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   424921篇
  免费   39209篇
  国内免费   28621篇
耳鼻咽喉   3267篇
儿科学   5611篇
妇产科学   5088篇
基础医学   46678篇
口腔科学   7023篇
临床医学   58630篇
内科学   58628篇
皮肤病学   4732篇
神经病学   20499篇
特种医学   15844篇
外国民族医学   247篇
外科学   39258篇
综合类   77442篇
现状与发展   97篇
一般理论   47篇
预防医学   30926篇
眼科学   11933篇
药学   46062篇
  482篇
中国医学   26983篇
肿瘤学   33274篇
  2024年   1409篇
  2023年   6062篇
  2022年   15876篇
  2021年   20347篇
  2020年   15877篇
  2019年   13142篇
  2018年   13727篇
  2017年   13099篇
  2016年   12146篇
  2015年   18655篇
  2014年   23334篇
  2013年   21602篇
  2012年   31969篇
  2011年   35668篇
  2010年   24001篇
  2009年   19600篇
  2008年   24221篇
  2007年   24076篇
  2006年   22899篇
  2005年   21738篇
  2004年   14769篇
  2003年   14156篇
  2002年   11774篇
  2001年   10023篇
  2000年   9744篇
  1999年   9676篇
  1998年   5995篇
  1997年   5755篇
  1996年   4496篇
  1995年   4185篇
  1994年   3542篇
  1993年   2298篇
  1992年   2884篇
  1991年   2505篇
  1990年   2137篇
  1989年   1876篇
  1988年   1539篇
  1987年   1426篇
  1986年   1139篇
  1985年   824篇
  1984年   478篇
  1983年   352篇
  1982年   199篇
  1981年   236篇
  1980年   153篇
  1979年   214篇
  1978年   110篇
  1977年   80篇
  1974年   78篇
  1972年   78篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Bone marrow stromal cells (MSCs) increase vascular endothelial growth factor (VEGF) expression and promote angiogenesis after stroke. Angiopoietin-1 (Ang1) and its receptor Tie2 mediate vascular integrity and angiogenesis as does VEGF and its receptors. In this study, we tested whether MSC treatment of stroke increases Ang1/Tie2 expression, and whether Ang1/Tie2 with VEGF/ vascular endothelial growth factor receptor 2 (VEGFR2) (Flk1), in combination, induced by MSCs enhances angiogenesis and vascular integrity. Male Wistar rats were subjected to middle cerebral artery occlusion (MCAo) and treated with or without MSCs. Marrow stromal cell treatment significantly decreased blood-brain barrier (BBB) leakage and increased Ang1, Tie2, and occludin (a tight junction protein) expression in the ischemic border compared with MCAo control. To further test the mechanisms of MSC-induced angiogenesis and vascular stabilization, cocultures of MSCs with mouse brain endothelial cells (MBECs) or astrocytes were performed. Supernatant derived from MSCs cocultured with MBECs significantly increased MBEC expression of Ang1/Tie2 and Flk1 compared with MBEC alone. Marrow stromal cells cocultured with astrocytes also significantly increased astrocyte VEGF and Ang1/Tie2 expression compared with astrocyte culture alone. Conditioned media from MSCs alone, and media from cocultures of MSCs with astrocytes or MBECs, all significantly increased capillary tube-like formation of MBEC compared with control Dulbecco's modified Eagle's medium media. Inhibition of Flk1 and/or Ang1 significantly decreased MSC-induced MBEC tube formation. Knockdown of Tie2 expression in MBECs significantly inhibited MSC-induced tube formation. Our data indicate MSC treatment of stroke promotes angiogenesis and vascular stabilization, which is at least partially mediated by VEGF/Flk1 and Ang1/Tie2.  相似文献   
102.
Glial glutamate transporter-1 (GLT-1) plays an essential role in removing glutamate from the extracellular space and maintaining the glutamate below neurotoxic level in the brain. To explore whether GLT-1 plays a role in the acquisition of brain ischemic tolerance (BIT) induced by cerebral ischemic preconditioning (CIP), the present study was undertaken to observe in vivo changes in the expression of GLT-1 and glial fibrillary acidic protein (GFAP) in the CA1 hippocampus during the induction of BIT, and the effect of dihydrokainate (DHK), an inhibitor of GLT-1, on the acquisition of BIT in rats. Immunohistochemistry for GFAP showed that the processes of astrocytes were prolonged after a CIP 2 days before the lethal ischemic insult, which could protect pyramidal neurons in the CA1 hippocampus against delayed neuronal death induced normally by lethal ischemic insult. The prolonged processes extended into the area between the pyramidal neurons and tightly surrounded them. These changes made the pyramidal layer look like a 'shape grid'. Simultaneously, the prolonged and extended processes showed a great deal of GLT-1. Western blotting analysis showed significant upregulation of GLT-1 expression after the CIP, especially when it was administered 2 days before the subsequent lethal ischemic insult. Neuropathological evaluation by thionin staining showed that DHK dose-dependently blocked the protective role of CIP against delayed neuronal death induced normally by lethal brain ischemia. It might be concluded that the surrounding of pyramidal neurons by astrocytes and upregulation of GLT-1 induced by CIP played an important role in the acquisition of the BIT induced by CIP.  相似文献   
103.
