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   3138717篇
  免费   221864篇
  国内免费   8402篇
耳鼻咽喉   43006篇
儿科学   99880篇
妇产科学   85679篇
基础医学   441185篇
口腔科学   88209篇
临床医学   284901篇
内科学   616149篇
皮肤病学   73640篇
神经病学   255884篇
特种医学   120931篇
外国民族医学   800篇
外科学   475572篇
综合类   63022篇
现状与发展   5篇
一般理论   1146篇
预防医学   235653篇
眼科学   71030篇
药学   231576篇
  10篇
中国医学   6544篇
肿瘤学   174161篇
  2019年   24031篇
  2018年   34215篇
  2017年   26350篇
  2016年   30473篇
  2015年   34319篇
  2014年   47142篇
  2013年   70506篇
  2012年   93697篇
  2011年   99028篇
  2010年   59613篇
  2009年   57241篇
  2008年   93236篇
  2007年   98842篇
  2006年   100739篇
  2005年   96652篇
  2004年   93142篇
  2003年   89719篇
  2002年   86967篇
  2001年   155622篇
  2000年   159601篇
  1999年   134664篇
  1998年   37545篇
  1997年   33157篇
  1996年   33397篇
  1995年   32276篇
  1994年   29625篇
  1993年   27731篇
  1992年   104462篇
  1991年   100361篇
  1990年   97354篇
  1989年   94051篇
  1988年   86129篇
  1987年   84424篇
  1986年   79123篇
  1985年   75558篇
  1984年   55908篇
  1983年   47349篇
  1982年   27357篇
  1981年   24344篇
  1979年   49469篇
  1978年   34447篇
  1977年   29468篇
  1976年   26954篇
  1975年   28859篇
  1974年   34293篇
  1973年   32481篇
  1972年   30493篇
  1971年   28411篇
  1970年   26465篇
  1969年   25328篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
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   
12.
13.
14.
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   
15.
16.
17.
Abstract

Supporting patients in making informed healthcare decisions is a cornerstone of ethical medical practice. Surgeons frequently draw for and show images to patients when consenting them for operations but the value of this practice in informed decision-making is unclear. An audit was conducted in a General Surgery Department. 244 patients completed questionnaires on the value of visual materials when giving consent for surgery. The complexity of the operations was classified into “simple”, “moderate” or “complex”. 100% of patients felt they had given informed consent to surgery. 62% of patients received at least one form of visual material during the consenting process. All patients who received a drawing, and 99% of those provided with other images, valued these resources. Visual materials were considered more useful to patients when giving consent for moderate or complex operations than simple ones. Approximately one third of patients who did not receive visual materials would have appreciated these when making an informed decision. This research highlights the value of surgeons drawing for, and providing other visual resources to, their patients as part of the consent process. There is a role for further research and training materials in drawing skills for surgeons.  相似文献   
18.
19.
20.
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