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   19731篇
  免费   961篇
  国内免费   654篇
耳鼻咽喉   90篇
儿科学   102篇
妇产科学   206篇
基础医学   4067篇
口腔科学   195篇
临床医学   887篇
内科学   2318篇
皮肤病学   216篇
神经病学   4309篇
特种医学   236篇
外国民族医学   1篇
外科学   875篇
综合类   1296篇
现状与发展   3篇
预防医学   272篇
眼科学   130篇
药学   5072篇
中国医学   146篇
肿瘤学   925篇
  2023年   90篇
  2022年   143篇
  2021年   303篇
  2020年   278篇
  2019年   286篇
  2018年   283篇
  2017年   328篇
  2016年   350篇
  2015年   453篇
  2014年   701篇
  2013年   1086篇
  2012年   755篇
  2011年   969篇
  2010年   822篇
  2009年   985篇
  2008年   1090篇
  2007年   932篇
  2006年   880篇
  2005年   811篇
  2004年   799篇
  2003年   745篇
  2002年   590篇
  2001年   503篇
  2000年   445篇
  1999年   404篇
  1998年   504篇
  1997年   480篇
  1996年   423篇
  1995年   421篇
  1994年   372篇
  1993年   355篇
  1992年   321篇
  1991年   293篇
  1990年   265篇
  1989年   263篇
  1988年   204篇
  1987年   220篇
  1986年   165篇
  1985年   297篇
  1984年   423篇
  1983年   241篇
  1982年   318篇
  1981年   223篇
  1980年   159篇
  1979年   121篇
  1978年   72篇
  1977年   60篇
  1976年   45篇
  1975年   19篇
  1974年   23篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
本文报告口服Sumatriptan 100mg对偏头痛急性发作119例次的治疗结果。治疗后4h内显效91例次(76.5%),好转16例次(13.4%),无效12例次(10.1%),总有效率为89.9%。对偏头痛伴随症状恶心、呕吐和畏光、畏声的缓解率分别为94.2%、96%和94.3%。  相似文献   
52.
用单侧输尿管梗阻的方法诱导小鼠肾间质纤维化,并从中成功地培养出了成纤维细胞。对成纤维细胞血管紧张素Ⅱ1A(AT1A)受体的表达与细胞增殖和分泌细胞外基质的关系进行了研究。结果发现,从肾间质纤维化组织中培养出的成纤维细胞,细胞增殖和产生纤维连接蛋白及层粘连蛋白的能力明显高于从正常肾间质中培养的成纤维细胞。在单侧输尿管梗阻小鼠的血浆和肾组织中血管紧张素Ⅱ的活性显著升高。从肾间质纤维化组织中培养出的成纤维细胞,AT1A受体的表达在蛋白质和分子水平上均有明显增高。表明,在肾间质纤维化过程中肾素-血管紧张素系统被激活,对刺激成纤维细胞增殖和产生细胞外基质起着重要作用。  相似文献   
53.
黄芪注射液对严重创伤患者的免疫调节   总被引:1,自引:0,他引:1  
目的 探讨黄芪注射液对严重创伤患者的免疫调节作用。方法 选择 5 0例严重创伤患者 (ISS ,创伤严重度评分≥16 ) ,检测应用黄芪注射液 ( 4 0ml)前后T淋巴细胞亚群血清IL 2及可溶性白介素 2受体 (SIL 2R)。结果 严重创伤患者伤后IL 2、CD4 +和CD4 +/CD8+减低 ,而SIL 2R和CD8+升高 ,黄芪治疗组在伤后 14d血中IL 2、T淋巴细胞CD4 +亚群、CD4 +/CD8+降低及SIL 2R、CD8+升高程度均低于治疗前 ,P <0 .0 5。结论 严重创伤患者伤后细胞免疫功能明显抑制 ,应用黄芪注射液可以增加机体免疫功能  相似文献   
54.
In the present study we have investigated the clearance kinetics and tissue distribution of monomeric (m) IgG and soluble aggregates of IgG (AIgG) and immune complexes (IC) in normal and Kupffer cell (KC) depleted rats. In normal rats, clearance of mIgG occurred in a biphasic manner with a first half-life (T1/2) (T1) of 36.3 +/- 6.3 min and a second T1/2 (T2) of 168.4 +/- 4.7 min. AIgG composed of 20-27 IgG molecules per aggregate were cleared significantly faster than mIgG with a T1 of 2.5 +/- 0.1 min and a T2 of 32.5 +/- 5.6 min. KC depletion did not have a significant effect on the clearance rate of mIgG (T1: 33.4 +/- 8.9 min; T2; 159.5 +/- 12.5 min), while clearance of AIgG was delayed significantly with T1 4.8 +/- 0.7 min and T2 41.2 +/- 3.2 min. Eight minutes after injection, 77% of AIgG was found in the liver in normal rats while 62% was found in the liver of KC-depleted rats. Double immunofluorescence studies indicated that AIgG in the liver was associated with KC and endothelial cells (EC) in normal rats. In KC-depleted rats, AIgG was strongly associated with EC. A similar staining pattern was observed when IgG-immune IC were administered. The clearance of AIgG in KC-depleted rats was inhibited fully by pre-administration of high concentrations of IgG but not by pretreatment with IgA. asialofetuin (ASFe) or ovalbumin (OVA). Aggregated F(ab')2IgG was cleared with a comparable rate to mIgG from the circulation, again suggesting Fc gamma receptor-mediated elimination of AIgG by EC. There was a reduced degradation of AIgG in rats depleted of KC as compared with normal rats. These data suggest binding and degradation of AIgG by EC in vivo.  相似文献   
55.
