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   4950篇
  免费   387篇
  国内免费   131篇
耳鼻咽喉   771篇
儿科学   37篇
妇产科学   29篇
基础医学   438篇
口腔科学   405篇
临床医学   305篇
内科学   392篇
皮肤病学   47篇
神经病学   465篇
特种医学   146篇
外国民族医学   1篇
外科学   727篇
综合类   605篇
预防医学   237篇
眼科学   47篇
药学   425篇
  6篇
中国医学   177篇
肿瘤学   208篇
  2024年   8篇
  2023年   67篇
  2022年   171篇
  2021年   174篇
  2020年   153篇
  2019年   171篇
  2018年   151篇
  2017年   191篇
  2016年   187篇
  2015年   195篇
  2014年   336篇
  2013年   366篇
  2012年   290篇
  2011年   319篇
  2010年   282篇
  2009年   263篇
  2008年   256篇
  2007年   231篇
  2006年   227篇
  2005年   179篇
  2004年   171篇
  2003年   148篇
  2002年   121篇
  2001年   90篇
  2000年   101篇
  1999年   77篇
  1998年   83篇
  1997年   64篇
  1996年   70篇
  1995年   36篇
  1994年   37篇
  1993年   34篇
  1992年   30篇
  1991年   15篇
  1990年   15篇
  1989年   12篇
  1988年   18篇
  1987年   17篇
  1986年   16篇
  1985年   20篇
  1984年   14篇
  1983年   8篇
  1982年   6篇
  1981年   13篇
  1980年   11篇
  1979年   9篇
  1978年   6篇
  1977年   2篇
  1976年   3篇
  1974年   2篇
排序方式: 共有5468条查询结果,搜索用时 0 毫秒
101.
Aims To evaluate the long term results of tongue base reduction with hyoepiglottoplasty as a surgical option in the treatment of severe obstructive sleep apnea. Material and Method Severe obstructive sleep apnea patients diagnosed as upper airway narrowing at the tongue base level were treated with transcervical tongue base reduction with hyoepiglottoplasty. Seven years after single stage multilevel surgery, the patients were reevaluated clinically, radiologically and polysomnographic records were taken. Preoperative, early postoperative and long-term postoperative parameters were compared to determine the success rate of the surgical technique. Results In the postoperative long-term follow-up Epworth sleepiness scale (ESS) scores were reduced to 4 and 6 respectively 2 months after surgery despite the initial values of 17 and 15. BMI were decreased from 29.7 and 27.9 kg/m2 respectively to 26 and 24 kg/m2. The apnea/hypopnea index (AHI) were reduced to 14.1 and 16.2 respectively from 68.6 and 83.83. O2 nadir was 55 and 66% respectively and improved to 86 and 89%. Flexible nasopharyngoscopy revealed competent airway in both retropalatal and retroglossal level. Bed partners scored snoring as 2/10 and 4/10 corresponding to very mild and moderate. Daytime somnolence and witnessed apneic periods were completely disappeared in both patients. Conclusion Open tongue base resection with hyoepiglottoplasty is effective among all other surgical corrections of sleep apnea even after 7 years postoperatively.  相似文献   
102.
针对平原型生活垃圾填埋场的设计,以浙江省嘉善县生活垃圾填埋场二期工程为例,从地下水位、地基承载力、土方平衡等方面介绍了库区基底高程、环库区垃圾堤坝顶高程、垃圾堆体顶高程这3个关键参数的确定过程.  相似文献   
103.

Background

The effect of time and temperature on beta‐2 transferrin stability in cerebrospinal fluid (CSF) is not well established. After collecting nasal CSF for testing, beta‐2 transferrin has been found to be stable and detectable for 1 week, whether being refrigerated or stored at room temperature. The purpose of this study was to determine if beta‐2 transferrin remained detectable longer than 1 week and whether refrigeration improved its detectability.

Methods

In patients undergoing therapeutic CSF diversion, 2‐mL CSF samples were collected from 18 patients. The samples were divided and stored either at room temperature, or at 4°C, and tested for beta‐2 transferrin at 7 and 14 days. CSF was collected from external ventricular drains (EVDs) (n = 15), lumbar drains (n = 2), and subdural drains (n = 1).

