首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   724篇
  免费   28篇
  国内免费   21篇
儿科学   5篇
妇产科学   17篇
基础医学   85篇
口腔科学   13篇
临床医学   45篇
内科学   73篇
皮肤病学   1篇
神经病学   261篇
特种医学   35篇
外科学   59篇
综合类   29篇
预防医学   41篇
眼科学   6篇
药学   62篇
中国医学   16篇
肿瘤学   25篇
  2023年   47篇
  2022年   39篇
  2021年   81篇
  2020年   64篇
  2019年   21篇
  2018年   19篇
  2017年   37篇
  2016年   31篇
  2015年   33篇
  2014年   73篇
  2013年   23篇
  2012年   38篇
  2011年   20篇
  2010年   53篇
  2009年   40篇
  2008年   8篇
  2007年   20篇
  2006年   14篇
  2005年   9篇
  2004年   5篇
  2003年   9篇
  2002年   4篇
  2001年   7篇
  2000年   6篇
  1999年   7篇
  1998年   13篇
  1997年   5篇
  1996年   14篇
  1995年   8篇
  1994年   6篇
  1993年   4篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   2篇
排序方式: 共有773条查询结果,搜索用时 15 毫秒
121.
122.
123.
Climate change presents a threat to the sustainability of cities and their societies, and must be adequately addressed. Urban environments (cities) are responsible for the creation of a significant amount of greenhouse gas emissions which are the source of climate change. Cities have been increasingly the focus of action to address climate change, yet emissions are not significantly reducing. Additionally, there a lack of integration between adaptation and mitigation. This prevents responses adequate to limit global warming to 1.5OC, and to be well adapted to anticipated changes. This paper critically analyses existing definitions and typologies of climate change actions. A definition of ‘climate change transformation’ is proposed which includes the integration of adaptation and mitigation goals to enable a new regime in which global warming is limited to 1.5OC. A new three-part typology: ‘coping, malaction and transformation,’ is presented for categorising climate change actions by the extent to which they integrate adaptation and mitigation, and define a new regime. The typology is accompanied by illustrations to demonstrate the relationship between adaptation and mitigation. The definition, typology and illustration serve to guide effective climate change decision making, and provides principles to guide application in urban environments.  相似文献   
124.
125.
Treatment with bone marrow stromal cells (BMSCs) ameliorates neurological functional deficits after stroke. Nerve growth factor (NGF) is a neurotrophic factor that supports the survival and growth of neural cells. Noggin, an antagonist of bone morphogenetic protein (BMP), promotes the differentiation of stem cells into neurons. In this study, we hypothesize that transfection of NGF and Noggin in BMSC treatment of stroke promotes BMSC neuronal differentiation and improves functional outcome after stroke. Adenovirus was used to trasfect NGF and Noggin and the transfection efficiency was measured by Western blot and immunostaining in vitro. The transfected BMSCs with NGF and/or Noggin were administered intravenously at 5 days after middle cerebral artery occlusion (MCAo) in rats. The neurological functional outcome and BMSC migration and differentiation in the ischemic brain were measured. The transplantation of BMSCs with NGF or Noggin elicited neurological functional improvement, promoted BMSCs present in the ischemic brain, and also up-regulated neuro-like cell differentiation as well as increased synaptophysin expression in the ischemic brain compared with nontreatment control animals (P< 0.05). Treatment of stroke with a combination of transfection of NGF and Noggin in BMSCs induced a synergistic effect on improved neurological functional outcome, BMSCs present in the ischemic brain, and synaptophysin expression in the ischemic brain compared with BMSCs transfected with an NGF- or Noggin-alone group (P < 0.05). These data demonstrate that increasing NGF or Noggin expression in BMSCs contributes to brain plasticity after stroke and that a synergistic effect is induced on the coexistence of NGF and Noggin in BMSCs treatment of stroke.  相似文献   
126.
