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   233084篇
  免费   15779篇
  国内免费   5375篇
耳鼻咽喉   1691篇
儿科学   3539篇
妇产科学   4124篇
基础医学   29210篇
口腔科学   4541篇
临床医学   22482篇
内科学   31522篇
皮肤病学   2835篇
神经病学   15189篇
特种医学   10764篇
外国民族医学   12篇
外科学   19289篇
综合类   30951篇
现状与发展   23篇
一般理论   8篇
预防医学   17715篇
眼科学   3447篇
药学   27988篇
  79篇
中国医学   13752篇
肿瘤学   15077篇
  2024年   537篇
  2023年   3034篇
  2022年   6608篇
  2021年   8936篇
  2020年   7596篇
  2019年   7301篇
  2018年   7382篇
  2017年   7913篇
  2016年   7933篇
  2015年   7678篇
  2014年   9515篇
  2013年   13864篇
  2012年   11210篇
  2011年   13482篇
  2010年   9091篇
  2009年   9170篇
  2008年   10991篇
  2007年   12041篇
  2006年   11389篇
  2005年   10563篇
  2004年   9147篇
  2003年   8123篇
  2002年   6674篇
  2001年   6098篇
  2000年   5110篇
  1999年   4364篇
  1998年   3629篇
  1997年   3718篇
  1996年   3396篇
  1995年   3053篇
  1994年   2834篇
  1993年   2352篇
  1992年   2134篇
  1991年   1961篇
  1990年   1671篇
  1989年   1390篇
  1988年   1304篇
  1987年   1174篇
  1986年   1067篇
  1985年   1553篇
  1984年   1200篇
  1983年   898篇
  1982年   967篇
  1981年   778篇
  1980年   733篇
  1979年   576篇
  1978年   386篇
  1977年   340篇
  1976年   324篇
  1975年   214篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Inthistwoyears,westudiedonCVAofchronicpulmonaryheartdiseaseandpulmonaryheartdiseasepatients,andfoundmanyCVAindexofthesepatientswereabnormal,andwereinfluencedbymanyfactors.Thechangeofpulmonaryheartdiseaseasfollowing.1Subjectsandmethods1.1Subjects32caseswerefromin-patientsofourhospital,in-cluding30malesand2females,age64~82,averageage(72±8).Thediagnosisofpulmonaryheartdiseaseaccordedwiththecriteriainstitutedonthesecondpulmonaryheartdiseasespecialmeetingin1997…  相似文献   
73.
74.
Summary The prevalence of smoking, hypertension and diabetes mellitus was assessed in 221 patients suffering from internal carotid stenosis and compared with the prevalences in two sex- and age-matched control groups composed of subjects having normal Doppler findings and from non-neurological outpatients. Of the subjects with carotid stenosis 27.6% were hypertensive smokers in comparison with 9.5% and 17.2% in the two control groups. The difference of the stenosis cohort from the two control groups was significant (P<0.01 and P=0.016 respectively). There was no statistically significant differences between the occurrence of diabetes and hypertension in non-smokers and patients who smoked. In 394 investigated patients suffering from carotid stenosis or occlusion an obstruction index, based on the Doppler shift frequency, was calculated. This index was lowest in the normotentive non-smokers. It was only insignificantly higher in the hypertensive non-smokers but significantly so in the normotensive smokers. The index was highest in the hypertensive non-smokers. It was concluded that cigarette smoking, especially if associated with hypertension, is a determinant risk factor for carotid stenosis and occlusion.  相似文献   
75.
[(1R)‐endo]‐(+)‐3‐bromocamphor was dehalogenated with tritium gas to [3‐3H]camphor and via [3‐3H]phenylborneol converted to [3‐3H]deramciclane isolated as the fumarate salt (specific activity 51.8 GBq/mmol). This three step synthesis from [3‐3H]camphor gave an overall yield of 22%. Benzyloxy‐acetic acid methyl ester was reduced with sodium‐borotritide to 2‐benzyloxy‐ethanol‐[1‐3H], and through a four step procedure was converted to 2‐dimethylaminoethyl‐[2‐3H] chloride. The latter was condensed with the sodium derivative of 2‐phenylborneol giving rise to [2‐dimethylamino‐[2‐3H]ethoxy]deramciclane isolated as the fumarate (specific activity 8.177 GBq/mmol). This six step synthesis from [3H]NaBH4 gave an overall yield of 6%. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   
76.
目的探索以虚拟现实技术为基础的枢椎椎弓根螺钉置人方法。方法选取8具成人颅一颈椎标本,采用改良四柱式定位框架固定于枕颈,使颅-颈-肩形成统一刚体,保持空间位置恒定,CT薄层扫描获取枢椎三维定位信息,采用Aero—Tech立体定向手术规划系统三维建模,设计安全、可视化、个体化的虚拟置钉路径,反复虚拟演示验证钉道安全后,导向弓把持下置人导向钢针,复查CT评价置钉的准确性。结果16个枢椎椎弓根置钉过程中,方向出现偏差(横突孔突破)1个,失败率为6.25%。结论目标椎弓根的容积三维重建、置钉路径可视化设计和虚拟演示,使操作过程简单、直观而精确,不需要线形和角性参数的测量;加上导向抓持装置提供的稳定性,使该技术具有很好的临床应用前景。  相似文献   
77.
