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   1172篇
  免费   84篇
  国内免费   22篇
耳鼻咽喉   1篇
儿科学   144篇
妇产科学   26篇
基础医学   146篇
口腔科学   14篇
临床医学   103篇
内科学   216篇
皮肤病学   14篇
神经病学   117篇
特种医学   86篇
外国民族医学   1篇
外科学   157篇
综合类   28篇
预防医学   82篇
眼科学   3篇
药学   88篇
中国医学   1篇
肿瘤学   51篇
  2023年   5篇
  2022年   5篇
  2021年   7篇
  2020年   11篇
  2019年   19篇
  2018年   20篇
  2017年   14篇
  2016年   22篇
  2015年   19篇
  2014年   25篇
  2013年   34篇
  2012年   51篇
  2011年   43篇
  2010年   27篇
  2009年   31篇
  2008年   44篇
  2007年   43篇
  2006年   57篇
  2005年   52篇
  2004年   49篇
  2003年   46篇
  2002年   43篇
  2001年   41篇
  2000年   34篇
  1999年   36篇
  1998年   26篇
  1997年   30篇
  1996年   21篇
  1995年   16篇
  1994年   18篇
  1993年   23篇
  1992年   29篇
  1991年   30篇
  1990年   33篇
  1989年   31篇
  1988年   27篇
  1987年   25篇
  1986年   22篇
  1985年   25篇
  1984年   17篇
  1983年   20篇
  1982年   13篇
  1979年   8篇
  1977年   7篇
  1975年   9篇
  1974年   6篇
  1973年   8篇
  1970年   5篇
  1969年   4篇
  1968年   6篇
排序方式: 共有1278条查询结果,搜索用时 31 毫秒
1.
2.
OBJECTIVE: The development of acute renal failure following cardiac surgery is a rare but devastating complication with high morbidity and mortality. This study aimed to assess the incidence of acute renal failure necessitating continuous renal replacement therapy (CRRT) in patients who required cardiopulmonary bypass, to determine the factors associated with mortality and to evaluate long-term outcome. METHODS: Patients who underwent cardiac surgery between October 1997 and 2003 and treated with CRRT were included (n=98). Six patients were then excluded (already in established renal failure pre-operatively) and one patient lost to follow-up. A retrospective analysis was carried out. RESULTS: Overall CRRT was used in 2.9% (92/3172). The mean (SD) age of patients was 68 (10) years. Their mean pre-operative creatinine level and duration of cardiopulmonary bypass were 154 (87)micromol/l and 160 (84)min, respectively. Mean duration from surgery to establishment of CRRT was 50 (42)h. Mean creatinine level prior to hospital discharge was 168 (93)micromol/l. Thirty-day mortality was 42%. Significant risk factors for death were complex procedures (odds ratio=9.9), gastro-intestinal complications (OR=7.2), cross-clamp time over 88min (OR=5.9), re-exploration (OR=4.0) and patients age over 75 years (OR=3.3). Actuarial 1 and 5-year survivals (95% CI) were 53 (43, 63) % and 52 (42, 62) %, respectively. Only 2 (2.2%) patients required long term renal support. CONCLUSIONS: Acute renal failure necessitating the use of CRRT is a rare but serious complication post cardiopulmonary bypass. In the long-term, surviving patients are not likely to require further renal support.  相似文献   
3.
A series of experiments evaluated the determinants of preference for mixtures of ethanol plus sucrose relative to sucrose in rats. One dipper served 10% ethanol mixed with 10% sucrose, and the second dipper served 10% sucrose. Lever presses operated each dipper according to a variable-interval 5-s schedule. In three experiments the subjects were given pre-session meals of sucrose (2.5–20 ml) or sucrose (20 ml) plus chow (5 or 10 g). Pre-session meals decreased responding maintained by sucrose but not responding maintained by ethanol mixture. In two experiments body weight was varied from 85% to 125% of the initial free-feeding values. Increases in body weight, like pre-session meals, decreased responding reinforced by sucrose, but typically did not decrease responding reinforced by ethanol mixture. Throughout most of the study, ethanol consumption remained at about 1.25 ml per half hour session (3–4 g/kg per 30 min). For example, pre-session access to ethanol mixture decreased within-session ethanol consumption, but total consumption, counting both sources, remained about 1.25 ml/session. The within-session patterns of responding also differed. Responding reinforced by ethanol mix decreased as a function of ethanol consumption, whereas responding reinforced by sucrose was relatively constant throughout the session. The simplest explanation of the results is that ethanol's pharmacological consequences regulated preference.  相似文献   
4.
