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   2595篇
  免费   152篇
  国内免费   75篇
耳鼻咽喉   2篇
儿科学   186篇
妇产科学   136篇
基础医学   282篇
口腔科学   67篇
临床医学   285篇
内科学   586篇
皮肤病学   77篇
神经病学   90篇
特种医学   427篇
外国民族医学   1篇
外科学   163篇
综合类   50篇
预防医学   208篇
眼科学   21篇
药学   121篇
  2篇
肿瘤学   118篇
  2023年   7篇
  2021年   23篇
  2020年   16篇
  2019年   23篇
  2018年   47篇
  2017年   35篇
  2016年   31篇
  2015年   45篇
  2014年   67篇
  2013年   76篇
  2012年   72篇
  2011年   79篇
  2010年   105篇
  2009年   95篇
  2008年   83篇
  2007年   134篇
  2006年   76篇
  2005年   86篇
  2004年   49篇
  2003年   46篇
  2002年   46篇
  2001年   52篇
  2000年   43篇
  1999年   52篇
  1998年   131篇
  1997年   159篇
  1996年   134篇
  1995年   109篇
  1994年   116篇
  1993年   98篇
  1992年   36篇
  1991年   40篇
  1990年   45篇
  1989年   59篇
  1988年   53篇
  1987年   55篇
  1986年   58篇
  1985年   50篇
  1984年   32篇
  1983年   18篇
  1982年   28篇
  1981年   30篇
  1980年   28篇
  1979年   9篇
  1978年   17篇
  1977年   21篇
  1976年   33篇
  1975年   19篇
  1970年   5篇
  1967年   9篇
排序方式: 共有2822条查询结果,搜索用时 15 毫秒
1.
Cutaneous plasmacytosis is a rare disorder characterized by a benign proliferation of mature plasma cells that appears as multiple dark-brown to purplish skin lesions, often associated with polyclonal hypergammaglobulinaemia. We present the case of a 55-year-old Caucasian man who suffered from a cutaneous plasmacytosis associated with two different carcinomas. Cutaneous plasmacytosis seems to be a reactive process because most cases reported are not associated with any apparent underlying disease. Nevertheless, because few reported cases were associated with malignancies, screening of additional neoplasms would be justified.  相似文献   
2.
3.
The inference that mitral valve replacement (MVR) may produce left ventricular outflow tract (LVOT) obstruction has been made, but no comparative hemodynamic studies with various types of prostheses have been done. The purpose of the present study was to compare the gradients created across the LVOT with MVR in young sheep with small left ventricular cavities. Mitral valve replacement was accomplished using cardiopulmonary bypass and hypothermic cardioplegic arrest. Five animals were used for each of the following valves studied: 25-mm Ionescu-Shiley bovine pericardial valve, 25-mm Hancock porcine aortic valve, 2M-6120 28-mm Starr-Edwards ball-valve prosthesis, 25-mm Bj?rk-Shiley 60-degree flat tilting-disc prosthesis, and 25-mm St. Jude Medical hemidisc valve. Gradients across the LVOT were measured after MVR and then during infusion of isoproterenol hydrochloride (0.05 micrograms/kg/min). Following MVR, only the Starr-Edwards valve produced an LVOT gradient (32 +/- 23 mm Hg). Substantial gradients after MVR were seen, however, with isoproterenol administration with the Ionescu-Shiley (47 +/- 4 mm Hg), Hancock (13 +/- 8 mm Hg), and Starr-Edwards (65 +/- 30 mm Hg) valves but not with the low-profile valves (Bj?rk-Shiley and St. Jude Medical). The results of the present study demonstrate that MVR can produce LVOT obstruction. The greatest degree of obstruction was with the high-profile mechanical and bioprosthetic valves.  相似文献   
4.
