全文获取类型
收费全文 | 1557篇 |
免费 | 171篇 |
国内免费 | 98篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 9篇 |
妇产科学 | 2篇 |
基础医学 | 319篇 |
口腔科学 | 2篇 |
临床医学 | 39篇 |
内科学 | 104篇 |
皮肤病学 | 2篇 |
神经病学 | 1085篇 |
特种医学 | 9篇 |
外科学 | 13篇 |
综合类 | 66篇 |
现状与发展 | 1篇 |
预防医学 | 10篇 |
眼科学 | 3篇 |
药学 | 126篇 |
中国医学 | 24篇 |
肿瘤学 | 11篇 |
出版年
2024年 | 1篇 |
2023年 | 21篇 |
2022年 | 13篇 |
2021年 | 52篇 |
2020年 | 42篇 |
2019年 | 60篇 |
2018年 | 42篇 |
2017年 | 43篇 |
2016年 | 73篇 |
2015年 | 66篇 |
2014年 | 103篇 |
2013年 | 112篇 |
2012年 | 110篇 |
2011年 | 124篇 |
2010年 | 115篇 |
2009年 | 118篇 |
2008年 | 127篇 |
2007年 | 124篇 |
2006年 | 108篇 |
2005年 | 67篇 |
2004年 | 64篇 |
2003年 | 30篇 |
2002年 | 37篇 |
2001年 | 20篇 |
2000年 | 7篇 |
1999年 | 18篇 |
1998年 | 15篇 |
1997年 | 10篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 2篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1826条查询结果,搜索用时 15 毫秒
991.
Mandairon N Sacquet J Garcia S Ravel N Jourdan F Didier A 《The European journal of neuroscience》2006,24(12):3578-3588
In the main olfactory bulb, stimuli are coded within the spatio-temporal pattern of mitral cells' activity. Granule cells are interneurons that shape the mitral cells' activity, and are continuously generated in the adult main olfactory bulb. However, the role of granule cell renewal remains elusive. We show here that an associative olfactory discrimination task reduces the survival of newborn neurons. However, when the olfactory task involves perceptually related odorants, the learning process is slower and does not induce such a reduction in the number of new neurons. Mapping newborn cells within the granule cell layer of the main olfactory bulb reveals a clustered distribution that evolves with learning as a function of odorant similarity and partly overlaps with the immediate-early gene Zif268 expression pattern. These data provide insight into the functional mechanisms underlying olfactory discrimination learning, and promote the importance of neurogenesis as a cellular basis for the restructuring of odor images in the main olfactory bulb. 相似文献
992.
Targeted transgene expression in neuronal precursors: watching young neurons in the old brain 总被引:5,自引:0,他引:5
Couillard-Despres S Winner B Karl C Lindemann G Schmid P Aigner R Laemke J Bogdahn U Winkler J Bischofberger J Aigner L 《The European journal of neuroscience》2006,24(6):1535-1545
Progress in the field of neurogenesis is limited by the lack of animal models allowing direct detection and analysis of living cells participating in neurogenesis. We engineered a transgenic mouse model that expresses the fluorescent reporter proteins enhanced green fluorescent protein or Discoma sp. reef coral red fluorescent protein under the control of the doublecortin (DCX) promoter, a gene specifically and transiently active in neuronal precursors and young neurons. The expression of the reporter proteins correlated with expression of the endogenous DCX protein, and with developmental and adult neurogenesis. Neurogenesis was unaffected by the presence of the fluorescent proteins. The transgenic mice allowed direct identification of the very few newly generated neurons present in the aged brain. We performed electrophysiological analysis and established that newly generated hippocampal granule cells in aged and young mice shared identical physiological properties. Hence, although the rate of neurogenesis tapers with ageing, a population of highly excitable young neurons indistinguishable to those found in younger animals is continuously generated. Therefore, maintenance of the fundamental properties of neuronal precursors even at advanced age suggests that stimulation of neurogenesis may constitute a valid strategy to counteract age-related neuronal loss and cognitive declines. 相似文献
993.
994.