目的:评价直肠癌根治术中用Foley尿管气囊压迫治疗骶前静脉丛大出血(MPVP)的临床价值。方法:分析1995~2005年用Foley尿管气囊压迫治疗骶前静脉丛大出血6例的临床资料。结果:6例骶前大出血中全部用Foley尿管气囊压迫控制出血,术中出血量为800~1700mL,Foley尿管于术后4d拔除3例,5d1例,6d2例,均无再出血,会阴切口均一期愈合。结论:Foley尿管气囊压迫治疗骶前静脉丛大出血是一种简单安全有效的治疗方法。  相似文献   
104.
105.
106.
The impact of obesity on female reproductive function   总被引:1,自引:0,他引:1  
Obesity may be described as the new worldwide epidemic, and its serious impact on morbidity and mortality are well known. As more and more women become obese, the reproductive problems associated with obesity present an ever-growing challenge to physicians involved in their fertility care. The spectrum of reproductive problems associated with obesity encompasses a wide range of disorders including infertility problems, miscarriage and pregnancy complications. In this review, we aim to discuss the impact of obesity on the various aspects of female reproductive function with focus on the clinical aspects of fertility problems in obese women. We finally comment on the available therapeutic options available to this group of women.  相似文献   
107.
In this paper, we address the problem of stable tracking control of a flexible macro-micro manipulator (M(3)) system. A two-layer neural network is utilized to approximate the nonlinear robot dynamic behavior of the M(3) system, and the controllers for the macro and micro arms are developed without any need for prior knowledge of the dynamic model of the controlled M(3) system. A learning algorithm for the neural network using Lyapunov stability theory is derived. It is shown that both the tracking error and the weight-tuning error are uniformly ultimately bounded under this new control scheme. Simulation results are presented and compared to those obtained using a PD controller.  相似文献   
108.
通过对中南地区1577例正常人的血清α_1-抗胰蛋白酶(α_1-AT)水平的测定,结果20~40岁组正常值为136.9mg%,41~60岁组正常值为129.3mg%,男女性别间的α_1-AT水平差异无显著意义。而两个年龄组间差异有显著意义。并对测定结果作了分型。  相似文献   
109.
目的 探讨显微外科治疗颅脑外伤后肢体痉挛状态的疗效.方法 回顾分析2006年7月至2008年7月实施的21例显微外科治疗颅脑外伤后肢体痉挛状态,根据不同病例采用相应的选择性周围神经部分切断术,包括:胫神经、肌皮神经、正中神经、尺神经和腰骶段脊神经后根,共计50个肢体.结果 术后随访2~24个月,全部患者术后立即感相应肢体痉挛状态缓解,随访期间缓解率为98%(49/50).随访期间运动功能改善率为86%(18/21),生活质量提高率为95%(20/21).术后发生肢体麻木、疼痛等感觉异常26个(52%),肌力下降18个(36%),随访期间均见好转.术后痉挛状态复发1个(2%).结论 选择性周围神经部分切断术是治疗颅脑外伤后肢体痉挛状态安全有效的方法.选择适应证及手术时机和术后坚持康复训练是保证疗效的关键.  相似文献   
110.
微血管减压术治疗舌咽神经痛16例临床分析   总被引:4,自引:1,他引:3  
目的 研究舌咽神经痛 (glossopharyngealneuralgia,GPN)手术治疗的最佳术式 ,评估微血管减压手术(microvasculardecompression ,MVD)的效果、并发症和随访结果 ,探讨可能的治疗机制。方法  2 0 0 0年 12月到2 0 0 3年 10月间 ,16例GPN患者接受了MVD ,无一例行神经根切断术。患者全部进行了电话或信件随访。结果 15例患者术后疼痛消失 ,1例患者为不典型GPN ,术后疼痛减轻。 1例患者术后出现轻度声音嘶哑和吞咽困难 ,1例患者出现偶发干咳。本组患者平均随访时间为 14 .1± 6 .3月 ,随访期间无一例复发。结论 MVD是治疗舌咽神经痛的一种安全、有效的手术方式 ,尤其适用于典型的GPN患者。  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