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   54861篇
  免费   5917篇
  国内免费   2433篇
耳鼻咽喉   478篇
儿科学   454篇
妇产科学   544篇
基础医学   6443篇
口腔科学   1775篇
临床医学   5066篇
内科学   6158篇
皮肤病学   562篇
神经病学   3807篇
特种医学   1956篇
外国民族医学   2篇
外科学   5335篇
综合类   10223篇
现状与发展   6篇
一般理论   2篇
预防医学   7602篇
眼科学   1070篇
药学   5889篇
  74篇
中国医学   3386篇
肿瘤学   2379篇
  2024年   310篇
  2023年   1140篇
  2022年   2262篇
  2021年   2714篇
  2020年   2335篇
  2019年   1857篇
  2018年   1817篇
  2017年   2102篇
  2016年   1999篇
  2015年   2145篇
  2014年   3398篇
  2013年   4043篇
  2012年   3277篇
  2011年   3733篇
  2010年   2943篇
  2009年   3027篇
  2008年   2984篇
  2007年   3039篇
  2006年   2601篇
  2005年   2374篇
  2004年   1875篇
  2003年   1658篇
  2002年   1212篇
  2001年   1103篇
  2000年   1000篇
  1999年   826篇
  1998年   640篇
  1997年   594篇
  1996年   504篇
  1995年   475篇
  1994年   452篇
  1993年   354篇
  1992年   343篇
  1991年   272篇
  1990年   261篇
  1989年   216篇
  1988年   177篇
  1987年   175篇
  1986年   140篇
  1985年   178篇
  1984年   131篇
  1983年   86篇
  1982年   82篇
  1981年   78篇
  1980年   69篇
  1979年   57篇
  1978年   38篇
  1977年   34篇
  1976年   34篇
  1974年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
目的 研究主、被动最大张口度(AMMO、PMMO)与颞下颌关节强直严重程度的关系。方法 选取28只健康雄性绵羊随机分为实验组和对照组,每组各14只。实验组绵羊双侧颞下颌关节模拟髁突矢状骨折,其中左侧翼外肌被切断以阻断其功能;对照组绵羊未进行手术。于术前及术后12、24周对所有绵羊体重、AMMO、PMMO、颞下颌关节形态学特点进行测量评估。结果 实验组只有右侧保留翼外肌功能的颞下颌关节发生了骨强直。术后12、24周,实验组绵羊AMMO、PMMO、极限距离均显著低于对照组,差异均有统计学意义(均P < 0.05)。实验组绵羊AMMO和PMMO与骨融合区宽度、长度、面积及钙化程度均呈负相关(均P < 0.05),其中骨融合区面积为主要影响因素(术后12、24周相关系数r分别为-0.94、-0.95)。结论 颞下颌关节强直动物模型中阻断翼外肌功能可阻止骨强直的发生;对于早期髁突矢状骨折,可通过牙合垫或牙合板进行张口训练,进而阻断翼外肌功能。当颞下颌关节发生骨强直时,骨融合区面积越大,张口受限越明显。  相似文献   
12.
Esophageal adenocarcinoma is the fastest rising cancer in the United States. It develops from long‐standing gastroesophageal reflux disease which affects >20% of the general population. It carries a very poor prognosis with 5‐year survival <20%. The disease is known to sequentially progress from reflux esophagitis to a metaplastic precursor, Barrett''s esophagus and then onto dysplasia and esophageal adenocarcinoma. However, only few patients with reflux develop Barrett''s esophagus and only a minority of these turn malignant. The reason for this heterogeneity in clinical progression is unknown. To improve patient management, molecular changes which facilitate disease progression must be identified. Animal models can provide a comprehensive functional and anatomic platform for such a study. Rats and mice have been the most widely studied but disease homology with humans has been questioned. No animal model naturally simulates the inflammation to adenocarcinoma progression as in humans, with all models requiring surgical bypass or destruction of existing antireflux mechanisms. Valuable properties of individual models could be utilized to holistically evaluate disease progression. In this review paper, we critically examined the current animal models of Barrett''s esophagus, their differences and homologies with human disease and how they have shaped our current understanding of Barrett''s carcinogenesis.  相似文献   
13.
BackgroundTheoretical models argue that coping reduces stress responses, yet no studies have tested whether coping moderates the prospective stress effects on sleep in daily life.PurposeThis study tested if coping moderates the stress-sleep association using a daily, intensive longitudinal design across 7–12 days.Methods326 young adults (Mage = 23.24 ± 5.46) reported perceived stress and coping (problem-focused, emotional-approach, and avoidance) every evening between 20:00–02:00, providing over 2400 nights of sleep data and 3000 stress surveys from all participants. Actigraphy and sleep diaries measured total-sleep-time and sleep efficiency. Multilevel models tested the interaction effects of within- and between-person stress and coping on sleep.ResultsWithin-person problem-focused and emotional-approach coping moderated the within-person stress effects on actigraphic total-sleep-time (both p = 0.02); higher stress predicted shorter total-sleep-time only during high use of problem-focused or emotional-approach coping (both p = 0.01). Between-person avoidance moderated the between-person stress effect on actigraphic total-sleep-time (p = 0.04); higher stress predicted shorter total-sleep-time for high avoidance coping (p = 0.02). Within-person emotional-approach coping buffered the between-person stress effect on actigraphic sleep efficiency (p = 0.02); higher stress predicted higher sleep efficiency for high emotional-approach coping (p = 0.04).ConclusionsThis study showed that daily coping moderates the effects of evening stress on sleep that night. More efforts to cope with stress before bedtime had a short-term cost of shorter sleep that night. However, high use of emotional-approach coping buffered the impact of stress to promote sleep efficiency.  相似文献   
14.
Objective: Keyes’ two continua model is a useful concept in which mental health and mental illness exist on two separate axes. Based on this model, this study examined the prevalence and correlates of three mental health categories among older adults in China.

