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   1616篇
  免费   219篇
  国内免费   18篇
耳鼻咽喉   16篇
儿科学   57篇
妇产科学   20篇
基础医学   121篇
口腔科学   10篇
临床医学   216篇
内科学   429篇
皮肤病学   35篇
神经病学   286篇
特种医学   107篇
外科学   227篇
综合类   54篇
现状与发展   20篇
预防医学   93篇
眼科学   58篇
药学   50篇
中国医学   2篇
肿瘤学   52篇
  2024年   6篇
  2023年   42篇
  2021年   19篇
  2020年   26篇
  2019年   14篇
  2018年   56篇
  2017年   51篇
  2016年   37篇
  2015年   46篇
  2014年   54篇
  2013年   78篇
  2012年   58篇
  2011年   60篇
  2010年   67篇
  2009年   83篇
  2008年   77篇
  2007年   63篇
  2006年   57篇
  2005年   65篇
  2004年   54篇
  2003年   48篇
  2002年   51篇
  2001年   46篇
  2000年   48篇
  1999年   37篇
  1998年   33篇
  1997年   46篇
  1996年   51篇
  1995年   37篇
  1994年   28篇
  1993年   28篇
  1992年   25篇
  1991年   26篇
  1990年   27篇
  1989年   35篇
  1988年   31篇
  1987年   27篇
  1986年   23篇
  1985年   28篇
  1984年   15篇
  1983年   11篇
  1982年   13篇
  1981年   7篇
  1980年   8篇
  1978年   15篇
  1977年   12篇
  1976年   11篇
  1975年   7篇
  1972年   6篇
  1964年   6篇
排序方式: 共有1853条查询结果,搜索用时 15 毫秒
1.
2.
BACKGROUND: Endothelin, a peptide with strong vasoconstrictive and mitogenic properties, has been found to increase after cardiac transplantation. We therefore assessed the association between its precursor peptide, big endothelin-1, and intimal hyperplasia and coronary flow reserve after heart transplantation. METHODS: Thirty-five patients without hemodynamically significant coronary artery disease after heart transplantation were investigated: Average peak flow velocity in the left anterior descending artery (LAD) was assessed by intracoronary Doppler at baseline as well as after injection of adenosine; coronary flow reserve was calculated as a ratio of both and was corrected for patient age and baseline average peak flow velocity. Lumen, intima + media and total vessel area were measured by intracoronary ultrasound. The plasma concentration of big endothelin-1 in venous blood was determined by radioimmunoassay. RESULTS: Patients with elevated big endothelin-1 levels (>2 fmol/ml) tended to have a decreased corrected coronary flow reserve (2.60 +/- 0.9 vs 3.21 +/- 1.0, p = 0.078). They also had a significantly larger intima + media area (5.82 +/- 2.9 vs 2.37 +/- 2.9 mm(2), p = 0.004) and total vessel area (18.36 +/- 5.8 vs 12.81 +/- 4.8 mm(2), p = 0.012) than those with normal plasma concentrations. CONCLUSIONS: Our study suggests an association between elevated big endothelin-1 plasma levels and the development of intimal hyperplasia and reduction of coronary flow reserve after cardiac transplantation.  相似文献   
3.
4.
5.
We studied a cohort of 496 patients who had multiple sclerosis (MS) for at least 10 years. Ten years after disease onset, 151 had benign MS defined as an Extended Disability Status Scale (EDSS) ≤3. Between benign and non-benign patients we compared gender, age at clinical onset, relapsing–remitting or primary progressive, symptoms at onset, recovery from first relapse, time between first and second relapse, number of relapses in the first 5 years, use of immunomodulatory drugs, and EDSS scores at 2, 5 and 10 years. A multivariate regression analysis showed that a relapsing–remitting course, a low EDSS score at 5 years, and a low number of relapses in the first 5 years were predictive for benign MS at 10 years. Other factors had no additional value. Thirty-five of the 51 patients (69%) with benign MS at 10 years were still benign at 20 years. A low 10-year EDSS score was the only clinical variable associated with a benign course at 20 years. Our results suggest that within the first 5 years from onset it is not possible to predict a benign course. Disease course, EDSS score and relapse rate at 5 years are predictors for benign MS at 10 years.  相似文献   
6.
A randomized controlled trial of sedation in the critically ill   总被引:2,自引:0,他引:2  
A randomized controlled trial comparing: a) a combination of oral chloral hydrate and promethazine to b) a continuous intravenous midazolam infusion, for maintenance sedation in critically ill children, was carried out. The level of sedation was assessed four hourly using a specifically devized sedation scale. Forty-four children entered the study of whom two were subsequently excluded. The number of satisfactory assessments (desired and actual levels of sedation equal) was significantly greater in the chloral hydrate and promethazine group (Chi-squared P <0.01; confidence intervals of the difference 0.06 to 0.20). The number of assessments at level 5 on the sedation scale (patient restless/distressed) was significantly greater in the midazolam group (Chi-squared P <0.05). The total number of satisfactory assessments in the two groups were only 61 and 48% respectively, suggesting that sedation can be considerably improved. Chloral hydrate and promethazine are more effective than midazolam as maintenance sedation in critically ill children. It is possible to prospectively study the efficacy of sedative drugs in critically ill children.  相似文献   
7.
8.
9.
10.
The distribution of parvalbumin-like immunoreactivity was studied in the embryonic and postnatal chicken retina. In post-hatched chickens, parvalbumin-like immunoreactivity was confined to amacrine cells. Three distinct subpopulations were identifiable based upon soma position and level of dendritic arborization in the inner plexiform layer. The primary dendrites from parvalbumin-immunoreactive amacrine cells descended vertically into the inner plexiform layer and eventually branched to give rise to a laminarly arrayed plexus in sublamina I, sublamina V and, to a lesser extent, at the boundary between sublaminae III and IV. Parvalbumin-like immunoreactive amacrine cells projecting to sublamina I of the inner plexiform layer were consistently monostratified. Some, but not all, contributed thick fibers to sublamina I that could be followed for long distances across the retina and were generally not radially organized. The parvalbumin-like immunoreactive cells that projected to sublamina V gave rise to a primary dendrite from which three to five fibers branched radially. Collateral branches of these same primary dendrites gave rise to the parvalbumin-like immunoreactive plexus at the interface between sublaminae III and IV. In prenatal chickens, parvalbumin-like immunoreactivity was not detected until embryonic day 14. At this time it appeared as a faint band at the inner nuclear layer-inner plexiform layer boundary in the central retina. By embryonic day 18 the intensity of immunoreactivity and the complexity of the arborizations of the parvalbumin-like immunoreactive dendrites approached that seen in the post-hatched chicken. In the chicken retina, parvalbumin-like immunoreactivity was displayed by morphologically distinct subpopulations of amacrine cells suggesting that these amacrine cells may subserve diverse functions.(ABSTRACT TRUNCATED AT 250 WORDS)  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