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   1548篇
  免费   102篇
  国内免费   25篇
耳鼻咽喉   1篇
儿科学   150篇
妇产科学   14篇
基础医学   148篇
口腔科学   68篇
临床医学   149篇
内科学   357篇
皮肤病学   40篇
神经病学   28篇
特种医学   330篇
外科学   94篇
综合类   22篇
预防医学   72篇
眼科学   24篇
药学   87篇
  1篇
中国医学   1篇
肿瘤学   89篇
  2021年   13篇
  2020年   8篇
  2019年   12篇
  2018年   23篇
  2017年   17篇
  2016年   23篇
  2015年   31篇
  2014年   26篇
  2013年   48篇
  2012年   10篇
  2011年   12篇
  2010年   40篇
  2009年   79篇
  2008年   19篇
  2007年   39篇
  2006年   38篇
  2005年   31篇
  2004年   22篇
  2003年   25篇
  2002年   20篇
  2001年   20篇
  2000年   22篇
  1999年   31篇
  1998年   102篇
  1997年   117篇
  1996年   113篇
  1995年   77篇
  1994年   82篇
  1993年   98篇
  1992年   18篇
  1991年   17篇
  1990年   19篇
  1989年   45篇
  1988年   39篇
  1987年   26篇
  1986年   32篇
  1985年   32篇
  1984年   17篇
  1983年   15篇
  1982年   19篇
  1981年   34篇
  1980年   20篇
  1979年   9篇
  1978年   9篇
  1977年   21篇
  1976年   19篇
  1959年   14篇
  1957年   10篇
  1955年   15篇
  1954年   10篇
排序方式: 共有1675条查询结果,搜索用时 46 毫秒
991.
目的通过对社区获得性肠杆菌肺炎与普通肺炎的临床对比研究,探讨社区获得性肠杆菌肺炎新的流行病学变化趋势及其特点。方法10例社区获得性肠杆菌肺炎与20例社区获得性普通肺炎进行配对研究,回顾性分析其临床特点、易患因素、病原学检查特点以及抗生素治疗特点。结果(1)社区获得性肠杆菌肺炎的临床症状、生化检查、胸部X线表现等无特殊性,两组病死率比较差异无显著性。(2)患有基础疾病者易发生社区获得性肠杆菌肺炎。(3)不适合抗生素使用时间的过度延长引起一个复杂的疾病过程,而适合抗生素使用的延迟未引起患者病死率的明显增加。结论(1)对因社区获得性肺炎住ICU的患者,如果具备年老,至少有一种基础疾病存在,有既往住院史,有既往抗菌素使用史等特点,应警惕社区获得性肠杆菌肺炎的可能。(2)对疑诊患者早期病原学检查有助于抗生素的合理的选择。  相似文献   
992.
Several studies have shown that the human papilloma virus (HPV) test is a more sensitive and objective primary cervical cancer screening tool than cytology. Therefore, conversion of cytology into HPV screening (as is planned in The Netherlands and some other European regions) will result in a better protection against cervical cancer and high-grade precursor lesions. Moreover, offering self-sampling for HPV testing will increase screening attendance by re-attracting former non-attendees. However, triage of HPV positive women is necessary because the specificity of HPV testing is 2–4% lower than of cytology. Several triage strategies have been evaluated, of which two, with cytology testing included, are feasible and were recently recommended. As an alternative for cytology triage, objective, non-morphological disease markers are upcoming and so far have shown promising results. Finally, HPV testing can also contribute to a more efficient monitoring of women treated for high-grade cervical precursor lesions, permitting fewer follow-up visits.  相似文献   
993.
广西藤茶中黄酮类成份的提取工艺研究   总被引:18,自引:0,他引:18  
目的:提取分离藤(Ampelosis grossdentata)中的双氢杨梅树皮素(dihydromyricetin)和杨梅素(Myricetin)。方法:采用新的水提取和溶剂分离的方法,经化学和光谱鉴定确定结构。结果:提取产物经确证为双氢杨梅树皮素(dihydromyricetin)和杨梅素(Myricetin),平均收率分别为19.6%和0.51%。结论:该提取法经济、简便,易于操作并且提取率  相似文献   
994.
995.

Background  

To date, online public healthcare reports have not been effectively used by consumers. Therefore, we qualitatively examined how healthcare consumers process and evaluate comparative healthcare information on the Internet.  相似文献   
996.

Background  

Many tuberculosis (TB) patients in Indonesia are diagnosed late. We seek to document patient journeys toward TB diagnosis and treatment and factors that influence health care seeking behavior.  相似文献   
997.
化学修饰为小干扰RNA(siRNA)治疗面临的诸多挑战提供了解决方法。此综述考察现有的各种siRNA修饰方法,包括RNA和双链siRNA结构的各个方面。然后考察化学修饰siRNA的应用,重点关注其作用的专一性(消除免疫反应和杂交依赖性的脱靶作用)和转运方法,同时对酶稳定性和效价也进行了讨论。  相似文献   
998.

