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   1473篇
  免费   132篇
  国内免费   59篇
耳鼻咽喉   5篇
儿科学   48篇
妇产科学   26篇
基础医学   200篇
口腔科学   34篇
临床医学   219篇
内科学   291篇
皮肤病学   8篇
神经病学   85篇
特种医学   123篇
外科学   240篇
综合类   41篇
一般理论   2篇
预防医学   97篇
眼科学   24篇
药学   107篇
中国医学   11篇
肿瘤学   103篇
  2023年   19篇
  2022年   29篇
  2021年   55篇
  2020年   28篇
  2019年   37篇
  2018年   60篇
  2017年   47篇
  2016年   51篇
  2015年   45篇
  2014年   74篇
  2013年   62篇
  2012年   104篇
  2011年   89篇
  2010年   73篇
  2009年   56篇
  2008年   65篇
  2007年   81篇
  2006年   58篇
  2005年   46篇
  2004年   53篇
  2003年   37篇
  2002年   42篇
  2001年   19篇
  2000年   9篇
  1999年   14篇
  1998年   38篇
  1997年   36篇
  1996年   21篇
  1995年   30篇
  1994年   18篇
  1993年   17篇
  1992年   6篇
  1991年   11篇
  1990年   15篇
  1989年   17篇
  1988年   16篇
  1987年   11篇
  1986年   17篇
  1985年   15篇
  1984年   13篇
  1983年   7篇
  1982年   10篇
  1981年   14篇
  1980年   11篇
  1979年   12篇
  1977年   17篇
  1976年   11篇
  1973年   8篇
  1970年   5篇
  1966年   9篇
排序方式: 共有1664条查询结果,搜索用时 15 毫秒
41.
OBJECTIVE: In several large, well-designed, randomized, double-blind studies, the opiate antagonist naltrexone demonstrated efficacy in the treatment of alcohol dependence. Specifically, when combined with certain psychosocial therapies, naltrexone reduces the number of drinking days, heavy drinking, and time to relapse to alcohol use in alcohol-dependent individuals. Whether this efficacy can be generalized to individuals who have alcohol use disorders and present for treatment at front-line community treatment programs has not been well established. METHODS: A total of 145 patients who presented for treatment at a rural community substance abuse treatment center were randomized to receive naltrexone 50 mg daily plus usual program treatment (n = 54), placebo plus usual treatment (n = 43), or usual treatment alone (n = 48) for 12 week. A total of 133 participants had at least one follow-up visit. Primary outcome measures included percent days drinking, average drinks per drinking day, average drinks per day, heavy drinking days (four or more for women and six or more for men), and time to first heavy drinking day. Secondary measures included changes in serum biological markers (alkaline phosphatase, alanine transaminase, aspartate transaminase, and gamma-glutamyltransferase), craving, and psychosocial functioning. RESULTS: In the intention-to-treat analysis, there were no between-group differences for any of the primary drinking outcomes at 12 weeks. In post hoc exploratory analyses, the entire sample of participants was divided into two new groups: (1) people who drank during the 2 weeks before the start of medication (entry drinkers) and (2) people who did not drink during this interval (entry abstainers). Entry abstainers were at an advantage at study entry in that they were significantly more likely to have an inpatient hospitalization immediately before entry into outpatient treatment. Mixed-model analysis of variance revealed a main effect for entry group at the 12-week treatment endpoint on the primary outcome measures of percent days drinking, average drinks per drinking day, average drinks per day, heavy drinking days, and time to first heavy drinking day. Participants in any of the randomized groups who were entry abstainers had significantly better improvement on all of the primary outcome measures. The abstainer groups that were randomized to placebo and usual treatment had significantly better outcomes than the entry drinkers in those perspective groups. However, for the naltrexone-treated group, entry drinkers and entry abstainers had similar improvement in drinking-related outcomes. CONCLUSIONS: These data suggest that naltrexone may offer particular benefit to patients who continue to drink during the early stages of the trial as compared with those who have achieved abstinence before treatment entry.  相似文献   
42.