The aim of this study was to evaluate the cerebral synthesis of eicosanoids in the asphyctic newborn and to investigate the relation between the prostanoid profiles in cerebrospinal fluid (CSF) and the appearance and severity of hypoxic-ischaemic encephalopathy (HIE). Levels of 6-keto-PGF 1-α, TXB2, PGE2 and PGF2-α in CSF were measured in 40 full term newborns during the first day of life. Thirty of these newborns had birth asphyxia and were divided into three groups: 10 without HIE, 12 with mild HIE and 8 with moderate-severe HIE. They were compared to a control group of 10 non-hypoxic newborns. Determinations of the metabolites in CSF were performed by RIA and expressed as pg/ml (mean ± SD). The CSF TXB2 (thromboxane A2 metabolite) in asphyxiated newborns was always higher than in the control group (28.12 ± 10.6), and related to the severity of HIE ( p = 0:005): without HIE (50.84 ± 16.4; p = 0:02), mild HIE (80.65 ± 12.64; p ± 0:01) and moderate-severe HIE (178.14 ± 20.5; p < 0:01). The CSF 6-keto-PGF 1-α (prostacyclin metabolite) in asphyxiated newborns was always higher than in the control group (80.55 ± 12.56), but indirectly related to the severity of HIE: without HIE (240.95 ± 28.12; p < 0:01), mild HIE (183.65 ± 30.1; p < 0:01) and moderate-severe HIE (140.55 ± 25.12; p < 0:01). In the moderate-severe HIE group, the increase in TXB2 was higher than the rise in 6-keto-PGF 1-α.  相似文献   
5.
6.
Occurrence of the t(2;5)(p23;q35) in non-Hodgkin's lymphoma   总被引:9,自引:3,他引:6  
Primary CD30(Ki-1)-positive anaplastic large-cell lymphoma (ALCL) is considered by some to be a distinct clinicopathologic entity associated with the t(2;5) (p23;q35). However, the specificity of t(2;5) for ALCL has not been carefully studied. Therefore, we performed a detailed analysis of all cases of ALCL with abnormal cytogenetics results in the Nebraska Lymphoma Study Group registry, as well as all other cases of non-Hodgkin's lymphoma with t(2;5) in the registry. We found the t(2;5) in only five of 10 cases of ALCL, four of whom were young patients. However, we also found the t(2;5) in 11 other cases of nonanaplastic lymphoma, including eight children with typical peripheral T-cell lymphomas of various types. The t(2;5) was also found in three older adults with B-cell lymphomas of various types. Thus, the t(2;5) was not specific for CD30+ ALCL. However, t(2;5) may define a clinicopathologic entity in children and young adults characterized by variable morphologies with a T-cell or indeterminate phenotype, CD30-positivity, nodal disease with frequent extranodal involvement, advanced stage, and an excellent response to therapy, including bone marrow transplantation for relapsed disease. The clinical relevance of the t(2;5) in older patients requires further study.  相似文献   
7.
8.
9.
To identify risk factors for fractures in multi-ethnic women, we studied 159,579 women enrolled in the Women's Health Initiative. In general, risk factors for fractures were similar across ethnic groups. However, irrespective of their ethnicity, women with multiple risk factors have a high risk of fracture. Targeting these high-risk women for screening and intervention could reduce fractures. INTRODUCTION: Fracture rates tend to be lower in minority women, but consequences may be greater. In addition, the number of fractures is expected to increase in minority women because of current demographic trends. There are limited prospective data on risk factors for fractures in minority women. MATERIALS AND METHODS: We studied 159,579 women 50-79 yr of age enrolled in the Women's Health Initiative. Information on risk factors was obtained by questionnaire or examination. Nonspine fractures that occurred after study entry were identified over an average follow-up of 8 +/- 2.6 (SD) yr. RESULTS: Annualized rates (%) of fracture in whites, blacks, Hispanics, Asians, and American Indians were 2.0, 0.9, 1.3, 1.2, and 2.0, respectively. Significant predictors [HR (95% CI)] of fractures by ethnic group were as follows: blacks: at least a high school education, 1.22 (1.0, 1.5); (+) fracture history, 1.7 (1.4, 2.2); and more than two falls, 1.7 (1.9, 2.0); Hispanics: height (>162 cm), 1.6 (1.1, 2.2); (+) fracture history, 1.9 (1.4, 2.5); more than two falls, 1.8 (1.4, 2.3); arthritis, 1.3 (1.1, 1.6); corticosteroid use, 3.9 (1.9, 8.0); and parental history of fracture, 1.3 (1.0, 1.6); Asians: age (per 5 yr), 1.2 (1.0, 1.3); (+) fracture history, 1.5 (1.1, 2.0); current hormone therapy (HT), 0.7 (0.5, 0.8); parity (at least five), 1.8 (1.1, 3.0); more than two falls, 1.4 (1.1, 1.9); American Indian: (+) fracture history, 2. 9 (1.5, 5.7); current HT, 0.5 (0.3, 0.9). Women with eight or more risk factors had more than a 2-fold higher rate of fracture compared with women with four or fewer risk factors. Two ethnicity x risk factor interactions were identified: age and fall history. CONCLUSIONS: Irrespective of their ethnicity, women with multiple risk factors have a high risk of fracture. Targeting these high-risk women for screening and intervention could reduce fractures.  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