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   2688456篇
  免费   193477篇
  国内免费   7844篇
耳鼻咽喉   36216篇
儿科学   89470篇
妇产科学   74637篇
基础医学   378832篇
口腔科学   73239篇
临床医学   242146篇
内科学   532836篇
皮肤病学   65532篇
神经病学   223041篇
特种医学   105468篇
外国民族医学   752篇
外科学   403208篇
综合类   51157篇
现状与发展   5篇
一般理论   993篇
预防医学   201040篇
眼科学   59838篇
药学   195842篇
  8篇
中国医学   5595篇
肿瘤学   149922篇
  2021年   21094篇
  2019年   21724篇
  2018年   31425篇
  2017年   24323篇
  2016年   28547篇
  2015年   32023篇
  2014年   43114篇
  2013年   64241篇
  2012年   86087篇
  2011年   90115篇
  2010年   54270篇
  2009年   51769篇
  2008年   84407篇
  2007年   89832篇
  2006年   91569篇
  2005年   88063篇
  2004年   84588篇
  2003年   81826篇
  2002年   78952篇
  2001年   131139篇
  2000年   134018篇
  1999年   112930篇
  1998年   32141篇
  1997年   28635篇
  1996年   28770篇
  1995年   27860篇
  1994年   25473篇
  1993年   23805篇
  1992年   86286篇
  1991年   82704篇
  1990年   79940篇
  1989年   77160篇
  1988年   70416篇
  1987年   68898篇
  1986年   64419篇
  1985年   61360篇
  1984年   45586篇
  1983年   38437篇
  1982年   22792篇
  1981年   20277篇
  1979年   39731篇
  1978年   27973篇
  1977年   23673篇
  1976年   21887篇
  1975年   23454篇
  1974年   27453篇
  1973年   25991篇
  1972年   24389篇
  1971年   22586篇
  1970年   20728篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
In the current immunosuppressive therapy era, vessel thrombosis is the most common cause of early graft loss after renal transplantation. The prevalence of IgA anti–β2-glycoprotein I antibodies (IgA-aB2GPI-ab) in patients on dialysis is elevated (>30%), and these antibodies correlate with mortality and cardiovascular morbidity. To evaluate the effect of IgA-aB2GPI-ab in patients with transplants, we followed all patients transplanted from 2000 to 2002 in the Hospital 12 de Octubre prospectively for 10 years. Presence of IgA-aB2GPI-ab in pretransplant serum was examined retrospectively. Of 269 patients, 89 patients were positive for IgA-aB2GPI-ab (33%; group 1), and the remaining patients were negative (67%; group 2). Graft loss at 6 months post-transplant was significantly higher in group 1 (10 of 89 versus 3 of 180 patients in group 2; P=0.002). The most frequent cause of graft loss was thrombosis of the vessels, which was observed only in group 1 (8 of 10 versus 0 of 3 patients in group 2; P=0.04). Multivariate analysis showed that the presence of IgA-aB2GPI-ab was an independent risk factor for early graft loss (P=0.04) and delayed graft function (P=0.04). There were no significant differences regarding patient survival between the two groups. Graft survival was similar in both groups after 6 months. In conclusion, patients with pretransplant IgA-aB2GPI-ab have a high risk of early graft loss caused by thrombosis and a high risk of delayed graft function. Therefore, pretransplant IgA-aB2GPI-ab may have a detrimental effect on early clinical outcomes after renal transplantation.  相似文献   
103.
Introduction: To increase students’ understanding of what it means to be a physician and engage in the everyday practice of medicine, a humanities program was implemented into the preclinical curriculum of the medical school curriculum. The purpose of our study was to determine how medical students’ views of being a doctor evolved after participating in a required humanities course.

Methods: Medical students completing a 16-clock hour humanities course from 10 courses were asked to respond to an open-ended reflection question regarding changes, if any, of their views of being a doctor. The constant comparative method was used for coding; triangulation and a variety of techniques were used to provide evidence of validity of the analysis.

Results: A majority of first- and second-year medical students (rr?=?70%) replied, resulting in 100 pages of text. A meta-theme of Contextualizing the Purpose of Medicine and three subthemes: the importance of Treating Patients Rather than a Disease, Understanding Observation Skills are Important, and Recognizing that Doctors are Fallible emerged from the data.

Conclusions: Results suggest that requiring humanities as part of the required preclinical curriculum can have a positive influence on medical students and act as a bridge to contextualize the purpose of medicine.  相似文献   
104.
Animal and human studies suggest fish oil and green tea may have protective effect on prostate cancer. Fatty acid synthase (FAS) has been hypothesized to be linked to chemoprotective effects of both compounds. This study evaluated the independent and joint effects of fish oil (FO) and green tea supplement (epigallocatechin-3-gallate, EGCG) on FAS and Ki-67 levels in prostate tissue. Through a double-blinded, randomized controlled trial with 2 × 2 factorial design, 89 men scheduled for repeat prostate biopsy following an initial negative prostate biopsy were randomized into either FO alone (1.9 g DHA + EPA/day), EGCG alone (600 mg/day), a combination of FO and EGCG, or placebo. We used linear mixed-effects models to test the differences of prostate tissue FAS and Ki-67 by immunohistochemistry between pre- and post-intervention within each group, as well as between treatment groups. Results did not show significant difference among treatment groups in pre-to-post-intervention changes of FAS (P = 0.69) or Ki-67 (P = 0.26). Comparing placebo group with any of the treatment groups, we did not find significant difference in FAS or Ki-67 changes (all P > 0.05). Results indicate FO or EGCG supplementation for a short duration may not be sufficient to produce biologically meaningful changes in FAS or Ki-67 levels in prostate tissue.  相似文献   
105.
106.
107.
Analyzing functional species’ characteristics (species traits) that represent physiological, life history and morphological characteristics of species help understanding the impacts of various stressors on aquatic communities at field conditions. This research aimed to study the combined effects of pesticides and other environmental factors (temperature, dissolved oxygen, dissolved organic carbon, floating macrophytes cover, phosphate, nitrite, and nitrate) on the trait modality distribution of aquatic macrofauna communities. To this purpose, a field inventory was performed in a flower bulb growing area of the Netherlands with significant variation in pesticides pressures. Macrofauna community composition, water chemistry parameters and pesticide concentrations in ditches next to flower bulb fields were determined. Trait modalities of nine traits (feeding mode, respiration mode, locomotion type, resistance form, reproduction mode, life stage, voltinism, saprobity, maximum body size) likely to indicate pesticides impacts were analyzed. According to a redundancy analysis, phosphate -and not pesticides- constituted the main factor structuring the trait modality distribution of aquatic macrofauna. The functional composition could be ascribed for 2–4 % to pesticides, and for 3–11 % to phosphate. The lack of trait responses to pesticides may indicate that species may have used alternative strategies to adapt to ambient pesticides stress. Biomass of animals exhibiting trait modalities related to feeding by predation and grazing, presence of diapause form or dormancy, reproduction by free clutches and ovoviviparity, life stage of larvae and pupa, was negatively correlated to the concentration of phosphate. Hence, despite the high pesticide pollution in the area, variation in nutrient-related stressors seems to be the dominant driver of the functional composition of aquatic macrofauna assembly in agricultural ditches.  相似文献   
108.
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