背景:动脉内膜损伤是动脉瘤发生的始动因素,内皮祖细胞能修复受损的动脉内膜。 目的:建立大鼠颅内动脉瘤模型,探讨动脉瘤大鼠内皮祖细胞数量变化及意义。 方法:40只SD大鼠随机分为两组,正常组作为正常对照,不给予任何干预。模型组大鼠手术结扎双侧肾动脉后支以及左侧颈总动脉,术后喂食含8%氯化钠鼠粮。于2周,1,2,3个月末测量大鼠内皮祖细胞变化,并与3个月末测量各组大鼠血压及动脉瘤大小,RT-PCR检测willis环相关基因表达。 结果与结论:模型组大鼠内皮祖细胞数目于2周后就开始下降,与正常组比较差异有显著性意义(P < 0.05),一直持续到3个月末(P < 0.01)。模型组大鼠动脉瘤壁基质金属蛋白酶9表达明显高于正常组正常大鼠(P < 0.01),而内皮型一氧化氮合酶明显低于正常(P < 0.05)。结果提示循环内皮祖细胞数量降低可能是动脉瘤生成的一个重要因素。  相似文献   
127.
背景:近年来的研究显示,在胚胎神经系统发育过程中,Hes1的表达调控对保持神经干细胞的数量、调控其分化至关重要。此外,成年个体内处于静止期的纤维母细胞重新获得分裂增殖的能力需要Hes1表达的上调。这表明Hes1在成体中也与某些潜在干细胞的增殖具有密切的关系。因此研究Hes1在成体神经干细胞中的表达及其与成体神经细胞生成的关系也就被提上日程。但Hes1在成年个体神经系统的表达至今未明。 目的:观察和分析小鼠脑中不同部位Hes1的表达及Hes1阳性细胞的细胞类型。 方法:12只成年雄性C57BL/6小鼠随机数字表法分为单染组和双染组,每组6只。单染组直接取材,采用免疫组织化学技术检测Hes1在小鼠脑中各部位的表达。双染组小鼠以200 mg/kg Brdu的剂量每天腹腔注射1次,连续注射3 d,第4天取材,采用双标记物染色观察分析海马区Hes1阳性细胞的细胞类型。 结果与结论:在所有观察的解剖部位中,Hes1表达于所有存在神经细胞的部位,Brdu阳性细胞几乎全部表达Hes1,NeuN阳性细胞全部表达Hes1,而神经胶质原纤维酸性蛋白阳性细胞则完全不表达Hes1。由此可知,Hes1表达于神经细胞和神经干细胞中,胶质细胞不表达Hes1。  相似文献   
128.
BACKGROUND:Endogenous neural progenitor cells play a beneficial role for cognitive recovery following traumatic brain injury.However,there are few classification-control studies aimed at varying graded brain trauma.OBJECTIVE:To observe the effects of adult endogenous neurogenesis on cognitive function repair and regeneration of neural progenitor cells following varying graded traumatic hippocampal injury to determine the significance of endogenous neurogenesis in the repair of brain injury.DESIGN,TIME AND SETTING:A randomized,controlled,animal experiment was performed at the Key Laboratory of Injuries,Variations and Regeneration of Nervous System,Tianjin Medical University General Hospital,from February to October 2009.MATERIALS:Mouse anti-rat 5-bromodeoxyuridine (BrdU) and neuronal nuclei (NeuN) monoclonal antibodies were purchased from Millipore Corporation,USA.METHODS:A total of 45 Wistar rats were randomly assigned to three groups.Mild and severe injury groups were respectively subjected to (182 ± 2) kPa and (284 ± 4) kPa lateral fluid percussion to establish models of brain injury,and the control group was subjected to surgery with no lateral fluid percussion.MAIN OUTCOME MEASURES:Cognitive function was estimated using the Morris water maze.Proliferation,survival,and differentiation of newly generated cells in the injured hippocampus were observed through the use of immunofluorescent staining.RESULTS:At 7 days post-injury,the number of BrdU+ cells in the hippocampal dentate gyrus significantly increased in the mild and severe injury groups compared with the control group (P<0.01).At 61 days post-injury,the number of BrdU7NeuN+ cells in the hippocampal dentate gyrus was significantly greater in the mild injury group compared with the severe injury and control groups (P< 0.01).In addition,the control group exhibited the greatest proportion of surviving cells that differentiated into mature neurons compared with the injury groups (P< 0.01).Moreover,at 61 days post-injury,cognitive function in rats with mild injury recovered to normal levels,whereas the severe injury group exhibited cognitive deficits (P< 0.01).CONCLUSION:Traumatic brain injury may be a stimulation factor for proliferation of neural progenitor cells in the adult hippocampus but severe brain trauma does not lead to an increased number of newly generated cells.Endogenous adult neurogenesis repairs neurological functions to an extent.However,recovery of neurological function remains limited following severe traumatic brain injury.  相似文献   
129.