Background contextLarge, prominent osteophytes along the anterior aspect of the cervical spine have been reported as a cause of dysphagia. Improvement of swallowing after surgical resection has been reported in a few case reports with short-term follow-up. The current report describes outcomes of a series of five patients with surgical treatment for this rare disorder, with a long-term follow-up.PurposeTo study the clinical and radiographic outcomes of a case series of patients surgically treated for dysphagia secondary to cervical diffuse idiopathic skeletal hyperostosis (DISH).Study designRetrospective review of a case series.Patient sampleFive cases from a University Hospital.Outcome measuresClinical and imagenological follow-up.MethodsThe records of five patients with dysphagia who had undergone anterior surgical resection of prominent osteophytes secondary to DISH were reviewed. Extrinsic esophageal compression secondary to anterior cervical osteophytes was radiographically confirmed via preoperative barium esophagogram swallowing study. All patients underwent anterior cervical osteophytes resection without fusion. Postoperatively, patients were followed-up clinically and radiographically with routine lateral cervical radiographs.ResultsPreoperative esophagogram showed that the esophageal obstruction was present at one level in three cases and two levels in two cases. The C3–C4 level was involved in three cases, C4–C5 in three cases, and C5–C6 in one case. There were no postoperative complications, including recurrent laryngeal nerve palsy, wound infection, or hematomas. All patients had resolution of dyphagia soon after surgery (within 2 weeks). Postoperative radiographs demonstrated complete removal of osteophytes. At final follow-up, ranging from 1 to 9 years (average 59.8 months, median 53 months), no patients reported recurrence of dysphagia. Final radiographic examination demonstrated minimal regrowth of the osteophytes.ConclusionsAlthough rarely indicated, surgical resection of anterior cervical osteophytes from DISH causing dyphagia produces good clinical and radiographical outcomes. After thorough evaluation to rule out other intrinsic or extrinsic causes of swallowing difficulty, surgical treatment of this uncommon condition might be considered.  相似文献   
78.
Lesion evolution during focal cerebral ischemia may depend on flow restrictions or on accumulation of toxic mediators within the infarct and expansion of these factors to the periinfarct region. So far, the precise contribution of flow dependent versus spreading-mediated impairment of viable periinfarct tissue has not been determined. Therefore, we measured lesion expansion, flow restrictions and glutamate distribution on serial brain sections at different time points after experimental focal ischemia.Permanent focal ischemia was induced by occlusion of the right middle cerebral artery in male rats and the flow reduction was subsequently measured at 1, 12 and 24 h using iodo[14C]antipyrine autoradiography. Additionally, the necrotic volume was determined on serial brain sections and the glutamate content was measured in tissue samples from adjacent microdissections.Twelve hours after focal ischemia no noteworthy viable areas with blood flow restrictions of 20-40 ml 100 g− 1 min− 1 existed but at 24 h the necrotic tissue exceeded the hemodynamically compromised region by 40 ± 21 mm3 (24%). Furthermore, at 12 and 24 h the glutamate content was elevated in areas surrounding the infarct.Relevant flow restrictions are detectable only during early stages of infarct maturation, whereas the propagation of secondary factors may be the predominant mechanism for delayed infarct evolution.  相似文献   
79.
80.
Background/aims: The objective and quantitative assessment of the skin is important in medical and cosmeceutical research. Assessment of color is an important element for analyzing the surface of the skin, which is usually determined subjectively by a doctor or using color analysis devices. These devices, however, cannot provide correct color information because color is construed from the mean value of the observation region, and analysis of color distribution is impossible. The purpose of this paper is to develop an objective analysis method to permit skin color measurement of each pixel unit of an image and analyze the distribution of skin surface color. Methods: The Skin Color Distribution Analyzer (SCDA) is an analysis method newly developed at the Research Institute for Skin Image at Korea University. The SCDA system presented in this paper performed a novel form of quantitative and objective analysis of skin color distribution using each pixel color model parameter found in image wavelength information. In this paper, distribution analysis was conducted on normal skin and skin lesions and skin affected by artificially induced irritant contact dermatitis and pigmented nevous. The method selected a grade using a color model parameter. Twenty healthy Korean males participated in this study. A comparative study of the eight anatomical areas was performed, including the exposure and non‐exposure parts and the medial aspect and the lateral aspect of the forearm. A reliability test for the SCDA system was also conducted with a spectrometer (SPEC) using the color analysis method. Results: Each skin lesion was precisely segmented by grade and each parameter hada different statistical significance for results of analysis of distribution in pigmented nevous and the artificially induced irritant contact dermatitis. Parameters L*, b*, a*, and EI showed salient traits. Showed resemble measured result in the SCDA system and the SPEC of normal skin. The exposed site, in comparison with the non‐exposed site, showed a notable difference in the L* parameter and a significant statistical difference in the x and z parameters, except b*. The comparison of the medial and lateral aspects of the forearm showed a notable difference in the L* parameter and a significant statistical difference in the parameters except y and b*. In the reliability test result using the SCDA system and the SPEC, the SCDA system was highly reliabile in terms of the CV value in all color model parameters. Conclusions: The color distribution analysis method using the SCDA system has revealed an aspect that the existent method of medical research has not shown, and is considered to be more reliable than other methods. This method can provide better study findings because it can be applied to other fields in addition to the medical science field and the ripple effect is thought to be bigger in other science field too.  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