Mediastinal pseudocyst is an unusual complication of pancreatitis, with only four cases previously reported in children. The extent of the pseudocyst can be defined by computed tomography or magnetic resonance imaging scan and preoperative aspiration of cyst fluid for amylase level can establish the diagnosis. Endoscopic retrograde cholangiopancreatography to define ductal anatomy can help plan the appropriate drainage procedure. Although exceedingly rare, the diagnosis of pseudocyst should be considered for any cystic mass in the abdomen or thorax, even in the absence of elevated amylase or history suggesting pancreatitis.  相似文献   
5.
6.
7.
This case report describes a dog suffering from a co‐infection with Babesia and Anaplasma parasites. Anaplasma platys was found to be responsible for the anaplasmosis by molecular biology techniques, while microscopical and serological evidence was found for a coexistent babesiosis, although this could not be confirmed by polymerase chain reaction. Moreover, the possible risk of import of exotic pathogens is highlighted.  相似文献   
8.
Our earlier studies using the Consortium to Establish a Registry of Alzheimer's Disease neuropsychological battery showed that delayed recall was a highly sensitive indicator of early Alzheimer's disease. None of the learning and memory measures in the battery were found to be useful in staging the severity of this form of dementia. This study explores the nonmemory functions (fluency, naming, and praxis) of the Consortium to Establish a Registry of Alzheimer's Disease battery and asks whether performance on any of these measures adds to the detection of early Alzheimer's disease or is sensitive to the later progression of the illness. We stratified patients with this disease according to severity (mild, moderate, severe), and compared them with age-, education-, and gender-matched control subjects (group N = 49 each). Multivariate procedures and cutting scores were used to determine the efficacy of the various measures in distinguishing between the cases and control subjects. Impairment of delayed recall was again found to be the best discriminator for detecting mild cases of Alzheimer's disease. Confrontation naming was the only nonmemory factor that assisted in this discrimination. For staging the illness, a combination of measures including fluency, praxis, and recognition memory best differentiated cases with mild dementia from those with either moderate or severe stages of disease. Measures of delayed recall quickly "bottomed out" in the patients with Alzheimer's disease and proved of little value in staging the disorder.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
9.
Tumor vascularity has been proposed as a prognostic indicator for a number of solid tumors. Although a correlation between microvessel number and metastatic behavior has also been suggested for cutaneous melanoma, the small number of cases studied to date allows one to draw only preliminary conclusions. In this study, we have assessed tumor vascularity in cutaneous melanoma by comparing 60 cases of metastasizing and non-metastasizing tumors matched for tumor thickness, age, sex, and anatomic site. Ulex europaeus agglutinin I appeared to be the most suitable vascular marker for this study. Our results indicate that there was no statistically significant difference between the two groups with regard to tumor vascularity. Even after identifying 15 cases of thin (<1.0 mm thick) melanoma, there was no significant difference in the number of microvessels between metastasizing and non-metastasizing tumors. Comparison of patterns of vascular microarchitecture also failed to discriminate between the two groups. Thus, our results indicate that tumor vascularity may not be an independent prognostic factor for cutaneous melanoma.  相似文献   
10.
Uptake and transport of horseradish peroxidase (HRP) have been observed in both Peyer's patches (PP) and jejunal epithelium (JE), and the quantities transported across each tissue were compared. Steady-state was reached much faster in PP than in JE. In Ringer solution, no significant difference was found between the HRP fluxes conveyed through PP and JE. In the presence of 10 mM glucose, slight net secretion was observed in JE but not in PP. In both tissues, the transport mechanism was shown to be sensitive to metabolic inhibitors. By contrast, in PP, ammonia did not significantly enhance intact HRP fluxes. Intracellular transfer and catabolism were estimated by measuring transepithelial fluxes of tritiated HRP. In PP, fluxes from mucosa to serosa and from serosa to mucosa were both greatly reduced (9.18 +/- 3.9 and 10.5 +/- 5.1 pmol X h-1 X cm-2, respectively) compared with JE (106.02 +/- 16 and 31.3 +/- 9.3). These results indicate that intact HRP fluxes are similar in PP and JE, but that tritiated HRP fluxes (intact plus degraded HRP fluxes) are smaller in PP. Together, these results suggest that the specific characteristics of HRP transport across PP are fast uptake and reduced degradation.  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