for cortical map reorganization. Short-term synaptic dynamics have not been considered. We developed a brain slice preparation involving rat whisker barrel cortex in vitro. Here we report that sensory deprivation alters short-term synaptic dynamics in both vertical and horizontal excitatory pathways within the supragranular cortex. Moreover, modifications of horizontal pathways amplify changes in the vertical inputs. Our findings help to explain the functional cortical reorganization that follows persistent changes of sensory experience. 相似文献
228.
伯醛化合物加成在富电子碳碳双键的自由基链反应可以通过硫醇的催化作用来实现,硫醇的作用表现为一个极性可逆的催化剂,它可以促使氢原子从醛完全转移至加成自由基上,该自由基是载链酰基自由基加成至烯酰胺上所生成的 相似文献
229.
Plasmodium falciparum-infected erythrocytes modulate the maturation of dendritic cells. 总被引:34,自引:0,他引:34
B C Urban D J Ferguson A Pain N Willcox M Plebanski J M Austyn D J Roberts 《Nature》1999,400(6739):73-77
The malaria parasite Plasmodium falciparum is one of the most successful human pathogens. Specific virulence factors remain poorly defined, although the adhesion of infected erythrocytes to the venular endothelium has been associated with some of the syndromes of severe disease. Immune responses cannot prevent the development of symptomatic infections throughout life, and clinical immunity to the disease develops only slowly during childhood. An understanding of the obstacles to the development of protective immunity is crucial for developing rational approaches to prevent the disease. Here we show that intact malaria-infected erythrocytes adhere to dendritic cells, inhibit the maturation of dendritic cells and subsequently reduce their capacity to stimulate T cells. These data demonstrate both a novel mechanism by which malaria parasites induce immune dysregulation and a functional role beyond endothelial adhesion for the adhesive phenotypes expressed at the surface of infected erythrocytes. 相似文献
230.
We investigated localities from which Eutamias atristriatus Bailey, 1913 (= Tamias minimus atristriatus ) and Zapus luteus Miller, 1911 (= Zapus hudsonius luteus ) were collected during a 1902 survey in the Sacramento Mountains, New Mexico, by the United States Biological Survey. The locality from which the holotype of Eutamias atristriatus was collected is restricted to James Canyon rather than the Rio Pe?asco. Locality records indicate that the historical distribution of Zapus hudsonius luteus and its obligate wetland habitat were broader than currently realized. 相似文献