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   763篇
  免费   113篇
  国内免费   2篇
耳鼻咽喉   3篇
儿科学   56篇
妇产科学   3篇
基础医学   125篇
口腔科学   22篇
临床医学   67篇
内科学   186篇
皮肤病学   18篇
神经病学   75篇
特种医学   55篇
外科学   47篇
综合类   16篇
预防医学   51篇
眼科学   80篇
药学   34篇
肿瘤学   40篇
  2022年   6篇
  2021年   7篇
  2020年   8篇
  2019年   13篇
  2018年   15篇
  2017年   11篇
  2016年   19篇
  2015年   23篇
  2014年   31篇
  2013年   24篇
  2012年   17篇
  2011年   19篇
  2010年   20篇
  2009年   27篇
  2008年   18篇
  2007年   22篇
  2006年   23篇
  2005年   14篇
  2004年   20篇
  2003年   25篇
  2002年   17篇
  2001年   28篇
  2000年   20篇
  1999年   14篇
  1998年   30篇
  1997年   30篇
  1996年   29篇
  1995年   17篇
  1994年   29篇
  1993年   17篇
  1992年   21篇
  1991年   22篇
  1990年   11篇
  1989年   21篇
  1988年   22篇
  1987年   14篇
  1986年   16篇
  1985年   18篇
  1984年   11篇
  1983年   9篇
  1982年   8篇
  1981年   8篇
  1980年   10篇
  1979年   9篇
  1978年   7篇
  1977年   8篇
  1976年   12篇
  1974年   15篇
  1972年   7篇
  1945年   5篇
排序方式: 共有878条查询结果,搜索用时 0 毫秒
51.
This article describes the curriculum design and development of an online Master's degree program in Rehabilitation Counseling at the University of South Carolina. The use of Bloom's Taxonomy as a method for selecting distance education techniques and teaching methods to ensure equivalency of the educational experience to traditional classroom teaching is described. The author presents tables to demonstrate the cognitive competencies, traditional and distance education methods, and use of synchronous and asynchronous methods in reaching desired educational objectives. This process has resulted in the creation of a program that offers distance education options, traditional classroom options, or a blend of approaches. The menu of options has met the unique learning needs of all students and has offered students with disabilities a level playing field on which to build rehabilitation counseling competencies.  相似文献   
52.
53.
OBJECTIVE: Almost 90% of type 1 diabetes appears in individuals without a close family history. We sought to evaluate the best current predictive strategy, multiple defined autoantibodies, in a long-term prospective study in the general population. RESEARCH DESIGN AND METHODS: Autoantibodies to pancreatic islets (islet cell antibodies [ICAs]) and defined autoantibodies (d-aab) to human GAD, IA2/ICA512, and insulin were tested in 4,505 Washington schoolchildren. Eight years later, 3,000 (67%) subjects were recontacted, including 97% of subjects with any test >99th percentile. RESULTS: Six subjects developed diabetes (median interval 2.8 years), all from among the 12 individuals with multiple d-aab, representing 50% positive predictive value (95% CI 25-75%) and 100% sensitivity (58-100%). Among the others, diabetes occurred in 0 of 6 with one d-aab plus ICA, 0 of 26 with ICA only, 0 of 7 with one d-aab equaling the 99th percentile and another d-aab equaling the 97.5th percentile, 0 of 86 with one d-aab, and 0 of 2,863 with no d-aab or ICA. Adjusted for verification bias, multiple d-aab were 99.9% specific (99.86-99.93%). At this age, new d-aab seldom appeared. Once present, d-aab usually persisted regardless of disease progression, although less so for insulin autoantibodies. Insulin secretion by sequential glucose tolerance testing remained normal in four multiple d-aab subjects not developing diabetes. Of children developing diabetes, five of six (83%) would be included if HLA-DQ genotyping preceded antibody testing, but HLA-DQ did not explain outcomes among high-risk subjects, even when considered along with other genetic markers. CONCLUSIONS: Multiple d-aab were established by age 14 years and prospectively identified all schoolchildren who developed type 1 diabetes within 8 years.  相似文献   
54.
In this study, we describe the isolation and characterization of a new adenylyl cyclase from Trypanosoma brucei and its activation by dimerization of the catalytic domain. In agreement with the current nomenclature of trypanosomal adenylyl cyclases, this new gene is termed GRESAG4.4B. The complete ORF of the GRESAG4.4B gene encodes a protein of 1291 amino acids. Its predicted protein structure is consistent with the structure of other trypanosomal cyclases, and with the cyclases of L. donovani. GRESAG 4.4B is constitutively expressed during the life cycle of trypanosomes. GRESAG4.4B is a member of a gene family, which contains at least six members, which are all clustered on chromosome IV. The catalytic domain of GRESAG4.4B is able to dimerize spontaneously. However, these spontaneously formed, stable dimers only show minimal enzymatic activity. The addition of a leucine zipper (LZ) derived from the S. cerevisiae GCN 4 gene to the N-terminus of the catalytic domain of GRESAG4.4B strongly activated its enzymatic activity. The LZ appears to enforce a distinct conformation of the dimer, which leads to an increased enzymatic activity, and thus may mimic the effect of ligand-induced dimerization of adenylyl cyclase in vivo.  相似文献   
55.
