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   1655907篇
  免费   135448篇
  国内免费   6714篇
耳鼻咽喉   23732篇
儿科学   53830篇
妇产科学   42311篇
基础医学   227798篇
口腔科学   41655篇
临床医学   168968篇
内科学   339686篇
皮肤病学   38037篇
神经病学   141505篇
特种医学   59480篇
外国民族医学   446篇
外科学   243628篇
综合类   29767篇
现状与发展   73篇
一般理论   518篇
预防医学   137390篇
眼科学   35665篇
药学   113052篇
  6篇
中国医学   3731篇
肿瘤学   96791篇
  2021年   16285篇
  2020年   13628篇
  2019年   16607篇
  2018年   28743篇
  2017年   22599篇
  2016年   24428篇
  2015年   26830篇
  2014年   39130篇
  2013年   53352篇
  2012年   62406篇
  2011年   65191篇
  2010年   42827篇
  2009年   42554篇
  2008年   59316篇
  2007年   60978篇
  2006年   62266篇
  2005年   58090篇
  2004年   54674篇
  2003年   50770篇
  2002年   49051篇
  2001年   68247篇
  2000年   69265篇
  1999年   58794篇
  1998年   18501篇
  1997年   16886篇
  1996年   16581篇
  1995年   15747篇
  1994年   13765篇
  1993年   12674篇
  1992年   44959篇
  1991年   44052篇
  1990年   42290篇
  1989年   40201篇
  1988年   37189篇
  1987年   36038篇
  1986年   34446篇
  1985年   32619篇
  1984年   24529篇
  1983年   20917篇
  1982年   12677篇
  1979年   21963篇
  1978年   15709篇
  1977年   12999篇
  1976年   12556篇
  1975年   12948篇
  1974年   15749篇
  1973年   15438篇
  1972年   14350篇
  1971年   13343篇
  1970年   12371篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
33.
34.
35.
36.
37.
AIM: To evaluate whether the introduction of a strict protocol approach based on the systemic evaluation of critically ill pregnant women with complications of abortion affected outcome. SETTING: Indigent South Africans managed in the regional and tertiary hospitals of the Pretoria Academic Complex. METHOD: Since 1997 a standard definition of severe acute maternal morbidity (SAMM) has been used in the Pretoria Academic Complex. All cases of SAMM and maternal deaths were entered on the Maternal Morbidity and Mortality Audit System programme. A comparison of outcome of severely ill women who had complications of abortion was made between 1997-1998 (original protocol) and 2002-2004 (strict protocol). OUTCOME MEASURES: The mortality index and prevalence of organ system failure or dysfunction. RESULTS: In 1997-1998 there were 43 women with SAMM who survived and a further 10 maternal deaths due to complications of abortion, compared with 107 women with SAMM and 7 maternal deaths during 2002-2004. The mortality index declined from 18.9% in 1997-1998 to 6.1% in 2002-2004 (p = 0.02, odds ratio 0.28, 95% confidence limits 0.10 - 0.79). Significantly more women had hypovolaemic shock in 2002-2004 compared with 1997-1998 (54.4% v. 35.8%, p = 0.04), but fewer women had immune system failure including septic shock (18.4% v. 47.2%, p = 0.0002) and metabolic dysfunction (0 v. 5.7%, p = 0.03) and there was a trend to less renal failure (10.5% v. 22.6%, p = 0.06) and cardiac failure (4.4% v. 13.2%, p = 0.08). CONCLUSION: The strict protocol approach based on systemic evaluation in managing critically ill pregnant women with complications of abortion, coupled with an intensive, regular feedback mechanism, has been associated with a reduction in the mortality index.  相似文献   
38.
39.
The New Zealand obese mouse (NZO/Hl) is characterised by hereditary obesity and type-2 diabetes, including insulin resistance, hyperinsulinaemia, and glucose intolerance. In other diabetic models, it has been revealed that the proper functioning of the glucose transporter isoform 2 (GLUT2) is essential for adequate secretion of insulin. The aim of this study was to compare the distribution of islet cells and GLUT2, as well as the expression of GLUT2-mRNA, in the pancreas of NZO mice and metabolically unimpaired NMRI (Naval Medical Research Institute) mice. Pancreas tissue was obtained from different stages of development. For molecular determination of the expression level of GLUT2-mRNA, total-RNA was extracted from the pancreas and analysed by quantitative real-time RT-PCR. All investigated NZO mice displayed increased weight, elevated hyperinsulinaemia, and slightly enhanced blood glucose levels compared with the NMRI control mice. By means of immunofluorescence microscopy drastically reduced insulin levels were detected, which might be compensated by the observed islet cell hyperplasia and hypertrophy. Furthermore, the normally peripheral localisation of the alpha-cells within islets was disturbed. By contrast, there were no changes in somatostatin cell distribution. However, considerable differences appeared with regard to GLUT2: whereas the beta-cells of NMRI mice showed dense immunostaining of the GLUT2 transporter on the cell surface, in all age groups of NZO mice, GLUT2 on the plasma membranes was reduced and dispersed in the cytoplasm. These findings agree with the molecular biological results, which displayed decreased mRNA-expression of GLUT2. In summary, the observed alteration of islet morphology and of GLUT2 expression in diabetic mice complements our previous results from a superfusion protocol and further clarifies the mechanisms of diabetogenesis in NZO mice.  相似文献   
40.
Sniff nasal inspiratory pressure (SNIP) measurement is a volitional noninvasive assessment of inspiratory muscle strength. A maximum of 10 sniffs is generally used. The purpose of the present study was to investigate whether the maximum SNIP improved after the tenth sniff. In total, 20 healthy volunteers and 305 patients with various neuromuscular and lung diseases were encouraged to perform 40 and 20 sniffs, respectively. The best SNIP among the first 10 sniffs was lower than the best SNIP among the next 10 sniffs in the healthy volunteers and patients. The SNIP improvement after the twentieth sniff was marginal. In conclusion, a learning effect persists after the tenth sniff. The current authors suggest using 10 additional sniffs when the best result of the first 10 sniffs is slightly below normal, or when sniff nasal inspiratory pressure is used to monitor a progressive decline in inspiratory muscle strength.  相似文献   
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