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   209742篇
  免费   3160篇
  国内免费   203篇
耳鼻咽喉   1529篇
儿科学   7681篇
妇产科学   3926篇
基础医学   19939篇
口腔科学   2765篇
临床医学   15369篇
内科学   38194篇
皮肤病学   1323篇
神经病学   18428篇
特种医学   10096篇
外国民族医学   4篇
外科学   35160篇
综合类   3150篇
现状与发展   3篇
一般理论   27篇
预防医学   20385篇
眼科学   4032篇
药学   12182篇
  1篇
中国医学   891篇
肿瘤学   18020篇
  2023年   365篇
  2022年   859篇
  2021年   1674篇
  2020年   1003篇
  2019年   1290篇
  2018年   23223篇
  2017年   18299篇
  2016年   20513篇
  2015年   2197篇
  2014年   2462篇
  2013年   2793篇
  2012年   9931篇
  2011年   23757篇
  2010年   20323篇
  2009年   12825篇
  2008年   21468篇
  2007年   23684篇
  2006年   2501篇
  2005年   3880篇
  2004年   4916篇
  2003年   5616篇
  2002年   3595篇
  2001年   628篇
  2000年   709篇
  1999年   434篇
  1998年   390篇
  1997年   326篇
  1996年   225篇
  1995年   202篇
  1994年   187篇
  1993年   135篇
  1992年   184篇
  1991年   243篇
  1990年   250篇
  1989年   201篇
  1988年   155篇
  1987年   141篇
  1986年   112篇
  1985年   146篇
  1984年   96篇
  1983年   75篇
  1982年   80篇
  1981年   55篇
  1980年   82篇
  1979年   59篇
  1978年   50篇
  1974年   57篇
  1938年   63篇
  1932年   57篇
  1930年   48篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
31.
To determine the protective effect of aloe-emodin (AE) from high glucose induced toxicity in RIN-5F (pancreatic β-cell) cell and restoration of its function was analyzed. RIN-5F cells have been cultured in high glucose (25 mM glucose) condition, with and without AE treatment. RIN-5F cells cultured in high glucose decreased cell viability and increased ROS levels after 48 hr compared with standard medium (5.5 mM glucose). Glucotoxicity was confirmed by significantly increased ROS production, increased pro-inflammatory (IFN-γ, IL-1β,) & decreased anti-inflammatory (IL-6&IL-10) cytokine levels, increased DNA fragmentation. In addition, we found increased Bax, caspase 3, Fadd, and Fas and significantly reduced Bcl-2 expression after 48 hr. RIN-5F treated with both high glucose and AE (20 μM) decreased ROS generation and prevent RIN-5F cell from glucotoxicity. In addition, AE treated cells cultured in high glucose were transferred to standard medium, normal responsiveness to glucose was restored within 8hr and normal basal insulin release within 24 hr was achieved when compared to high glucose.  相似文献   
32.
33.
34.
35.

Background and study aims

Acute upper gastrointestinal bleeding is one of the main causes of hospitalisation. The purpose of this study was to determine the prognostic factors in non-variceal upper gastrointestinal bleeding.

Patients and methods

Clinical outcomes, demographic and laboratory variables of the subjects were collected from the HIS software and national code with the SQL format from three hospitals in Qazvin. The data were linked to the database software designed by the author. Clinical and upper endoscopic findings of patients’ records were collected through a questionnaire form in the designed software database.

Results

In this study, 29.2% of patients with favourable outcome and 64.2% of patients with unfavourable clinical outcomes had a history of anticoagulant drug use before hospitalisation (p?<?0.001). The prevalence of chronic cardiovascular disease, chronic liver disease, chronic lung disease, diabetes and dialysis was higher in subjects with poor clinical outcomes than those with a favourable clinical outcome.53.1% of subjects with favourable clinical outcome and 90.5% of subjects with undesirable clinical outcomes received packed red blood cell transfusion (p?<?0.001). 16.1% of subjects with desirable clinical outcome and 86.3% of subjects with undesirable clinical outcomes received endoscopic haemostatic treatment which was statistically significant (p?<?0.001).

Conclusion

Undesirable clinical outcome in patients with acute non-variceal upper gastrointestinal bleeding has a significant statistical association with longer hospitalisation, chronic underlying disease, anticoagulant administration, packed red blood cell infusion, higher Forrest stage, low systolic blood pressure, higher age, low haemoglobin, low platelet count, high INR and high BUN at the onset of diagnosis.  相似文献   
36.
37.
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   
38.
39.
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   
40.
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