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   126432篇
  免费   9107篇
  国内免费   214篇
耳鼻咽喉   1138篇
儿科学   3449篇
妇产科学   2610篇
基础医学   19719篇
口腔科学   3304篇
临床医学   10650篇
内科学   25684篇
皮肤病学   2193篇
神经病学   12311篇
特种医学   5151篇
外国民族医学   9篇
外科学   15820篇
综合类   530篇
现状与发展   1篇
一般理论   106篇
预防医学   14464篇
眼科学   1973篇
药学   7404篇
中国医学   237篇
肿瘤学   9000篇
  2023年   547篇
  2022年   905篇
  2021年   1965篇
  2020年   1425篇
  2019年   2072篇
  2018年   2603篇
  2017年   2210篇
  2016年   2406篇
  2015年   2686篇
  2014年   3675篇
  2013年   4808篇
  2012年   7406篇
  2011年   7493篇
  2010年   3873篇
  2009年   4058篇
  2008年   6624篇
  2007年   6844篇
  2006年   6592篇
  2005年   6232篇
  2004年   5325篇
  2003年   5022篇
  2002年   4569篇
  2001年   4460篇
  2000年   4404篇
  1999年   3939篇
  1998年   1600篇
  1997年   1316篇
  1996年   1392篇
  1995年   1132篇
  1994年   1067篇
  1993年   963篇
  1992年   2693篇
  1991年   2405篇
  1990年   2303篇
  1989年   2139篇
  1988年   1967篇
  1987年   1709篇
  1986年   1628篇
  1985年   1561篇
  1984年   1117篇
  1983年   970篇
  1982年   523篇
  1981年   461篇
  1980年   394篇
  1979年   867篇
  1978年   521篇
  1977年   426篇
  1974年   419篇
  1973年   418篇
  1972年   368篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
In a nationwide survey the nutritional status was assessed of 539 apparently healthy, independently living elderly aged 65-79 years. Anthropometric data showed no energy deficits. The prevalence of anemia was 4 and 1% among men and women, respectively. Many elderly showed a low level of 25-hydroxyvitamin D in plasma (less than 31 nmol/L: men 35%; women 43%), indicating a marginal status. Although the prevalence of low blood levels of folate, pyridoxal-5'-phosphate, and total carotenoids was higher among the elderly than among younger adults, clear (clinical) signs of nutritional deficiencies were not observed. Prevalence of obesity (13%), hypercholesterolemia (38%), and hypertension (63%) was found to be high, the percentages being higher for women than for men. Several indicators of the nutritional status appeared to differ among age groups. It is concluded that few differences can be considered as being due to physiological aging, which finding should be reflected in reference values for elderly people.  相似文献   
142.
Benzalkonium chloride was assayed by on-line extraction of the benzalkonium ion with picrate to chloroform. The absorbance of picrate was measured. The extractions were performed with a home-made flow injection extraction unit. Calibration curves (1.5-180 x 10(-4)% w/v) were straight lines (r = 0.9993) and the relative standard deviation of a series of injections was less than or equal to 2%. Pharmaceutical benzalkonium preparations, containing xylometazoline, timolol, phenylephrine or carbachol could also be assayed. The method was compared with a modified HPLC assay.  相似文献   
143.
144.
This report provides transmission electron microscopic observations on the early pathogenesis of persistent hyperplastic tunica vasculosa lentis/persistent hyperplastic primary vitreous (PHTVL/PHPV) in affected canine fetuses at days 28-44 postcoitum. The retrolental tissue by which this anomaly is characterized consists of loosely arranged fibroblasts in a randomly oriented meshwork of collagenous fibrils. Some of these cells contain melanosomes at day 44. In one day-44 eye, cells of neuroectodermal origin (Müller cells; fibrous astrocytes) were observed. From day 37 onward, the posterior subcapsular part of the lens contains rounded, increased intercellular spaces, resembling vacuoles, which deform the shape of the lens fibers. The posterior lens capsule develops normally until day 30. From day 35 onward the capsule has an amorphous ultrastructure, as opposed to the clearly laminated ultrastructure in reference eyes at day 35. In addition, the capsule's thickness increases until day 35, and, instead of growing thicker, decreases thereafter. Based on these results, it is hypothesized that a primary metabolic disorder in the lens fibers, subsequently leading to the formation of an abnormal posterior lens capsule, constitutes the primary defect in the sequence of events leading to PHTVL/PHPV.  相似文献   
145.
Summary: Purpose: Quantitative MRI techniques provide an unparalleled opportunity to examine in vivo the relationship between the extent and laterality of hippocampal pathology and associated neuropsychological deficits. The purpose of this study was to examine the nature of the relationship between quantitative measures of hippocampal pathology and neuropsychological measures, using a multivariate approach. Methods: We examined the relationship between two MRI measures of hippocampal structure; hippocampal volumes (HCvol) and T2 relaxation times (HCT2), and memory performance, in 80 presurgical temporal lobe epilepsy patients. Results: As a group, patients with left hippocampal sclerosis (LHS) performed more poorly that those with right hippocampal sclerosis (RHS) on immediate and delayed prose recall. In the group as a whole, right hippocampal volume was significantly correlated with the delayed recall of a complex figure. None of the verbal memory test scores were significantly correlated with the right or left HCvol or HCT2 measures. However, stepwise multiple regression analyses indicated that up to a third of the variation in specific test scores could be explained by the quantitative MRI hippocampal measures in conjunction with chronological age, and age at onset of habitual epilepsy. Left hippocampal measures explained 24% of the variance in the story-recall tasks, while right hippocampal measures explained 18% of the variance in a design-learning task and 32% of the variance in a figure-recall task. Conclusions: Our results provide some support for the lateralised model of material specific memory deficits, but suggest that a number of demographic and epilepsy-related factors may interact with the extent and laterality of hippocampal pathology in shaping the nature of the associated neuropsychological deficit.  相似文献   
146.