The mapping of 5-HT2 receptors in the brain using functional imaging techniques has been limited by a relative lack of selective radioligands. Iodine-123 labelled 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-iodo-2-methoxybenzamide (123I-5-I-R91150 or123I-R93274) is a new ligand for single-photon emission tomography (SPET), with high affinity and selectivity for 5-HT2A receptors. This study reports on preliminary123I-5-I-R91150 SPET, wholebody and blood distribution findings in five healthy human volunteers. Maximal brain uptake was approximately 2% of total body counts at 180 min post injection (p.i.). Dynamic SPET sequences were acquired with the brain-dedicated, single-slice multi-detector system SEM-810 over 200 min p.i. Early peak uptake (at 5 min p.i.) was seen in the cerebellum, a region free from 5HT2A receptors. In contrast, radioligand binding in the frontal cortex increased steadily over time, up to a peak at approximately 100–120 min p.i. Frontal cortex-cerebellum activity ratios reached values of 1.4, and remained stable from approximately 100 min p.i. onwards. Multi-slice SPET sequences showed a pattern of regional variation of binding compatible with the autoradiographic data on the distribution of 5-HT2A receptors in (cerebral cortex>striatum>cerebellum). These findings suggest that123I-5-I-R91150 may be used for the imaging of 5-HT2A receptors in the living human brain with SPET.  相似文献   
56.
Glutamate is the primary excitatory amino acid in the mammalian central nervous system. Normal excitation of glutamate receptors initiates the stimulation of phospholipases and lipases with the generation of second messengers that are necessary for normal cell function. The overstimulation of glutamate receptors can initiate a cascade of biochemical events including stimulation of membrane phospholipid turnover, excessive calcium entry, abnormal phosphorylation, and proteolysis. These events may be responsible for neuronal injury and degeneration found in Alzheimer disease, ischemia, spinal cord trauma, epilepsy, and Huntington disease.  相似文献   
57.
用苔盼蓝及吖啶橙染色,DNA片段检定与DNA电泳等方法进行组织胺诱导胸腺细胞凋亡的研究,旨在探讨其可能机制及其在胸腺细胞负选择中的作用。结果表明,组织胺诱导使体外培养的胸腺细胞出现典型的细胞调亡。雷尼替丁可阻断上述作用,提示胸腺细胞存在H_2受体,活化该受体可能在胸腺细胞的负选择中起重要作用。  相似文献   
58.
In this study, the behavioural response to dopamine D1-like receptor agonists (SKF 38393, SKF 81297 and SKF 77434) and D2-like receptor agonists (quinpirole and RU 24213), administered alone and in combination to rats treated repeatedly with electroconvulsive shock (five ECS over 10 days) or sham, was tested. Agonist-induced behaviour was monitored by automated activity meters and direct observation using a checklist scoring method. Repeated ECS (compared to sham controls) had no significant effect on the behavioural response to SKF 38393 (7.5 mg/kg SC), SKF 81297 (0.2 mg/kg SC), SKF 77434 (0.1 mg/kg SC), quinpirole (0.1 and 0.25 mg/kg SC) or RU 24213 (0.3 mg/kg SC), when administered alone. In contrast, repeated ECS markedly increased locomotion (activity counts and scores) induced by the non-selective dopamine agonist apomorphine (0.5 mg/kg SC) and by co-administration of a D1-like agonist plus a D2-like agonist [SKF 38393 (7.5 mg/kg SC) plus quinpirole (0.25 mg/kg SC), SKF 81297 (0.2 mg/kg SC) plus quinpirole (0.1 mg/kg SC), and SKF 77434 (0.1 mg/ kg SC) plus RU 24213 (0.3 mg/kg SC)]. This ECS-induced enhancement of dopamine-mediated behaviour was observed for up to 3 weeks after cessation of ECS treatment. In addition, ECS also enhanced the locomotor response to intra-accumbens SKF 38393 plus quinpirole (0.4 and 1.0 μg/side, respectively). These results provide evidence that the enhancement of dopamine function by repeated ECS requires concomitant stimulation of both D1-like and D2-like receptors, and that this effect is long-lasting. Received: 24 January 1997 /Final version: 5 March 1997  相似文献   
59.
Summary.  Platelet membranes provide procoagulant surfaces for the assembly and expression of the factor X-activating complex and promote the proteolytic activation and assembly of the prothrombinase complex resulting in normal hemostasis. Recent studies from our laboratory and others indicate that platelets possess specific, high-affinity, saturable, receptors for factors XI, XIa, IX, IXa, X, VIII, VIIIa, V, Va and Xa, prothrombin, and thrombin. Studies described in this review support the hypothesis that the factor X-activating complex on the platelet surface consists of three receptors (for the enzyme, factor IXa; the substrate, factor X; and the cofactor, factor VIIIa), the colocalization of which results in a 24 million-fold acceleration of the rate of factor X activation. Whether the procoagulant surface of platelets is defined exclusively by procoagulant phospholipids, or whether specific protein receptors exist for the coagulant factors and proteases, is currently unresolved. The interaction between coagulation proteins and platelets is critical to the maintenance of normal hemostasis and is pathogenetically important in human disease.  相似文献   
60.
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