Background and purpose:

Cyclooxygenase inhibitors function to reduce levels of prostaglandin E2 (PGE2) and are broadly efficacious in models of bladder overactivity. We therefore investigated a regulation of urinary bladder function in conscious rats by modulation of the EP3 receptor for PGE2.

Experimental approach:

The activity of the EP3 receptor agonist GR63799X, and EP3 receptor antagonists, CM9 and DG041, at recombinant EP3 receptors was evaluated in vitro. In vivo, intraduodenal dosing during conscious, continuous-filling cystometry of spontaneously hypertensive rats was utilized to determine the urodynamic effect of EP3 receptor modulation.

Key results:

GR63799X dose-dependently (0.001–1 mg·kg−1) reduced bladder capacity, as indicated by a reduction in both the micturition interval and volume of urine per void. In contrast, CM9 (10 and 30 mg·kg−1) and DG041 (30 mg·kg−1) enhanced bladder capacity, as indicated by significantly longer micturition intervals and larger void volumes. CM9 and DG041 inhibited the responses to GR63799X supporting the in vivo activity of these pharmacological agents at the EP3 receptor. In addition to its effect on bladder capacity, GR63799X increased endogenous urine production. Intra-arterial infusion of saline mimicked the enhancement of urine flow observed with GR63799X, and the response was inhibited by CM9.

Conclusions and implications:

These data support the EP3 receptor as a modulator of urinary bladder activity in the conscious rat, and in addition, indicate a role for EP3 receptor activity in regulating urine flow.  相似文献   
999.

Background and purpose:

Activation of cannabinoid (CB) receptors decreases nociceptive transmission in inflammatory or neuropathic pain states. However, the effects of CB receptor agonists in post-operative pain remain to be investigated. Here, we characterized the anti-allodynic effects of WIN 55,212-2 (WIN) in a rat model of post-operative pain.

Experimental approach:

WIN 55,212-2 was characterized in radioligand binding and in vitro functional assays at rat and human CB1 and CB2 receptors. Analgesic activity and site(s) of action of WIN were assessed in the skin incision-induced post-operative pain model in rats; receptor specificity was investigated using selective CB1 and CB2 receptor antagonists.

Key results:

WIN 55,212-2 exhibited non-selective affinity and agonist efficacy at human and rat CB1 versus CB2 receptors. Systemic administration of WIN decreased injury-induced mechanical allodynia and these effects were reversed by pretreatment with a CB1 receptor antagonist, but not with a CB2 receptor antagonist, given by systemic, intrathecal and supraspinal routes. In addition, peripheral administration of both CB1 and CB2 antagonists blocked systemic WIN-induced analgesic activity.

Conclusions and implications:

Both CB1 and CB2 receptors were involved in the peripheral anti-allodynic effect of systemic WIN in a pre-clinical model of post-operative pain. In contrast, the centrally mediated anti-allodynic activity of systemic WIN is mostly due to the activation of CB1 but not CB2 receptors at both the spinal cord and brain levels. However, the increased potency of WIN following i.c.v. administration suggests that its main site of action is at CB1 receptors in the brain.British Journal of Pharmacology (2009) 157, 645–655; doi:10.1111/j.1476-5381.2009.00184.x; published online 3 April 2009  相似文献   
1000.

BACKGROUND:

The myocardial extracellular matrix is believed to be central to the remodelling that takes place following myocardial infarction. The contribution of markers of collagen metabolism to this process remains less well understood. The present study examined the contribution of some of the markers of collagen metabolism in cardiac remodelling, as well as the effect of spironolactone on the remodelling process.

OBJECTIVES:

To investigate the pathological contribution of markers of collagen metabolism, including matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), type I collagen carboxyterminal telopeptide (ICTP) and procollagen type I carboxyterminal propeptide (PICP), in cardiac remodelling following ischemic cardiomyopathy, and to examine the pharmacoregulatory effects of spironolactone on collagen metabolism.

METHOD:

Eighty-six consecutive patients (62 men and 24 women) with chronic heart failure of ischemic etiology (patient group) and 25 age-matched controls were enrolled in the study. The subjects in the patient group were randomly assigned into a spironolactone or nonspironolactone group. Plasma levels of MMP-9, TIMP-1, ICTP and PICP were measured using ELISA and radioimmunoassay techniques. Furthermore, left ventricular diastolic diameter and ejection fraction were assessed using two-dimensional and Doppler echocardiography.

RESULTS:

The plasma concentrations of MMP-9, TIMP-1 and the MMP-9 to TIMP-1 ratio, as well as ICTP, were significantly increased in the patient group. The PICP to ICTP ratio in the patient group was significantly lower than that in the age-matched control subjects. After a follow-up period of 24 weeks, the PICP to ICTP ratio increased, and MMP-9, TIMP-1 and the MMP-9 to TIMP-1 ratio decreased in the spironolactone subgroup.

CONCLUSIONS:

Biomarkers of collagen degradation were elevated and correlated with depressed heart function; spironolactone may partially reverse the dysregulation in collagen metabolism.  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