背景:大量的实验证明将骨髓间充质干细胞移植到复制的中枢神经系统疾病大鼠模型后,能迁移到损伤部位,表达神经细胞的潜在特性并且提高神经功能。 目的:验证骨髓间充质干细胞对拟人类血管性痴呆模型大鼠学习记忆障碍的改善作用。 方法:分离SD大鼠骨髓间充质干细胞,于细胞移植前掺入10 mg/L的BrdU进行标记。建立Wistar大鼠血管性痴呆样学习记忆障碍动物模型,随机分为模型组、假手术组与移植组。移植组致伤后第14天,通过立体定向途径移植骨髓间充质干细胞到大鼠海马,假手术组给予等量生理盐水,模型组大鼠不做处理。采用Morris水迷宫检测大鼠空间学习记忆能力。损伤后第90天处死大鼠,观察海马组织有无Brdu+神经元特异性烯醇化酶、Brdu+胶质纤维酸性蛋白免疫组织化学双染阳性细胞,并且观察从侧脑室到海马是否存在神经元前体细胞的标志Doublecortin (DCX)吻侧迁移流。 结果与结论:①移植组大鼠采用Morris水迷宫检测大鼠空间学习记忆能力逃避潜伏期及跨越平台次数优于模型组及假手术组(P < 0.05)。②移植组大鼠海马组织及其周围可见免疫组织化学双染阳性细胞,但未见从侧脑室到海马关于神经元前体细胞的标志Doublecortin (DCX)吻侧迁移流。结果提示,骨髓间充质干细胞移植可以促进脑损伤大鼠的神经功能的恢复,其机制可能与移植细胞分化为神经元样和神经胶质细胞样细胞,并分泌或促进宿主分泌神经营养因子有关。  相似文献   
130.
Prostate cancer (CaP) has become the most frequent cancer in France and represents the 4th cause of mortality by cancer. Main risk factors include age, family history, black ethnic origin and carcinogenesis results from interaction between environmental and endogen factors. This work aimed to review main data and strategic trends about evolution of prevention and early diagnosis of CaP. Research topics considered as priorities results from the main objective including definition of most efficient medico-economic strategies according to epidemiology, diagnostic and therapeutic modalities and ethno-sociologic particularities, including in the schema presently used (PSA/biopsies): 1) new markers (genetic, serum and urinary), measurable environmental risk factors and potential prevention actions; 2) functional imaging (new techniques including contrast echography, dynamic MRI, spectro-MRI) in order to avoid unnecessary biopsies (60-70% biopsies are negative); 3) optimization of biopsies technique in identifying tumor zones in order to decrease false negative biopsies (about 15% of CaP < 0,5 cm3 but of high grade are missed in the first set of biopsies) and in improving the representativity of the tumor sample biopsied (discordance of about 40% between biopsy data and complete pathological analysis of prostatectomy specimen); 4) development of predictive models in order to perform individual prediction taking into account several risk factors (clinical and molecular) and genes/environment interactions in order to offer rational help in diagnostic and primary prevention procedures.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号