Many animals estimate their self-motion and the movement of external objects by exploiting panoramic patterns of visual motion. To probe how visual systems process compound motion patterns, superimposed visual gratings moving in different directions, plaid stimuli, have been successfully used in vertebrates. Surprisingly, nothing is known about how visually guided insects process plaids. Here, we explored in the blowfly how the well characterized yaw optomotor reflex and the activity of identified visual interneurons depend on plaid stimuli. We show that contrary to previous expectations, the yaw optomotor reflex shows a bimodal directional tuning for certain plaid stimuli. To understand the neural correlates of this behavior, we recorded the responses of a visual interneuron supporting the reflex, the H1 cell, which was also bimodally tuned to the plaid direction. Using a computational model, we identified the essential neural processing steps required to capture the observed response properties. These processing steps have functional parallels with mechanisms found in the primate visual system, despite different biophysical implementations. By characterizing other visual neurons supporting visually guided behaviors, we found responses that ranged from being bimodally tuned to the stimulus direction (component-selective), to responses that appear to be tuned to the direction of the global pattern (pattern-selective). Our results extend the current understanding of neural mechanisms of motion processing in insects, and indicate that the fly employs a wider range of behavioral responses to multiple motion cues than previously reported.  相似文献   
43.
Splenectomy in myeloid metaplasia   总被引:3,自引:0,他引:3  
Silverstein  MN; ReMine  WH 《Blood》1979,53(3):515-518
Between 1960 and 1977, 50 patients with agnogenic myeloid metaplasia were splenectomized. Twenty-five of 26 patients with painful splenomegaly, 4 of 9 patients with refractory hemolytic anemia, 4 of 10 patients with refractory thrombocytopenia, and 4 of 4 patients with portal hypertension showed significant benefit from the procedure. There were five immediate postoperative deaths. Four of these deaths occurred early in our series of splectomies for myeloid metaplasia before 1970. Only one death has occurred in the last 21 patients operated on. Survival following splenectomy averaged 25.5 mo.  相似文献   
44.
AIM: To evaluate existing evidence for the association between different type of brassiere exposures and the risk of breast cancer. METHODS: Ovid Medline, CINAHL, Cochrane Data Base of Systematic Reviews, Pubmed, Scopus, Proquest, Sciencedirect, Wiley Online Library, WanFang Data, Hong Kong Index to Chinese Periodicals, China Journal Net, Chinese Medical Current Contents, Chinese Biomedical Literature Database, China Academic Journals Full-Text database, Taiwan Electronic Periodical Services and HyRead; reference lists of published studies; original research studies published in English or Chinese examining the association between type and duration of brassiere-wearing and breast cancer risk. Data were abstracted by a first reviewer and verified by a second. Study quality was rated according to predefined criteria. “Fair” or “good” quality studies were included. Results were summarised by meta-analysis whenever adequate material was available. RESULTS: Twelve case-control studies were included in the review. Meta-analysis showed brassiere wearing during sleep was associated with a two times of increased odds. CONCLUSION: The present review demonstrates insufficient evidence to establish a positive association between the duration and type of brassiere wearing and breast cancer. Further research is essential; specifically, a large-scale epidemiological study of a better design is needed to examine the association between various forms of brassiere exposure in detail and breast cancer risk, with adequate control of confounding variables.  相似文献   
45.