Methods: Cross-sectional data were derived from Wave 1 of the Study on Global AGEing and Adult Health. Participants were categorized into complete mental health (CMH), complete mental illness (CMI), and moderate mental health (MMH) groups. Multinomial logistic regressions were used.

Results: The prevalence of CMH, CMI, and MMH in China was 18%, 16%, and 66%, respectively. Being female, unmarried, younger, and feeling unhealthy were more likely to result in placement in the CMI category. Employment, education, and cognitive function were identified as important protective factors of CMH. Age, income, urban or rural residence, and physical function difficulty were associated with all three categories.

Discussion: We demonstrated the utility of the two continua model in identifying mental health needs in Chinese contexts. The findings suggest that future policy reforms and clinical interventions should establish a more comprehensive mental health category as a screening tool nationwide. The promotion of social engagement could play an important role in treating mental illness and improving positive mental health.  相似文献   

15.
The aim of the present study was to evaluate the antimicrobial activity of two synbiotic combinations, Lactobacillus fermentum with short-chain fructooligosaccharides (FOS-LF) and Bifidobacterium longum with isomaltooligosaccharides (IMO-BL), against enterohaemorrhagic Escherichia coli O157:H7 and enteropathogenic E. coli O86. Antimicrobial activity was determined (1) by co-culturing the synbiotics and pathogens in batch cultures, and (2) with the three-stage continuous culture system (gut model), inoculated with faecal slurry from an elderly donor. In the co-culture experiments, IMO-BL was significantly inhibitory to both E. coli strains, while FOS-LF was slightly inhibitory or not inhibitory. Factors other than acid production appeared to play a role in the inhibition. In the gut models, both synbiotics effectively inhibited E. coli O157 in the first vessel, but not in vessels 2 and 3. E. coli O86 was not significantly inhibited.  相似文献   
16.
目的观察比较不同脉冲波形的低频率电刺激对海马电点燃癫痫模型小鼠的作用差异。方法采用电点燃刺激法建立小鼠癫痫模型, 观察正弦波、单相方波、双相方波低频率电刺激对模型小鼠癫痫行为发作及后放电持续时间的影响, 并比较不同时间点给予正弦波低频率电刺激的抗癫痫作用。结果与对照组比较, 正弦波低频率电刺激30 s能降低小鼠海马电点燃癫痫发作等级(2.85 ± 0.27 vs 4.75 ±0.12, P < 0.05)、减少大发作概率(53.6% vs 96.5%, P < 0.01) 和缩短后放电持续时间[(16.22 ± 1.69) s vs (30.29 ± 1.12) s, P < 0.01], 而单相方波和双相方波低频率电刺激30 s没有明显的抗癫痫作用。常用的单相方波低频率电刺激15 min能降低小鼠海马电点燃发作等级(3.58 ± 0.16, P < 0.05)、减少大发作概率(66.7%, P < 0.01);但对海马后放电持续时间及大发作持续时间无影响(均 P>0.05)。此外, 电点燃刺激前预先给予或结束后3 s内给予正弦波低频率电刺激具有明显的抗癫痫作用( P < 0.05或 P < 0.01), 而电点燃刺激结束10 s给予正弦波低频率电刺激则无上述抗癫痫作用。 结论低频率电刺激抗癫痫作用受波形参数的影响, 其中正弦波低频率电刺激能有效抑制小鼠海马电点燃癫痫的发作。  相似文献   
17.
18.
19.
20.
《Vaccine》2022,40(28):3851-3860
We propose a probabilistic model to quantify the cost-benefit of mass Vaccination Scenarios (VSs) against COVID-19. Through this approach, we conduct a six-month simulation, from August 31st, 2021 to March 3rd, 2022, of nine VSs, i.e., the three primary vaccine brands in Brazil (CoronaVac, AstraZeneca and Pfizer), each with three different vaccination rates (2nd doses per week). Since each vaccine has different individual-level effectiveness, we measure the population-level benefit as the probability of reaching herd immunity (HI). We quantify and categorize the cost-benefit of VSs through risk graphs that show: (i) monetary cost vs. probability of reaching HI; and (ii) number of new deaths vs. probability of reaching HI. Results show that AstraZeneca has the best cost-benefit when prioritizing acquisition costs, while Pfizer is the most cost-beneficial when prioritizing the number of deaths. This work provides helpful information that can aid public health authorities in Brazil to better plan VSs. Furthermore, our approach is not restricted to Brazil, the COVID-19 pandemic, or the mentioned vaccine brands. Indeed, the method is flexible so that this study can be a valuable reference for future cost-benefit analyses in other countries and pandemics, especially in the early stages of vaccination, when data is scarce and uncertainty is high.  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