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   1257687篇
  免费   79081篇
  国内免费   1739篇
耳鼻咽喉   18027篇
儿科学   41066篇
妇产科学   32977篇
基础医学   178829篇
口腔科学   35210篇
临床医学   109101篇
内科学   237615篇
皮肤病学   29270篇
神经病学   98171篇
特种医学   51325篇
外国民族医学   224篇
外科学   192989篇
综合类   22835篇
现状与发展   1篇
一般理论   324篇
预防医学   84290篇
眼科学   29323篇
药学   99052篇
  7篇
中国医学   3258篇
肿瘤学   74613篇
  2021年   9449篇
  2019年   9606篇
  2018年   14994篇
  2017年   11834篇
  2016年   13826篇
  2015年   15239篇
  2014年   19589篇
  2013年   28597篇
  2012年   40568篇
  2011年   42664篇
  2010年   24531篇
  2009年   22019篇
  2008年   39396篇
  2007年   42526篇
  2006年   42978篇
  2005年   41655篇
  2004年   39867篇
  2003年   38358篇
  2002年   36993篇
  2001年   65379篇
  2000年   66793篇
  1999年   55426篇
  1998年   13890篇
  1997年   12228篇
  1996年   11938篇
  1995年   11100篇
  1994年   10020篇
  1993年   9513篇
  1992年   39756篇
  1991年   38112篇
  1990年   37557篇
  1989年   35989篇
  1988年   32367篇
  1987年   31519篇
  1986年   29622篇
  1985年   27771篇
  1984年   20247篇
  1983年   16998篇
  1982年   9457篇
  1979年   18188篇
  1978年   12266篇
  1977年   10940篇
  1976年   9523篇
  1975年   10954篇
  1974年   12608篇
  1973年   12178篇
  1972年   11650篇
  1971年   10938篇
  1970年   10038篇
  1969年   9668篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
In light of the pharmacophoric structural requirements for achieving anticonvulsant activity, a series of N-(1-methyl-4-oxo-2-un/substituted-1,2-dihydroquinazolin-3[4H]-yl)benzamide (4a-g) and N-(1-methyl-4-oxo-2-un/substituted-1,2-dihydroquinazolin-3[4H]-yl)-2-phenylacetamide (4h-n) derivatives were synthesized in two steps starting from the reaction of N-methyl isatoic anhydride with the appropriate hydrazide and followed by condensation with the appropriate aldehyde. The anticonvulsant activities of the synthesized compounds were evaluated according to the anticonvulsant drug development (ADD) programme protocol. Among the synthesized compounds, 4n showed promising activity in both the maximal electroshock (MES) and pentylenetetrazole (PTZ) tests with median effective dose (ED50) values of 40.7 and 6 mg/kg, respectively. The six most promising derivatives, 4b , 4a , 4c , 4f , 4j , and 4i , showed very low ED50 values in the PTZ test (3.1, 4.96, 8.68, 9.89, 12, and 13.53 mg/kg, respectively). All the tested compounds showed no to low neurotoxicity in the rotarod test with a wide therapeutic index. Docking studies of compound 4n suggested that GABAA binding could be the mechanism of action of these derivatives. The in silico drug likeliness parameters indicated that none of the designed compounds violate Lipinski's rule of five and that they are able to cross the blood–brain barrier.
Hit, Lead & Candidate Discovery
  相似文献   
84.
Background and Aims: Gastric antral vascular ectasia (GAVE) is commonly found in patients with cirrhosis, but it is also associated with other diseases in the absence of cirrhosis. Whether GAVE confers a different severity of gastrointestinal (GI) bleeding between patients with and without cirrhosis remains unknown. We aim to examine whether there is a difference in clinically significant GI bleeding due to GAVE in patients with or without cirrhosis. Methods: This is a retrospective case-control study of patients who were diagnosed with GAVE between January 2000 and June 2014. Patients were categorized into cirrhosis and noncirrhosis groups, and those with an additional GI bleeding source were excluded. Univariate comparisons and multivariable models were constructed using logistic regression. Results: In total, 110 patients diagnosed with GAVE on esophagogastroduodenoscopy (EGD) were included in our analysis; 84 patients had cirrhosis (76.4%) and 26 (23.6%) did not. Active GI bleeding was more prevalent in patients without cirrhosis (63.4% vs. 32.1%, p=0.003) despite similar indications for EGD, and endoscopic treatment with argon plasma coagulation (APC) was required more often in this group, approaching statistical significance (27% vs. 10.7%, p=0.056). There was no difference in bleeding severity, as evidenced by similar re-bleeding rates, surgery, or death attributed to uncontrolled bleeding. The strongest independent risk factor for GI bleeding was the absence of cirrhosis (odds ratio (OR): 5.151 (95% confidence interval (CI): 1.08-24.48, p=0.039). Conclusions: Patients with GAVE in the absence of cirrhosis are at higher risk for active GI bleeding and require more frequent endoscopic treatment than similar patients with cirrhosis. It may be worthwhile to treat GAVE in this population even in the absence of active bleeding.  相似文献   
85.
86.
87.
88.
89.

Background

Physicians treating nonvalvular atrial fibrillation (AF) assess stroke and bleeding risks when deciding on anticoagulation. The agreement between empirical and physician-estimated risks is unclear. Furthermore, the association between patient and physician sex and anticoagulation decision-making is uncertain.

Methods

We pooled data from 2 national primary care physician chart audit databases of patients with AF (Facilitating Review and Education to Optimize Stroke Prevention in Atrial Fibrillation and Coordinated National Network to Engage Physicians in the Care and Treatment of Patients with Atrial Fibrillation Chart Audit) with a combined 1035 physicians (133 female, 902 male) and 10,927 patients (4567 female and 6360 male).

Results

Male physicians underestimated stroke risk in female patients and overestimated risk in male patients. Female physicians estimated stroke risk well in female patients but underestimated the risk in male patients. Risk of bleeding was underestimated in all. Despite differences in risk assessment by physician and patient sex, > 90% of patients received anticoagulation across all subgroups. There was modest agreement between physician estimated and calculated (ie, CHADS2 score) stroke risk: Kappa scores were 0.41 (0.35-0.47) for female physicians and 0.34 (0.32-0.36) for male physicians.

Conclusions

Our study is the first to examine the association between patient and physician sex influences and stroke and bleeding risk estimation in AF. Although there were differences in agreement between physician estimated stroke risk and calculated CHADS2 scores, these differences were small and unlikely to affect clinical practice; further, despite any perceived differences in the accuracy of risk assessment by sex, most patients received anticoagulation.  相似文献   
90.
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