Radiation-induced red cell damage: role of reactive oxygen species   总被引:1,自引:1,他引:1  
BACKGROUND: Cellular blood components are irradiated to prevent graft- versus-host disease in transfusion recipients at risk for this syndrome. Because gamma radiation can result in the production of reactive oxygen species, the role of reactive oxygen species was investigated in radiation-induced red cell damage. STUDY DESIGN AND METHODS: Whole blood from normal donors was exposed to various doses of t-butyl hydroperoxide (0-1 mM) and/or to gamma-radiation (0-50 Gy). Oxidative damage was assessed by the extent of lipid peroxidation (measured by thiobarbituric acid-reactive substances [TBARS]) and hemoglobin oxidation. Fresh blood was divided into three parts-one initially irradiated and stored, another stored with portions irradiated weekly, and a third stored without irradiation. TBARS and hemoglobin oxidation were measured weekly. RESULTS: As expected, t- butyl hydroperoxide induced TBARS formation and hemoglobin oxidation in a dose-dependent fashion. The gamma-radiation not only increased hemoglobin oxidation and TBARS formation, but also enhanced the t-butyl hydroperoxide effect on red cells. Red cell storage increased TBARS generation and hemoglobin oxidation in a time-dependent fashion. When radiation was administered either initially or after weekly storage, TBARS production and hemoglobin oxidation were increased over that measured in unirradiated paired controls. CONCLUSION: Gamma radiation at clinically used doses increases lipid peroxidation and hemoglobin oxidation in human red cells. The effect of gamma-radiation is accentuated by blood storage and induces damage independent of time of storage.  相似文献   
46.
WH Visser  MD  ; RHM de  Vriend  MSc ; NHWM Jaspers  MSc  ; MD Ferrari  MD  PhD 《Headache》1996,36(8):471-475
Sumatriptan, notably after subcutaneous administration, is highly effective in the acute treatment of migraine in the majority of patients. The response is consistent within patients and over time. To determine risk factors for nonresponse to sumatriptan, we compared clinical characteristics. In responders and nonresponders and, within patients, between attacks with and without response. We found no differences at the strict level of significance (P<0.001 because of multiple comparisons), but only tendencies for differences (0.001相似文献   
47.
Background Heart failure (HF) is a physically and socially debilitating disease that carries the burden of hospital re-admission and mortality. As an aging society, Hong Kong urgently needs to find ways to reduce the hospital readmission of HF patients. This study evaluates the effects of a nurse-led HF clinic on the hospital readmission and mortality rates among older HF patients in Hong Kong. Methods This study is a retrospective data analysis that compares HF patient in a nurse-led HF clinic in Hong Kong compared with HF patients who did not attend the clinic. The nurses of this clinic provide education on lifestyle modification and symptom monitoring, as well as titrate the medications and measure biochemical markers by following established protocols. This analysis used the socio-demographic and clinical data of HF patients who were aged ≥ 65 years old and stayed in the clinic over a six-month period. Results The data of a total of 78 HF patients were included in this data analysis. The mean age of the patients was 77.38 ± 6.80 years. Approximately half of the HF patients were male (51.3%), almost half were smokers (46.2%), and the majority received ≤ six years of formal education. Most of the HF patients (87.2%) belonged to classes II and III of the New York Heart Association Functional Classification, with a mean ejection fraction of 47.15 ± 20.31 mL. The HF patients who attended the clinic (n = 38, 75.13 ± 5.89 yrs) were significantly younger than those who did not attend the clinic (n = 40, 79.53 ± 6.96 yrs) (P = 0.04), and had lower recorded blood pressure. No other statistically significant difference existed between the socio-demographic and clinical characteristics of the two groups. The HF patients who did not attend the nurse-led HF clinic demonstrated a significantly higher risk of hospital readmission [odd ratio (OR): 7.40; P < 0.01] than those who attended after adjusting for the effect of age and blood pressure. In addition, HF patients who attended the clinic had lower mortality (n = 4) than those who did not attend (n = 14). However, such a difference did not reach statistical significance when the effects of age and blood pressure were adjusted. A significant reduction in systolic blood pressure [F (2, 94) = 3.39, P = 0.04] and diastolic blood pressure [F (2, 94) = 8.48, P < 0.01] was observed among the HF patients who attended the clinic during the six-month period. Conclusions The finding of this study suggests the important role of nurse-led HF clinics in reducing healthcare burden and improving patient outcomes among HF patients in Hong Kong.  相似文献   
48.
