全文获取类型
收费全文 | 4201篇 |
免费 | 116篇 |
国内免费 | 22篇 |
专业分类
耳鼻咽喉 | 36篇 |
儿科学 | 71篇 |
妇产科学 | 26篇 |
基础医学 | 154篇 |
口腔科学 | 82篇 |
临床医学 | 573篇 |
内科学 | 1248篇 |
皮肤病学 | 93篇 |
神经病学 | 152篇 |
特种医学 | 90篇 |
外科学 | 414篇 |
综合类 | 219篇 |
预防医学 | 382篇 |
眼科学 | 54篇 |
药学 | 621篇 |
中国医学 | 65篇 |
肿瘤学 | 59篇 |
出版年
2024年 | 11篇 |
2023年 | 115篇 |
2022年 | 157篇 |
2021年 | 208篇 |
2020年 | 195篇 |
2019年 | 190篇 |
2018年 | 183篇 |
2017年 | 116篇 |
2016年 | 69篇 |
2015年 | 55篇 |
2014年 | 208篇 |
2013年 | 196篇 |
2012年 | 145篇 |
2011年 | 171篇 |
2010年 | 154篇 |
2009年 | 137篇 |
2008年 | 111篇 |
2007年 | 104篇 |
2006年 | 92篇 |
2005年 | 66篇 |
2004年 | 35篇 |
2003年 | 48篇 |
2002年 | 39篇 |
2001年 | 30篇 |
2000年 | 20篇 |
1999年 | 25篇 |
1998年 | 16篇 |
1997年 | 24篇 |
1996年 | 15篇 |
1995年 | 13篇 |
1994年 | 11篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1990年 | 7篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 63篇 |
1984年 | 132篇 |
1983年 | 151篇 |
1982年 | 120篇 |
1981年 | 113篇 |
1980年 | 119篇 |
1979年 | 112篇 |
1978年 | 118篇 |
1977年 | 55篇 |
1976年 | 102篇 |
1975年 | 81篇 |
1974年 | 92篇 |
1973年 | 68篇 |
排序方式: 共有4339条查询结果,搜索用时 15 毫秒
91.
92.
93.
94.
95.
96.
BackgroundOn January 2, 2020, the US Food and Drug Administration (FDA) released the electronic cigarette (e-cigarette) flavor enforcement policy to prohibit the sale of all flavored cartridge–based e-cigarettes, except for menthol and tobacco flavors.ObjectiveThis research aimed to examine the public perception of this FDA flavor enforcement policy and its impact on the public perception of e-cigarettes on Twitter.MethodsA total of 2,341,660 e-cigarette–related tweets and 190,490 FDA flavor enforcement policy–related tweets in the United States were collected from Twitter before (between June 13 and August 22, 2019) and after (between January 2 and March 30, 2020) the announcement of the FDA flavor enforcement policy. Sentiment analysis was conducted to detect the changes in the public perceptions of the policy and e-cigarettes on Twitter. Topic modeling was used for finding frequently discussed topics about e-cigarettes.ResultsThe proportion of negative sentiment tweets about e-cigarettes significantly increased after the announcement of the FDA flavor enforcement policy compared with before the announcement of the policy. In contrast, the overall sentiment toward the FDA flavor enforcement policy became less negative. The FDA flavor enforcement policy was the most popular topic associated with e-cigarettes after the announcement of the FDA flavor enforcement policy. Twitter users who discussed about e-cigarettes started to talk about other alternative ways of getting e-cigarettes after the FDA flavor enforcement policy.ConclusionsTwitter users’ perceptions of e-cigarettes became more negative after the announcement of the FDA flavor enforcement policy. 相似文献
97.
98.
Kaposi肉瘤的治疗应依据不同临床类型,制定个体化方案.常用治疗方法有电化学疗法、放疗、物理治疗(如硝酸银、液氮冷冻、弹力长筒袜)和皮损内注射等,适用于经典型Kaposi肉瘤及其他类型Kaposi肉瘤的皮肤损害.常用治疗药物有足叶乙甙、紫杉醇、阿霉素、雷帕霉素、吉西他滨等,适用于各型Kaposi肉瘤.Kaposi肉瘤的治疗尚缺乏标准化指南,以上治疗远期疗效欠佳.目前,新治疗靶标的研究主要集中在阻止成瘤过程、炎症调控、阻止病毒复制、细胞周期的调控等方面. 相似文献
99.
I.James Sarfeh 《American journal of surgery》1981,142(4):511-513
Portacaval and mesocaval interposition shunts using vascular prosthetic grafts were compared in 37 cirrhotic patients without portal vein thrombosis who were operated on for previous or active variceal hemorrhage. Operative indications and severity of liver disease were similar in the two groups of patients having one or the other procedure. The major difference in results was that none of the 23 patients with portacaval H-graft shunts had rebleeding, while 4 of 14 had rebleeding from varices after mesocaval interposition shunting. This contributed to the higher operative mortality associated with the latter procedure. The index of operative difficulty, as judged by blood loss and length of operation, and postshunt encephalopathy rates were similar for both procedures. Thus, while the mesocaval interposition shunt offers none of the reported theoretical advantages over portacaval H-graft shunt, it does place patients at greater risk of postoperative variceal rehemorrhage. It is concluded that the portacaval interposition shunt, because of its effectiveness and technical expediency, may be the operation of choice in cirrhotic patients with bleeding varices who are not otherwise candidates for other procedures which reduce portal flow less drastically. 相似文献
100.