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   240474篇
  免费   5827篇
  国内免费   172篇
耳鼻咽喉   1960篇
儿科学   8393篇
妇产科学   4672篇
基础医学   27058篇
口腔科学   3307篇
临床医学   19006篇
内科学   43577篇
皮肤病学   1696篇
神经病学   22521篇
特种医学   11639篇
外国民族医学   46篇
外科学   37086篇
综合类   2863篇
一般理论   88篇
预防医学   23562篇
眼科学   3954篇
药学   14082篇
中国医学   787篇
肿瘤学   20176篇
  2022年   402篇
  2021年   1068篇
  2020年   706篇
  2019年   979篇
  2018年   22969篇
  2017年   18080篇
  2016年   20343篇
  2015年   2017篇
  2014年   2212篇
  2013年   3244篇
  2012年   10005篇
  2011年   24052篇
  2010年   20982篇
  2009年   13382篇
  2008年   22240篇
  2007年   24548篇
  2006年   3559篇
  2005年   5036篇
  2004年   6304篇
  2003年   6985篇
  2002年   5234篇
  2001年   2454篇
  2000年   2633篇
  1999年   2190篇
  1998年   1127篇
  1997年   985篇
  1996年   797篇
  1995年   831篇
  1994年   733篇
  1993年   720篇
  1992年   1534篇
  1991年   1536篇
  1990年   1499篇
  1989年   1436篇
  1988年   1186篇
  1987年   1173篇
  1986年   1093篇
  1985年   1024篇
  1984年   751篇
  1983年   700篇
  1982年   508篇
  1981年   462篇
  1980年   440篇
  1979年   646篇
  1978年   412篇
  1977年   387篇
  1975年   397篇
  1974年   448篇
  1973年   362篇
  1972年   364篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
12.
While peer support has been investigated in multiple clinical contexts, its application to the postpartum setting is unknown. The aim was to assess acceptability of a postpartum peer support program for women with diabetes. Observational survey-based needs assessment of forty low-income women with diabetes, receiving care at a major medical institution. Mean age and gravidity were 30.7 years and 3.15 ± 1.67 respectively. 45 % expressed interest in a “buddy.” There was no significant difference between groups desiring and not desiring this program. A majority of respondents desired telephone, text messaging, and in-person contacts (79.2, 72.1, 83.8 %), with 72.5 % of patients desiring diabetes-related activities during clinic waiting time. Many women desire a postpartum diabetes reciprocal peer program for support outside of clinician visits. Patients are receptive to educational services during their wait and outside of clinic time, a potentially valuable opportunity to share important health information.  相似文献   
13.
14.
Clinical Oral Investigations - The aim of this study was the analysis of WNT10A variants in seven families of probands with various forms of tooth agenesis and self-reported family history of...  相似文献   
15.
The aim of this study was to analyse the effect of body mass index (BMI), both low and high values, on the perioperative complication rate in patients with oral squamous cell carcinoma (OSCC). The medical records of 259 patients operated between 2014 and 2017 for OSCC were reviewed. Univariate and multivariate analyses were performed. Sixty of the 259 patients developed 87 complications. Low or high BMI was not associated with the perioperative complication rate. A longer operating time and increased blood loss were associated with a higher perioperative complication rate and higher Clavien–Dindo grade. Low BMI, American Society of Anesthesiologists score 2 and 3, a longer operating time, and increased blood loss were associated with a longer hospital stay. Low BMI was associated with a longer hospital stay. Neither low nor high BMI was associated with the perioperative complication rate. A longer operating time and increased blood loss were associated with a higher perioperative complication rate and higher Clavien–Dindo grade.  相似文献   
16.
Genetic and epigenetic alterations importantly contribute to the pathogenesis of lung cancer. In the study, we measured the frequency and distribution of molecular abnormalities of EGFR as well as the aberrant promoter methylations of BRCA1, MGMT, MLH1, and RASSF1A in Vietnamese lung adenocarcinomas. We investigated the association between genetic and epigenetic alteration, and between each abnormality with clinicopathologic parameters. Somatic EGFR mutation that was found in 49/139 (35.3%) lung adenocarcinomas showed a significant association with young age, female gender, and non-smokers. EGFR overexpression was identified in 82 tumors (59.0%) and statistical relationships with EGFR or BRCA1 methylation but not EGFR mutation. In addition, EGFR, BRCA1, MGMT, MLH1, and RASSF1A methylations were found in 33 (23.7%), 41 (29.5%), 46 (33.1%), 28 (20.1%), and 41 (29.5%) cases of a total of 139 lung adenocarcinomas, respectively. The RASSF1A methylation was found to be linked to the smoking habit. Methylations in MGMT and RASSF1A were also found to correlate with metastasis status. Furthermore, the distribution of EGFR mutation and that of BRCA1, MGMT or RASSF1A methylation were significantly exclusive in lung adenocarcinomas. The main finding of our study demonstrate that epigenetic abnormalities might play a critical role for the lung tumorigenesis in patients with smoking history and metastasis, and partly affect the predictive value of EGFR mutations through blocking expression due to promoter EGFR hypermethylation. Mutually exclusive distribution of genetic and epigenetic alterations reflects differently biological characteristics in the etiology of lung adenocarcinomas.  相似文献   
17.
18.
19.
20.
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   
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