目的:蒿甲醚除了具有良好的临床治疗作用外,对正常组织有极大的副作用。实验拟观察蒿甲醚对大鼠肺泡Ⅱ型上皮细胞的影响。方法:实验于2005-09-20/2007-03-10在山东省泰山医学院生命科学研究所、中心实验室和机能实验室完成。①实验材料:蒿甲醚购自昆明制药厂,分析纯,使用前先进行预处理,处理方法:研磨后用溶液配成1g/L的母液,超声助溶解后供实验用。Wistar大鼠70只,体质量(70±15)g,雌雄不拘,由山东大学医学院实验动物中心提供。实验过程中对动物处置符合动物伦理学标准。②实验方法:将大鼠随机分为普通饲料对照组(n=10)和实验组(n=60),实验组分6个亚组,分别在饲料中加入0.1,0.2,0.4,0.8,1.6,3.2mg/kg的蒿甲醚。采用单细胞凝胶电泳技术观察大鼠肺泡Ⅱ型上皮细胞DNA的改变。结果:70只大鼠,饲养过程中实验组死亡6只,死亡原因为饲料添加蒿甲醚造成。当饲料中的蒿甲醚浓度为0.1mg/kg时,大鼠肺泡Ⅱ型上皮细胞DNA损伤率与对照组相比,差异无统计学意义;饲料中的蒿甲醚浓度超过0.2mg/kg时,大鼠肺泡Ⅱ型上皮细胞DNA损伤率明显增加,与对照组相比,差异有统计学意义。且损伤程度与饲料中蒿甲醚含量呈正相关。结论:当饲料中的蒿甲醚浓度超过0.2mg/kg时,蒿甲醚可在一定程度上改变肺泡Ⅱ型上皮细胞的DNA生物学特性。且随着蒿甲醚浓度的升高,这种损害更为明显。  相似文献   
49.
Tuberous sclerosis complex is an autosomal dominant neurocutaneous disorder marked by hamartoma growth in multiple organ systems. We performed mutational analyses on 325 individuals with definite tuberous sclerosis complex diagnostic status. We identified mutations in 72% (199/257) of de novo and 77% (53/68) of familial cases, with 17% of mutations in the TSC1 gene and 50% in the TSC2 gene. There were 4% unclassified variants and 29% with no mutation identified. Genotype/phenotype analyses of all observed tuberous sclerosis complex findings in probands were performed, including several clinical features not analyzed in two previous large studies. We showed that patients with TSC2 mutations have significantly more hypomelanotic macules and learning disability in contrast to those with TSC1 mutations, findings not noted in previous studies. We also observed results consistent with two similar studies suggesting that individuals with mutations in TSC2 have more severe symptoms. On performing meta-analyses of our data and the other two largest studies in the literature, we found significant correlations for several features that individual studies did not have sufficient power to conclude. Male patients showed more frequent neurologic and eye symptoms, renal cysts, and ungual fibromas. Correlating genotypes with phenotypes should facilitate the disease management of tuberous sclerosis complex.  相似文献   
50.
Two hundred twenty isolates of Vibrio cholerae O1 and O139 collected from 1994 to 2002 in Hong Kong were analyzed by pulsed-field gel electrophoresis (PFGE). Chromosomal DNAs from all V. cholerae isolates in agarose plugs were digested with the restriction enzyme NotI, resulting in 20 to 27 bands. Sixty distinctive PFGE patterns in the range of 10 to 300 kb were noted among 213 isolates typeable by PFGE. By comparing the common PFGE patterns obtained from four well-defined outbreaks of V. cholerae O1 and O139 with those obtained from other, epidemiologically unrelated isolates during the study period, indistinguishable and similar PFGE patterns were identified, indicating their close relatedness, in agreement with the results of epidemiological investigations. Heterogeneous PFGE patterns (with four to six banding differences), however, were identified among strains that were imported from other parts of Asia, including Indonesia, India, and Pakistan. Correlations with epidemiological information further support the usefulness of PFGE as an epidemiological tool in laboratory investigations of suspected outbreaks. Standardization of PFGE methodology will allow international comparison of fingerprint patterns and will form the basis of a laboratory network for tracking V. cholerae.  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