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   34227篇
  免费   3235篇
  国内免费   928篇
耳鼻咽喉   381篇
儿科学   682篇
妇产科学   403篇
基础医学   4302篇
口腔科学   644篇
临床医学   3706篇
内科学   6413篇
皮肤病学   656篇
神经病学   1964篇
特种医学   1561篇
外国民族医学   3篇
外科学   4646篇
综合类   2544篇
现状与发展   3篇
一般理论   4篇
预防医学   2666篇
眼科学   1029篇
药学   3209篇
  23篇
中国医学   1133篇
肿瘤学   2418篇
  2024年   114篇
  2023年   504篇
  2022年   1278篇
  2021年   1874篇
  2020年   1187篇
  2019年   1220篇
  2018年   1320篇
  2017年   1026篇
  2016年   1126篇
  2015年   1439篇
  2014年   1756篇
  2013年   1888篇
  2012年   2874篇
  2011年   2709篇
  2010年   1672篇
  2009年   1407篇
  2008年   2052篇
  2007年   1866篇
  2006年   1645篇
  2005年   1471篇
  2004年   1189篇
  2003年   1100篇
  2002年   953篇
  2001年   817篇
  2000年   756篇
  1999年   612篇
  1998年   257篇
  1997年   218篇
  1996年   173篇
  1995年   141篇
  1994年   120篇
  1993年   104篇
  1992年   201篇
  1991年   161篇
  1990年   169篇
  1989年   150篇
  1988年   139篇
  1987年   111篇
  1986年   94篇
  1985年   83篇
  1984年   65篇
  1983年   56篇
  1982年   39篇
  1981年   23篇
  1980年   27篇
  1979年   32篇
  1978年   17篇
  1976年   18篇
  1975年   15篇
  1970年   16篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
A Vietnamese social work and youth studies student describes her experiences and her feelings as a volunteer intern in an urban shelter program for children and youth in the United States.  相似文献   
62.
Elevated NMDA receptors in parkinsonian striatum.   总被引:3,自引:0,他引:3  
Dopamine-glutamate interactions contribute to normal striatal function and have been implicated in neurotoxicity at nigrostriatal dopamine (DA) terminals. The present study examined the striata of idiopathic Parkinson's disease (PD) patients and age-matched controls for regional differences in the DA transporter and binding to N-methyl-D-aspartate (NMDA) receptors. [3H]Mazindol labeling of the DA transporter was reduced by 70-80% in the caudate and putamen of PD patients, with reductions being more extensive dorsally than ventrally. In contrast, L-[3H]glutamate binding to NDMA-sensitive receptors was 20-40% higher in PD cases than in controls. These findings raise the possibility that modifications occur within corticostriatal glutamate synapses of PD patients, possibly as a consequence of reduced nigrostriatal DA activity.  相似文献   
63.
Background and aims Insulinomas are rare endocrine disorders. Pre-operatively, conventional imaging techniques often fail to localise the tumor. In addition, due to the lack of quick insulin assays, intra-operative confirmation of complete resection was impossible until recently. Materials and methods Six patients with biochemical evidence of an insulinoma underwent pre-operative localisation studies and selective arterial calcium injection (SACI). In addition, insulin was measured before surgery and every 10–15 min after resection of the tumor using a quick insulin assay. Results Pre-operative localisation studies identified the tumor correctly as follows: endosonography: three of four, magnetic resonance imaging: two of four and SACI: six of six. Tumors in the head and body were enucleated while those in the tail were resected (n = 2, each). Those three patients, in whom magnetic resonance imaging and/or endosonography could localise the tumors pre-operatively, underwent laparoscopic surgery while the remaining three patients underwent open surgery. Intra-operatively, insulin dropped to normal levels within 20 min in all cases. After a follow-up of 0.8–3 years, all patients remained biochemically cured. Conclusions Pre-operatively, SACI appears to be a very sensitive localisation technique and may be most helpful in guiding the surgeon if conventional imaging techniques fail to localise the tumor. Complete removal of an insulinoma can be reliably predicted using a quick insulin assay. This paper was presented at the 2nd Biennial Meeting of the European Society of Endocrine Surgeons (ESES), May 18–20, 2006, Krakow, Poland.  相似文献   
64.
凋亡抑制蛋白XIAP与肿瘤多药耐药   总被引:1,自引:0,他引:1  
XIAP(X-linked inhibitor of apoptosis protein)是凋亡抑制蛋白(inhibitors of apoptosis protein,IAP)家族中最有效的内源性凋亡抑制因子,可以通过直接抑制caspases或者参与信号转导途径抑制细胞凋亡。研究发现,XIAP与肿瘤多药耐药有密切关系,并且有可能成为逆转肿瘤多药耐药提高化疗效果的治疗新靶点。  相似文献   
65.

Background  

Cancer cells recurrently develop into acquired resistance to the administered drugs. The iatrogenic mechanisms of induced chemotherapy-resistance remain elusive and the degree of drug resistance did not exclusively correlate with reductions of drug accumulation, suggesting that drug resistance may involve additional mechanisms. Our aim is to define the potential targets, that makes drug-sensitive MCF-7 breast cancer cells turn to drug-resistant, for the anti-cancer drug development against drug resistant breast cancer cells.  相似文献   
66.