Julie Dechartres Jodi L. Pawluski Marie‐Madeleine Gueguen Amin Jablaoui Emmanuelle Maguin Moez Rhimi Thierry D. Charlier 《Journal of neuroendocrinology》2019,31(9)
Glyphosate is found in a large array of non‐selective herbicides such as Roundup® (Monsanto, Creve Coeur, MO, USA) and is by far the most widely used herbicide. Recent work in rodent models suggests that glyphosate‐based herbicides during development can affect neuronal communication and result in altered behaviours, albeit through undefined mechanisms of action. To our knowledge, no study has investigated the effects glyphosate or its formulation in herbicide on maternal behaviour and physiology. In the present study, relatively low doses of glyphosate (5 mg kg‐1 d‐1), Roundup® (5 mg kg‐1 d‐1 glyphosate equivalent), or vehicle were administered by ingestion to Sprague‐Dawley rats from gestational day (GD) 10 to postpartum day (PD)22. The treatments significantly altered licking behaviour toward pups between PD2 and PD6. We also show in the dams at PD22 that Roundup exposure affected the maturation of doublecortin‐immunoreactive new neurones in the dorsal dentate gyrus of the hippocampus of the mother. In addition, the expression of synaptophysin was up‐regulated by glyphosate in the dorsal and ventral dentate gyrus and CA3 regions of the hippocampus, and down‐regulated in the cingulate gyrus. Although a direct effect of glyphosate alone or its formulation on the central nervous system is currently not clear, we show that gut microbiota is significantly altered by the exposure to the pesticides, with significant alteration of the phyla Bacteroidetes and Firmicutes. This is the first study to provide evidence that glyphosate alone or in formulation (Roundup) differentially affects maternal behaviour and modulates neuroplasticity and gut microbiota in the mother. 相似文献
995.
Sophie Lumineau Jodi L. Pawluski Thierry D. Charlier Amandine Beylard Nadge Aigueperse Aline Bertin Frdric Lvy 《Journal of neuroendocrinology》2019,31(9)
Maternal behaviour develops differently depending on the characteristics of an individual, such as age or emotional reactivity. Social motivation, defined as the propensity to establish social contact, has received little attention in relation to maternal behaviour in birds. In addition, the transition to motherhood is a time of plasticity in the brain of the new mother in mammals. However, it remains to be determined how maternal brain plasticity is affected in avian species. The present study investigated how a the social motivation of a mother alters maternal behaviour and brain plasticity of the Japanese quail (Coturnix japonica). Adult females from lines selected for high and low social motivation were exposed to chicks for 11 days. After maternal care testing, and at matched time points in controls, the brains of females were perfused for assessment of doublecortin‐immunoreactive staining, a marker of neurogenesis, in the subventricular zone (SVZ), a neurogenic niche. The results obtained showed that high socially motivated female quail spent significantly less time performing maternal behaviour when exposed to chicks compared to low socially motivated females. Moreover, the warming of chicks by high socially motivated females involved less covering postures and mothers were more rejecting of chicks. Interestingly, the plasticity indicators in the SVZ did not differ between low and high socially motivated females and were not associated with differences in maternal caregiving when using doublecortin‐immunoreactive staining. Thus, high social motivation in this avian species does not favour maternal behaviour and this level of motivation to the mother is not related to changes in neuroplasticity in the SVZ of the female quail. 相似文献
996.
Hidenori Ito Rika Morishita Makoto Mizuno Hidenori Tabata Koh‐ichi Nagata 《Hippocampus》2019,29(7):569-578
The hippocampus is generally considered as a brain center for learning and memory. We have recently established an electroporation‐mediated gene transfer method to investigate the development of neonatal dentate granule cells in vivo. Using this new technique, we introduced knockdown vectors against Rac1 small GTPase into precursors for dentate granule cells at postnatal day 0. After 21 days, Rac1‐deficient cells were frequently mispositioned between the granule cell layer (GCL) and hilus. About 60% of these mislocalized cells expressed a dentate granule cell marker, Prox1. Both the dendritic spine density and the ratio of mature spine were reduced when Rac1 was silenced. Notably, the deficient cells have immature thin processes during migrating in the early neonatal period. Knockdown of another Rac isoform, Rac3, also resulted in mislocalization of neonatally born dentate granule cells. In addition, knockdown of Cdc42, another Rho family protein, also caused mislocalization of the cell, although the effects were moderate compared to Rac1 and 3. Despite the ectopic localization, Rac3‐ or Cdc42‐disrupted mispositioned cells expressed Prox1. These results indicate that Rho signaling pathways differentially regulate the proper localization and differentiation of dentate granule cells. 相似文献
997.
998.
