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   180390篇
  免费   1687篇
  国内免费   14篇
耳鼻咽喉   1180篇
儿科学   6927篇
妇产科学   3166篇
基础医学   17210篇
口腔科学   1628篇
临床医学   12909篇
内科学   31704篇
皮肤病学   721篇
神经病学   17010篇
特种医学   9103篇
外科学   29401篇
综合类   2561篇
一般理论   11篇
预防医学   18739篇
眼科学   2915篇
药学   9798篇
中国医学   632篇
肿瘤学   16476篇
  2022年   61篇
  2021年   110篇
  2020年   77篇
  2019年   118篇
  2018年   22001篇
  2017年   17441篇
  2016年   19597篇
  2015年   975篇
  2014年   903篇
  2013年   913篇
  2012年   7184篇
  2011年   21133篇
  2010年   18918篇
  2009年   11642篇
  2008年   19688篇
  2007年   21868篇
  2006年   735篇
  2005年   2391篇
  2004年   3566篇
  2003年   4472篇
  2002年   2644篇
  2001年   430篇
  2000年   596篇
  1999年   319篇
  1998年   305篇
  1997年   288篇
  1996年   190篇
  1995年   172篇
  1994年   173篇
  1993年   134篇
  1992年   160篇
  1991年   211篇
  1990年   235篇
  1989年   184篇
  1988年   200篇
  1987年   163篇
  1986年   127篇
  1985年   151篇
  1984年   116篇
  1983年   122篇
  1982年   70篇
  1981年   60篇
  1980年   75篇
  1979年   61篇
  1978年   66篇
  1974年   59篇
  1970年   66篇
  1969年   51篇
  1938年   65篇
  1932年   61篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Journal of Thrombosis and Thrombolysis - Over the last few years data from our group have indicated that α-synuclein is important in development of immune cells as well as potentially...  相似文献   
12.
Dehydrogenase activity is frequently used to assess the general condition of microorganisms in soil and activated sludge. Many studies have investigated the inhibition of dehydrogenase activity by various compounds, including heavy metal ions. However, the time after which the measurements are carried out is often chosen arbitrarily. Thus, it can be difficult to estimate how the toxic effects of compounds vary during the reaction and when the maximum of the effect would be reached. Hence, the aim of this study was to create simple and useful mathematical model describing changes in dehydrogenase activity during exposure to substances that inactivate enzymes. Our model is based on the Lagergrens pseudo-first-order equation, the rate of chemical reactions, enzyme activity, and inactivation and was created to describe short-term changes in dehydrogenase activity. The main assumption of our model is that toxic substances cause irreversible inactivation of enzyme units. The model is able to predict the maximum direct toxic effect (MDTE) and the time to reach this maximum (TMDTE). In order to validate our model, we present two examples: inactivation of dehydrogenase in microorganisms in soil and activated sludge. The model was applied successfully for cadmium and copper ions. Our results indicate that the predicted MDTE and TMDTE are more appropriate than EC50 and IC50 for toxicity assessments, except for long exposure times.  相似文献   
13.
14.
Contraceptive use is an important strategy for the prevention of unwanted pregnancy and avoidance of induced abortion. Of all the contraception methods, emergency contraceptive (EC) offers the last chance to achieve this. However, few studies have documented the use of EC among young people in Ghana. This study explored knowledge and usage of EC as well as the factors associated with it among University of Cape Coast students. Data were obtained on the knowledge and usage of ECs among University of Cape Coast students in 2013. Logistic regression analysis was used to investigate the association between students’ socio-demographic characteristics and EC knowledge and use. More male students (72 %) than females (59 %) were sexually active. Fifty-seven percent of the respondents had ever heard of EC and 36 % had ever used EC. Although males were more likely to be sexually active, females were more likely to have knowledge of EC use compared to males. The study underscores the need to increase awareness regarding EC among University students in order to offer them the opportunity that EC provides if other forms of contraceptives are missed.  相似文献   
15.
16.
Gastroesophageal reflux is the most common benign disorder of the esophagus and laparoscopic Nissen fundoplication has become the standard surgical treatment for its treatment. In our area, where the use of bougie calibration is debatable, postoperative dysphagia is encountered often after this surgery although it is usually not permanent. The aim of this study was to investigate the effect of using a soft silicone tube 39 F in diameter for esophageal calibration during laparoscopic Nissen fundoplication on the incidence of postoperative dysphagia. We divided cases scheduled to undergo laparoscopic Nissen fundoplication between January 2009 and November 2010 into two groups, each consisting 25 patients. Esophageal calibration with a 39 F silicone orogastric tube was used for the first group while there was no operative calibration in the second group. The surgical duration was recorded; the presence and severity of the postoperative dysphagia was calculated by using a dysphagia severity scoring system during the 1-year postoperative follow-up. The dysphagia severity scores were significantly lower in group 1 than group 2 on the postoperative second day and at the end of the first week and first month. We did not find a significant difference at the end of the 6-month and first year. There was also no significant difference regarding surgery duration. The use of a soft orogastric tube 39 F in diameter for esophagus calibration during laparoscopic Nissen fundoplication has significantly decreased the incidence of postoperative transient dysphagia without affecting the duration of surgery. Although dysphagia gradually resolves in the majority of patients, a safe and easy calibration method for its prevention is worth developing, and we believe that the use of our method in larger series could be beneficial.  相似文献   
17.
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