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   13430篇
  免费   731篇
  国内免费   95篇
耳鼻咽喉   88篇
儿科学   227篇
妇产科学   124篇
基础医学   2151篇
口腔科学   98篇
临床医学   1377篇
内科学   3026篇
皮肤病学   357篇
神经病学   1330篇
特种医学   582篇
外科学   2028篇
综合类   50篇
一般理论   2篇
预防医学   663篇
眼科学   216篇
药学   931篇
中国医学   40篇
肿瘤学   966篇
  2023年   63篇
  2022年   84篇
  2021年   260篇
  2020年   154篇
  2019年   229篇
  2018年   322篇
  2017年   201篇
  2016年   238篇
  2015年   274篇
  2014年   376篇
  2013年   518篇
  2012年   915篇
  2011年   1031篇
  2010年   614篇
  2009年   545篇
  2008年   881篇
  2007年   1018篇
  2006年   915篇
  2005年   964篇
  2004年   902篇
  2003年   872篇
  2002年   851篇
  2001年   149篇
  2000年   112篇
  1999年   148篇
  1998年   213篇
  1997年   163篇
  1996年   162篇
  1995年   110篇
  1994年   112篇
  1993年   109篇
  1992年   97篇
  1991年   57篇
  1990年   47篇
  1989年   60篇
  1988年   49篇
  1987年   47篇
  1986年   51篇
  1985年   29篇
  1984年   46篇
  1983年   38篇
  1982年   42篇
  1981年   30篇
  1980年   34篇
  1979年   24篇
  1978年   19篇
  1977年   16篇
  1976年   10篇
  1975年   8篇
  1974年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
This case report illustrates atypical magnetic resonance (MR) imaging findings in a liver hemangioma mimicking a malignant lesion—lower signal intensity than cerebrospinal fluid on T2-weighted spin-echo images and lack of early enhancement on dynamic contrast material—enhanced gradient-echo images. Pathologic analysis demonstrated nearly total replacement of the vascular cavities by dense fibrous tissue. In this rare, sclerosed form, this lesion could not be defined as a hemangioma with MR imaging.  相似文献   
32.
Evaluative composite measurement scales (CMS) are increasingly used in medicine to measure complex constructs in the absence of a reference criterion or ‘gold standard’. However, the level of measurement provided by these instruments has usually been given little attention. This paper explores the influence of the characteristics of the item set and weighting on the level of measurment of an evaluative CMS. The approach is illustrated with an application to the scoring system of the Nottingham Health Profile. Simulations are provided to indicate when the composite score of item responses, on an ordinal or pass—fail scale, could be considered to achieve the properties of an interval scale.  相似文献   
33.
A 28-year-old mentally retarded, institutionalised woman was referred to us for evaluation of multiple plantar warts and ingrown nails of both great toes. The patient was born to unrelated parents of North African origin and had one brother and three half-brothers, all of whom were healthy. Physical examination revealed short stature, slight obesity, facial abnormalities (Fig. 1), short and broad thumbs and big toes (Figs. 2 and 3). A keloid was found on the right forearm, that had developed after surgical correction of a fracture (Fig. 4). Ill-defined hyperpigmented macules were observed on the trunk. The patient also presented pruritic eczematous lesions of the limbs and the back that had been present for some years and were recurrent despite treatment with emollients and local steroids. Androgenetic-type alopecia of moderate severity was seen on the vertex of the scalp. Past medical history included polydactylism of the feet and clinodactyly of the thumbs (both corrected surgically), respiratory tract infections, Wolf-Parkinson-White syndrome and refractive errors necessitating glasses.  相似文献   
34.
