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   3682篇
  免费   174篇
  国内免费   20篇
耳鼻咽喉   22篇
儿科学   57篇
妇产科学   45篇
基础医学   427篇
口腔科学   93篇
临床医学   233篇
内科学   783篇
皮肤病学   51篇
神经病学   266篇
特种医学   146篇
外科学   637篇
综合类   24篇
预防医学   62篇
眼科学   112篇
药学   553篇
中国医学   12篇
肿瘤学   353篇
  2023年   21篇
  2022年   55篇
  2021年   77篇
  2020年   50篇
  2019年   57篇
  2018年   77篇
  2017年   47篇
  2016年   86篇
  2015年   75篇
  2014年   93篇
  2013年   101篇
  2012年   184篇
  2011年   205篇
  2010年   131篇
  2009年   103篇
  2008年   185篇
  2007年   226篇
  2006年   197篇
  2005年   212篇
  2004年   210篇
  2003年   182篇
  2002年   200篇
  2001年   94篇
  2000年   100篇
  1999年   113篇
  1998年   40篇
  1997年   44篇
  1996年   34篇
  1995年   28篇
  1994年   23篇
  1993年   20篇
  1992年   68篇
  1991年   57篇
  1990年   61篇
  1989年   55篇
  1988年   56篇
  1987年   39篇
  1986年   31篇
  1985年   25篇
  1984年   34篇
  1983年   24篇
  1982年   15篇
  1981年   7篇
  1980年   12篇
  1979年   25篇
  1978年   18篇
  1977年   9篇
  1974年   15篇
  1971年   7篇
  1969年   7篇
排序方式: 共有3876条查询结果,搜索用时 15 毫秒
1.
2.
3.
We report a case of a 68‐year‐old right‐handed man with sporadic amyotrophic lateral sclerosis (ALS) and argyrophilic grain disease (AGD) having a 22‐month duration. His initial symptoms were dysarthria and swallowing difficulty at the age of 67. Subsequently bulbar palsy and pyramidal signs developed. His cognitive functions including face recognition, personality, and behavior were not changed compared with that of before the disease onset. However, magnetic resonance imaging disclosed severe right side‐predominant temporal atrophy. The neurological diagnosis was bulbar type ALS. Pathological examination disclosed histological evidence of ALS, including loss of Betz cells and lower motor neurons, corticospinal tract degeneration, and Bunina bodies. In addition, severe neuronal loss in the bilateral temporal cortex with an anterior gradient was found. Ubiquitin‐positive inclusions were encountered in the spinal anterior horn cells and hippocampal dentate gyrus, while few ubiquitin‐positive inclusions were noted in the affected temporal cortex. The amygdala, especially the basolateral nuclear group, was severely affected by neuronal loss with tissue rarefaction. Moderate neuronal loss was encountered in the parahippocampal gyrus, and to a lesser degree, in the ambient gyrus. Unexpectedly, many argyrophilic grains, coiled bodies, tau‐positive bush‐like astrocytes, pretangles, and ballooned neurons were found in the limbic system and temporal cortex. In the hippocampus, selective tau accumulation with minor neurofibrillary changes was observed in CA2 neurons. The present case suggests that (i) ALS and AGD do rarely coexist, and (ii) when ALS patients have severe temporal atrophy, not only ALS with dementia but also concurrent AGD should be considered in the differential diagnosis.  相似文献   
4.
Objective: We assessed the current role of preoperative and intraoperative autologous blood donation in pediatric open-heart surgery. Methods: Group 1 consisted of 51 patients between 5 and 10 years old who underwent preoperative autologous blood donation. Group 2 consisted of 50 age-matched patients without preoperative donation as controls. Intraoperative donation was conducted in both groups prior to cardiopulmonary bypass. We evaluated perioperative blood cell count, blood loss, and the need for homologous blood products. Results: No serious complications occurred in preoperative or intraoperative donation. Total preoperative donation storage was 17.5±3.4 mL/kg. Intraoperative donation was 21.7 ±6.1 mL/kg in Group 1 and 12.8±4.0 mL/kg in Group 2 (p<0.001). On admission, serum hemoglobin was lower in Group 1 (12.2±1.0 g/dL versus 13.6±1.6 g/dL, p<0.001) but returned postoperatively to the preoperative value. It hovered at a depressed level in Group 2 (12.2±1.4 versus 10.2±1.1 g/dL, p<0.001). The homologous blood requirement was significantly less in Group 1 than in Group 2 (0% versus 10%, p<0.05). Postoperative platelet counts showed similar curves, and blood loss was not statistically significantly different between groups. Conclusion: Preoperative and intraoperative donations are safe and continue to contribute uniquely to blood conservation, providing important options in comprehensive blood conservation programs in current pediatric open-heart surgery.  相似文献   
5.
6.