Results

Of the 18 CSF samples originally testing positive for beta‐2 transferrin, none turned negative at 7 or 14 days, in both the refrigerated and room temperature groups (95% confidence interval [CI], 0% to 18.5%).

Conclusion

Beta‐2 transferrin remained detectable for 14 days in all CSF samples, regardless of being stored at 4°C or room temperature.
  相似文献   
104.

Essentials

  • Emerging evidence shows that patients with liver disease are not protected from thrombotic events.
  • We assessed the risk of venous thromboembolism (VTE) in patients with liver disease.
  • The presence of VTE resulted in an increase in mortality for patients with liver disease.
  • Hospitalized patients with moderate‐severe liver disease had low risk of VTE during admission.

Summary

Background and Aims

Patients with liver disease were traditionally believed to be protected against development of blood clots, but some studies have shown a potential increased risk of venous thrombotic complications. We assessed the risk of venous thromboembolism (VTE) in patients with liver disease.

Methods

Data in discharge reports of patients with liver disease and control patients without liver disease were analyzed from the national inpatient sample. Incidence of VTE was compared in patients with mild, moderate‐severe or no liver disease, and the impact on in‐hospital mortality and length of stay was calculated.

Results

The overall incidence of VTE for patients with no liver disease, mild liver disease and moderate‐severe liver disease was 2.7, 2.4 and 0.9 per 100 patient discharges, respectively. In the presence of VTE, in‐hospital mortality was 10.8%, 5.8%, and 21.7% for the no liver disease, mild disease and moderate‐severe liver disease, respectively. The presence of VTE resulted in an increase in mortality for patients with no liver disease (OR, 1.16; 95% CI, 1.14–1.18) and moderate‐severe liver disease (OR, 1.63; CI 95%, 1.42–1.88).

