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   4450篇
  免费   415篇
  国内免费   17篇
耳鼻咽喉   20篇
儿科学   143篇
妇产科学   119篇
基础医学   457篇
口腔科学   178篇
临床医学   405篇
内科学   971篇
皮肤病学   60篇
神经病学   497篇
特种医学   195篇
外国民族医学   1篇
外科学   467篇
综合类   99篇
现状与发展   1篇
一般理论   8篇
预防医学   404篇
眼科学   172篇
药学   238篇
中国医学   2篇
肿瘤学   445篇
  2021年   52篇
  2020年   40篇
  2019年   61篇
  2018年   78篇
  2017年   51篇
  2016年   63篇
  2015年   51篇
  2014年   107篇
  2013年   128篇
  2012年   172篇
  2011年   167篇
  2010年   121篇
  2009年   84篇
  2008年   175篇
  2007年   193篇
  2006年   182篇
  2005年   176篇
  2004年   180篇
  2003年   147篇
  2002年   173篇
  2001年   157篇
  2000年   138篇
  1999年   130篇
  1998年   63篇
  1997年   47篇
  1996年   43篇
  1995年   45篇
  1994年   52篇
  1992年   99篇
  1991年   105篇
  1990年   107篇
  1989年   120篇
  1988年   100篇
  1987年   122篇
  1986年   81篇
  1985年   86篇
  1984年   62篇
  1983年   51篇
  1982年   45篇
  1981年   44篇
  1979年   63篇
  1978年   63篇
  1977年   45篇
  1976年   50篇
  1975年   45篇
  1974年   51篇
  1973年   58篇
  1972年   51篇
  1971年   40篇
  1968年   44篇
排序方式: 共有4882条查询结果,搜索用时 15 毫秒
101.
102.
Because of better awareness and understanding of its pathophysiology, the cardiorenal syndrome (CRS) is more often diagnosed and better managed. The echocardiographic evaluation of CRS now benefits from three-dimensional speckle tracking echocardiography (3D-STE), which allows multidimensional and real-time evaluation of regional myocardial and overall cardiac function, and helps assessing the degree of myocardial damage. This article describes the application of 3D-STE in evaluating the myocardial motion in patients with CRS.  相似文献   
103.
In germinal centers, B lymphocytes are intimately associated with follicular dendritic cells (FDCs). It has been hypothesized that FDCs are involved in the regulation of B-cell growth and differentiation through cell-cell interactions. In this study, highly enriched preparations of FDCs were isolated by cell sorting using the FDC restricted monoclonal antibody DRC-1. When irradiated FDCs were cultured with mitogen stimulated B cells, B cell 3H-TdR uptake was inhibited by up to 80%. This inhibitory effect was not seen when paraformaldehyde fixed FDCs were added to B-cell cultures, suggesting that the FDCs needed to be metabolically active. Moreover, supernatants from cultured FDCs were similarly able to inhibit B-cell proliferation. These results demonstrate that FDCs may downregulate the clonal expansion of B cells that occurs within lymphoid follicles as part of the normal physiologic immune response. Potentially, the loss of the inhibitory role of FDCs in vivo may be of importance in certain infectious and neoplastic processes in which germinal centers are affected.  相似文献   
104.

Aim

Recent studies revealed a correlation between skeletal muscle mass index and density with longevity; these studies largely evaluated appendicular skeletal muscles in older Caucasians. This retrospective cohort study assessed the association between axial skeletal muscles size and density with survival in African Americans with type 2 diabetes mellitus.

Methods

Psoas and paraspinous muscle mass index (cross sectional area/height2) and radiographic density (in Hounsfield Units) were measured using computed tomography in African American-Diabetes Heart Study participants, 314 women and 256 men, with median (25th, 75th quartile) age 55.0(48.0, 62.0) and 57.0(50.0, 64.0) years, respectively. Covariates in fully-adjusted model included age, sex, BMI, smoking, hormone replacement therapy (women), cardiovascular disease, hypertension, coronary artery calcified plaque mass, carotid artery calcified plaque mass, and African ancestry proportion.

Results

After median of 7.1(5.9, 8.2) years follow-up, 30(9.6%) of women and 49(19.1%) of men were deceased. In fully-adjusted models, psoas muscle mass index and paraspinous muscle mass index were inversely associated with mortality in men (psoas muscle mass index, hazard ratio [HR]?=?0.61, P?=?0.004; paraspinous muscle mass index, HR?=?0.64, P?=?0.004), but not in women. Psoas and paraspinous muscle densities did not associate with all-cause mortality. A penalized Cox regression that involved all covariates and predictors associated with mortality showed that only paraspinous muscle mass index remained a significant predictor of mortality (HR =?0.65, P?=?0.02).

Conclusion

Independent from established risk factors for mortality, higher psoas and paraspinous muscle index associate with reduced all-cause mortality in middle-aged African American men with type 2 diabetes mellitus.  相似文献   
105.
Ganesan  TS; Min  GL; Goldman  JM; Young  BD 《Blood》1987,70(3):873-876
Four patients with Philadelphia (Ph') positive chronic myeloid leukemia (CML) were studied before, after, and on relapse following allogeneic bone marrow transplantation (BMT). Southern analysis of DNA from cells collected before and at relapse after BMT was performed in order to investigate the origin of the leukemia at relapse. Using minisatellite probes we showed that the relapse occurred in cells of host origin in all four patients and this was confirmed with a Y chromosome specific probe in two male patients who had a female donor. Furthermore, using two probes for the breakpoint cluster region (bcr) on chromosome 22, we showed that leukemic cells at relapse bore identical rearrangements to those in the disease at time of presentation of each patient. We conclude that relapse in all four patients is due to re-emergence of the original leukemic clone.  相似文献   
106.
107.
108.
The REFLEX study (NCT00404352) established that subcutaneous (sc) interferon (IFN) β-1a reduced the risks of McDonald MS (2005 criteria) and clinically definite multiple sclerosis (CDMS) in patients with a first clinical demyelinating event suggestive of MS. The aim of this subgroup analysis was to assess the treatment effect of sc IFN β-1a in patient subgroups defined by baseline disease and demographic characteristics (age, sex, use of steroids at the first event, classification of first event as mono- or multifocal, presence/absence of gadolinium-enhancing lesions, count of <9 or ≥9 T2 lesions), and by diagnosis of MS using the revised McDonald 2010 MS criteria. Patients were randomized to the serum-free formulation of IFN β-1a, 44 μg sc three times weekly or once weekly, or placebo, for 24 months or until diagnosis of CDMS. Treatment effects of sc IFN β-1a on McDonald 2005 MS and CDMS in the predefined subgroups were similar to effects found in the intent-to-treat population. McDonald 2010 MS was retrospectively diagnosed in 37.7 % of patients at baseline. Both regimens of sc IFN β-1a significantly reduced the risk versus placebo of McDonald 2005 MS and CDMS, irrespective of McDonald 2010 status at baseline (risk reductions between 29 and 51 %). The effect of sc IFN β-1a was not substantially influenced by baseline patient demographic and disease characteristics, or baseline presence/absence of McDonald 2010 MS.  相似文献   
109.
110.
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