We report satisfactory results with a new operative treatment, conducted via an extensive anterolateral approach, involving 360 degree circumferential capsulotomy, for residual subluxation in congenital dislocation of the hip (CDH). Long-term radiographic results of this procedure (group A) were compared retrospectively with the results of partial capsulotomy (group B), which preserved the posteroinferior joint capsule. The mean center edge angle in group A (22.5°) was greater than that in group B (16.0°). Satisfactory results were achieved in 11 of 15 hips (73%) (Severin class I or II) in group A, and in 5 of 12 hips (42%) in group B. These results suggest that whole circumferential capsulotomy can remove obstacles to complete reduction, and that acetabular development can be expected in hips reduced by the procedure, without the performance of innominate osteotomy. We believe that our technique is a useful alternative for the treatment of residual subluxation in CDH.  相似文献   
7.
The vasodilator effects of C-type natriuretic peptide (CNP) were investigated in isolated rat cerebral arterioles. CNP caused dose-dependent vasodilation, maximally by 10.0±2.2% at 10−6 M. The median effective concentration (EC50) was 5.2×10−10 M. In contrast, atrial natriuretic peptide and B-type natriuretic peptide, other members of the natriuretic peptide family, produced little or no vasodilation. Pretreatment with methylene blue (10−4 M) abolished CNP-induced vasodilation, whereas pretreatment with NG-monomethyl--arginine or indomethacin did not inhibit vasodilation. Thus, CNP is suggested to cause significant vasodilation in cerebral arterioles via a cyclic guanosine monophosphate-dependent mechanism. © 1997 Elsevier Science B.V. All rights reserved.  相似文献   
8.
We investigated the involvements of sympathetic and nonadrenergic nervous systems in the inhibitory reflex following bronchoconstriction in dogs. Inhalations of a 0.00125% solution of histamine and Ascaris suum antigen (3 mg protein) to the bronchial side induced reflex tracheal constriction following bronchoconstriction. An intra-arterial infusion of 5 micrograms/min of atropine to the tracheal site changed the reflex tracheal constrictions by histamine and antigen inhalations into tracheal dilatations. The reflex tracheal dilatations were abolished by the combination of intra-arterial propranolol (100 micrograms) and transections of both the bilateral superior laryngeal nerves and the spinal cord at the C1 level. The reflex tracheal constrictions induced by histamine and antigen inhalations were increased with 100 micrograms propranolol. Furthermore, the reflex tracheal constrictions were enhanced by the combination of 100 micrograms propranolol and transection of the spinal cord. These findings indicate that during the constriction of the bronchial smooth muscle, not only a reflex tracheal constriction mechanism but also one of reflex dilatation operates and that the latter reflex response may be mainly mediated by the sympathetic nerves, with partial involvement of the nonadrenergic nerves. This inhibitory reflex may attenuate asthmatic bronchoconstriction.  相似文献   
9.
H J Jeon  T Akagi  Y Hoshida  K Hayashi  T Yoshino  T Tanaka  J Ito  T Kamei  K Kawabata 《Cancer》1992,70(10):2451-2459
BACKGROUND. The breast is rarely a primary site for extranodal malignant lymphoma. Most reported primary non-Hodgkin malignant lymphomas of the breast (PBL) are of B-cell phenotype. METHODS. Histologic and immunohistochemical analyses of seven patients with PBL and a statistical analysis of 152 patients with PBL reported in the Japanese literature were performed. RESULTS. Malignant lymphoma could not be predicted preoperatively with clinical and radiologic findings; breast carcinoma, fibroadenoma, and phyllodes tumor were the preoperative diagnoses. All patients were women; they ranged in age from 31 to 80 years (mean, 57.6 years). The right breast was involved initially in five patients. In four, only the breast was involved (Stage I), whereas in three, the ipsilateral axillary lymph nodes (Stage II) were involved at diagnosis. According to the Working Formulation, all patients belonged to the intermediate grade and were classified as having diffuse large cell (five patients) or mixed (two patients) lymphoma. Immunophenotypic analysis revealed that all patients had B-cell lymphoma. No patients had lymphoepithelial lesions, which is the characteristic feature in categorizing a lymphoma as a mucosa-associated lymphoid tissue (MALT) lymphoma. A statistical analysis of the patient reported in the Japanese literature has divided PBL into two types: a bilateral type that affects younger women and a unilateral type that has a broad age distribution, but preponderantly occurs in older women. The age and stage at diagnosis were significant prognostic factors in predicting the survival time, but the location and size of the tumor at initial presentation, histopathologic type, terminal leukemic manifestation, and treatment modality were not. CONCLUSIONS. This study indicates that most PBL are diffuse large cell lymphoma of B-cell phenotype and that the age and stage at diagnosis are significant prognostic factors.  相似文献   
10.
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