Islet cell carcinomas of the pancreas: a twenty-year experience   总被引:16,自引:0,他引:16  
Unlike its lethal exocrine counterpart, islet cell carcinoma of the pancreas is an indolent neuroendocrine neoplasm. The majority of these tumors are hormonally active. When functioning, a number of clinical syndromes (for example, hyperinsulinism, Zollinger-Ellison and Cushing's syndromes) may be evident. Fifty-eight patients surgically treated between 1965 and 1984 were retrospectively analyzed. The purpose of this study was to determine the distribution of functioning versus nonfunctioning tumors and the response to type of therapy. Mean postoperative follow-up was 7.4 years. Survival and prognostic indices were calculated by the Kaplan-Meier method and compared with log-rank tests. Of the group, 54% had functioning and 46% nonfunctioning tumors. Gastrinomas were the most common functioning tumors encountered (19%). Of interest was the finding that nonfunctioning tumors increased steadily during the last 15 years of the study (25% to 65%). Curative resections were performed in 15 (26%) and noncurative procedures in 43 patients (74%), with an overall operative mortality rate of 3%. Symptomatic improvement was achieved in 90% (curative) and 51% (noncurative). Survival at 3 years was 87% and 66% for the curative and noncurative groups, respectively (p less than 0.1), with an overall 5-year survival of 42%. The absence of hepatic metastases was a major predictor of survival at 3 years (82% vs 56%, p less than 0.05). Survival was statistically better at 3 years in those patients with gastrinomas compared with patients with nonfunctioning tumors (91% vs 58%, p less than 0.05). Although surgical cure is rare, significant long-term palliation may be achieved in a large percentage of patients with an aggressive surgical approach, occasional total gastrectomy, combination chemotherapy, H2 blockade, when indicated, and, most recently, with the new long-acting analogue of somatostatin.  相似文献   
147.
Twenty adult surgical patients were anaesthetized with high-dose midazolam and alfentanil by infusion, vecuronium, and intubated and ventilated with 50% N2O in O2. The midazolam and alfentanil infusions were stopped at the end of surgery. Residual neuromuscular blockade and ventilatory depression were antagonized and the patients extubated. In the recovery room, patients were randomly allocated to receive either flumazenil 1 mg of placebo i.v. Before, and until 2 h after injection, patients were asked to perform psychomotor tests. In addition, sedation, comprehension and orientation were scored. The flumazenil (n = 10) and the placebo (n = 10) groups were comparable. Prior to injection all patients were heavily sedated. After flumazenil all were awake within 2-3 min, but fell asleep again 15-60 min later. The improvement in test scores was sustained for a longer time. After placebo, patients awoke in 1-2 h. At 60 and 120 min, test scores in the two groups were similar. Heart rate, blood pressure and respiration rate did not change. No side-effects were observed or reported. It is concluded that flumazenil is an effective and safe antagonist of high dose midazolam, with a rapid onset but a short duration of action.  相似文献   
148.
Percutaneous nephrolithotomy (PCN) enables the urologist to remove upper urinary tract stones through a percutaneous nephrostomy tract. The principal advantages of PCN are the low morbidity, shortened hospital stay and rapid recovery. Percutaneous puncture failed in 5 (11%) of the first 44 patients with upper tract urolithiasis treated by PCN at Tygerberg Hospital. In 35 patients (80%) PCN cleared the kidney of stones but in 4 patients (9%) all stone fragments were not removed during the procedure. If the puncture and dilatation was successful, then 90% of patients were stone-free after PCN. Complications were minimal except for a diabetic who died of septicaemia. PCN is an alternative to open renal surgery in the management of most upper urinary tract stones. The technique is readily mastered by any urologist experienced in endoscopic surgery.  相似文献   
149.
In a group of patients with keratoconjunctivitis sicca (KCS) associated with Sj?gren's syndrome (SJ) a significant decrease in tear fluid lactoferrin concentration and tear film break-up time was demonstrated in comparison with a matched group in which KCS was not associated with any systemic disease. The Schirmer values were also lower in the SJ of patients and these differences almost reached statistical significance. None of these parameters in itself appeared to be of any clinical value to differentiate between KCS that was or was not associated with SJ. The combination of the tear fluid lactoferrin concentration, the Schirmer I test values and the tear film break-up time, however, provide a basis for differential diagnosis that is clinically of some value.  相似文献   
150.
Ink and bytes]     
Paper journals--and books--will continue to exist, despite the digital revolution. Electronic media are superior for storage and retrieval of information, but far less so for intellectual digestion. The Dutch Journal of Medicine is proud of its recently completed electronic archive, in the form of digital images (1857-1985) and full text (from 1986 onwards). At the same time the Journal's supporting Society cherishes a valuable book collection, with some 700 titles before the year 1800 alone. Recently, a curator and a professional librarian were appointed. Part of the Society's assets have been transferred to a special fund for the support of projects on the borderline between medicine and other disciplines, such as history, philosophy, sociology and art.  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