Conclusions

Patients with moderate‐severe liver disease have a lower risk of VTE than those without liver disease. Development of thrombosis during admission increased the risk of in‐hospital mortality.
  相似文献   
105.
目的了解我国医学知识库的研究现状和成果,展望国内医学知识库研究的发展趋势。方法检索21世纪以来中国知网(CNKI)、万方医学网、重庆维普全文数据库等国内主要文献数据库刊载的医学知识库研究文献,从文献发表时间、文献研究领域、文献研究内容、研究类型4个方面进行计量分析。结果文献数量基本保持递增趋势;研究领域与内容逐渐深入拓展;在实际研究中,以应用研究为主导。结论医学知识库在我国属于新兴研究领域,其研究仍是未来学术界关注的热点。  相似文献   
106.
目的厚朴酚性成分具有杀菌、消炎、燥湿、止痒等作用,通过制备乳膏对其提取物进行开发利用。方法根据厚朴酚、和厚朴酚的特点及乳膏基质的特点,筛选处方组成,并对制备工艺进行研究,通过对乳膏的外观性状、透皮、稠度和稳定性等指标进行考察,筛选最佳的处方组成,并制备厚朴乳膏。结果由该比例的组成制备的厚朴乳膏,重现性好,乳膏色泽较纯正,均匀细腻,稠度适宜,易涂布,稳定性好、透皮吸收等均较好,可以作为最佳配比来制备厚朴乳膏。结论厚朴乳膏可以作为一种新制剂进行开发利用。  相似文献   
107.
Structured training in endonasal endoscopic sinus surgery (EESS) and skull base surgery is essential considering serious potential complications. We have developed a detailed concept on training these surgical skills on the lamb’s head. This simple and extremely cheap model offers the possibility of training even more demanding and advanced procedures in human endonasal endoscopic surgery such as: frontal sinus surgery, orbital decompression, cerebrospinal fluid-leak repair followed also by the naso-septal flap, etc. Unfortunately, the sphenoid sinus surgery cannot be practiced since quadrupeds do not have this sinus. Still, despite this anatomical limitation, it seems that the lamb’s head can be very useful even for the surgeons already practicing EESS, but in a limited edition because of a lack of the experience and dexterity. Only after gaining the essential surgical skills of this demanding field it makes sense to go for the expensive trainings on the human cadaveric model.  相似文献   
108.
BACKGROUND & AIMS: Hepatic production and release of endothelin 1 plays a central role in experimental hepatopulmonary syndrome after common bile duct ligation by stimulating pulmonary endothelial nitric oxide production. In thioacetamide-induced nonbiliary cirrhosis, hepatic endothelin 1 production and release do not occur, and hepatopulmonary syndrome does not develop. However, the source and regulation of hepatic endothelin 1 after common bile duct ligation are not fully characterized. We evaluated the sources of hepatic endothelin 1 production after common bile duct ligation in relation to thioacetamide cirrhosis and assessed whether transforming growth factor beta1 regulates endothelin 1 production. METHODS: Hepatopulmonary syndrome and hepatic and plasma endothelin 1 levels were evaluated after common bile duct ligation or thioacetamide administration. Cellular sources of endothelin 1 were assessed by immunohistochemistry and laser capture microdissection of cholangiocytes. Transforming growth factor beta1 expression and signaling were assessed by using immunohistochemistry and Western blotting and by evaluating normal rat cholangiocytes. RESULTS: Hepatic and plasma endothelin 1 levels increased and hepatopulmonary syndrome developed only after common bile duct ligation. Hepatic endothelin 1 and transforming growth factor beta1 levels increased over a similar time frame, and cholangiocytes were a major source of each peptide. Transforming growth factor beta1 signaling in cholangiocytes in vivo was evident by increased phosphorylation and nuclear localization of Smad2, and hepatic endothelin 1 levels correlated directly with liver transforming growth factor beta1 and phosphorylated Smad2 levels. Transforming growth factor beta1 also stimulated endothelin 1 promoter activity, expression, and production in normal rat cholangiocytes. CONCLUSIONS: Cholangiocytes are a major source of hepatic endothelin 1 production during the development of hepatopulmonary syndrome after common bile duct ligation, but not in thioacetamide-induced cirrhosis. Transforming growth factor beta1 stimulates cholangiocyte endothelin 1 expression and production. Cholangiocyte-derived endothelin 1 may be an important endocrine mediator of experimental hepatopulmonary syndrome.  相似文献   
109.
目的 评价国家一类新药盐酸关附甲素(GFA)注射液治疗室性心律失常的疗效和安全性.进一步评价较长时间用药的疗效及安全性.方法 随机开放多中心阳性药对照试验,由全国5个中心完成.入选不伴严重器质性心脏病的频发室性期前收缩(用动态心电图评价)病人,室性期前收缩平均每小时≥150次,伴或不伴短阵室性心动过速.采用3:1随机对照使用GFA或盐酸普罗帕酮.采用静脉负荷加维持量的方法维持6 h.GFA组6 h取得疗效者延长用药至24 h.用药前一天和用药日均进行24 h动态心电图及心电监测进行疗效评价.监测生命体征、心电图及观察不良事件.结果 共入选200例病人,用药前二组患者基线资料相匹配.减少室性期前收缩的疗效有高于盐酸普罗帕酮(分别为66.9%;54.5%)的趋势.总有效率GFA组与盐酸普罗帕酮组无统计学差异.GFA抑制室性期前收缩的程度以及控制室性期前收缩的作用出现时间好于及早于盐酸普罗帕酮组.GFA较长时间用药可使疗效提高,耐受性较好.结论 GFA控制室性心律失常安全有效,其疗效相当于盐酸普罗帕酮,较长时间用药耐受性较好.  相似文献   
110.
Increased germ cell apoptosis is related to oxidative DNA damage; therefore, we investigated whether there was a significant change in apurinic/apyrimidinic endonuclease (APE) in varicoceles. Experimental varicoceles were created by partial ligation of the left renal vein of adult male Sprague-Dawley rats, which were sacrificed at 1, 3 and 6 weeks after varicocele creation. Testicular tissues were sampled for TUNEL, Western blotting and immunohistochemistry. There was a significant increase in apoptotic germ cells in the ipsilateral testes 6 weeks after varicocele creation. Increased activation of p53, Bax and cleaved caspase-3 in the left testes was also noted. APE increased activation until 3 weeks after varicocele creation, and then decreased at 6 weeks after varicocele surgery. The spermatocytes were immunostained for both 8-hydroxy-2′-deoxyguanosine and APE, but the spermatogonia revealed only APE immunopositivity in the defective tubules. These results suggest that repression of APE is an underlying mechanism of augmented p53-dependent apoptosis in varicocele-induced rat testes and that remaining APE in the spermatogonia plays a decisive role in regaining testicular spermatogenic function after varicocelectomy.  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