Neural androgen receptors affect the number of surviving new neurones in the adult dentate gyrus of male mice 下载免费PDF全文
Adult hippocampal neurogenesis occurs in many mammalian species. In rats, the survival of new neurones within the hippocampus is modulated by the action of androgen via the androgen receptor (AR); however, it is not known whether this holds true in mice. Furthermore, the evidence is mixed regarding whether androgens act in neural tissue or via peripheral non‐neural targets to promote new neurone survival in the hippocampus. We evaluated whether the action of androgen via AR underlies the survival of new neurones in mice, and investigated whether increasing AR selectively in neural tissue would increase new neurone survival in the hippocampus. We used the cre‐loxP system to overexpress AR only in neural tissues (Nestin‐AR). These males were compared with wild‐type males, as well as control males with 1 of the 2 mutations required for overexpression. Mice were gonadectomised and injected with the DNA synthesis marker, bromodeoxyuridine (BrdU) and for 37 days (following BrdU injection), mice were treated with oil or dihydrotestosterone (DHT). Using immunohistochemistry, proliferation (Ki67) and survival (BrdU) of new neurones were both evaluated in the dorsal and ventral dentate gyrus. Dihydrotestosterone treatment increased the survival of new neurones in the entire hippocampus in wild‐type mice and control mice that only have 1 of 2 necessary mutations for transgenic expression. However, DHT treatment did not increase the survival of new neurones in mice that overexpressed AR in neural tissue. Cell proliferation (Ki67) and cell death (pyknotic cells) were not affected by DHT treatment in wild‐type or transgenic males. These results suggest that androgens act via neural AR to affect hippocampal neurogenesis by promoting cell survival; however, the relationship between androgen dose and new neurone survival is nonlinear. 相似文献
999.
Neural stem/progenitor cells are activated during tail regeneration in the leopard gecko (Eublepharis macularius) 下载免费PDF全文
As for many lizards, the leopard gecko (Eublepharis macularius) can self‐detach its tail to avoid predation and then regenerate a replacement. The replacement tail includes a regenerated spinal cord with a simple morphology: an ependymal layer surrounded by nerve tracts. We hypothesized that cells within the ependymal layer of the original spinal cord include populations of neural stem/progenitor cells (NSPCs) that contribute to the regenerated spinal cord. Prior to tail loss, we performed a bromodeoxyuridine pulse‐chase experiment and found that a subset of ependymal layer cells (ELCs) were label‐retaining after a 140‐day chase period. Next, we conducted a detailed spatiotemporal characterization of these cells before, during, and after tail regeneration. Our findings show that SOX2, a hallmark protein of NSPCs, is constitutively expressed by virtually all ELCs before, during, and after regeneration. We also found that during regeneration, ELCs express an expanded panel of NSPC and lineage‐restricted progenitor cell markers, including MSI‐1, SOX9, and TUJ1. Using electron microscopy, we determined that multiciliated, uniciliated, and biciliated cells are present, although the latter was only observed in regenerated spinal cords. Our results demonstrate that cells within the ependymal layer of the original, regenerating and fully regenerate spinal cord represent a heterogeneous population. These include radial glia comparable to Type E and Type B cells, and a neuronal‐like population of cerebrospinal fluid‐contacting cells. We propose that spinal cord regeneration in geckos represents a truncation of the restorative trajectory observed in some urodeles and teleosts, resulting in the formation of a structurally distinct replacement. 相似文献
1000.
Kengo Saito Taro Koike Fumiaki Kawashima Hirofumi Kurata Taku Shibuya Takemasa Satoh Yoshio Hata Hisao Yamada Tetsuji Mori 《The Journal of comparative neurology》2018,526(12):1927-1942
In the adult rodent subventricular zone (SVZ), there are neural stem cells (NSCs) and the specialized neurogenic niche is critical to maintain their stemness. To date, many cellular and noncellular factors that compose the neurogenic niche and markers to identify subpopulations of Type A cells have been confirmed. In particular, neurotransmitters regulate adult neurogenesis and mature neurons in the SVZ have been only partially analyzed. Moreover, Type A cells, descendants of NSCs, are highly heterogeneous and more molecular markers are still needed to identify them. In the present study, we systematically classified NeuN, commonly used as a marker of mature and immature post‐mitotic neurons, immunopositive (+) cells within the adult mouse SVZ. These SVZ‐NeuN+ cells (SVZ‐Ns) were mainly classified into two types. One was mature SVZ‐Ns (M‐SVZ‐Ns). Neurochemical properties of M‐SVZ‐Ns were similar to those of striatal neurons, but their birth date and morphology were different. M‐SVZ‐Ns were generated during embryonic and early postnatal stages with bipolar peaks and extended their processes along the wall of the lateral ventricle. The second type was small SVZ‐Ns (S‐SVZ‐Ns) with features of Type A cells. They expressed not only markers of Type A cells, but also proliferated and migrated from the SVZ to the olfactory bulb. Furthermore, S‐SVZ‐Ns could be classified into two types by their spatial locations and glutamic acid decarboxylase 67 expression. Our data indicate that M‐SVZ‐Ns are a new component of the neurogenic niche and S‐SVZ‐Ns are newly identified subpopulations of Type A cells. 相似文献