全文获取类型
收费全文 | 220404篇 |
免费 | 6012篇 |
国内免费 | 3439篇 |
专业分类
耳鼻咽喉 | 1574篇 |
儿科学 | 7217篇 |
妇产科学 | 3467篇 |
基础医学 | 20812篇 |
口腔科学 | 2218篇 |
临床医学 | 18130篇 |
内科学 | 36865篇 |
皮肤病学 | 1048篇 |
神经病学 | 18385篇 |
特种医学 | 10441篇 |
外国民族医学 | 13篇 |
外科学 | 33263篇 |
综合类 | 12356篇 |
现状与发展 | 13篇 |
一般理论 | 4篇 |
预防医学 | 21665篇 |
眼科学 | 3864篇 |
药学 | 14392篇 |
56篇 | |
中国医学 | 4344篇 |
肿瘤学 | 19728篇 |
出版年
2024年 | 224篇 |
2023年 | 866篇 |
2022年 | 2134篇 |
2021年 | 2655篇 |
2020年 | 2128篇 |
2019年 | 1663篇 |
2018年 | 23434篇 |
2017年 | 18856篇 |
2016年 | 20818篇 |
2015年 | 3027篇 |
2014年 | 3527篇 |
2013年 | 3396篇 |
2012年 | 10429篇 |
2011年 | 24823篇 |
2010年 | 21705篇 |
2009年 | 13951篇 |
2008年 | 22198篇 |
2007年 | 24227篇 |
2006年 | 2850篇 |
2005年 | 4183篇 |
2004年 | 4967篇 |
2003年 | 5941篇 |
2002年 | 3869篇 |
2001年 | 1379篇 |
2000年 | 1288篇 |
1999年 | 891篇 |
1998年 | 629篇 |
1997年 | 688篇 |
1996年 | 412篇 |
1995年 | 392篇 |
1994年 | 341篇 |
1993年 | 221篇 |
1992年 | 186篇 |
1991年 | 209篇 |
1990年 | 226篇 |
1989年 | 173篇 |
1988年 | 124篇 |
1987年 | 103篇 |
1986年 | 66篇 |
1985年 | 66篇 |
1984年 | 32篇 |
1983年 | 34篇 |
1982年 | 34篇 |
1980年 | 43篇 |
1938年 | 60篇 |
1937年 | 25篇 |
1935年 | 22篇 |
1934年 | 30篇 |
1932年 | 56篇 |
1930年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Konrad Matyja Anna Małachowska-Jutsz Anna K. Mazur Kazimierz Grabas 《Ecotoxicology (London, England)》2016,25(5):924-939
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
22.
23.
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
24.
25.
26.
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
27.
28.
29.
目的了解上海市黄浦区社会办医疗美容机构的管理人员和医师对《医疗美容管理办法》相关内容的掌握情况,发现存在的问题并提出改善建议.方法采用现场调查与现场问卷调查相结合的方式,对在上海市黄浦区开展医疗美容科目的所有社会办医疗机构(共计38家)进行全覆盖现场调查,并对其中的管理人员41人、相关医师31人进行问卷调查.结果38家社会办医疗美容机构中,美容外科和美容皮肤科的开展率较高,分别为96.8%和97.2%,而美容牙科开展率为52.4%,美容中医科开展率最低(25.0%).管理人员关于非主诊医师可在主诊医师指导下工作的知晓率仅68.3%.关于美容外科、皮肤科、中医科、牙科主诊医师应具备的工作年限,管理人员答对率为90.2%,医师答对率为72.0%,二者有显著性差异(P<0.05).结论社会办医疗美容机构中的二级科目设置需进一步优化,以减少资源空置.应加强对医疗机构管理人员和医师的法律培训,改变经营模式,制定明确的准入与退出机制,从而减少违法违规行为的发生. 相似文献
30.