Purpose To determine the efficacy of a cystoscopic approach, as definitive treatment of ureteral fistulae, after failure of antegrade ureteral stent insertion.Methods Of 43 ureter fistulae encountered over 4 years, 10 postoperative and/or postradiotherapy fistulae could not be stented via an antegrade approach alone. A cystoscopic approach was used, with the antegrade approach available as back-up, if necessary.Results In two patients the ureteral orifice could not be visualized cystoscopically, thus precluding the retrograde approach. In the eight remaining patients, the retrograde approach alone never allowed successful stenting. In six patients, combined antegrade and retrograde approaches permitted stent insertions. In three of those six patients, a complex catheterization procedure was necessary. In two patients the combined approach failed altogether. Therefore, 6 of 10 patients underwent a successful stenting procedure with the combined approach; all ultimately closed the fistula.Conclusion Antegrade stent insertion remains the treatment of choice for ureteral leaks. If the antegrade approach fails, the retrograde approach alone is not likely to be successful. Instead, a combination of both approaches often does succeed.  相似文献   
35.
The polymerization of lactides with various D /L enantiomeric compositions using achiral Schiff's base/aluminium methoxide as initiator (SALENAlOCH3) in dichloromethane solution at 70°C is reported. The conversion was kept below 70% in order to limit transesterification reactions. The polymers obtained after precipitation show a narrow molecular weight distribution (ratio of weight- to number-average molecular weights M w/M n = 1,1–1,2) and an optical rotation higher than that expected from the optical purity of the starting monomers. The examination of the thermal properties reveals that whatever their enantiomeric composition all the prepared polymers are crystalline. This unusual behavior is explained by an end-chain propagation mechanism producing stereocopolymers with long enantiomeric sequences, i.e., increased isotacticity as substantiated by an examination of the microstructure of the polymers by means of 13C nuclear magnetic resonance. A stereocomplex formation was observed for stereocopolymers with optical purities below 40%.  相似文献   
36.
The diagnosis of nontraumatic intracranial hemorrhage is currently made by computed tomography and is rarely problematic. The causes of bleeding are very numerous. It is important to determine the cause of the hemorrhage promptly, because there may be a recurrence of bleeding. Guidelines for radiologists are proposed and discussed here.  相似文献   
37.
OBJECTIVES: This article examines the differences found between clientele with severe mental health problems and their key health workers in terms of assessing service users' needs in 6 Quebec service areas. METHOD: We questioned 165 pairs of users and staff, using the Camberwell Assessment of Needs questionnaire. The profile of serious and overall problems encountered by clientele from each of the sites was compared. RESULTS: The sites with the greatest degree of user-staff agreement in identifying problems were also the ones where users considered that local services best met their needs. CONCLUSIONS: The study demonstrated that, in needs assessment, major differences exist between the perceptions of users and their key workers in the various sites. These differences can be explained in part by users' individual characteristics, by types of needs, by local particularities, and by service use.  相似文献   
38.
39.
Suramin is an antitrypanosomal compound with confirmed efficacy against several human malignancies. It is generally assumed that its mechanism of action includes the interaction with different growth factors, unlike most of the anticancer drugs. Its anticancer activity has not been testedin vivo against squamous cell carcinoma. The purpose of this study was to assess the efficacy and toxicity of suraminin vivo andin vitro on the VX2 tumor model at therapeutic monitored plasma concentrations. We determined the pharmacokinetics of suramin in rabbits, and modelized its administration in order to obtain plasma concentrations between 150 and 300 μg/ml throughout the treatment course of 3 weeks. Under these conditions, antitumor effects of suramin were evaluatedin vivo by comparing liver tumor involvement in suramin-treated and control rabbits. Liver involvement was quantified by image analysis andin vitro effects were also determined at the same concentrations.In vivo, suramin promoted liver tumor growth significantly (p<0.05), compared to untreated controls.In vitro, suramin significantly stimulated tumor cell growth at concentrations above 200 μg/ml (p<0.01). Suramin may have stimulatory effects on tumor growth in squamous cell carcinoma at relevant plasma drug concentrations. Caution should be taken in further trials in patients with squamous cell carcinomas.  相似文献   
40.
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