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   1427719篇
  免费   126095篇
  国内免费   5203篇
耳鼻咽喉   18910篇
儿科学   46021篇
妇产科学   38616篇
基础医学   200956篇
口腔科学   40612篇
临床医学   154036篇
内科学   280125篇
皮肤病学   29529篇
神经病学   123218篇
特种医学   51489篇
外国民族医学   366篇
外科学   200569篇
综合类   29037篇
现状与发展   41篇
一般理论   485篇
预防医学   126946篇
眼科学   30979篇
药学   100299篇
  6篇
中国医学   3201篇
肿瘤学   83576篇
  2021年   13277篇
  2020年   11496篇
  2019年   13441篇
  2018年   22437篇
  2017年   18841篇
  2016年   20214篇
  2015年   22202篇
  2014年   30120篇
  2013年   42853篇
  2012年   47897篇
  2011年   50340篇
  2010年   33290篇
  2009年   33186篇
  2008年   46151篇
  2007年   47672篇
  2006年   48695篇
  2005年   45951篇
  2004年   43318篇
  2003年   40968篇
  2002年   39624篇
  2001年   62559篇
  2000年   63594篇
  1999年   53848篇
  1998年   16496篇
  1997年   15015篇
  1996年   14912篇
  1995年   13996篇
  1994年   12609篇
  1993年   11786篇
  1992年   42284篇
  1991年   41387篇
  1990年   39947篇
  1989年   37851篇
  1988年   35063篇
  1987年   34066篇
  1986年   32496篇
  1985年   30965篇
  1984年   23309篇
  1983年   19887篇
  1982年   12002篇
  1979年   20902篇
  1978年   14978篇
  1977年   12220篇
  1976年   11984篇
  1975年   12199篇
  1974年   14889篇
  1973年   14545篇
  1972年   13442篇
  1971年   12481篇
  1970年   11556篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
A randomized clinical trial was performed to compare the efficacy of bilateral oophorectomy with that of tamoxifen at a dose of 10 mg twice daily in premenopausal women with metastatic breast cancer, and to examine the efficacy of each as a crossover treatment. Initial treatment responses were seen in ten of 27 patients (37%) treated with oophorectomy and seven of 26 patients (27%) treated with tamoxifen. The difference was not statistically significant. Crossover responses were seen in five of 15 patients (33%) treated with oophorectomy, including three responses in ten prior tamoxifen nonresponders; and two of 18 patients (11%) treated with tamoxifen. Time to progression distributions were not significantly different during initial treatment, and no significant differences in survival were noted. Thus, there was no overall disadvantage to the use of tamoxifen as opposed to oophorectomy as initial hormonal therapy, and a failure to respond to tamoxifen did not preclude a response to subsequent oophorectomy. Exploratory data analysis within subsets indicated consistent differential treatment effects in the visceral dominant patients. Of the 16 such patients treated with oophorectomy, eight (50%) experienced objective responses but there were no responses in the 14 patients treated with tamoxifen. In the nine visceral dominant crossover patients who had not responded to initial tamoxifen, three (33%) subsequently responded to oophorectomy. Time to progression distributions within the visceral dominant subset appeared to be better for the patients treated initially with oophorectomy. However, one must be very cautious in drawing conclusions from exploratory subset analyses, especially with the small sample size. Further studies would be required to test any hypothesis of differential organ site responsiveness.  相似文献   
993.
994.
995.
Temporoparietal and posterior cingulate metabolism deficits characterize patients with Alzheimer's disease (AD). A H(2)(15)O resting PET scan covariance pattern, derived by using multivariate techniques, was previously shown to discriminate 17 mild AD patients from 16 healthy controls. This AD covariance pattern revealed hypoperfusion in bilateral inferior parietal lobule and cingulate; and left middle frontal, inferior frontal, precentral, and supramarginal gyri. The AD pattern also revealed hyperperfusion in bilateral insula, lingual gyri, and cuneus; left fusiform and superior occipital gyri; and right parahippocampal gyrus and pulvinar. In an independent sample of 23 outpatients with mild cognitive impairment (MCI) followed at 6-month intervals, the AD pattern score was evaluated as a predictor of cognitive decline. In this MCI sample, an H2(15)O resting PET scan was carried out at baseline. Mean duration of follow-up was 48.8 (SD 15.5) months, during which time six of 23 MCI patients converted to AD. In generalized estimating equations (GEE) analyses, controlling for age, sex, education, and baseline neuropsychological scores, increased AD pattern score was associated with greater decline in each neuropsychological test score over time (Mini Mental State Exam, Selective Reminding Test delayed recall, Animal Naming, WAIS-R digit symbol; Ps<0.01-0.001). In summary, a resting PET covariance pattern previously reported to discriminate AD patients from control subjects was applied prospectively to an independent sample of MCI patients and found to predict cognitive decline. Independent replication in larger samples is needed before clinical application can be considered.  相似文献   
996.
997.
998.
OBJECTIVE: Avoidance of potential iatrogenic nerve injury during insertion of Ilizarov fine wires into areas of high anatomic risk by using a modified nerve stimulation technique. INDICATIONS: Application of the Ilizarov ring fixator to areas of high anatomic hazard, in situations where anatomic topography may be distorted by previous surgery, trauma, or congenital anomalies. CONTRAINDICATIONS: Use of systemic muscle relaxants. Caution in patient with cardiac pacemaker. SURGICAL TECHNIQUE: Preliminary experiments showed that a standard nerve-stimulating device can deliver a negatively charged, monophasic square pulse of current through Ilizarov wires. During the application of an Ilizarov frame to potentially hazardous anatomic regions, providing no systemic muscle relaxants are used, a voltage field sufficient to cause nerves in close proximity to the Ilizarov wire to depolarize is produced. Identification of a distal muscle twitch provoked by the stimulation may indicate a potential for iatrogenic nerve injury. RESULTS: Results show that with the nerve stimulator set at 2.5 mA (pulsed at a frequency of 2 Hz), peripheral nerves are stimulated if they lie within 5 mm of the wires. Should a distal muscle twitch occur, wires should be repositioned so that equivalent stimulation produces no twitch. The technique was used during Ilizarov frame application in ten patients, with only a single occurrence of distal muscle twitches in a lower-leg frame. Following repositioning of the Ilizarov wire in this case, no further twitches were observed, indicating that no Ilizarov wire was inserted close to peripheral nerves. No neurologic impairment was present postoperatively.  相似文献   
999.
1000.
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