The activity of urea cycle enzymes was assayed in duodenal biopsy specimens obtained from a female infant who presented with neonatal hyperammonaemia. All enzyme levels were normal except N-acetyl glutamate-dependent carbamyl phosphate synthetase 1 (CPS1) which was half the mean activity in normal control specimens. A similar deficiency of CPS1 was also shown in duodenal specimens from the patient's mother who became slightly symptomatic after relatively high protein meals and during pregnancy, and had spontaneously modified her diet to one with protein restriction. The patient is growing normally on a dietary regimen similar to that spontaneously adopted by her mother. Urea cycle enzyme activity in the duodenal biopsy material from the controls was similar to that found in the normal human liver and appears to have distinct advantages as a means of assaying for urea cycle defects in patients with hyperammonaemia and their relatives.  相似文献   
56.
A controlled trial of elective intervention with continuous inflating pressure (CIP) was performed in infants with severe hyaline membrane disease who weighed more than 1000 g at birth. Infants entered the trial if their arterial oxygen tension (PaO2) fell below 60 mmHg while breathing a fractional inspired oxygen concentration (F1O2) greater than 0-95. 11 out of 12 infants in the CIP-treated group and 10 out of 12 in the control group survived. 7 treated and 6 control infants required mechanical ventilation. When CIP was started the Pao2 of the treated infants increased, and they breathed high concentrations of oxygen for a significantly shorter period than the control infants. During the 31-month duration of the trial 107 other infants with severe hyaline membrane disease were admitted who did not meet the criteria for entry to the trial. 37 survived after breathing high concentrations of oxygen (F1O2 greater than 0-60) spontaneously without any ventilatory assistance, and the remaining 70 infants were already being ventilated on their arrival in the unit, usually because they had required mechanical ventilation during transfer from other hospitals. The neonatal survival rate for those infants born in this hospital during the study period was 88% (50 out of 57 infants) and for those referred from other hospitals it was 69% (51 out of 74 infants). The maximum further increase in overall survival rate that might have been achieved in our population of infants if CIP had been initiated very early in the course of the illness was 5%--i.e. from 77% (101/131) to 82% (107/131).  相似文献   
57.
Gastroduodenoscopy and retrograde cholangiopancreatography has been performed on 25 occasions in 20 children aged between 7 and 16. Radiographs of the clinically relevant duct or ducts were achieved in 96% of attempts, with no complications. The diagnostic information proved useful clinically; in particular it provided a precise map if biliary or pancreatic surgery was being contemplated. Several unexpected congenital duct anomalies were found. This and other recent reports, particularly from Germany, indicate that endoscopic retrograde cholangiopancreatography deserves greater application in children, and can also be used in babies.  相似文献   
58.
A model of viral wheeze in nonasthmatic adults: symptoms and physiology.   总被引:4,自引:0,他引:4  
Episodic wheezing associated with viral infections of the upper respiratory tract (URT) is a common problem in young children but also occurs in adults. It is hypothesized that an experimental infection with human coronavirus (HCoV), the second most prevalent common cold virus, would cause lower respiratory tract (LRT) changes in adults with a history of viral wheeze. Twenty-four viral wheezers (15 atopic) and 19 controls (seven atopic) were inoculated with HCoV 229E and monitored for the development of symptoms, changes in airway physiology and provocative concentration of methacholine causing a 20% fall in forced expiratory volume in one second (FEV1) (PC20). At baseline, viral wheezers were similar to controls in PC20 (mean+/-SD log2PC20: 5.1+/-1.9 and 5.8+/-1.4 g x L(-1), respectively) but had a lower FEV1 than controls (mean+/-SD 85.8+/-11.4 and 95.6+/-13.2% predicted, respectively p < 0.05). Nineteen viral wheezers and 11 controls developed colds. Viral wheezers with colds reported significantly more URT symptoms than controls (median scores (interquartile range): 24 (10-37) and 6 (4-15), respectively p = 0.014). Sixteen viral wheezers and no controls reported LRT symptoms (wheeze, chest tightness and shortness of breath). The viral wheezers with colds had small (3-4%) reductions in FEV1 and peak expiratory flow on days with LRT symptoms (days 3-6), but a progressive reduction in PC20 from baseline on days 2, 4 and 17 after inoculation (by 0.82, 1.35 and 1.82 doubling concentrations, respectively). The fall in PC20 affected both atopic and nonatopic subjects equally. There were no changes in FEV1 or PC20 in controls. An adult model of viral wheeze that is independent of atopy and therefore, of classical atopic asthma was established.  相似文献   
59.
60.
Since the NHS reforms, health authorities have been purchasing health care and have been advised that publichealth considerations must inform all NHS activities, and that the Director of Public Health must be supported by a team of qualified support staff. This survey of directors of public health and health authority chief executives in England shows the skills currently available to support health authority purchasing, and the perceived importance of this wide range of skills to the purchasing process. Future models of purchasing will need to ensure access by purchasers to public health and multi-disciplinary advice.  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