Hemorrhagic disseminated intravascular coagulation (DIC) associated with the presence of underlying advanced or metastatic tumors are often difficult to control by conventional methods. We report the use of recombinant activated factor VII (rFVIIa) in patients with cancer and bleeding secondary to DIC. A total of 18 patients with cancer met pre-defined criteria for DIC. All patients had failed to respond to transfusion with blood products and treatment of the underlying malignancy prior to the introduction of rFVIIa. The median laboratory data at the time of treatment with rFVIIa were as follows: hemoglobin, 7.7 g/dl; platelets, 54 x 10(9)/l; prothrombin time, 21 s; activated partial thromboplastin time, 41 s fibrinogen, 83 mg/dl; D-dimer, 17 microg/ml; and antithrombin, 32%. The dose of rFVIIa was 90 microg/kg and the median number of doses administered was 5 (range, 3-10). Serial measurements of coagulation parameters were obtained at frequent intervals during treatment with rFVIIa. Of the 18 patients, 15 responded with cessation of bleeding and improvement in coagulation data. The prothrombin time and activated partial thromboplastin time normalized in all responding patients within 24 h of treatment. The median fibrinogen was 214 mg/dl while the median D-dimer was 6 microg/dl at 48 h following the administration of rFVIIa. No thromboembolic complications were observed following rFVIIa. Our data provide evidence that rFVIIa can be used successfully to control the hemorrhagic episodes associated with DIC. Although this type of treatment appears to be safe, close monitoring of the patients is warranted.  相似文献   
67.
OBJECTIVE: Septal-lateral annular cinching ('SLAC') corrects both acute and chronic ischemic mitral regurgitation in animal experiments, which has led to the development of therapeutic surgical and interventional strategies incorporating this concept (e.g., Edwards GeoForm ring, Myocor Coapsys, Ample Medical PS3). Changes in left ventricular (LV) transmural cardiac and fiber-sheet strains after SLAC, however, remain unknown. METHODS: Eight normal sheep hearts had two triads of transmural radiopaque bead columns inserted adjacent to (anterobasal) and remote from (midlateral equatorial) the mitral annulus. Under acute, open chest conditions, 4D bead coordinates were obtained using videofluoroscopy before and after SLAC. Transmural systolic strains were calculated from bead displacements relative to local circumferential, longitudinal, and radial cardiac axes. Transmural cardiac strains were transformed into fiber-sheet coordinates (X(f), X(s), X(n)) oriented along the fiber (f), sheet (s), and sheet-normal (n) axes using fiber (alpha) and sheet (beta) angle measurements. Results: SLAC markedly reduced (approximately 60%) septal-lateral annular diameter at both end-diastole (ED) (2.5+/-0.3 to 1.0+/-0.3 cm, p=0.001) and end-systole (ES) (2.4+/-0.4 to 1.0+/-0.3 cm, p=0.001). In the LV wall remote from the mitral annulus, transmural systolic strains did not change. In the anterobasal region adjacent to the mitral annulus, ED wall thickness increased (p=0.01) and systolic wall thickening was less in the epicardial (0.28+/-0.12 vs 0.20+/-0.06, p=0.05) and midwall (0.36+/-0.24 vs 0.19+/-0.11, p=0.04) LV layers. This impaired wall thickening was due to decreased systolic sheet thickening (0.20+/-0.8 to 0.12+/-0.07, p=0.01) and sheet shear (-0.15+/-0.07 to -0.11+/-0.04, p=0.02) in the epicardium and sheet extension (0.21+/-0.11 to 0.10+/-0.04, p=0.03) in the midwall. Transmural systolic and remodeling strains in the lateral midwall (remote from the annulus) were unaffected. CONCLUSIONS: Although SLAC is an alluring concept to correct ischemic mitral regurgitation, these data suggest that extreme SLAC adversely effects systolic wall thickening adjacent to the mitral annulus by inhibiting systolic sheet thickening, sheet shear, and sheet extension. Such alterations in LV strains could result in unanticipated deleterious remodeling and warrant further investigation.  相似文献   
68.
汉语成语结尾字事件相关电位N400的研究   总被引:10,自引:2,他引:8  
陈璇  宋旻烨 《广东医学》2003,24(7):711-713
目的 通过记录汉语成语结尾字匹配与不匹配事件相关电位N400的变化,探讨视觉词语认知模式及汉字认知加工特征。方法发采用南方医院研制的事件相关电位仪,对15例21—36岁健康人右利手受试者中,进行汉语成语正常结尾字(匹配字)与歧义字(不匹配字)N400的研究。结果 受试者对结尾词匹配与不匹配组的N400成分在潜伏期及波幅差异有显著性(P≤0.01),不匹配组的N400波幅高,潜伏期长。N400广泛分布于各区,左侧比右侧波幅偏高。结论 汉语成语结尾字匹配与不匹配的N400与字词认知中的语义密切相关,有一定的临床价值,可用于临床多种伴有语言障碍疾病的评估。  相似文献   
69.
70.
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