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   3440243篇
  免费   247496篇
  国内免费   9373篇
耳鼻咽喉   48517篇
儿科学   111814篇
妇产科学   97645篇
基础医学   483701篇
口腔科学   97626篇
临床医学   310215篇
内科学   672667篇
皮肤病学   81908篇
神经病学   281385篇
特种医学   133154篇
外国民族医学   1122篇
外科学   518274篇
综合类   72868篇
现状与发展   11篇
一般理论   1315篇
预防医学   258530篇
眼科学   79338篇
药学   253650篇
  12篇
中国医学   7150篇
肿瘤学   186210篇
  2018年   36524篇
  2017年   28443篇
  2016年   32683篇
  2015年   36581篇
  2014年   50501篇
  2013年   76499篇
  2012年   100899篇
  2011年   106941篇
  2010年   64305篇
  2009年   61415篇
  2008年   100437篇
  2007年   107395篇
  2006年   108806篇
  2005年   104681篇
  2004年   101010篇
  2003年   97828篇
  2002年   94699篇
  2001年   161113篇
  2000年   165253篇
  1999年   139684篇
  1998年   40219篇
  1997年   35879篇
  1996年   35494篇
  1995年   34269篇
  1994年   31608篇
  1993年   29642篇
  1992年   109116篇
  1991年   105366篇
  1990年   102364篇
  1989年   99307篇
  1988年   91609篇
  1987年   89861篇
  1986年   84861篇
  1985年   81142篇
  1984年   60839篇
  1983年   51668篇
  1982年   30986篇
  1981年   27754篇
  1979年   55298篇
  1978年   39289篇
  1977年   33872篇
  1976年   31051篇
  1975年   34044篇
  1974年   40124篇
  1973年   38517篇
  1972年   36386篇
  1971年   33955篇
  1970年   31672篇
  1969年   30554篇
  1968年   28355篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
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   
102.
103.
104.
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   
105.
106.
107.
108.
109.
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   
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